Covert extraterritorial behavior of female hooded warblers

Extraterritorial forays are one specialized tactic that femalesuse to obtain extrapair copulations (EPCs). By radio-trackingfemale hooded warblers (Wilionia citrina) during the breedingseason, we found that females made covert forays onto neighboringterritories. Almost 80% of females made extraterritorial foraysduring their fertile stages, but none visited territories duringthe nonfertile (incubation) stage, which is consistent withthe extraterritorial foray hypothesis. Females that left theirterritories visited from one to four neighboring territories,and they intruded at a rate of 0.6 territories/h. The propensityof females to foray from their territory did not correlate withbody size or age of the social mate. One female that left herterritory obtained an extrapair fertilization. Females may useforays to assess male quality as well as participate in extrapaircopulations. An alternative hypothesis for extra-territorialforays is that females may foray onto neighboring territoriesto obtain food during the energetically stressful period ofegg production. The extraterritorial foray hypothesis and foraginghypothesis may not be mutually exclusive. Females may obtainbenefits of foraging while at the same time assessing malesfor EPCs. Extraterritorial behavior of female birds may be morecommon than previously believed and in many cases may only beruled out through radio-tracking