Juvenile Songbirds Compensate for Displacement to Oceanic Islands during Autumn Migration

To what degree juvenile migrant birds are able to correct for orientation errors or wind drift is still largely unknown. We studied the orientation of passerines on the Faroe Islands far off the normal migration routes of European migrants. The ability to compensate for displacement was tested in naturally occurring vagrants presumably displaced by wind and in birds experimentally displaced 1100 km from Denmark to the Faroes. The orientation was studied in orientation cages as well as in the free-flying birds after release by tracking departures using small radio transmitters. Both the naturally displaced and the experimentally displaced birds oriented in more easterly directions on the Faroes than was observed in Denmark prior to displacement. This pattern was even more pronounced in departure directions, perhaps because of wind influence. The clear directional compensation found even in experimentally displaced birds indicates that first-year birds can also possess the ability to correct for displacement in some circumstances, possibly involving either some primitive form of true navigation, or ‘sign posts’, but the cues used for this are highly speculative. We also found some indications of differences between species in the reaction to displacement. Such differences might be involved in the diversity of results reported in displacement studies so far

Contrasting use of space by two migratory Afro-Palearctic warblers on their African non-breeding grounds

In migratory birds, constraints due to breeding are relaxed during the non-breeding season and thus, social behaviours and spatial associations are potentially more directly coupled to food resources and habitats. Use of space and territorial behaviour has rarely been studied in Afro-Palearctic migrants. Variation in strategies could exist among species within the same habitat because of differences in foraging, diet and microhabitat. We compare use of space and association with conspecifics in Common Chiffchaffs Phylloscopus collybita and Subalpine Warblers Sylvia cantillans at a non-breeding site in northern Senegal using radio telemetry and playback experiments. Home ranges of Chiffchaffs were larger and overlapped more than those of Subalpine Warblers. Though Chiffchaffs were often close together, we found no signs of spatial association among individuals in either species. Chiffchaffs showed no clear pattern of territorial response to conspecific song; whereas, playback elicited a territorial response in most Subalpine Warblers. Our results suggest species-specific differences in use of space that might reflect differences in foraging ecology and microhabitat

Satellite tracking resident songbirds in tropical forests.

Advances in tracking technology have helped elucidate the movements of the planet's largest and most mobile species, but these animals do not represent faunal diversity as a whole. Tracking a more diverse array of animal species will enable testing of broad ecological and evolutionary hypotheses and aid conservation efforts. Small and sedentary species of the tropics make up a huge part of earth's animal diversity and are therefore key to this endeavor. Here, we investigated whether modern satellite tracking is a viable means for measuring the fine-scale movement patterns of such animals. We fitted five-gram solar-powered transmitters to resident songbirds in the rainforests of New Guinea, and analyzed transmission data collected over four years to evaluate movement detection and performance over time. Based upon the distribution of location fixes, and an observed home range shift by one individual, there is excellent potential to detect small movements of a few kilometers. The method also has clear limitations: total transmission periods were often short and punctuated by lapses; precision and accuracy of location fixes was limited and variable between study sites. However, impending reductions in transmitter size and price will alleviate many issues, further expanding options for tracking earth's faunal diversity

Orientation of vagrant birds on the Faroe Islands in the Atlantic Ocean

Migratory birds are frequently found far outside their normal range but the phenomenon is poorly understood. We used radio telemetry to track individual migratory flights of several species of songbirds on the Faroe Islands, far west of their normal migration route. Birds with expected easterly and south-easterly migration direction departed westwards out over the Atlantic Ocean, indicating that these birds are actively flying in the "wrong" direction and that their occurrence is not caused by wind drift. This is in contrast to the apparently normal south-westerly to easterly departure directions in birds expected to migrate south or southwest