Bald eagles (Haliaeetus leucocephalus) may be at risk from contaminants in their diet and young birds may be particularly sensitive to contaminant exposure. To evaluate potential risks from dietary mercury exposure to eagle nestlings in South Carolina (USA), we surveyed mercury concentrations in 34 nestlings over two breeding seasons (1998 and 1999). Samples were also obtained from several post...

A common feature of many birds breeding in seasonal environments is that fitnessrelated parameters such as nestling mass or survival decline as the breeding season progresses. Consequently, there is a tendency for early breeders to have better reproductive performance than individuals breeding later in the season. This variation could be caused by factors associated with the date of laying, suc...

Earlier studies of the starling (Sturnus vulgaris) population at Belmont, Lower Hutt, New Zealand, showed that nest productivity was low compared with other populations in New Zealand and elsewhere. Therefore, we investigated possible trade-offs between offspring number and quality (as measured by body mass and composition). We also compared these measures of offspring condition with preand pos...

Based on studies from the poultry literature, all birds are hypothesized to require at least 4 weeks to develop circulating mature B-cell lineages that express functionally different immunoglobulin specificities. However, many altricial passerines fledge at adult size less than four weeks after the start of embryonic development, and therefore may experience a period of susceptibility during th...

In many cooperatively-breeding species, the presence of one or more helpers improves the reproductive performance of the breeding pair receiving help. Helper contributions can take many different forms, including allo-feeding, offspring provisioning, and offspring guarding or defence. Yet, most studies have focussed on single forms of helper contribution, particularly offspring provisioning, an...

Ecological speciation predicts that hybrids should experience relatively low fitness in the local environments of their parental species. In this study, we performed a translocation experiment of nestling hybrids between collared and pied flycatchers into the nests of conspecific pairs of their parental species. Our aim was to compare the performance of hybrids with purebred nestlings. Nestling...

Invasive species have the potential to detrimentally affect native ecosystems by out competing or directly preying upon native organisms, and have been implicated in the extinction of endemic populations. One potentially devastating introduced species in the Galápagos Islands is the parasitic fly Philornis downsi. As larvae, P. downsi parasitize nestling birds and have been associated with high...

The nutritional stress hypothesis explains how learned features of song, such as complexity and local dialect structure, can serve as indicators of male quality of interest to females in mate choice. The link between song and quality comes about because the brain structures underlying song learning largely develop during the first few months post-hatching. During this same period, songbirds are...