Egg Losses and Nest Desertion in Greater Rheas Rhea-Americana

FERNANDEZ, GJ; JUAN C. REBOREDA

IBIS

Año: 2000 vol. 142 p. 29 - 34

Avian nest desertion should occur when the cost of attending the nest results in areduction of parental fitness. In Greater Rheas Rhea arnericana, the male incubates the eggsso that the decision to desert the nest is made exclusively by him. Because of constraints,the timing of desertion may affect the possibility of renesting. We estimated nest desertionrates through the breeding season and at different stages of the nesting cycle (laying andearly, mid- and late incubation). We also analysed the effect of egg losses at different stagesof the nesting cycle on the probability of deserting the nest. Nest desertion rates declinethroughout the breeding season. The probability of deserting the nest was higherduring the laying stage and decreased through incubation. For all stages, egg losses werehigher in nests that were deserted than in nests that were still active at the end of thecorresponding stage. Egg losses were less likely to elicit nest desertion as incubationadvanced. Egg losses in experimental (unattended) nests were not random. We postulatethat egg losses during the first stages of the nesting cycle would be a good predictor offuture egg losses and risk of nest failure. As females remain associated with the maleduring egg-laying and because incubation in rheas is an energetically costly activity thatmay affect renesting attempts, early nest desertion could increase a male's ability to remateand renest.