Maternal yolk androgens in avian eggs have been shown to affect numerous offspring traits. These changes in offspring phenotype represent examples of maternal effects and are thought to adjust offspring development to the posthatching environment. When studying the functional consequences of yolk hormones it is, therefore, crucial to manipulate the yolk androgen concentrations as well as the environmental conditions under which the study is performed. However, so far context-dependent effects of maternal yolk hormones have not sufficiently been taken into account, which might contribute to the current level of inconsistency in yolk androgen-mediated effects. We experimentally elevated the yolk testosterone concentrations and manipulated the sibling size hierarchy. We focused on the effects of yolk testosterone on growth and monitored begging behavior and parental feeding preferences in search of the underlying mechanisms of changes in growth. Experimental changes in the yolk testosterone concentrations significantly affected offspring phenotype. However, elevated yolk testosterone concentrations only improved the growth of chicks that were at a competitive disadvantage, whereas it benefited all chicks when placed in staged competition for food as juvenile. This emphasizes the compensatory role of yolk androgens in the context of hatching asynchrony and its context dependency. Enhanced growth did not coincide with intensified begging. Neither males nor females preferentially fed chicks hatching from eggs with elevated yolk testosterone concentrations. Enhanced growth rather resulted from yolk testosterone induced changes in physiology, of which the detailed mechanisms are yet unknown.

In this study, the functional morphology of the mandibular glands of pharaoh ant queens is investigated through histological and behavioural observations. The mandibular glands of queens of different age stages and mating status were examined at the light microscopical as well as the ultrastructural level. The results clearly show a high activity of the gland at the time of hatching, followed by a rapid degeneration independent of the queens' mating status. We therefore hypothesize the glandular secretion serves to stimulate workers to remove the queens' pupal skin. Experiments to compare hatching ability of isolated pupae and pupae assisted by workers confirmed the necessity of worker assistance, which is even more crucial to allow proper wing formation in queens and males. Together with the histological data, this suggests that the mandibular gland may indeed play a role in the social facilitation of hatching, although bioassays are required to give decisive answers about the mandibular gland's function.

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