Loading...
2 results
Search Results
Now showing 1 - 2 of 2
- Individual variation in migratory movements and winter behaviour of Iberian Lesser Kestrels Falco naumanni revealed by geolocatorsPublication . Catry, Inês; Dias, Maria P.; Catry, Teresa; Afanasyev, Vsevolod; Fox, James; Franco, Aldina M. A.; Shutherland, William J.The population decline of the Lesser Kestrel Falco naumanni has been the subject of studies across its Western Palaearctic breeding range, but little is known about its use of pre-migratory areas or African wintering quarters. We used geolocators to describe the temporal and spatial patterns of Portuguese Lesser Kestrel migration and wintering behaviour. Data on the complete migration were obtained from four individuals and another three provided further information. Prior to southward migration, Lesser Kestrels showed two different behaviours: northward-orientated movements to Spain and movements in the proximity of the breeding area. Autumn migration took place mostly in late September; spring departures occurred mainly in the first half of February. Wintering grounds included Senegal, Mauritania and Mali, with individuals overlapping considerably in Senegal. Movements registered within the wintering grounds suggest itinerant behaviour in relation to local flushes of prey. During spring migration, birds crossed the Sahara Desert through Mauritania, Western Sahara and Morocco before passing over the Mediterranean to reach Portugal. Autumn migration lasted 4.8 ± 1.1 days, and spring migration lasted 4.1 ± 0.3 days. The mean daily flight range varied between approximately 300 and 850 km for an entire journey of around 2500 km. Effective protection of roosting sites in both pre-migratory and wintering areas and maintaining grasshopper populations in Sahelian wintering quarters appear crucial in preserving this threatened migratory raptor across its African–Eurasian flyway. There was no evidence of any deleterious effects of fitting birds with loggers.
- Movements, winter distribution and activity patterns of Falkland and brown skuas: Insights from loggers and isotopesPublication . Phillips, Richard A.; Catry, Paulo; Silk, Janet R. D.; Bearhop, Stuart; McGill, Rona A R; Afanasyev, Vsevolod; Strange, Ian J.In the first published study of the wintering ranges and activity patterns of skuas from any colony, we combined tracking (geolocator) and stable isotope analysis in a comparison of migration behaviour of brown skuas Catharacta lonnbergi and Falkland skuas C. antarctica from South Georgia and the Falkland Islands, respectively. Brown skuas, particularly failed breeders, departed and returned to the colony much earlier than Falkland skuas, and 2 of 3 brown skuas performed a pre-laying exodus. During winter, brown skuas were distributed widely over deep, oceanic water within the Argentine Basin (37 to 52° S) between the Antarctic Polar Front and the northern sub-tropical Front. Falkland skuas, by comparison, wintered mainly in subantarctic waters around the central Patagonian shelf-break (40 to 52° S). Much greater overlap existed among core areas within than between species, and sex did not influence distribution. The partial inter-specific spatial segregation was also reflected in a divergence in activity patterns, with brown skuas in flight for a greater proportion, and more time on average, during both daylight and darkness. Both species of skua spent far more time on the water than do foraging albatrosses, and there was limited overlap between their nonbreeding distributions and those of large procellariids from the same archipelagos. Stable isotope signatures of brown skua feathers indicated that distributions of tracked birds were typical of most or all of the breeding population, and were consistent from year to year. None was characteristic of species that winter on adjacent continental shelves or off south-west Europe. Isotope values also suggested a mixed diet for brown skuas of zooplankton, low trophic-level squid and fish, with little or no reliance on seabird predation or fisheries.