Helping behavior in the brown-and-yellow marshbird (Pseudoleistes virescens): analyzing the advantages for females

MERMOZ, M. E.; FERNANDEZ, G. J.; MAHLER, B.

Cornell University, Ithaca, EEUU

Congreso; 12th International Behavioral Ecology Congress; 2008

ISBE

In near 3 % of birds, the reproductive system includes helpers-at-the nest. This surplus of labor could imply that nests with increasing number of helpers would obtain more food. Alternatively, parents with helpers could reduce their own effort and total food load would be similar. During 2001-2007 breeding seasons, we filmed nests in chick rearing stage and analyzed food delivery by parents and helpers. All helpers were males and most of them helped their parents in successive breeding seasons. Helpers that were not sons of the breeding pair were born close to the nest they helped. When their father died, the older helper inherited the parental territory and some of the siblings helped him in successive breeding attempts. Total food delivery rate increased with nest age, number of chicks, and number of attending adults. However, food delivery rate of working females was not affected by nest age, or number of adults but by other individuals’ delivery rate and the number of chicks. Finally, total food received per chick was positively affected by nest age and the number of adults, while negatively affected by the number of chicks. Therefore, females’ advantages of this reproductive system were twofold, as they reduced their own effort when the other adults work hard and their chicks still received more food with increasing number of attending adults. However, those chicks also paid the costs caused by a greater demand in the nest. The advantages this reproductive system has for males are still pending on paternity analysis.