| dc.description.abstract | Maternally-derived hormones are known to influence the growth and development of offspring. The differential deposition of these maternally-derived hormones into egg yolk is one way by which females can alter and impact their chicks’ survival. Yolk constituents, especially testosterone, have been described for a wide variety of species. However, few studies have focused on multiple maternally-derived hormones regulated by independent axis in the endocrine system, these of which have mainly focused on corticosterone and testosterone. We determined within and among female variation in testosterone and triiodothyronine concentrations in egg yolks of two free-living Franklin’s gull (Leucophaeus pipixcan) populations. We found that testosterone, not triiodothyronine, concentrations increased within the clutch with the third laid egg having significantly higher concentrations than the first laid egg. We also found that both testosterone and triiodothyronine concentrations increase within the breeding season with late season clutches having significantly higher hormone concentrations than early season clutches. | en_US |
