Novel role of insulin in the regulation of glucose excretion by mourning doves (Zenaida macroura).

In mammals, insulin primarily lowers plasma glucose (P) by increasing its uptake into tissues. Studies have also shown that insulin lowers P in mammals by modulating glomerular filtration rate (GFR). Birds have naturally high P and, although insulin administration significantly decreases glucose concentrations, birds are resistant to insulin-mediated glucose uptake into tissues.

Unpredictable food availability induces metabolic and hormonal changes independent of food intake in a sedentary songbird.

Environments often vary with regard to their temporal resource availability, but little is understood concerning how resource predictability impacts animals. The adaptive regulation hypothesis suggests that organisms act to conserve their current energetic state during periods of diminished food access and recuperate their energetic reserves (fat and muscle) during periods of greater food availability. In contrast, the chronic stress hypothesis suggests that variation in access to food can induce a prolonged stress response, resulting in maladaptive usage of energy reserves and increased behavioral activity.