Bat mortality: pesticide poisoning and migratory stress.

Organochlorine residues in the fat of young Mexican free-tailed bats, Tadarida brasiliensis, reached the brain and caused symptoms of poisoning after the fat mobilization that takes place during migratory flight was simulated. These chemical body burdens were obtained naturally under free-living conditions at the maternity roost. The data obtained support the hypothesis that pesticides have contributed to recent declines in populations of this bat.

Effects of dietary quality on basal metabolic rate and internal morphology of European starlings (Sturnus vulgaris).

European starlings (Sturnus vulgaris) were fed either a low- or high-quality diet to test the effects of dietary quality on basal metabolic rate (BMR) and internal morphology. Basal metabolic rate did not differ significantly between the two dietary groups, but internal morphology differed greatly. Starlings fed the low-quality diet had heavier gastrointestinal tracts, gizzards, and livers. Starlings fed the high-quality diet had heavier breast muscles. Starlings on the low-quality diet maintained mass, while starlings on the high-quality diet gained mass. Dry matter digestibility and energy digestibility were lower for starlings fed the low-quality diet, and their food and water intake were greater than starlings on the high-quality diet. The lack of dietary effect on BMR may be the result of increased energy expenditure of digestive organs paralleling a reduction of energy expenditure of organs and tissues not related to digestion (i.e., skeletal muscle). This trade-off in energy allocation among organs suggests a mechanism by which organisms may alter BMR in response to a change in seasonal variation in food availability.