YOLK ANDROGENS DO NOT INFLUENCE GROWTH OR BEGGING BEHAVIOR OF EUROPEAN STARLING (Sturnus vulgaris) CHICKS.

PILZ, K.; QUIROGA, M.; SMITH, H.

Scottdale

Congreso; Society for Behavioral Neuroendocrinology Annual Meeting; 2001

Society for Behavioral Neuroendocrinology & Arizona State University

Androgen hormones occur naturally in avian egg yolk. However,yolk androgen effects are little understood: yolk androgens enhancethe growth and begging behavior of canary chicks, but are detrimentalto the growth and survival of kestrel chicks. We examinedthe effects of yolk androgens on growth, development and beggingbehavior in a wild population of European starlings (Sturnus vulgaris).Freshly laid eggs were given one of five treatments: a smallsample of yolk was taken from the egg, or the egg yolk was injectedwith vehicle, testosterone, androstenedione, or testosterone andandrostenedione combined. Over 150 chicks were used in the experiment.Chicks were weighed daily and tarsus and wing lengthswere measured at 10 days of age. Chick begging behavior wasrecorded on the day of hatching and at 5 days of age. Developmentalmarkers were also monitored. We found a significant main effectof yolk androgen treatment on only two response variables: hatchweight and number of begging vocalizations given during hatchdaybegging tests. However, in neither of these cases did post hoctests reveal significant differences between an androgen-treatedgroup and the vehicle-treated group. The 3-way interaction of treatment,hatch weight, and age significantly affected chick growth(repeated measures ANOVA); however, post hoc tests again failedto reveal differences between androgen-treated and vehicle-treatedgroups. In summary, we found no convincing evidence that yolkandrogens affect chick growth, development or behavior in thispopulation of starlings. Effects of yolk androgens must be examinedin more avian species before we can begin to understand anyadaptive basis of yolk androgen allocation.