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1

Space use of adult Spanish Imperial Eagles Aquila adalberti

100%
Fernadez M., Oria J., Sanchez R., Gonzalez L. M., Margalida A.
Acta Ornithologica
|
2009
|
tom 44
|
nr 1
The ranges and space use of eight radio-tracked Spanish Imperial Eagles are described. The annual mean range was 25 146 ha during the breeding season (BS) and 20 557 ha in the non-breeding season (NBS). The eagles were found up to 35.9 km away from their nest during BS and nearly 62 km away during NBS. The maximum total distance covered in one day was 113.6 km, with males flying longer distances than females during BS. There was less overlap between ranges during BS, and the mean home range varied from 3881 ha in BS to 2085 ha in NBS. The areas where territorial behaviour (display flights, defence and/or aggression) was observed contained the nest-tree, the most frequently used perches, and the feeding ground nearest to the nest. Breeding home ranges were negatively correlated with densities of Rabbits Oryctolagus cuniculus. Breeding eagles whose home range had low rabbit densities travelled 16.2-28.9 km from their nest to reach distant, undefended feeding grounds with much higher rabbit densities. Our results suggest that home ranges varied with prey density and a bird's reproductive status. Larger breeding ranges are probably related to an increase in energy requirements, while habitat quality is probably a regulatory mechanism of space use. In terms of home range analysis methodology, our observations of eagle behaviour favour Cluster Analysis over Kernel, particularly for defining distant feeding grounds.
2

Influence of wind and geography on orientation behavior of adult Honey Buzzards Pernis apivorus during migration over water

80%
Agostini N., Premuda G., Mellone U., Panuccio M., Logozzo D., Bassi E., Cocchi L.
Acta Ornithologica
|
2005
|
tom 40
|
nr 1
71-74
During autumn migration across the Central Mediterranean, adult Honey Buzzards cross the sea at its narrowest point, between western Sicily (southern Italy) and the Cap Bon Peninsula (Tunisia). This study investigated the influence of prevailing winds and geography on the orientation behaviour of migrants during this sea crossing by observations over two islands, one on the northern side, the other on the southern side of the Channel of Sicily. The flock was taken as the sampling unit. Honey Buzzards reached the island of Marettimo, approx. 30 km off western Sicily and 130 km NE of the Cap Bon Peninsula, regardless of the direction of the prevailing winds (NW and S). By contrast, Honey Buzzards passed via Pantelleria, about 110 km SW of western Sicily and 70 km ESE of the Cap Bon peninsula, mostly during NW winds. Birds reached Pantelleria from the NE and left the island flying WNW. They applied true navigational abilities in choosing the shorter crossing between Pantelleria and Tunisia and showing a curvilinear migration. Our results agree in part with the "optimal use of wind" hypothesis. In particular, wind, geography and navigational abilities seem to interact to shape the orientation behaviour of migrating Honey Buzzards, perhaps to minimize the risks of non-stop powered flight over the water.
3

Nest quality in relation to adult bird condition and its impact on reproduction in Great Tits Parus major

80%
Alvarez E., Barba E.
Acta Ornithologica
|
2008
|
tom 43
|
nr 1
3-9
Birds' nests are special structures built with reproductive aims. Size and structure of the nest can arise from evolutionary trade-offs between benefits such as the insulation from unfavourable conditions, maintenance of eggs or chicks, or security against predation, and costs such as energy spent in construction of the nest and the risk of predation in more visible nests. Therefore, building a good nest is beneficial in terms of reproductive output but expensive in terms of time and energy, so probably only "good" parents would be able to build "good" nests. Our objective was to study possible relationships between the quality of the parents and the quality of the nest, and between the quality of the nest and breeding performance in a Great Tit Parus major population. We found positive relationships between different components of the nest quality and components of breeding performance. However, we did not find any significant relationship between quality of the parents and that of the nest. A weak, though significant positive correlation was found between female size and breeding success rate.
4

Migration pattern of Robin [Erithacus rubecula] on the basis of Polish ringing recoveries

80%
Remisiewicz M., Nowakowski J. K., Busse P.
The Ring
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1997
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tom 19
|
nr 1-2
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