Sexual, Seasonal and Group-Size Differences in the Allocation of Time Between Vigilance and Feeding in the Greater Rhea, Rhea-Americana

JUAN C. REBOREDA; FERNANDEZ, GJ

Ethology

Año: 1997 vol. 103 p. 198 - 207

We studied the effect of sex and group size on the proportion of time a Greater Rhea, Rhea americana, allocates to vigilance and feeding during the non-breeding season. We observed 88 focal rheas ranging from solitary individuals to groups of up to 26 birds. Individual vigilance was higher in rheas foraging alone than in groups. For all group sizes the males allocated a higher proportion of time to vigilance than the females. Solitary birds had longer vigilance bouts and shorter feeding bouts than birds foraging in groups. Males had shorter feeding bouts than females but there was no sex difference in the length of the vigilance bouts.