DIEL ACTIVITY OF RESIDENT AND IMMIGRANT WATERBIRDS AT LAKE TURKANA, KENYA

Authors
Citation
M. Fasola et L. Canova, DIEL ACTIVITY OF RESIDENT AND IMMIGRANT WATERBIRDS AT LAKE TURKANA, KENYA, Ibis, 135(4), 1993, pp. 442-450
Citations number
43
Categorie Soggetti
Ornithology
Journal title
IbisACNP
ISSN journal
00191019
Volume
135
Issue
4
Year of publication
1993
Pages
442 - 450
Database
ISI
SICI code
0019-1019(1993)135:4<442:DAORAI>2.0.ZU;2-V
Abstract
Of the 42 dominant species of waterbirds at Lake Turkana, Kenya, 14 fo raged uniformly throughout the day and night, five foraged mostly duri ng the night, five foraged during both the night and day but with diur nal peaks, 17 were exclusively diurnal and only one was exclusively no cturnal. Species with uniform feeding activity usually captured small prey, using tactile or visual plus tactile cues; most diurnal species captured large prey, using visual cues. However, some species which fe d mostly at night, or uniformly, relied exclusively on visual cues. We found support from only one species that moonlight influenced foragin g activities. Palaearctic immigrants spent significantly more time for aging than partial migrants and residents; they were also smaller and mainly microphagous. Only gulls and terns were restricted to diurnal f eeding, presumably by their need to see and capture prey while flying. The other groups were formed by species which foraged uniformly over 24 h or partially by day or night. These patterns indicate that in mos t waterbirds feeding activities are not basically tied to any phase of the diel cycle. Since most waterbirds display some degree of nocturna l activity, time budget studies based only on diurnal observations are likely to be misleading.