It remains largely unknown which factors affect the innate immune responses of free-living birds. Nevertheless, the degree of innate immunity may play a crucial role in an individual's survival as it procures the first defence against pathogens. We manipulated the ectoparasite load of great tit (Parus major) nests by infesting them with hen fleas (Ceratophyllus gallinae) before egg laying. We s...

Post-mating sexually selected signals are expected to indicate parental quality. The good parent model assumes that expression of the sexual character positively reflects parental ability, resulting in a potential link between the exaggeration of the character and nestling-fitness traits. We tested this prediction in a population of a monogamous passerine, the magpie (Pica pica), for which nest...

Renesting after nest predation is ultimately an adaptive response to increase productivity in birds. However, renesting also increases reproductive effort to replace lost clutches. We investigated the consequences of this increased reproductive effort by determining whether renesting in female indigo buntings (Passerina cyanea) is associated with a decline in body condition (size-corrected mass...

How nestling birds respond to stressful situations may constitute an important survival component that has lasting developmental effects on the hypothalamic pituitary adrenal (HPA) axis. As birds are exposed to increasing amounts of potential anthropogenic stressors through land use change, understanding how these factors contribute to HPA development is important. We examined whether condition...

Tree swallows (Tachycineta bicolor) were used as a sentinel species to monitor the contamination and bioavailability of polychlorinated biphenyls (PCBs) in the Hudson River watershed. Several tree swallow nest box colonies around and downstream from Hudson Falls, NY, were studied. Tree swallow eggs, adults, and 5-, 10-, and 15-day-old nestlings were collected and analyzed for 103 PCB congeners....

We studied the reproductive biology of a box-nesting population of Tree Swallows Tachycineta bicolor in southeastern Wisconsin, USA. We were interested particularly in the relationship between laying order and hatching order and the extent to which each was a predictor of nestling body mass. We found that laying order was a significant predictor of hatching order. Laying and hatching order were...

Carotenoids cannot be synthesized by birds and thus have to be ingested with food, suggesting that carotenoid-based plumage coloration is environmentally determined. However signaling functions ascribed to plumage imply that plumage coloration is the outcome of an evolutionary process based on genetic variation. By means of a cross-fostering design we show significant effects of both a common r...