Patterns of stress response to foreign eggs by a rejecter host of an obligate avian brood parasite.

One of the most effective defenses of avian hosts against obligate brood parasites is the ejection of parasitic eggs from the nests. Despite the clear fitness benefits of this behavior, individuals within so-called "egg-rejecter" host species still show substantial variation in their propensity to eliminate foreign eggs from the nest. We argue that this variation can be further understood by studying the physiological mechanisms of host responses to brood parasitic egg stimuli: independent lines of research increasingly support the hypothesis that stress-related physiological response to parasitic eggs may trigger egg rejection.

Non-invasive elevation of circulating corticosterone increases the rejection of foreign eggs in female American robins (Turdus migratorius).

Avian obligate brood parasites rely on other species to raise their offspring. In turn, many brood parasite hosts have evolved defensive behaviors to reduce the costs of brood parasitism, yet the proximate bases underlying these defenses remain poorly understood. Recent studies regarding the potential endocrine mechanisms of foreign-egg rejection have implicated corticosterone as a physiological mediator of anti-parasitic defenses.

Ground nesting by arboreal American robins ().

Animals with dependent and vulnerable young need to decide where to raise their offspring to minimize ill effects of weather, competition, parasitism, and predation. These decisions have critical fitness consequences through impacting the survival of both adults and progeny. Birds routinely place their nest in specific sites, allowing species to be broadly classified based on nest location (e.

Early acoustic experience alters genome-wide methylation in the auditory forebrain of songbird embryos.

Early exposure to salient cues can critically shape the development of social behaviors. For example, both oscine birds and humans can hear and learn to recognize familiar sounds in ovo and in utero and recognize them following hatching and birth, respectively. Here we demonstrate that different chronic acoustic playbacks alter genome-wide methylation of the auditory forebrain in late-stage zebra finch (Taeniopygia guttata) embryos.

Inter-Individual Variation in Anti-Parasitic Egg Rejection Behavior: A Test of the Maternal Investment Hypothesis.

Hosts of avian brood parasites may reduce or forego the costs of caring for foreign young by rejecting parasitic eggs from the nest. Yet, many host species accept parasitic eggs and, even among rejecter species, some individuals go on to incubate and hatch them. The factors explaining the variation in egg rejection between species have received much theoretical and empirical attention, but the causes of intraspecific variation in different individuals' propensity for accepting parasitic eggs are less well understood.