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  • Author: Ugis Bergmanis x
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Cainism, nestling management in Germany in 2004-2007 and satellite tracking of juveniles in the Lesser Spotted Eagle (Aquila pomarina)

The Lesser Spotted Eagle belongs to a species with obligatory cainism, which means that in the natural state it is rare that two young eagles fledge, although as a rule two chick's hatch. The breeding population in Germany is at the western edge of the species' range and is declining (a 23% decrease between 1993 and 2007). Local extinction can be anticipated and therefore nestling management has been implemented in the German federal state of Brandenburg since 2004 as a conservation measure by using human intervention to prevent the death of the younger sibling. This is in addition to other methods such as nest-site protection, habitat preservation, legislation etc. Furthermore, in 2007, second hatched eagle chicks (Abels) from Latvia were translocated for the first time. The managed pairs (nests physically inspected) were on average more successful than the unmanaged pairs (nests not physically inspected). It cannot be determined as to whether the inspection of the nests had a negative effect on breeding. Breeding success of the pairs present in Brandenburg, including non-breeders, increased by 57 % in 2007 due to nestling management, and that of the managed pairs alone by 67 %. In 2007 the behaviour of six young eagles was studied using satellite telemetry. This study determined that the Abels migrated as well as the first hatched eagle chicks (Cains), and that their survival chances were equally good. The Abels imported from Latvia migrated in two out of three cases along the same route as the German Lesser Spotted Eagles to the Bosporus. One Latvian Abel which fledged in Germany was tracked by satellite to Zambia where many Lesser Spotted Eagles winter. A German Abel wintered North of the Equator in the Sudan and neighbouring countries for over six months and started its return migration on 27 April 2008.

Colour ringing of the Spotted Eagles (Aquila pomarina, Aquila clanga and their hybrids) in Europe - a review

During the years 2000-2008 1377 Spotted Eagles (SE) (Aquila pomarina, Aquila clanga and their hybrids) have been colour ringed in Europe. Out of these, 1303 (94.6 %) were young birds and 74 (5.4 %) were adults. Out of the total, 1290 (93.7 %) were the Aquila pomarina Lesser Spotted Eagles (LSE) - 1229 (95.3 %) young and 61 (4.7 %) adults, 50 (3.6 %) were the Aquila clanga Greater Spotted Eagles (GSE) - 44 (88.0 %) young and 6 (12.0 %) adults and 37 (2.7 %) were the Aquila pomarina x Aquila clanga hybrids (LSE x GSE) - 30 (81.1 %) young and 7 (18.9 %) adults. With respect to the individual European countries the following SE species and numbers were ringed: Slovakia 636 (46.2 %), Poland 333 (24.2 %), Estonia 153 (11.1 %), Germany 116 (8.4 %), Lithuania 68 (4.9 %), Latvia 45 (3.3 %) and Belarus 26 (1.9 %). In the article authors presents a review on Spotted Eagle colour ringing programmes running in individual European countries.

Abstract

We analysed the population size, population dynamics and reproduction success of the lesser spotted eagle in Latvia from 1988 to 2014. While the overall population did not show a statistically significant trend during any of the periods analysed (long, medium and short term), the populations in the individual study areas changed differently: of five research plots, populations were stable in two, increased in one, and decreased in two research plots. Using the existing research plots as samples of breeding numbers in areas of different breeding density classes based on forest management units, the total breeding population in Latvia was estimated. The overall number of breeding pairs in 2012-2014 was between 3700-4000. During the period 1988-2014, 65.62% of all pairs recorded as present on their home range, made a breeding attempt and laid eggs. The reproductive success ratio was 0.49 young per occupied territory with an adult pair of birds and 0.74 young per breeding pair which laid eggs. Overall, during the 21 -year research period there was a stable long-term trend in reproductive success (young per pair present on home range). Rarely, indeed only in 1 .89% of all cases did two young fledge. The total number of young (young per 100 km2) shows stable long-, medium- and short-term trends with an average value of 5.1 young per 100 km2.