Movements by juvenile and immature Steller's Sea Eagles Haliaeetus pelagicus tracked by satellite

Abstract

Twenty‐four juvenile Steller's Sea Eagles Haliaeetus pelagicus were tracked via satellite from natal areas in Magadan, Kabarovsk, Amur, Sakhalin and Kamchatka. Nestling dispersal occurred between 9 September and 6 December (n = 24), mostly 14 September–21 October, and did not differ among regions or years. Most eagles made stopovers of 4–28 days during migration. Migration occurred 9 September–18 January, mostly along previously described routes, taking 4–116 days to complete (n = 18). Eagles averaged 47.8 km/day excluding stopovers; 22.9 km/day including stopovers. The mean degrees of latitude spanned during migration was: Kamchatka, 2.1; Magadan, 11.6; Amur, 7.3; and Sakhalin, 1.1. Eagle winter range sizes varied. Eagles concentrated in 1–3 subareas within overall winter ranges. The mean size of the first wintering subareas was 274 km2, the second 529 km2, and the third 1181 km2. Second wintering areas were south of first wintering areas. Spring migration started between 2 February and 31 March. Two eagles from Magadan were tracked onto summering grounds, well south of their natal areas. Both had early and late summering areas. One bird was followed for 25 months. It initiated its second autumn migration in the first half of October and arrived on its wintering grounds on 26 December. The second autumn migration covered 1839 km (20.9–22.4 km/day). Unlike its first winter when it used two subareas, this bird used only one subarea in 1998–99, but this was located near wintering areas used in 1997–98. It left its wintering ground between 13 April and 13 May, and arrived on its summering grounds between 7 June and 8 July. Unlike most satellite radiotracking studies, data are presented from a relatively large number of birds from across their breeding range, including new information on eagle movements on the wintering grounds and during the second year.

A non-invasive genetic evaluation of population size, natal philopatry, and roosting behavior of non-breeding eastern imperial eagles (Aquila heliaca) in central Asia

“…Because eagles exhibit delayed sexual maturity, research on eagle ecology is further complicated by the presence of pre-reproductive non-breeders. Limited data suggest that pre-adults often exhibit wide-ranging itinerant behavior prior to their recruitment into a breeding population (Watson 1997;Harmata et al 1999;Ferrer 2001;Real and Manosa 2001;McGrady et al 2003). Further evidence also suggests that, following this exploratory period, some individuals ultimately return to breed near their natal territories (Watson 1997).…”

Dispersal of Golden EaglesAquila chrysaetosduring their first year of life

“…Satellite telemetry with conventional PTTs (i.e. non-GPS) is, however, less accurate than conventional VHF radiotracking (Keating et al 1991) and thus unsuitable for studies that demand very precise knowledge of individuals' locations (McGrady et al 2003). However, in species such as the Golden Eagle, with individuals moving several kilometres in one day, this is not an important limitation for the monitoring of juvenile dispersal.…”

“…The development of lightweight satellite telemetry in the last decade has allowed the study of both migratory and dispersal movements of medium to large birds using satellite transmitters, or PTTs (Fuller et al 1995, Kenward 2001, McGrady et al 2003. Since 2002 we have been using this technology to monitor the movements of Golden Eagles in Spain.…”

Autumn migration of Montagu’s harriers Circus pygargus tracked by satellite telemetry

“…During the last decade, satellite telemetry has enabled detailed tracking of bird movements (Kenward 2001;McGrady et al 2003;Cadahía et al 2005;Soutullo et al 2006a, b, c), particularly migration (Berthold et al 1995;Fuller et al 1995;Meyburg et al 1995Meyburg et al , 1998Hake et al 2001Hake et al , 2003Kjellén et al 2001;Ganusevich et al 2004;Judas et al 2006), resulting in the identification of wintering grounds and the mapping of migration routes (see Guan and Higuchi 2000 for a review). Although satellite telemetry has been mostly used in large bird species to date, the development of smaller transmitters now allows the use of this technology with lighter species (Soutullo et al 2007).…”