Meeting Abstract
Selective pressures produced by climate variability have led to differential thermal tolerances amongst animal species. Endothermic animals expend large amounts of energy maintaining their body temperature, and the critical temperatures (maximum highs and minimum lows) that they are able to tolerate depend largely upon the geographic range that they evolved in. When temperatures become unfavorable, adaptations that allow organisms to respond plastically provide an advantage. Those unable to physically migrate must deal with elevated heat metabolically. Altricial nestling birds, which are born naked and unfeathered, cannot maintain their own body temperature until their feathers grow in, and are essentially ectothermic in the early stages of their development. While in the nest, their growth, body condition, and immune response are directly linked to the microclimate in which they are raised. Factors that disrupt their development, then, can be costly. By experimentally manipulating the temperature of nest boxes, I am quantifying a response to heat in eastern bluebird (Sialia sialis) nestlings using heat-shock protein 70 as a biomarker for physiological stress. Heat-shock protein 70 is constitutively expressed at baseline levels, but is upregulated under high temperatures. The effects of high HSP70 levels are not known, but there are implications for reduced lifespan and changes in immune effects in other organisms. I am also measuring changes in body condition as well as differing loads of a parasitic bacteria that degrades feathers and thrives under a temperature optimum. Parasites often impose a cost to physical condition, so any observed changes in growth rate under heat must also be examined in relation to parasite load.
