Satellite tracking of two Lesser Spotted Eagles, Aquila pomarina, migrating from Namibia B-U. Meyburg1, D.H. Ellis2, C. Meyburg3, J.M. Mendelsohn4 & W. Scheller5 1World Working Group on Birds of Prey, Wangenheimstr. 32, 14193 Berlin, Germany 2USGS Patuxent Wildlife Research Center, HCR 1 Box 4420, Oracle, AZ 85623, U.S.A. 331, Avenue du Maine, F-75015 Paris, France 4P.O. Box 80044, Olympia, Windhoek, Namibia 5Danschowstr. 16, 17166 Teterow, Germany (Meyburg et al. 1993, 1995a). In another on-going study begun in Meyburg, B-U., Ellis, D.H., Meyburg, C., Mendelsohn, J.M. & 1997, 11 adults have so far been fitted with solar-powered PTTs Scheller, W. 2001. Satellite tracking of two Lesser Spotted Eagles, which have only very recently become available. Owing to the Aquila pomarina, migrating from Namibia. Ostrich 72(1&2): limited, one year maximum life of the 30–50 g battery-powered 35–40. PTTs available at the time of this study, it was not possible to One immature and one subadult Lesser Spotted Eagle, Aquila investigate the migratory strategies of immature Lesser Spotted pomarina, were followed by satellite telemetry from their non- Eagles, which were believed not to return to the breeding range breeding areas in Namibia. Both birds were fitted with transmitters of the species until they reach sexual maturity (Meyburg 1991, (PTTs) in February 1994 and tracked, the immature for six months 1994, 1996), since they are observed only extremely rarely in and three weeks, the subadult for eight months and two weeks, over Europe. The only way to solve the question of where these birds distances of 10 084 and 16 773 km, respectively. During their time in Namibia both birds’ movements were in response to good local rain- spent the time prior to becoming adult was to equip them with fall. The immature eagle left Namibia at the end of February, the transmitters in Africa. Whether solar-powered PTTs last long subadult at the end of March. They flew to their respective summer enough to study this problem by fitting them to nestlings quarters in Hungary and the Ukraine, arriving there 2.5 and 1.5 remains to be seen. months later than the breeding adults. The immature eagle took over two months longer on the homeward journey than a breeding METHODS male followed by telemetry in a previous study. On returning, the On 9 February 1994, an immature Lesser Spotted Eagle was immature eagle followed the narrow flightpath through Africa used trapped with a bal-chatri in northern Namibia near Tsumkwe by other Lesser Spotted Eagles on their outward migration. It (Otjozondjupa Region) (19° 32’S, 20° 17’E) and fitted with a PTT. reached this corridor, which runs roughly between longitudes 31° The bird weighed 1650 g and its entire body was more than and 36° East from Suez to Lake Tanganyika, veering from the short- usually covered with the typical whitish-yellow spots of juvenile est route in a direction east-northeast through Angola and Zambia and immature Lesser Spotted Eagles. The rust-yellow spot on to the southern end of Lake Tanganyika. The route taken by the the nape, typical at least for juveniles, was already missing. The subadult bird on its return migration differed markedly from that of iris was already almost as yellow as in adult birds. We estimated all Lesser Spotted Eagles tracked to date, running further west through the Democratic Republic of Congo where, level with the its age to be almost two years. equator, it flew over the eastern rainforest of that country. The out- Another Lesser Spotted Eagle was similarly trapped with a ward migration, however, followed the same corridor and coincided bal-chatri on 11 February, near Tsintsabis (18° 42’S, 17° 33’E) in in time with the migration of adults. [A German translation of the Oshikoto Region and fitted with a PTT.This bird weighed 1920 g abstract is provided on p. 40.] with a crop full of frogs. It was a subadult female; it was virtually adult, as evidenced by its uniform brown plumage, including just a few isolated lighter patches. The iris was already com- INTRODUCTION pletely yellow. We estimated it to be almost three years old, but Ringing, with a recovery rate of only c. 2.5%, has so far produced possibly older. little concrete information regarding migration and wintering To achieve as long a life as possible, the transmitters were pro- behaviour of the Lesser Spotted Eagle, Aquila pomarina (Danko grammed to remain inactive for 4.33 and 5.6 days between each et al. 1996). As a rule, this method merely provides the place of 8-hour active phase. Further details regarding satellite tracking ringing and that of the bird’s death as well as the age it attained. of raptors can be found in e.g. Meyburg et al. (1993, 1995b, 1996, Knowledge of the migration dynamics, the route taken, speed of 1998). travel and resting-places can be acquired only by means of satel- For the tracing of the birds’ movements and computer calcula- lite telemetry. Owing to ever-increasing reduction in size and tion of distances covered between Argos locations we used an other improvements to satellite transmitters, technically called integrated global mapping system displaying a true mercator platform transmitter terminals (PTTs), it has, in recent years, projection. The migration routes were also traced by a variety of become possible to track medium-sized birds of prey (Meyburg CD-ROM-Atlases which included satellite photographs, in et al. 1993, 1996, 1998). Despite the considerable expense, satellite order to ascertain dependence on variables such as habitat types telemetry ranks as a cost-efficient way of studying bird migra- and altitude. For plotting the summering areas in Ukraine and tion (Hedenström 1997). Hungary, coloured maps of the Russian ordnance survey with a To investigate more fully the Lesser Spotted Eagles’ move- scale of 1:50 000 were used. ments outside the breeding season, we have fitted transmitters to birds in various breeding areas in Europe (Germany, Latvia, RESULTS Slovakia). Four nestlings and four adults were equipped with The immature eagle was tracked for six months and three battery-powered transmitters in 1992–1994. The results of the weeks over a total distance of 10 084 km (107 fixes), the subadult tracking of these eight birds have already been published for eight months and two weeks over 16 773 km (57 fixes). The 0030-6525 Ostrich (March 2001) 72(1&2): 35–40 35 subadult bird spent only five months outside Africa during the Kavango, but is considerably more arid. Rains fall even more northern hemisphere breeding season. sporadically with annual totals of 250–350 mm being character- ized by coefficients of variation of 45–50% in annual rainfall. Movements in Namibia Again, almost all the rain falls during the southern summer The immature eagle remained in Namibia for about two months. Much of the vegetation is dominated by mopane weeks, until at least 22 February. Following capture, it flew some Hardwickia (Colophospermum) mopane and shrubs. Both the 300 km north to the Okavango River and then due west some Kavango and Kunene are very sparsely populated by people. 700 km to the Kunene Region where it lingered from 13 to 22 Feb- ruary at 17° 42’S, 14° 4’E. The minimum distance in Namibia was Migration route of the immature eagle 997 km (Fig. 1). The immature eagle left Namibia in a northeasterly direction. The subadult remained in Namibia some seven weeks after It was located first in Angola (16° 11’S, 15° 14’E) on 26 February. having been trapped. It first moved about 400 km south, and From there veering east-northeast it crossed Angola and Zambia then also flew to the Kunene region, moving about 900 km in a in an almost straight line. On 11 March, south of the southern northwesterly direction to do so. From here, it moved back to the end of Lake Tanganyika (at 10° 10’S, 30° 45’E), it abruptly area where it had been caught and stayed in the vicinity from 10 changed direction about 45° to the north. Then, heading almost to 27 March. Its nomadic movements over seven weeks covered due north between longitudes 31 and 33, its migration contin- at least 1277 km (Fig. 1). ued through western Tanzania and Uganda, eastern Sudan and The two birds were caught in areas that had between 150 and Egypt, reaching the Red Sea (27° 22’N, 33° 18’E) on 27 April on a 220% more rain than average by the end of January 1994. The level with the southern tip of the Sinai Peninsula (Fig. 2). Kunene area to which both birds moved between 13 and 27 The migration then followed the known route for these eagles February had not had particularly good rains before the third (Meyburg et al. 1995a) along the Mediterranean coast, through week of February. During this time, the area received a total of Israel, Lebanon, Syria and across Turkey. The Gulf of Iskenderun 120 mm of rain, a very good fall for that part of Namibia, and was overflown on 6 May and the Bosphorus on May 12 (Fig. 3). NDVI (normalized difference vegetation index) analysis of Thereafter the migration continued, heading northwest NOAA images showed that the entire area to which both eagles through Bulgaria and Rumania until, on 26 June the eagle had moved had a massive growth of vegetation. The area of in- reached its boreal summer quarters (47° 1’N, 21° 11’E) in eastern creased vegetation growth in the northwest of Namibia covered Hungary in the neighbourhood of the village of Szeghalom, about 4500 km2.