Douglas Causey

Ecology of Avian Influenza Virus in Birds

Abstract Avian influenza A virus (an orthomyxovirus) is a zoonotic pathogen with a natural reservoir entirely in birds. The influenza virus genome is an 8-segment single-stranded RNA with high potential for in situ recombination. Two segments code for the hemagglutinin (H) and neuraminidase (N) antigens used for host-cell entry. At present, 16 H and 9 N subtypes are known, for a total of 144 possible different influenza subtypes, each with potentially different host susceptibility. With >10,000 species of birds found in nearly every terrestrial and aquatic habitat, there are few places on earth where birds cannot be found. The avian immune system differs from that of humans in several important features, including asynchronous B and T lymphocyte systems and a polymorphic multigene immune complex, but little is known about the immunogenetics of pathogenic response. Postbreeding dispersal and migration and a naturally high degree of environmental vagility mean that wild birds have the potential to be vectors that transmit highly pathogenic variants great distances from the original sources of infection.

A System in Which Available Energy Per Se Controls Alpha Diversity: Marine Pelagic Birds

An attractive explanation for large‐scale gradients of species richness is that trophic energy flux defines living systems. It has yet to be shown that available energy may matter per se, that is, directly and independent of other potential determinants that are usually inescapably correlated (e.g., area, glacial history, or habitat complexity). By using a comprehensive conceptual framework addressing the variation of species richness, we report that in communities of birds regularly foraging in marine pelagic waters during the breeding season, species richness is above all directly linked to the appropriation of metabolic energy. Auxiliary energy supplied by wind and waves is likely to mitigate energetic constraints and thereby codetermine the expansion of niche space, along with an array of other subordinate factors. We emphasize that this system is markedly different from studied communities of terrestrial endotherms or marine exotherms in which habitat complexity and mutagenic solar radiation/temperature, respectively, may be more decisive than the appropriation of trophic energy flux shares as such. While the seabird system suggests that species‐energy curves may sometimes directly translate into species‐energy relationships, this situation may be rare rather than typical.

The Pelecaniform Birds

Abstract The Pelecaniformes is a traditional family of pelicans and allies, including all birds with four toes connected by webs and a gular pouch—tropicbirds, frigatebirds, gannets and boobies, cormorants, and anhingas. Recent studies show that these formerly uniting characters are in fact primitive and arose early in the evolutionary history of birds. The phylogeny is still unresolved without consensus, with some experts splitting the former order into a group including gannets and boobies, cormorants, and anhingas; a newly constituted group including pelicans, herons, and storks; and unrelated assemblage including tropicbirds and other groups. Regardless, the traditional pelecaniform assemblage shares common ecological and behavioral characteristics, including colonial breeding, piscivory, coastal and terrestrial nesting habitats, and upper trophic level feeding.

Variation in Age Ratio of Midcontinent Greater White-Fronted Geese During Fall Migration

Abstract Annual productivity is an important parameter for the management of waterfowl populations. Fall age ratio (juveniles:total birds) is an index of productivity of the preceding breeding seas...