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In the 19th century, Red kite (Milvus milvus) was very common and widespread in Sardinia, but in the mid-900 an important decline occurred. Since the 1970s the species has been studied more continuously, but in recent years the published data seem contradictory. In 2018-2020, authors carried out specific research to collect data on the population of the Red kite in Sardinia exploring both the historical range of the species and areas where the species was reported in the past. In 2018-2020, we estimated 10-13 breeding pairs in an area of about 3,440 km2 located in the north west of Sardinia. As regard wintering, we estimated 30-40 birds in winters 2018-2019 and 2019-2020, whereas 90-110 birds were counted in winter 2020-2021.

Background The Black Kite (Milvus migrans) is one of the most widespread raptors in the World. The Palaearctic is populated by two migrating subspecies, Milvus migrans migrans and Milvus migrans lineatus, in the western and eastern part of this realm, respectively. The intergradation zone of M. m. migrans/M. m. lineatus covers large areas in-between. Migration routes of M. m. migrans from Europe to Sub-Saharan Africa and the Middle East are well known including large waterbodies as main environmental obstacle. MethodsWe tagged with GPS/SMS/GPRS telemetry loggers 13 and 6 Black Kite pulli in lowland around Biysk and in mountains around Kosh-Agach. ResultsBlack Kites originating from Biysk migrated through the Western Circum-Himalayan Corridor. Black Kites originating from Kosh-Agach used the Trans-Himalayan Corridor crossing the Himalayas in altitudes of up to 6 256 m asl. The average total distance travelled of Black Kites from both subpopulations was 9 166 m without any significant differences between these subpopulations. Timing of autumn migration varied slightly among individuals in departure date (30 August ± 9 days) and differed more in arrival date (26 October ± 92 days). The timing of spring migration varied less in both departure date (17 April ± 12 days) and arrival date (09 May ± 14 days). Black Kites from both subpopulations wintered in low elevations of anthropogenic areas of Pakistan and India. Birds wintered on average for 190 days, and the mean area of individual home ranges was 4 704 km2. During the breeding period, birds occupied mainly natural or semi-natural habitats in southwestern Siberia, where they spent on average 106 days with an average home range size 3 554 km2. Conclusion Black Kites crossing the Himalayas fly and, moreover, stay for hours resting at night in the environment of mountains at altitudes over 5000 m. It seems that the vast breeding territory of Black Kites in the Palearctic realm is connected with the unusual behavioural flexibility of Black Kites to surmount various environmental obstacles on their migration routes.

From 2014 to 2020, 32 black kites from various European countries were tagged with telemetry devices and tracked to study their spatiotemporal behaviour. Eleven birds which crossed the Mediterranean Sea and the Black Sea directly over large water bodies out of traditional migration routes over the Strait of Gibraltar, the Dardanelles/the Bosporus area and the east coast of the Black Sea were selected for this study. Ten birds attempted to cross the Mediterranean Sea and one attempted to cross the Black Sea. All black kites crossed the sea successfully but in one case the bird failed. The maximum water crossing length was recorded at 542 km. The average speed of the birds crossing the sea included a broad range from 27.7 to 97 kph. There was a correlation between average speed and tail-wind speed during the crossing. We conclude that the most favourable conditions for black kites when crossing large water bodies such as the Mediterranean and Black seas were sunny to partly cloudy weather with temperatures over 20 °C, the speed of the tailwind of 1.1–10.8 m/s and the air pressure over the standard value of 1013 hPa.

The European population of Black Kites of the nominate subspecies Milvus migrans migrans (Boddaert, 1783) is estimated at 81,200–109,000 pairs. The birds winter in Africa but their natal dispersal remains largely unstudied. Here, we analyze the behavior of 25 GPS-tracked Black Kites tagged from 2014 until 2018 using GPS/GSM telemetry devices from 16 nests in Bulgaria, Czech Republic, Germany and Slovakia. We calculated juvenile Black Kite post-fledging areas (PFA) using Kernel density estimations 95% (KDE95) and minimum convex polygons 95% (MCP95). Our results revealed that the average occupied PFA for juvenile birds was 2.8 km2 (range 0.006–20.1 km2) as KDE95 and 0.3 km2 (range 0.07–1.35 km2) as MCP95. Birds left PFA from 29 July to 30 August (median 12 August). Two main migration routes were used by tagged birds, namely a southwestern European route crossing the Strait of Gibraltar and a southeastern European route to Turkey and the Middle East. Migration routes which directly crossed the Mediterranean Sea to Africa from Italy and Greece were rarely used. Winter quarters were located in sub-Saharan Africa throughout the belt from Senegal and Gambia to Ethiopia. Four Black Kites remained to stay in tropical Africa during their first summer, seven birds moved north but to substantially lower altitudes (in Morocco, Spain and Turkey) then those in their natal areas. During the second year, Black Kites wintered again in the tropical part of sub-Saharan Africa, summer quarters were located north from the winter quarters, three birds stayed throughout the summer in Africa, three in south to central Europe, one in Turkey and one in northwestern Russia. One 3-year-old bird (fourth calendar year) attempted to nest but it was unsuccessful and occurred 15.6 km from the natal nest. Temporary settlement areas (TSA) were commonly used by Black Kites during migratory routes, winter and summer quarters. The average home range size of TSA was 233.8 km2 (range 0.99–852 km2) as KDE95 and 140.2 km2 (range 0.1–1054 km2) as MCP95. As usual, siblings used the same migratory routes and also shared the same winter and summer quarters. Our findings suggest that the genetic background of the migration behavior of Black Kites is strong.

Some birds of the central European population of Red Kite Milvus milvus are non-migratory and winter within their natal area, whereas others migrate to southern Europe or even to northern Africa. To determine what factors affect the area use and communal roost use by Red Kites wintering in their natal area. We studied spatiotemporal activity and factors affecting area use by Red Kites wintering in their natal area in the tripoint border area of Austria, the Czech Republic, and Slovakia, using GPS/GSM telemetry devices. We characterized home ranges used by wintering Red Kites in natal areas. Birds wintered for an average of 146 days and spent 88% of the time within temporary settlement areas (TSAs). The number of TSAs used by one Red Kite during the winter varied from 1–4 (mean ± sd = 2 ± 1); the mean (± sd) size of the home range of TSAs was 190 ± 144 km2 as a 95% minimum convex polygon, 136 ± 82 km2 as a 95% kernel density estimate, and 41 ± 34 km2 as a 50% kernel density estimate (core activity area). Age, breeding status, and percentage of forest habitat were the main factors negatively related to home range size. Winter duration and the number of TSAs were positively related to the size of the home range. Young birds (before first breeding) and males explored larger areas and used more TSAs during winter. Wintering of Red Kites in their natal area may relate to the social refuge–territory prospecting hypothesis, breeding site fidelity, wintering site fidelity, and/or mate loyalty, and this understanding could lead to better conservation of Red Kites in central Europe.

Four red kites (Milvus milvus), (siblings, RK1, RK2, RK3 and RK4) from the same nest in north-eastern Austria were tagged with telemetry (GPS/GSM/UHF) loggers on 23 June 2018 during the pulli growth stage and tracked until 5 April 2019. RK1 (female), RK2 (male), RK3 (female) and RK4 (female) occupied post-fledging areas until 1 August 2018 when they then began to migrate following a south-eastern direction. RK1 wintered in central Italy and used three temporary settlement areas (TSA). RK2 and RK3 migrated to the Croatian coast of the Adriatic Sea and returned back to winter in their natal area. They used three and two TSA, respectively. RK4 reached the Italian coast of the Tyrrhenian Sea, crossing the sea in 12 h with an average flight speed of 58.6 km·h−1). The bird flew at an average altitude of 429 m above sea level before arriving in Algeria. RK4 then crossed the neighbouring border and wintered in Tunisia. It used two TSA (one in the Czech Republic and one in Tunisia). The migration behaviour and wintering locations among these floaters with the same genetic background during natal dispersal was substantially different and supposedly influenced by various environmental factors rather than by genetics.

The Black Kite (Milvus migrans) is one of the most widespread raptors in the world. The Palaearctic is populated by two migrating subspecies, Milvus migrans migrans and Milvus migrans lineatus, in the western and eastern part of this realm, respectively. There is a large intergradation zone of M. m. migrans/M. m. lineatus in-between. Although the migration routes of M. m. migrans from Europe to Sub-Saharan Africa and the Middle East are well known, detailed information about migration routes of Black Kites from intergradation zone are missing. Using satellite telemetry we are able to fill this gap in our knowledge of these birds. We tagged with GPS/SMS/GPRS telemetry loggers 13 and 6 Black Kite pulli in lowland around Biysk (Altai Krai, Russia) and in mountains around Kosh-Agach (Altai Republic, Russia), respectively. After fledging, Black Kites from both subpopulations stayed in a small, non-overlapping areas and then migrated to southern Asia through narrow corridors. Black Kites originating from Biysk migrated through the Western Circum-Himalayan Corridor. Black Kites originating from Kosh-Agach used the Trans-Himalayan Corridor crossing the Himalayas in altitudes of up to 6256 m asl. The average total distance travelled of Black Kites from both subpopulations was 9166 km without any significant differences between these subpopulations. Timing of both spring and autumn migration did not vary along different age groups. Black Kites from both subpopulations wintered in low elevations of Pakistan and India. Birds wintered on average for 190 days, and the mean area of individual home ranges in winter was 4704 km

Three black kite (Milvus migrans migrans) pulli (siblings, BK1, BK2, and BK3) from the same nest in eastern Slovakia were tagged with telemetry (GPS/GSM) loggers on 1 July 2016. BK1 (female), BK2 (male) and BK3 (female) occupied post-fledging areas until 12 August 2016 when they began to migrate southeast. BK1 wintered in Libya, returned to Turkey in the summer, then wintered in Israel. After spending the winter there, it returned to Europe, looped the Baltic Sea and stayed in western Russia throughout the summer. During the autumn, it passed Ukraine and travelled along the Black Sea and wintered in Syria then it moved again to Europe. It used 18 temporary settlement areas (TSA) during its journey until 12 June 2019 when it was roadkilled in Norway. BK2 migrated to the northern tip of the Red Sea and crossed the sea where positions of the bird spatiotemporally coincided with a position of transcontinental cargo ship. It is expected that the bird died whilst on the cargo ship and its body was passively carried on-board and discarded on the west coast of the Red Sea. BK3 reached the northern outpost of the Red Sea in Saudi Arabia. It then continued southeast along the east coast of the Red Sea to Yemen and crossed the Strait of Bab-el-Mandeb to Africa. It wintered mainly in Sudan, Southern Sudan and Uganda, then returned along the west coast of the Red Sea and the east coast of the Mediterranean Sea arriving to the Turkey/Syria border area. Only two TSA were revealed on its route. The migration behaviour among these floaters during natal dispersal was substantially different and covered surprisingly large parts of Europe and North and East Africa.