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Communication

Aspects of Movement Ecology and Habitat Use of Migratory Raptors Using Satellite Telemetry from India to Central Asia

by
Mohan Ram
1,*,
Devesh Gadhavi
2,
Aradhana Sahu
3,
Nityanand Srivastava
4,
Tahir Ali Rather
2,
Vidhi Modi
2,
Akshita Patel
2,
Lahar Jhala
1,
Yashpal Zala
1 and
Dushyantsinh Jhala
2
1
Wildlife Division, Sasan-Gir, Junagadh 362135, India
2
The Corbett Foundation, P.O. Tera, Taluka Abdasa, Kutch 370660, India
3
Wildlife Circle, Junagadh 362001, India
4
Chief Wildlife Warden, Gandhinagar 382010, India
*
Author to whom correspondence should be addressed.
Birds 2024, 5(3), 487-508; https://doi.org/10.3390/birds5030033
Submission received: 3 June 2024 / Revised: 23 July 2024 / Accepted: 24 July 2024 / Published: 15 August 2024
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Abstract

:

Simple Summary

The migration strategies, movement patterns, and habitat associations of long-distance migratory raptors remain largely unknown. We deployed PTT-GSM satellite transmitters on five raptor species, four of which are threatened, with the objective of investigating their daily and seasonal movement patterns, migration flyways, home-range patterns, and habitat associations in their wintering areas. This study shows that raptors wintering in Western India undertake annual migration across the Western Circum–Himalayan Corridor of the Central Asian Flyway (CAF) to circumvent some of the highest mountain ranges in the world.

Abstract

Single individuals of the Greater Spotted Eagle (Clanga clanga), Indian Spotted Eagle (Clanga hastata), Tawny Eagle (Aquila rapax), Western Marsh Harrier (Circus aeruginosus), and two Pallid Harriers (Circus macrourus) were deployed with satellite transmitters in 2021 to study their home ranges, habitat associations, movement, and migration patterns. Data were collected for a combined number of 2291 days, providing 84,544 locations. Home ranges were calculated as kernel utilization distributions and expressed as 95% KDE and core areas as 50% KDE. Overall, eagles had larger home ranges (mean ± SD) of 942.70 ± 937.83 km2 compared to harriers, 43.84 ± 35.55 km2. Among eagles, the Greater Spotted Eagle had the largest home-range size of 2147.03 km2 calculated in Kazakhstan, while the female Pallid Harrier had the smallest home range of 5.74 km2 in Russia. Daily and monthly distances varied among eagles and harriers. The female Pallid Harrier covered the longest average monthly distance of 8585.43 ± 11,943.39 km, while the shortest monthly distance of 1338.22 ± 716.38 km was traveled by the Indian Spotted Eagle. All tagged birds migrated toward higher latitudes in the Northern hemisphere, except the Indian Spotted Eagle, which migrated to Pakistan. The male Western Marsh Harrier covered the longest migration distance in a shorter span of time, while the female Pallid Harrier took the longest to cover its migration distance. Overall, the daily distance covered during migration varied from 115.09 km traveled by the Indian Spotted Eagle to an overwhelming distance of 2035.85 km covered by the male Western Marsh Harrier. Scrubs, water bodies, croplands, and settlements were important habitat features associated with eagles, while croplands, open scrub, and built-up areas were associated with the female Pallid Harrier. The male Western Marsh Harrier was found to be primarily associated with saltpans and salt-affected areas having emergent vegetation. This study presents new insights into the movement and spatial ecology of long-distance migrant raptors that winter in Western India. We provide preliminary support for the use of the Western Circum–Himalayan Corridor as one of the important corridors of the Central Asian Flyway that warrants much appreciation among the current set of flyway corridors.

1. Introduction

Out of 557 raptor species found worldwide, 18% are threatened by extinction, and 52% have globally declining population trends [1]. The Accipitriformes order is reported to have greater-than-average proportions of threatened and declining species [2]. Even for the raptor species that are listed as “Least Concern” on the IUCN List of Threatened Species, 38% of them are in decline [1,2]. Additionally, the majority of raptor groups exhibit lower Red List Indices [3] compared to birds in general [1], indicating that, on average, raptors face a heightened risk of extinction relative to the average bird. Thus, raptors exhibit a greater susceptibility to extinction in comparison to both avian and non-avian groups due to distinctive ecological characteristics and life history patterns [1].
Despite the recent rise in ornithological research in South Asia, raptors remain poorly studied, which hinders the development of effective conservation measures. This is true for many raptor species in the Old World, which spend more than half of the year migrating and on their wintering grounds [4]. Long-distance migrant raptors face a variety of threats along their migratory routes, at stopover sites, and in non-breeding areas that may carry unprecedented repercussions on their survival [5,6]. Thus, identifying migration routes between breeding and non-breeding areas of long-distance migrant raptors becomes crucial for their long-term conservation. With the advancement of satellite telemetry, a new avenue of understanding the spatial and movement ecology of a variety of birds has opened up. While many telemetry studies on raptors investigating their movement and migration patterns have been carried out worldwide, less than 1% of the total bird species found in India have been studied using satellite telemetry [7]. Thus, very little information exists for one of the important migration flyways, the Central Asian Flyway, which is used by hundreds of species that breed in Central–Northern Asia and spend their non-breeding season in the Indian subcontinent [8].
There are two major flyways for Asian raptors and other soaring birds that winter in the Indian subcontinent: (i) the ‘Eurasian–East African Flyway’, a western route extending from Central–Western Russia and Kazakhstan to Eastern Africa, and (ii) the ‘East Asian Continental Flyway,’ an eastern route from Eastern Russia and Japan to Southeast Asia, Indonesia, and Australia [6,8,9]. In contrast, the Central Asian Flyway is composed of several corridors used by thousands of soaring migrants from Kazakhstan, Central–Northern Russia, Mongolia, and Central–Northern China into the Indian subcontinent and vice versa [8]. A recent telemetry study [8] of Black Kites (Milvus migrans) in India reported that they use the East Asian Flyway, making a detour to circumvent exceptionally high Himalayan Mountain ranges. Other studies focusing on raptors [10,11] and cranes [12] wintering in Western India indicate the use of the Central Asian Flyway, traversing countries such as Pakistan, Afghanistan, Uzbekistan, and Turkmenistan, to reach Kazakhstan and Russia and vice versa (Figure 1). Some raptor species, such as the Oriental Honey Buzzard (Pernis ptilorhynchus) and Grey-faced Buzzard (Butastur indicus), are known to use the East Asian Oceanic Flyway, migrating by island hopping [13,14].
In this study, we focus on satellite tracking of the Greater Spotted Eagle, Tawny Eagle, Indian Spotted Eagle, Western Marsh Harrier, and Pallid Harrier, to demonstrate their home-range patterns, daily and seasonal movement patterns, habitat use, and migration patterns along the Central Asian Flyway. The results of the first phase of this study were published in 2022, where we restricted ourselves to the basic information regarding home-range and movement patterns [10]. In this study, we also included the female Pallid Harrier and male Western Marsh Harrier, which were not included in our previous study. In addition, we also attempted to assess the habitat factors influencing their occurrence within wintering grounds, which was not assessed in our previous work [10].
The Greater Spotted Eagle occupies a fragmented breeding range, spanning Estonia, Finland, Poland, Belarus, Russia, Kazakhstan, Mainland China, and Mongolia [15,16]. During the winter season, it is reported to migrate to East and North Africa, the Middle East, the Indian subcontinent, South Asia, and Southeast Asia [17]. The tawny Eagle is a widespread raptor and can be found across extensive regions in Sub-Saharan Africa, with isolated populations in North Africa, the Middle East, and South Asia. The Indian Spotted Eagle breeds in the lowlands of India, Nepal, and Myanmar [18,19]. The Pallid Harrier nests in the steppes of Russia, Kazakhstan, and North–Western China and winters in Sub-Saharan Africa and the Indian subcontinent [20,21]. While its movement patterns and winter home ranges are well studied in the African range [22], there is currently limited information on this aspect in India [10]. The Western Marsh Harrier breeds across Europe, China, and Central Asia, including East and Central Russia [22], and is highly migratory, characterized as loop migration behaviour [23,24,25].

2. Materials and Methods

2.1. Study Area

The satellite tagging of raptors was carried out in the Asiatic Lion Landscape (ALL), north-western India, and Abdasa taluka of Kutch district in Gujarat, India (Figure 2).
Three species (Greater Spotted Eagle, male Pallid Harrier, and Indian Spotted Eagle) were tagged in the Asiatic Lion Landscape (ALL) located in the south-western part of the Saurashtra region of Gujarat, India, while the Tawny Eagle, male Western Marsh Harrier, and female Pallid Harrier were tagged in Abdasa taluka of Kutch district, Gujarat (Figure 2). A detailed description of the study area is available in Ram et al. [10].

2.2. Reconnaissance, Capture and Tagging

We led a team of forest officials, subject experts, and veterinarians based on our previous experience [10,11,12] to undertake a pilot survey within the study area so that suitable sites for setting up traps could be identified. The team collected preliminary data on the distribution, behaviour, and movement pattern of raptors using binoculars (Nikon Prostaff 7s 10 × 42, Nikon Vision Co. Ltd., Shinagawa-ku, Tokyo, Japan) and a fieldscope (Nikon Prostaff 5 Fieldscope, Nikon Vision Co., Ltd., Shinagawa-ku, Tokyo, Japan). The identified sites were later marked with a hand-held GPS (Garmin eTrex 30×) (Global Positioning System, Garmin, Olathe, KS, USA). The capturing and tagging of raptors for satellite telemetry were conducted in two phases. In the first phase, between 25 February and 26 March 2021, single individuals of Tawny Eagle, Indian Spotted Eagle, Greater Spotted Eagle, and male Pallid Harrier were captured. In the second phase, one male Western Marsh Harrier and one female Pallid Harrier were captured on 6 and 8 October 2021, respectively (Supplementary Material S1). The data obtained in the first phase for the four tagged raptors were published in Ram et al. [10] and, hence, are not included in this study. Here, we analysed the data obtained from (a) December 2021 to August 2022 for the Greater Spotted Eagle, from December 2021 to July 2023 for the Indian Spotted Eagle, and from December 2021 to April 2022 for the Tawny Eagle; (b) from October 2021 to July 2023 for the male Western Marsh Harrier; and (c) from October 2021 to July 2023 for female Pallid Harrier (Supplementary Material S1). The transmitter, deployed on the male Pallid Harrier that was tagged in the first phase, stopped working on 8 October 2021 and, therefore, is not included in this study. We deployed transmitters as backpacks with 11 mm Teflon ribbon for eagles and 5 mm Teflon ribbon for harriers by following a thoracic X-strap method, having a flat knot in the Teflon near the sternum [10]. The transmitters weighed less than 3% of the body mass of the raptors, as recommended [26,27].
We used a traditional Bal-Chatri trap that was constructed by uniformly attaching the top of the trap with about 15–20 nooses. The noose trap consisted of an anchor line with several monofilament fishing line nooses attached to it [28]. The Bal-Chatri trap was dome-shaped, having a height and width of 1 foot. We used live village chicken chicks as bait to lure the raptors towards the traps. The small door at the bottom permitted us to deposit and remove the baits. The traps were set near pre-roosting sites that were identified prior to the capturing. The traps were generally set before dawn and were continuously monitored by the team members from different vantage points. A quick response team with Kenwood wireless walkie-talkie (Model-NX-3220, JVCKENWOOD Corporation, Long Beach, CA, USA) remained on standby at an approximate distance of 250–300 m to immediately release the targeted/non-targeted birds if captured in the traps.
The captured birds were handled with care, and their heads were covered with specially designed headgear to minimise stress if required. The birds were always kept in the shade to counter the stress from heat during the tagging. Supplementary Material S2 contains photographic details of the tagging process.
The Solar 3D-GPS PTT, weighing 45 g (Argos Satellite Tag), was deployed on the Greater Spotted Eagle from Microwave Telemetry that utilised the Argos Satellite Data Collection Relay System (CLS America, Lanham, MD, USA). Meanwhile, Ornitela GSM tags weighing 10 to 25 g were deployed on the rest of the birds (Supplementary Material S1). The Ornitela tags (Ornitela, UAB, Vilnius, Lithuania) used the GSM network (cellular phone) to transmit data.

2.3. Statistical Analysis and Data Preparation

A total of 84,544 locations were obtained, out of which we retained 70,459 (83%) for analysis, and the rest were discarded due to inconsistencies, such as missing coordinates and locations having low accuracy. We chose high-accuracy locations belonging to LC3 for Solar 3D-GPS PTT and discarded the locations belonging to low-accuracy classes. Similarly, we discarded inconsistent locations, such as locations showing sudden and abruptly high elevation values. We retained only those locations from GPS-GSM transmitters that showed low dilution of precision values. We used an average number of 14,091.80 ± 7934.71 (mean ± SD) locations for each individual. Using these data, we calculated home ranges in breeding and non-breeding regions of raptors. We estimated home ranges using kernel density estimators (KDE) with the R package “adehabitatHR” [29] in R [30]. We used 95% kernels (95% KDE) to define the total home-range size and 50% kernels (50% KDE) to delimit the core areas or most intensively used areas. The smoothing parameter for all home-range estimations was set to the reference bandwidth denoted as ‘href’ [31].
We projected location fixes in UTM projection and calculated the daily and monthly distance traveled by each raptor species using the Tracking Analyst tool in ArcGIS version 10.8.1 [32]. We segregated the migration and non-migration seasons by visualising apparent directional movement patterns.
To investigate the habitat associations of raptors, we used the random forest (RF) algorithm [33] and executed it as regression using the R package ‘randomForest’ [34]. We prepared the data for RF modelling by creating a circular buffer of a 250 m radius around each presence location and randomly generated twice the number of pseudo-absence locations using ArcGIS. We were primarily interested in assessing the fine-scale habitat use and, thus, chose a 250 m spatial scale corresponding to the fourth-order habitat selection, as described by Johnson [35].
We ensured that each pseudo-absence location was at least 250 m away from each presence location to avoid pseudo-replication. We also applied spatial filtering of 300 m to the presence locations to reduce spatial autocorrelation that results due to the non-independence of variables sampled at nearby locations. Finally, we removed the additional pseudo-absence locations and retained an equal subset of pseudo-absence locations as the spatially filtered presence locations. We obtained the land use land cover map from Bhaskaracharya National Institute for Space Applications and Geo-Informatics (BISAG-N, Gujarat, India) for 2020 and reclassified each habitat category on a continuous scale using the reclassify tool in ArcGIS. We used focal statistics and extracted values to points within a radius of 250 m. We used 99 random permutations and cross-validation via a resampling strategy to assess the model efficiency. At each permutation, we divided the data into multiple subsets, using one set (one-tenth) for data validation and the remaining sets to train the model. We generated the Kappa index of agreement, model error variance, and OOB error rate as model performance matrices.

3. Results

3.1. Movement Patterns during Non-Migration Season

During the non-migration season, the female Pallid Harrier covered an average monthly distance (mean ± SD) of 4425.40 ± 7266.61 km, while the Indian Spotted Eagle covered 1218.06 ± 648.17 km (Table 1).
Likewise, the female Pallid Harrier covered a daily average distance (mean ± SD) of 145.46 ± 235.59 km, while it was just 41.22 ± 20.92 km in the case of the Indian Spotted Eagle (Table 1).
In the migration season, the female Pallid Harrier covered an average monthly distance of 32,084.31 ± 5347.40 km while covering a daily average distance of 1060.02 ± 193.51 km (Table 2).
The Indian Spotted Eagle covered a monthly average distance of 801.06 ± 377.90 km during migration to Pakistan, covering an average daily distance of 186.45 ± 66.79 km (Table 2).

3.2. Migration Patterns

During migration, all species used the Western Circum-Himalayan Corridor, and frequent stopover sites were located in Sindh and Baluchistan (Pakistan); Helmand and Nimruz (Afghanistan); Mary (Turkmenistan); Bukhara and Navoivy (Uzbekistan); and Kyzylorda, Aktobe, and Karaganda (Kazakhstan) (Figure 3). The detailed migration patterns of all tagged raptor species are provided in Figure 3.

3.2.1. Female Pallid Harrier

The female Pallid Harrier started its migration from India towards Russia on 27 March 2022, and it reached Russia on 16 April 2022 and stayed there until 04 September 2022. During its migration, it stayed for five days in Pakistan, three days in Afghanistan, one in Iran, two in Turkmenistan, three in Uzbekistan, and six in Kazakhstan, respectively. It reached Kazakhstan on 10 April 2022, crossed into Russia on 16 April 2022, and stayed there till September 2022. It covered a daily distance of 1098.01 km (Table 2) and flew at an average elevation of 658.69 ± 617.87 m above mean sea level (AMSL). It moved at an average speed of 43.92 km/day, excluding stopover days (Figure 4).
Its return migration started on 04 September 2022. During its return migration, it stayed in Kazakhstan for ten days and one day in Uzbekistan. It crossed into Turkmenistan on 15 September but did not stay there. It reached Afghanistan on the same day. It stayed in Afghanistan for 12 days; later, on 27 September, it crossed into Pakistan. It stayed in Pakistan for three days and entered India on 30 September 2022. When returning, it covered a daily distance of 1231.74 km to reach India, moving with an average speed of 82.11 km/day (excluding stopover days) and flew at an average elevation of 849.47 ± 586.63 m AMSL.
It stayed in India till March 2023 and started its second migration towards Kazakhstan on 21 March 2023 (Figure 4). It reached Pakistan on the same day and stayed there for two days, and on 23 March 2022, it reached Afghanistan and stayed there for a further three days. It took one day each to cross Turkmenistan and Uzbekistan and reached Kazakhstan on 28 March 2023 (Figure 4). It covered a daily distance of 850.34 km to reach Kazakhstan and flew at an average elevation of 732.68 ± 673.30 m AMSL and moved with an average speed of 44.75 km/day (excluding stopover days). The stopovers were located in six countries (see Supplementary Material S3). The total distance traveled during each migration is presented in Table 2.
Overall, the female Pallid Harrier covered an average distance of 32,084.31 ± 5347.40 during all migration journeys in 58 days, covering a daily average distance of 1060.02 ± 193.51 km and traveling with an average speed of 60.98 ± 21.17 km/day. The female Pallid Harrier made several detours to avoid crossing the high peaks of the mountainous ranges of the Hindu Kush in Afghanistan and the Zagros range in Iran.

3.2.2. Male Western Marsh Harrier Male

The male Western Marsh Harrier started its migration from Gujarat, India, on 9 April 2022 by crossing into Pakistan on the same day and staying there for three days. It took two days to cross Afghanistan and three days each to cross Turkmenistan and Uzbekistan. It reached Kazakhstan on 20 April 2022. It flew at an average elevation of 797.77 ± 924.25 m AMSL and covered a daily distance of 2035.85 km, moving with an average speed of 156.60 km/day (Figure 5).
It stayed in Kazakhstan till September 2022. The return migration started on 4 September 2022 when it crossed into Uzbekistan and stayed there for three days. It reached Turkmenistan on 7 September 2022, stayed there for two days, and reached Iran on 9 September 2022. It took one day to cross Iran and reached Afghanistan on 10 September 2022. After staying for two days in Afghanistan, it reached Pakistan on 12 September 2022 and stayed there for 21 days. It finally reached India on 3 October 2022 by flying at an average elevation of 300.19 ± 527.46 m AMSL. It covered a total daily distance of 1205.04 km by moving at an average speed of 150.63 km/day (excluding stopover days).
The second migration started on 1 April 2023 from India towards Kazakhstan (Figure 5). It reached Pakistan on 2 April 2023 and left on 4 April 2023. It stayed for two days in Afghanistan, one day in Turkmenistan, three days in Uzbekistan, and finally reached Kazakhstan on 11 April 2023. During this migration, it covered a daily distance of 2030.69 km by moving with an average speed of 225 km/day (excluding stopover days).
Overall, it covered an average distance of 26,309.91 ± 3896.57 km in 49 days by covering a daily average distance of 1757.19 ± 478.18 km (Table 2) and moving with an average speed of 129.80 ± 72.04 km/day. A detailed account of the stopovers used during its migration is provided in Supplementary Material S3, and the total distance covered during each migration is shown in Table 2. Like the female Pallid Harrier, it also made detours to avoid crossing the high-elevation peaks of the Hindu Kush and Zagros mountain ranges. It traveled across the arid regions of the Registan desert in Afghanistan, the Karakum desert in Turkmenistan, and the Kyzylkum desert in Uzbekistan.

3.2.3. Indian Spotted Eagle

The apparent directional movement of the Indian Spotted Eagle towards Pakistan was noticeable on 21 March 2022. By 25 March 2022, it reached Pakistan by covering a total distance of 1237.34 km and flew at an altitude of 440.51 ± 502.28 m AMSL. It moved at an average speed of 61.86 km/day (excluding stopover days) (Figure 6).
It stayed in Pakistan till November 2022, started migrating towards India on 29 November 2022, and reached India on 3 December 2022. It covered a daily distance of 115.09 km (Table 2) and flew at an average elevation of 311.66 ± 305.60 m AMSL. It moved at an average speed of 28.77 km/day. The second migration started on 17 February 2023, where the Indian Spotted Eagle covered a total distance of 590.83 km and a daily distance of 196.89 km (Table 2) by moving at an average speed of 65.59 km/day. It reached Pakistan on 21 February 2023 by flying at an average elevation of 382.48 ± 247.46 m AMSL (Figure 6).
It stayed in Pakistan till April 2023, and since 29 April 2023, there has been no communication with the transmitter. Overall, it covered an average distance of 801.06 ± 377.90 km in 13 days during its migration while covering a daily average distance of 186.45 ± 66.79 km and moving with an average speed of 46.03 ± 21.49 km/day. The stopovers used during its migration are provided in Supplementary Material S3, and the total distance traveled during each migration is presented in Table 2.

3.2.4. Greater Spotted Eagle

The Greater Spotted Eagle started migrating towards Russia on 31 March 2022 and reached Pakistan on 1 April 2022 (Figure 7).
It stayed in Pakistan till 5 April 2022, reached Afghanistan on the same day, stayed there for a day, and crossed into Uzbekistan on 6 April 2022. It stayed in Uzbekistan till 12 April 2022 and reached Kazakhstan on 13 April 2023. It covered a total distance of 3765.26 km and a daily distance of 268.94 km to reach Kazakhstan, traveling at an average speed of 19.21 ± 12.51 km/day and flying at an average elevation of 301.95 ± 594.51 m AMSL. After staying for about 29 days in Kazakhstan, it crossed into Russia on 13 May 2022 and stayed till August 2022. The communication with the transmitter stopped on 25 August 2022. The stopover locations used during its migration are provided in Supplementary Material S3.

3.2.5. Tawny Eagle

The tawny Eagle started migrating towards its breeding site on 22 April 2022 and reached Pakistan on 23 April 2022. It stayed in Pakistan for three days and reached Afghanistan on 26 April 2022. While in Afghanistan, we lost communication with the transmitter on 29 April 2022 (Figure 8).

3.3. Home Ranges

Overall, eagles had overwhelmingly larger home ranges (mean ± SD) of 942.70 ± 937.83 km2 compared to harriers, 43.84 ± 35.55 km2 (Table 3).
Likewise, the female Pallid Harrier had an overall smaller home range compared to the male Western Marsh Harrier (Table 3). Home ranges were calculated in non-breeding areas in India and in the breeding areas in Kazakhstan and Russia (Supplementary Material S4).

3.4. Habitat Associations

We assessed the habitat association of eagles and harriers during the winter season while they were in India. In the case of the Indian Spotted Eagle, we found open scrub, horticulture, and water bodies to be the most important variables influencing their occurrence. Among eight habitat variables that influenced the occurrence of the Greater Spotted Eagle in India, croplands, open scrub, and water bodies were the most important factors. At the same time, horticulture and salt-affected areas were the least important habitat variables. Out of seven habitat variables, only three were important for predicting the occurrence of the Tawny Eagle. Cropland was the most important habitat variable, while open scrub habitat was the least important habitat variable influencing the occurrence of the Tawny Eagle.
Among harriers, the male Western Marsh Harrier was found to occur mostly around saltpans and salt-affected habitats, while croplands and open scrub habitats were least important for determining its occurrence. Croplands and open scrub habitats were the most important variables for predicting the occurrence of the female Pallid Harrier. At the same time, dense scrub, grasslands, and built-up were the least important habitat variables.
We used partial dependence plots to assess the relationship between habitat variables and the occurrence of raptors. We found that the Indian Spotted Eagle showed a uniform relationship with horticulture, with no change in its occurrence as the percentage of horticulture increased. In contrast, open scrub and water bodies showed a positive relationship with the Indian Spotted Eagle (Supplementary Material S5). Open scrub showed a unimodal relationship with the presence of Indian Spotted Eagle, indicating that they preferred open scrub at 10% of its total availability. In contrast, the relationship with water bodies was bi-modal, indicating the regular use of water sources by the Indian Spotted Eagle. Open scrub was the most important habitat based on the variable importance plot followed by horticulture and water bodies (Figure 9).
Built-up, croplands, open scrub, settlements, and water bodies showed a positive relationship with the predicted occurrence of the Greater Spotted Eagle (Supplementary Material S5). The predicted occurrence of Greater Spotted Eagle increased as the percentage of built-up habitat reached 15% of its total availability, and the variable importance plot shows that built-up increased model improvement only by 0.04%; thus, though built-up was positively associated with the Greater Spotted Eagle, its importance was not statistically significant. There was a unimodal relationship between the Greater Spotted Eagle and croplands. The partial dependence graph further indicates that they are preferred between 60% and 80% of their availability, and the variable importance plot indicates croplands as the most important variable determining the occurrence of the Greater Spotted Eagle (Figure 9). Likewise, a unimodal relationship with open scrub habitat indicates that the Greater Spotted Eagle prefers open scrub habitats at a certain threshold, which was between 10 and 20% of the total available habitat. A similar unimodal relationship was observed for water bodies (Supplementary Material S5 for more details).
The tawny Eagle was positively associated with croplands and arid habitats such as deserts. Croplands were also the most important variable followed by arid or desert habitats that influenced the occurrence of the Tawny Eagle (Figure 9). The predicted occurrence showed a steady and uniform relationship with croplands and increased at a higher percentage of croplands (>80%) (Supplementary Material S5). The positive relationship was also evident for arid desert regions. Though there were no apparent peaks, the predicted occurrence increased smoothly as the percentage of arid habitats increased. The relationship between the Tawny Eagle and the open scrub habitat was not very pronounced as we observed a small peak in the predicted occurrence of Tawny Eagle at lower concentrations of open scrub at first. Thereafter, the predicted occurrences remained steady with no evident change beyond 20% of the available open scrub habitat (Supplementary Material S5). Croplands and arid regions together constituted about 79% of the total home-range size of the Tawny Eagle, while open scrub constituted only 15%.
The female Pallid Harrier was found to show a positive relationship with croplands and a bell-shaped relationship with built-up. At the same time, grasslands were preferred according to their availability, with high-use peaks occurring at around 60% of the availability and low-use peaks at a lower percentage of the available habitat (Supplementary Material S5). The relationship with croplands increased linearly, indicating a strong preference for croplands. At the same time, we observed a bell-shaped relationship with built-up, wherein the predicted occurrences reached the maximum at 10% of the availability of built-up and decreased afterwards. Built-up ranked last in the variable importance plot and contributed <2% in the overall model improvement. The grasslands were effective in determining the occurrence of Pallid Harrier at a lower concentration (~15%). The predicted occurrence declined afterward, with a gentle increase at a higher proportion of grasslands (between 60 and 80%). Though there was no pronounced dip in the predicted occurrences of the Pallid Harrier with a further increase in the proportion of the grassland, the relationship was, however, not so strong, as suggested by the variable importance plot (Figure 9). Grasslands, built-up, and dense scrub ranked behind cropland and open scrub in their relative importance, where grasslands contributed only 2% and built-up contributed <2% in the overall model improvement, as shown by the variable importance plot (Figure 9). The partial dependence plot showed that the occurrence of the female Pallid Harrier was highest at a lower percentage of open scrub, between 0 and 20%. The occurrences declined smoothly afterwards, indicating that Pallid Harrier may use open scrub habitats, usually at lower concentrations.
Saltpans and salt-affected areas were the most important habitat variables in the habitat association model of the male Western Marsh Harrier (Figure 9). We observed a multimodal relationship with saltpans, suggesting peaks of high and low occurrence of male Western Marsh Harrier in saltpans (Supplementary Material S5). The multiple peaks of high occurrences indicate the frequent use of saltpans by the Western Marsh Harrier. Salt-affected areas showed the most substantial influence on the occurrence of Western Marsh Harrier at lower availability, up to 1%, remaining constant afterwards, with a small second peak between 0.4 and 0.6% of the availability of salt-affected habitats. The male Western Marsh Harrier showed a stable and uniform relationship with croplands and open scrub habitats, indicating proportional use.
All multivariate habitat models were well supported and significant at p < 0.001 except for Tawny Eagle (Supplementary Material S6). Models for all species performed well except for the Tawny Eagle and female Pallid Harrier, which had relatively lower AUC values than other models (Supplementary Material S6).

4. Discussion

4.1. Home Ranges and Habitat Associations

We expected the home ranges of raptors to be smaller in breeding ranges compared to wintering areas. Our preliminary results suggested that this was the case for the female Pallid Harrier, Indian Spotted Eagle, and, to some extent, male Western Marsh Harrier. The prolonged telemetry study and tagging of more individuals in the coming years may provide actual insights into the home-range patterns of migratory raptors.
The home ranges of most vertebrates tend to increase with body mass, while they decrease with higher habitat productivity [36,37,38]. At the same time, variation in home-range size among different species has also been linked to factors, such as age and sex differences [38,39], dominance status [39], and trophic status [36,37]. Raptors provide an interesting case of investigating the inter-specific variations in their home ranges as they are adapted to exploit a wide variety of prey species utilizing different hunting tactics.
As found in a previous telemetry study [10], the home range of the Greater Spotted Eagle in Kazakhstan was very large compared to India. The home range encompassed water bodies and open natural lands interspersed with croplands. In India, home ranges were found to be located in open scrub habitats and croplands with the presence of water bodies. Our results agree with previous studies that the Greater Spotted Eagle prefers open natural habitats with the presence of water [10,40,41,42].
Croplands, open scrub, water bodies, saltpans, and settlements are very important habitat variables influencing its occurrence. The habitat model showed that the Greater Spotted Eagle preferred croplands at higher availability (60% to 80%), indicating croplands as the most important habitat variable. We observed a similar positive relationship with open scrub and water bodies. The home ranges of the Greater Spotted Eagle have been previously found near water bodies and open natural habitats [43]. In this study, we also observed water bodies, croplands, and open scrub habitats as important habitat constituents of its home range. Open scrub habitats can be treated in the context of the present study areas as open natural habitats that are characterized by the absence of tall and dense vegetation. We also observed a positive relationship with built-up, though the model improvement plot showed a very insignificant contribution of built-up in the overall performance of the habitat model.
There is very little information available on the Indian Spotted Eagle, and it is generally reported to prefer open landscapes and cultivated fields with the presence of water [44]. We observed a similar pattern of larger home ranges in Pakistan compared to those in India, as observed for the Greater Spotted Eagle. This may have been due to the breeding of the Indian Spotted Eagle in India. Home ranges tend to be smaller in the breeding season than during the non-breeding season. The Indian Spotted Eagle showed a preference for open scrub habitats, which may be utilized for foraging on small mammalian prey species [45]. The occurrence of the Indian Spotted Eagle was highest at around 10% of the total open scrub habitat available (range 0 to 20), which indicates that the Indian Spotted Eagle showed a preference for very specific availability. This specific preference may be attributed to the hunting of small mammalian prey species, such as rodents, in open scrub habitats. Sant et al. [44] observed that rodents constituted an important portion of its diet in Southern India. Another study [46] conducted in Northern India found that the Indian Spotted Eagle occurred mostly in unploughed fields, probably due to the high abundance of rodents. Sant et al. [44] also found that most of the habitat where the Indian Spotted Eagle nested in Belgaum, Karnataka, constituted privately owned agricultural lands with a high rodent population. Our results indicate that their habitat use is partially dictated by the presence of suitable prey species, and, thus, their habitat preference may differ regionally.
The tawny Eagle had established its home range in the North-Western state of Rajasthan, like the one established in 2022 [10]. The home-range size was relatively smaller than previously observed by Ram et al. [10]. We observed that the Tawny Eagle preferred croplands at a high percentage and was the most important habitat variable influencing its occurrence, and open scrub was ranked the third most important variable. In India, it is reported to occur in agricultural areas and near settlements [47]. Previously, we had found that the Tawny Eagle occurred in similar habitats that were characterized by agricultural fields and arid regions [10]. Tawny Eagles are reported to prefer a wide range of habitats, including deserts, open savannahs, open grasslands, and cultivated fields [48,49]. Our results also showed that Tawny Eagle preferred croplands and arid desert regions to a large extent and open scrub to a smaller extent. This low preference for open scrub (15% of the total home-range size) may have been due to the dominance of arid regions and croplands (89% of the total home-range size) within the home range of Tawny Eagle. The home range was established in the western part of the Jaisalmer district of Rajasthan state, which is mostly covered by the Thar desert, thus influencing habitat use in favour of arid regions and croplands.
The Pallid Harrier is reported to favour wet grasslands and marshlands, often in proximity to water bodies in its breeding range [50,51]. Our results indicated that the female Pallid Harrier established its home range in a mosaic of croplands and open scrub habitats, which together constituted 82% of the total area of its home-range size in Gujarat, India, while in Russia, the home range was located across wet, marsh grassland with a large number of small inland water bodies fed by the Irtysh River. Home ranges were significantly smaller in Russia and Kazakhstan compared to winter home ranges established in India, as observed previously [10]. In this study, we found croplands and open scrub as the most important variables; dense scrub and grasslands were moderately important habitat variables, constituting a total of 11% of its home-range size, while built-up was the least important variable. Open habitats with natural vegetation are the preferred habitats of Pallid Harriers that winter in eastern Africa [21]. In India, Pallid Harriers have been found to use tall grasslands for roosting while trees, stumps, and sometimes bare ground for pre-roosting in North-Western India [52] and Southern India [53]. In Gujarat, the grasslands of Blackbuck National Park hold as many as 3000 harriers, among which ~25% are Pallid Harriers using grasslands for roosting [52,54]. We found that open habitats such as croplands and open scrub were the two most important variables determining its occurrence. While croplands were positively associated with Pallid Harrier, we observed that the Pallid Harrier occurred at a lower concentration of open scrub habitat. Grasslands were also preferred at lower availability, probably due to the small proportion (6%) of grasslands in its home range. In general, the female Pallid Harrier occurred in a mosaic of habitats that included croplands, scrub, and grasslands, as found in similar telemetry studies [21]. The habitat preferences of the Pallid Harrier in wintering ranges are somewhat similar to that of Montagu’s Harrier (Circus pygargus), which uses mainly croplands for feeding in the winter season [55] and grasslands for roosting [52,53].
The male Western Marsh Harrier had a larger home range in Kazakhstan than in India for the first year (2022), while in the second year (2023), the home range in Kazakhstan was relatively smaller compared to India. Both home ranges were established at the same location across a wet, marsh, open natural landscape interspersed with many water bodies and river tributaries. Western Marsh Harriers prefer dense marsh vegetation either in fresh or brackish water [20]. In this study, it was mainly found to occur along saltpans and salt-affected areas, where it established home-ranges for both years. Other habitats used included croplands and open scrub, though to a lesser extent. A study in Keoladeo National Park in North-Western India showed that Western Marsh Harriers preferred grasslands, wetlands, and croplands, among other habitats [56].
Western Marsh Harrier showed site fidelity for the saltpans, returning to the same site in two years. These saltpans are bordered on the western side by a strip of mangrove habitat that may provide roosting sites for Western Marsh Harriers. In the absence of suitable open areas, Western Marsh Harriers are reported to use trees as pre-roost perches [56]. We observed that the predicted occurrence of Western Marsh Harrier remained uniform at small concentrations of saltpans and increased at medium (0.4 to 0.6%; range 0 to 1) and higher (0.8 to 0.9%) concentrations, indicating a strong preference for habitats with water as reported previously [20]. This preference for habitats with water may be linked to the changes in the abundance of prey with varied local environmental conditions.

4.2. Movement and Migration Patterns

As expected, all raptors covered more monthly and daily distances while migrating. For migratory birds, it is essential to properly identify migration routes and stopover locations for their management and conservation [57]. Migratory birds usually utilize a collection of migration routes between their breeding and non-breeding ranges known as flyways. A flyway generally encompasses hundreds of thousands of kilometres extending across international borders and covering the entire geographic range of species between their breeding and non-breeding areas [58]. The Central Asian Flyway is one of the nine global water bird flyways that is also used by long-distance migratory raptors [8]. This flyway comprises several corridors or routes used by raptors to circumvent one of the tallest mountain ranges in the world [8].
In our study, we observed that raptors trapped while wintering in the Gujarat state of India used the Western Circum-Himalayan Corridor of the Central Asian Flyway to migrate between breeding and non-breeding ranges. Previous telemetry studies also indicate that along with raptors, this corridor is also used by Common Cranes (Grus grus) and Demoiselle Cranes (Grus virgo) [12]. Raptors of several species have been found to use one of the four corridors of the Central Asian Flyway, as described by Kumar et al. [8] and Literák et al. [59]. The use of the Western portion of the Central Asian Flyway by raptors [10], vultures [11], and cranes [12] signify the passage of thousands of migratory raptors and waterbirds through this corridor that winter in the Gujarat state of Western India.
High-altitude flights over the Himalayas are a challenging endeavour that requires several physiological traits and high energy demands. Flapping birds such as Bar-headed Geese (Anser indicus) and Ruddy Shelduck (Tadornaferruginea) are known to reach high altitudes during their annual migration across the Himalayas and Tibetan Plateau [60,61]. Raptors, conversely, are soaring birds and use soaring and gliding flight patterns during migration [62]. This type of flight pattern is energetically more efficient and typical of large raptors [63]. The Western Circum-Himalayan Corridor enables raptors to avoid crossing the high-altitude Himalayas that demand high energy costs. During migration, the Greater Spotted Eagle used the Khyber Pass in the Khyber Pakhtunkhwa province of Pakistan, taking a detour to avoid crossing the Hindu Kush Mountain range, as reported in an earlier study [10]. It passed over the Zeravshan Mountain range in Tajikistan and southern Uzbekistan before reaching Kazakhstan. Tawny Eagle had previously migrated to Kazakhstan, and in the current study, the transmitter stopped sending signals from Afghanistan while it was on its migration. Thus, we could not be sure of its further migration route.
The migration patterns in Pallid Harrier are well-studied [64,65]. Being a broad-front migrant, it usually prefers to pass through narrow mountain passes or short-sea crossings [51]. During its migration, it crossed all major deserts in Afghanistan, Turkmenistan, and Uzbekistan. This route was identical to the route used in 2022, indicating fidelity to the migration route. In this study, the same route was used for all seasons, differing only by ~200 km at some places. In our previous study, we found that the male Pallid Harrier took almost the same number of days to reach its breeding ground, while it took longer to reach India during its return migration [10]. The migration route of the male Pallid Harrier was also the same as that used by the female Pallid Harrier in this study.
The male Western Marsh Harrier used the identical migration route for both the seasons. It crossed the Registan desert in Afghanistan, the Karakum desert in Turkmenistan, and the Kyzylkum desert in Uzbekistan before reaching the wet marshlands in Kazakhstan. We identified some of the important stopover sites used regularly by raptors, such as the Kyzylorda region in Kazakhstan and the Bukhara region in Uzbekistan (See Supplementary Material S3 for further details).
The results clearly indicate that all tagged birds followed almost the same migration route that was used previously [10]. Being soaring birds, raptors used a more efficient and energetically less demanding migration route to circumvent geographic barriers, such as the Himalayan Mountain range in Northern India and the Hindu Kush Mountain range in Afghanistan. However, harriers differ in flight pattern from eagles, as the former are only facultative soaring birds, and eagles are obligatory soaring birds, which is evident in their migration strategies [66].

4.3. Study Limitations and Future Prospects

The small sample size was one of the main limitations of our study, and, as such, the results of this study can be treated as preliminary. The high costs of the transmitters have an unintended effect on the sample size. Thus, there is a trade-off between the cost and the number of individuals that could be deployed with transmitters. All species studied here are migratory birds, and, thus, there is a small window of capturing them and fitting them with transmitters. The arrival dates of the raptors within the study area and the availability of the transmitters during that time put additional constraints on considering a large sample size.
Increasing the sample size and continued use of field observations coupled with satellite telemetry may improve our ability to understand the conservation needs of migratory raptors. This may depend on the cooperation of the range countries, sharing information and conducting regular workshops. The cost per unit transmitter is anticipated to decrease in the future, which may enable researchers to deploy more transmitters than at present. The future research may also divert its efforts into providing helpful information to managers rather than being exclusively academically inclined.

4.4. Conservation Implications

The major wintering sites for migrating raptors in India are changing rapidly, especially the size of preferred habitats such as grasslands and open natural ecosystems [67,68]. There has been unprecedented landscape change in the Indian subcontinent affecting grasslands and open savannahs, leading to a sharp decline in the number of raptors [69]. These declines are regarded as early signs of population decline at the continental scale [69]. Our study also indicated that grassland constituted a small proportion of raptor home ranges in the Kutch district. A total of 20 million hectares of grassland decreased in India from 1880 to 2010 [67]. During the same period, the cropland increased by 48 million hectares, and built-up increased five-fold from 0.46 million hectares to 2.04 million hectares [67]. Due to its ambiguous recognition as wastelands, grasslands or open natural ecosystems are often targeted for developmental projects [70], resulting in their rapid loss due to alteration or fragmentation [68,69]. The loss of preferred habitat may limit the availability of grasslands to migrant raptors in India, forcing them to move to other habitats [69]. Our study provides a subtle indication of such a shift in the habitat preferences of migrant raptors due to the loss of suitable habitat within the study area.
Studies indicate that near-natural protected grasslands are superior and important for grassland specialist species compared to other land use types [71]. Specialization in terms of diet or habitat preferences is reported to be a common feature among all negatively affected species due to the loss of their preferred habitats [71]. Though low-intensity croplands have been found to support substantial avifauna during the dry seasons in arid landscapes, they are not conducive to specialist species during all seasons [71].

5. Conclusions

In conclusion, our results concur with similar studies that raptors in wintering grounds use a variety of habitats that provide ample feeding opportunities. As reported in previous telemetry studies, home ranges, and daily movement patterns were influenced greatly by seasonal patterns. The Central Asian Flyway, particularly the Western Circum-Himalayan Corridor, was found to be used by raptors, cranes, and vultures in our previous study, which suggests the necessity of a better appreciation of this corridor. The strategic management of grasslands and open natural habitats at the landscape level interspersed with small protected areas should be emphasized for the conservation of migrant raptors across a larger spatial scale.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/birds5030033/s1, Supplementary Material S1: The tagging details of Eagles and Harriers in Gujarat, India; Supplementary Material S2: Photographic details of capture, reconnaissance, and satellite telemetry of Raptors in Gujarat, India; Supplementary Material S3: Details of stopover locations of Raptors during migration; Supplementary Material S4: Home range polygons of Greater Spotted Eagle, Indian Spotted Eagle, Tawny Eagle, Western Marsh Harrier male, and Pallid Harrier female. Home ranges were calculated in their breeding and non-breeding ranges; Supplementary Material S5: Partial dependence plots of Greater Spotted Eagle, Indian Spotted Eagle, Tawny Eagle, Western Marsh Harrier male, and Pallid Harrier female; Supplementary Material S6: Model validation matrices for the random forest habitat model of raptors.

Author Contributions

Conceptualization, M.R. and A.S.; data curation, M.R., A.S., D.G., T.A.R., V.M. and L.J.; formal analysis, M.R., A.S., D.G., T.A.R., V.M., L.J. and Y.Z.; funding acquisition, M.R., A.S. and N.S.; investigation, M.R., D.G., T.A.R., V.M., A.P., L.J., Y.Z. and D.J.; methodology, M.R., D.G., A.S., T.A.R. and V.M.; project administration, M.R. and A.S.; resources, M.R., D.G., D.J., A.S. and N.S.; software, T.A.R., D.G., V.M., Y.Z. and L.J.; supervision, M.R., A.S. and N.S.; validation, M.R., D.G., A.S., T.A.R., L.J. and V.M.; visualization, M.R. and D.G.; writing—original draft, M.R., D.G., T.A.R. and V.M.; writing—review and editing, M.R., D.G., T.A.R., V.M., A.P., L.J., Y.Z. and D.J. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding. It was undertaken by the Wildlife Division, Sasan-Gir, Gujarat Forest Department, and is one of the division’s works. Therefore, the work was conducted according to the funds received under different heads for such work.

Institutional Review Board Statement

All scientific research activities involved in this study were carried out after obtaining due permission from the competent authority [Chief Wildlife Warden, Gujarat state, Gandhinagar, India, (letter no.: WLP/T.27/B/7218/2020-21, dated 11 February 2021)]. All experimental methods and works were carried out in accordance with relevant guidelines and regulations suggested by the Principal Chief Conservator of Forests (Wildlife) and Chief Wildlife Warden, Gujarat Forest Department, Government of Gujarat. The technical experts, experienced bird trappers and handlers, and qualified and experienced veterinarians carried out the tagging work.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original contributions presented in the study are included in the article/Supplementary Materials; further inquiries can be directed to the corresponding author.

Acknowledgments

The authors would like to acknowledge the support extended by PCCF & HoFF, Gujarat State. We are grateful to DCF Kutch (West) Division; RFO Naliya (South) Range and their field staff for their on-field support. We also acknowledge the valuable input and support received from Kedar Gore, Director of The Corbett Foundation. We also acknowledge the technical and field support extended by the staff of The Corbett Foundation. We are also thankful to Nirav Bhatt and Prasad Ganpule for their technical input. We thank the Government of Gujarat and the Gujarat Forest Department for supporting this critical study. We also acknowledge the support of the staff at Gir Hi-Tech Monitoring Unit and Wildlife Division, Sasan-Gir, Gujarat.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. A crude description of the Central Asian Flyway (CAF) and the associated fly corridors. The red lines along the Westernmost and Easternmost represent the two major and traditional flyways, as described by Newton [6] and Bildstein [9]. The blue lines represent the Western Circum-Himalayan Corridor used by cranes, vultures, eagles, and harriers [10,11,12]. The terminology used by Kumar et al. [8] classified these fly corridors as Western Circum-Himalayan Corridor (blue lines), West Himalayan, and East Circum-Himalayan Corridor (White lines).
Figure 1. A crude description of the Central Asian Flyway (CAF) and the associated fly corridors. The red lines along the Westernmost and Easternmost represent the two major and traditional flyways, as described by Newton [6] and Bildstein [9]. The blue lines represent the Western Circum-Himalayan Corridor used by cranes, vultures, eagles, and harriers [10,11,12]. The terminology used by Kumar et al. [8] classified these fly corridors as Western Circum-Himalayan Corridor (blue lines), West Himalayan, and East Circum-Himalayan Corridor (White lines).
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Figure 2. Location of the study area. Panel (a) shows the location of Gujarat state in India, Panel (b) shows the location of Asiatic Lion Landscape (ALL) and Kutch district within Gujarat state, and Panel (c) shows the tagging locations of all raptor species.
Figure 2. Location of the study area. Panel (a) shows the location of Gujarat state in India, Panel (b) shows the location of Asiatic Lion Landscape (ALL) and Kutch district within Gujarat state, and Panel (c) shows the tagging locations of all raptor species.
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Figure 3. Migration pathways along with the stopover locations of all tagged raptor species. Each colour represents a different species.
Figure 3. Migration pathways along with the stopover locations of all tagged raptor species. Each colour represents a different species.
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Figure 4. Migration route of female Pallid Harrier between its breeding range (Russia and Kazakhstan) to India. The solid blue line indicates the migration route from India to Russia, the dashed blue line indicates the migration route from India to Kazakhstan, and the blue line with square boxes indicates the second migration route from Russia to India. The arrowheads represent the migration dates.
Figure 4. Migration route of female Pallid Harrier between its breeding range (Russia and Kazakhstan) to India. The solid blue line indicates the migration route from India to Russia, the dashed blue line indicates the migration route from India to Kazakhstan, and the blue line with square boxes indicates the second migration route from Russia to India. The arrowheads represent the migration dates.
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Figure 5. Migration route of male Western Marsh Harrier between its breeding range (Kazakhstan) to India. The solid purple line indicates the migration route from India to Kazakhstan, the dashed purple line indicates the migration route from India to Kazakhstan, and the purple line with square boxes indicates the second migration route from Kazakhstan to India. The arrowheads represent the migration dates.
Figure 5. Migration route of male Western Marsh Harrier between its breeding range (Kazakhstan) to India. The solid purple line indicates the migration route from India to Kazakhstan, the dashed purple line indicates the migration route from India to Kazakhstan, and the purple line with square boxes indicates the second migration route from Kazakhstan to India. The arrowheads represent the migration dates.
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Figure 6. Migration route of Indian Spotted Eagle between India and Pakistan. The solid pink line indicates the migration route from India to Pakistan, the dashed line indicates the second migration route from India to Pakistan, and the pink line with square boxes indicates the migration route from Pakistan to India. The arrowheads represent the migration dates.
Figure 6. Migration route of Indian Spotted Eagle between India and Pakistan. The solid pink line indicates the migration route from India to Pakistan, the dashed line indicates the second migration route from India to Pakistan, and the pink line with square boxes indicates the migration route from Pakistan to India. The arrowheads represent the migration dates.
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Figure 7. Migration route of Greater Spotted Eagle between India and Russia. The solid red line indicates the migration route from India to Russia.
Figure 7. Migration route of Greater Spotted Eagle between India and Russia. The solid red line indicates the migration route from India to Russia.
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Figure 8. Migration route of Tawny Eagle from India towards its breeding range. The solid orange line indicates the migration route from India to Afghanistan (contact was lost with the transmitter in Afghanistan).
Figure 8. Migration route of Tawny Eagle from India towards its breeding range. The solid orange line indicates the migration route from India to Afghanistan (contact was lost with the transmitter in Afghanistan).
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Figure 9. Variable importance plot for selected habitat variables used in the habitat model of (a) Indian Spotted Eagle, (b) Greater Spotted Eagle, (c) Tawny Eagle, (d) female Pallid Harrier, and (e) male Western Marsh Harrier based on the model improvement ratio. The variables are listed according to their relative importance. The X-axis represents the relative additional model improvement ratio (MIR) with the addition of each successive variable.
Figure 9. Variable importance plot for selected habitat variables used in the habitat model of (a) Indian Spotted Eagle, (b) Greater Spotted Eagle, (c) Tawny Eagle, (d) female Pallid Harrier, and (e) male Western Marsh Harrier based on the model improvement ratio. The variables are listed according to their relative importance. The X-axis represents the relative additional model improvement ratio (MIR) with the addition of each successive variable.
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Table 1. Estimates of monthly and daily distance covered by Indian Spotted Eagle, Greater Spotted Eagle, male Western Marsh Harrier, female Pallid Harrier, and Tawny Eagle during the non-migration season. Distances are expressed in km. Averages are expressed as (mean ± SD).
Table 1. Estimates of monthly and daily distance covered by Indian Spotted Eagle, Greater Spotted Eagle, male Western Marsh Harrier, female Pallid Harrier, and Tawny Eagle during the non-migration season. Distances are expressed in km. Averages are expressed as (mean ± SD).
SpeciesYearDaysAverage Monthly Distance Average Daily Distance
Indian Spotted Eagle2022–20235841218.06 ± 648.1741.22 ± 20.92
Greater Spotted Eagle2021–20222351678.11 ± 689.6356.14 ± 20.45
Male Western Marsh Harrier 2022–20235421806.57 ± 694.6859.69 ± 21.73
Female Pallid Harrier 2022–20235094425.40 ± 7266.61145.46 ± 235.59
Tawny Eagle20221432332.42 ± 1453.5088.61 ± 68.62
Table 2. Estimates of monthly and daily distance covered by Indian Spotted Eagle, Greater Spotted Eagle, male Western Marsh Harrier, female Pallid Harrier, and Tawny Eagle during migration season. Distances are expressed in km. Averages are expressed as (mean ± SD).
Table 2. Estimates of monthly and daily distance covered by Indian Spotted Eagle, Greater Spotted Eagle, male Western Marsh Harrier, female Pallid Harrier, and Tawny Eagle during migration season. Distances are expressed in km. Averages are expressed as (mean ± SD).
SpeciesYearMonthTotal Monthly DistanceTotal Daily Distance
Indian Spotted Eagle2022March1237.34247.47
2022November–December575.46115.09
2023February590.38196.79
Average--801.06 ± 377.90186.45 ± 66.79
Greater Spotted Eagle2022April3765.26268.95
Male Western Marsh Harrier2022April26,466.02035.85
2022September30,126.091205.04
2023April22,337.632020.69
Average --26,309.91 ± 3896.571757.19 ± 478.18
Female Pallid Harrier 2022March–April32,940.361098.01
2022September36,952.051231.74
2023March26,360.52850.34
Average--32,084.31 ± 5347. 40 1060.02 ± 193.51
Tawny Eagle2022April11,870.331978.39
Table 3. Average home-range (95% KDE) and core area (50%) estimation of male Western Marsh Harrier, female Pallid Harrier, Tawny Eagle, Indian Spotted Eagle, and Greater Spotted Eagle. Averages are expressed as (Mean ± SD). Home ranges and core areas are expressed in km2.
Table 3. Average home-range (95% KDE) and core area (50%) estimation of male Western Marsh Harrier, female Pallid Harrier, Tawny Eagle, Indian Spotted Eagle, and Greater Spotted Eagle. Averages are expressed as (Mean ± SD). Home ranges and core areas are expressed in km2.
Species PlaceTimeline95% KDE50% KDE
Male Western Marsh Harrier IndiaOctober 2021–April 202240.376.58
Kazakhstan April 2022–September 2022123.866.99
IndiaOctober 2022–March 2023 50.939.62
Kazakhstan April 2023–July 202342.590.88
Average--64.43 ± 39.886.01 ± 3.68
Female Pallid HarrierIndiaOctober 2021–March 202236.046.90
RussiaApril 2022–September 20225.741.61
IndiaOctober 2022–March 202335.707.07
Kazakhstan April 2023–July 202315.541.94
Average--23.25 ± 15.104.38 ± 3.01
Tawny EagleIndiaDecember 2021–April 20221628.35268.94
Indian Spotted EagleIndiaFebruary 2022–March 202236.875.11
PakistanMarch 2022–November 20221986.96140.80
IndiaDecember 2022–February 202358.705.17
PakistanMarch 2023–July 2023302.1513.73
Average --596.17 ± 934.9541.20 ±66.52
Greater Spotted EagleIndiaDecember 2021–April 2022438.8598.88
Kazakhstan May 2022–August 20222147.03164.18
Average--1292.94 ± 1207.86131.53 ± 46.17
Overall (Average)--463.21 ± 770.0849.22 ± 81.53
Average (Harriers)--43.84 ± 35.555.19 ± 3.23
Average (Eagles)--942.70 ± 937.8399.54 ± 99.80
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Ram, M.; Gadhavi, D.; Sahu, A.; Srivastava, N.; Rather, T.A.; Modi, V.; Patel, A.; Jhala, L.; Zala, Y.; Jhala, D. Aspects of Movement Ecology and Habitat Use of Migratory Raptors Using Satellite Telemetry from India to Central Asia. Birds 2024, 5, 487-508. https://doi.org/10.3390/birds5030033

AMA Style

Ram M, Gadhavi D, Sahu A, Srivastava N, Rather TA, Modi V, Patel A, Jhala L, Zala Y, Jhala D. Aspects of Movement Ecology and Habitat Use of Migratory Raptors Using Satellite Telemetry from India to Central Asia. Birds. 2024; 5(3):487-508. https://doi.org/10.3390/birds5030033

Chicago/Turabian Style

Ram, Mohan, Devesh Gadhavi, Aradhana Sahu, Nityanand Srivastava, Tahir Ali Rather, Vidhi Modi, Akshita Patel, Lahar Jhala, Yashpal Zala, and Dushyantsinh Jhala. 2024. "Aspects of Movement Ecology and Habitat Use of Migratory Raptors Using Satellite Telemetry from India to Central Asia" Birds 5, no. 3: 487-508. https://doi.org/10.3390/birds5030033

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