COVERT EXTRATERRITORIAL BEHAVIOR OF FEMALE HOODED WARBLERS

Extraterritorial forays are one specialized tactic that females use to obtain extrapair copulations (EPCs). By radio-tracking female hooded warblers (Wilsonia citrina) during the breeding season, we found that females made covert forays onto neighboring territories. Almost 80% of females made extraterritorial forays during their fertile stages, but none visited territories during the nonfertile (incubation) stage, wh ich is consistent with the extraterritorial foray hypothesis. Females that left their territories visited from one to four neighboring terri tories, and they intruded at a rate of 0.6 territories/h. The propensi ty of females to foray from their territory did not correlate with bod y size or age of the social mate. One female that left her territory o btained an extrapair fertilization. Females may use forays to assess m ale quality as well as participate in extrapair copulations. An altern ative hypothesis for extra-territorial forays is that females may fora y onto neighboring territories to obtain food during the energetically stressful period of egg production. The extraterritorial foray hypoth esis and foraging hypothesis may not be mutually exclusive. Females ma y obtain benefits of foraging while at the same time assessing males f or EPCs. Extraterritorial behavior of female birds may be more common than previously believed and in many cases may only be ruled out throu gh radio-tracking.