Meeting Abstract

P3.105  Thursday, Jan. 6  Offspring Sex Ratios in Lilac-Crowned Parrots (Amazona finschi) PEASE, S*; SALINAS-MELGOZA, A; RENTON, K; WRIGHT, T; New Mexico State University; New Mexico State University; Universidad Nacional Autonoma de Mexico; New Mexico State University shannonp@nmsu.edu

Evolutionary theory predicts that birds should adaptively adjust the sex ratio of their offspring in response to external factors that have a differential effect on the reproductive value of each gender. Factors hypothesized to affect reproductive output include maternal condition, mate attractiveness, sequence of laying and hatching, timing of births in the breeding season, and habitat quality. While some studies have shown extremely biased sex allocation patterns in birds, support for these hypotheses is inconsistent and most studies show little or no evidence of offspring sex ratio adjustment. This study examines adaptive sex ratio in the lilac-crowned amazon (Amazona finschi), a Neotropical parrot in Mexico, in relation to several factors. We identified the gender of 64 nestlings from 30 different clutches spanning seven years using a multiplex of primers (P2-P8-P0) to amplify intronic regions of the chromo-helicase-DNA binding (CHD) gene that differ in size between the Z and W sex chromosomes of birds. We found no associations between sex ratio and date of birth, order of hatching, or quality of the environment as measured by annual rainfall (cm) in the previous year. These results suggest that these factors provide insufficient differential costs or benefits with offspring gender to promote sex ratio bias. Alternatively, restrictions imposed by chromosomal sex-determination may prevent female lilac-crowned parrots from adaptively altering the sex ratio of their offspring.