Intraclutch Variation in Testosterone Content of Red-Winged Blackbird Eggs

Hatching asynchrony occurs in many avianspecies, often because parents initiate incubation before the last egg in the clutch has been laid.Because parents typically begin to feed individual young as soon as they hatch, earlier-hatched young start to grow before their younger siblings have hatched.This frequently results in a size hierarchy that is hatchingorder dependent among nestlings (Bryant 1978, Richter 1984, Greig-Smith 1985, Stokland and Amundsen 1988).Because access to food brought by parents is largely dependent on the size-related competitive abilities of the young (Ryden and