THE EFFECT OF GROUP-SIZE ON VIGILANCE AND FEEDING RATE IN SPICE FINCHES (LONCHURA-PUNCTULATA)

Citation
G. Beauchamp et B. Livoreil, THE EFFECT OF GROUP-SIZE ON VIGILANCE AND FEEDING RATE IN SPICE FINCHES (LONCHURA-PUNCTULATA), Canadian journal of zoology, 75(9), 1997, pp. 1526-1531
Citations number
48
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Zoology
Journal title
ISSN journal
0008-4301
Volume
75
Issue
9
Year of publication
1997
Pages
1526 - 1531
Database
ISI
SICI code
0008-4301(1997)75:9<1526:TEOGOV>2.0.ZU;2-Y
Abstract
We investigated group-size effects on individual vigilance levels and feeding rates in captive groups of spice finches (Lonchura punctulata) . The ''many-eyes'' hypothesis predicts a reduction in vigilance level s in larger groups that can cause higher feeding rates if the time thu s saved is used for foraging. We adopted a within-subject procedure wh ereby in each of six replicates we observed one adult male searching f or food in groups varying in size from one to five. As predicted, vigi lance levels decreased with group size up to four birds but increased in groups of five. Birds also collected seeds more quickly in larger g roups, reflecting (i) a decrease in vigilance levels in larger groups, (ii) a decrease in handling time, and (iii) an increase in search spe ed. Nearest neighbour distances were smaller in larger groups, a poten tial confounding factor in the analysis of vigilance time. Although th e results are partly consistent with the many-eyes hypothesis, we sugg est that the arrow of causation from vigilance to feeding time could b e reversed: the increase in feeding rates in larger groups, with a con comitant decrease in vigilance levels, would be caused by increased co mpetition.