1. Food-prey-predator interactions may involve both 'bottom-up' and 'top-down' processes. Conventionally, food-host-parasite interactions have been seen as governed solely from the 'bottom-up', i.e. well-fed hosts can better resist parasites and so suffer less parasitism. Recent studies on diverse endo- and ecto-parasites increasingly highlight that well-fed hosts provide parasites with a bette...

Many wild birds fast during reproduction, molting, migration, or because of limited food availability. Species that are adapted to fasting sequentially oxidize endogenous fuels in three discrete phases. We hypothesized that species not adapted to long fasts have truncated, but otherwise similar, phases of fasting, sequential changes in fuel oxidization, and similar changes in blood metabolites ...

Vocal learning in swamp sparrows, Melospiza georgiana, is subject to a host of sensory and motor limitations. One such limitation is that young swamp sparrows almost invariably crystallize their songs with a simple trilled syntax, irrespective of the syntax of vocal models from which they learn. A striking exception to this pattern was recently identified by Podos (1996, Animal Behaviour, 51, 1...

House sparrows, European starlings, and Carneux pigeons were inoculated with 4 influenza A (H5N1) viruses isolated from different avian species. We monitored viral replication, death after infection, and transmission to uninfected contact birds of the same species. Sparrows were susceptible to severe infection; 66%-100% of birds died within 4-7 days. High levels of virus were detected from orop...

Flexible metabolic phenotypes allow animals to adjust physiology to better fit ecological or environmental demands, thereby influencing fitness. Summit metabolic rate (Msum = maximal thermogenic capacity) is one such flexible trait. Skeletal muscle and heart masses and myocyte metabolic intensity are potential drivers of Msum flexibility in birds. We examined correlations of skeletal muscle and...

The Henslow’s Sparrow (Ammodramus henslowii), a species of conservation concern, winters primarily in longleaf pine (Pinus palustris) forest ecosystems in the southeastern U.S. These pine savannas have been reduced to 5% of their former range, with remaining patches requiring active management with fire to maintain characteristic structure and plant diversity. Wintering Henslow’s Sparrow abunda...

Genetic changes in avian influenza viruses influence their infectivity, virulence and transmission. Recently we identified a novel genotype of H9N2 viruses in widespread circulation in poultry in Pakistan that contained polymerases (PB2, PB1 and PA) and non-structural (NS) gene segments identical to highly pathogenic H7N3 viruses. Here, we investigated the potential of these viruses to cause di...

Local environmental features can shape hybrid zone dynamics when hybrids are bounded by ecotones or when patchily distributed habitat types lead to a corresponding mosaic of genotypes. We investigated the role of marsh-level characteristics in shaping a hybrid zone between two recently diverged avian taxa - Saltmarsh (Ammodramus caudacutus) and Nelson's (A. nelsoni) sparrows. These species occu...