COMPETITION FOR WINTER TERRITORIES IN A NEOTROPICAL MIGRANT - THE ROLE OF AGE, SEX AND COLOR

Hooded Warblers (Wilsonia citrina) defend long-term feeding territorie s during the nonbreeding season. Experimental removals of territory ow ners early iri the fall in Mexico resulted in rapid replacement by non territorial individuals (''floaters''). The sex ratio of replacement b irds was similar to that of territory owners in the same habitat, but virtually all replacements were hatching-year (HY) birds. Females were able to acquire and defend territories in the presence of male floate rs. Loss of wintering habitat would likely increase the proportion of nonterritorial birds and, therefore, increase overwinter mortality rat es, especially of HY birds. The extent of malelike coloration of femal es was riot correlated with habitat, indicating that dark females were not more likely to obtain territories in forested habitat where males predominate. Furthermore, the aggressive response of male territory o wners toward models did not depend on intruder color. These results su ggest that malelike coloration in females does not function in competi tive interactions with males. Intense competition for winter territori es coupled with reduced survivorship of winter floaters could constrai n breeding strategies if young produced late in the summer have little chance of obtaining winter territories.