Meeting Abstract

P1.31  Jan. 4  Hormonal differences between helpers and breeders in a cooperatively breeding bird MALUEG, AM*; MOORE, IT; WALTERS, JR; Virginia Tech; Virginia Tech; Virginia Tech almalueg@vt.edu

Red-cockaded woodpeckers (Picoides borealis) are cooperative breeders, living in family groups that consist of a breeding pair and zero to five non-breeding �helper� males. Helpers assist the breeding pair in territory defense, cavity construction, and care of offspring, including feeding and incubation, but do not copulate nor father any offspring. The physiological factors mediating reproductive suppression of helpers are poorly understood. Previous studies have shown that helpers and breeders of this species have similar levels of the hormones testosterone and prolactin. However, studies in other species have found that concentrations of stress hormones can differ between helpers and breeders, and these hormones are well known for their inhibitory effects on reproductive function. Helper red-cockaded woodpeckers may maintain higher levels of the stress hormone corticosterone due to mild aggression received from breeders and a low degree of control over resources such as food and mates. From April 10 to July 21 of 2006 we collected blood samples from breeding males and females and helper males living on Marine Corps Base Camp Lejeune in Jacksonville, North Carolina. Samples were collected during all phases of the breeding cycle (copulation, egg-lay/incubation, nestling provisioning, and fledgling provisioning). We collected samples for both baseline stress levels, which reflect the amount of stress experienced in daily living conditions, and maximal stress levels, which represent the magnitude of the stress response and reflect sensitivity to stressful events. We are investigating whether the observed differences in sexual behavior between breeder and helper red-cockaded woodpeckers may be attributed to differences in corticosterone concentrations.