| population differences in fever and sickness behaviors in a wild passerine: a role for cytokines. | immune responses benefit hosts by clearing pathogens, but they also incur physiological costs and tissue damage. while wild animals differ in how they balance these costs and benefits, the physiological mechanisms underlying such differential investment in immunity remain unknown. uncovering these mechanisms is crucial to determining how and where selection acts to shape immunological defense. among free-living song sparrows (melospiza melodia) in western north america, sickness-induced lethargy ... | 2010 | 21075952 |
| oestrogen regulates male aggression in the non-breeding season. | extensive research has focused on territorial aggression during the breeding season and the roles of circulating testosterone (t) and its conversion to 17beta-oestradiol (e2) in the brain. however, many species also defend territories in the non-breeding season, when circulating t-levels are low. the endocrine control of non-breeding territoriality is poorly understood. the male song sparrow of washington state is highly territorial year-round, but plasma t is basal in the non-breeding season (a ... | 2000 | 10885513 |
| regulation of territorial behavior in the sedentary song sparrow, melospiza melodia morphna. | male song sparrows (melospiza melodia morphna) of western washington state show year-round territoriality. although territorial aggression during the breeding season was accompanied by high circulating levels of luteinizing hormone (lh) and testosterone (t), similar aggression in the non-breeding season occurred when gonadal hormone levels were basal. experimental removal of territorial males in autumn resulted in new males taking over the territory within a few days. these males had basal level ... | 1994 | 8034278 |