Egg shape and color mediate acceptance thresholds in diverse avian host species with different rates of antiparasitic egg rejection.

Eggshell recognition in parental birds is vital for nest management, defense against brood parasitism, optimal embryonic development, and minimizing disease and predation risks. This process relies on acceptance thresholds balancing the risk of rejecting own eggs against the benefit of excluding foreign ones, following signal detection theory. We investigated the role of object shape in egg rejection decisions among three host species of the brown-headed cowbird (Molothrus ater), each with a varying known response to parasitic eggs.

Among-population variation in telomere regulatory proteins and their potential role as hidden drivers of intraspecific variation in life history.

Biologists aim to explain patterns of growth, reproduction and ageing that characterize life histories, yet we are just beginning to understand the proximate mechanisms that generate this diversity. Existing research in this area has focused on telomeres but has generally overlooked the telomere's most direct mediator, the shelterin protein complex. Shelterin proteins physically interact with the telomere to shape its shortening and repair.

Decision rules for egg-color-based rejection by two cavity-nesting hosts of the brown-headed cowbird.

Hosts of obligate avian brood parasites often evolve defense mechanisms to avoid rearing unrelated young. One common defense is egg rejection, for which hosts often rely on eggshell color. Most research has assumed that hosts respond to perceived color differences between their own eggs and parasite eggs regardless of the particular color; however, recent experiments have found that many hosts respond more strongly to brown foreign eggs than to equally dissimilar blue eggs.

Extensive regional variation in the phenology of insects and their response to temperature across North America.

Climate change models often assume similar responses to temperatures across the range of a species, but local adaptation or phenotypic plasticity can lead plants and animals to respond differently to temperature in different parts of their range. To date, there have been few tests of this assumption at the scale of continents, so it is unclear if this is a large-scale problem. Here, we examined the assumption that insect taxa show similar responses to temperature at 96 sites in grassy habitats across North America.

Strategic adjustment of parental care in tree swallows: life-history trade-offs and the role of glucocorticoids.

Life-history theory predicts that optimal strategies of parental investment will depend on ecological and social factors, such as current brood value and offspring need. Parental care strategies are also likely to be mediated in part by the hypothalamic-pituitary-adrenal axis and glucocorticoid hormones. Here, we present an experiment in tree swallows (), a biparental songbird with wide geographical distribution, asking whether parental care is strategically adjusted in response to signals of offspring need and brood value and if so, whether glucocorticoids are involved in these adjustments.

Development and cross-species testing of western bluebird (Sialia mexicana) microsatellite primers.

Western and eastern bluebirds (Sialia mexicana and S. sialis) are socially monogamous passerines that engage in extra-pair copulations. We obtained microsatellites from S.