PAIR INTERACTIONS IN RED-FACED WARBLERS

Forty pairs of breeding Red-faced Warblers (Cardellina rubrifrons) wer e observed in 1992 and 1993 on the Mogollon Rim, Arizona. Intrusions b y extra-pair males, interactions between pair members, and other pair interaction behaviors were recorded. The majority of intrusions occurr ed during the building stage of the nesting cycle. Males responded to intrusions during nest building by decreasing intra-pair distance. Mal es maintained shorter intra-pair distances by following the female whe n she initiated movements and by not initiating pair movements themsel ves. Intra-pair distances were as short or shorter during the incubati on period as during nest building, and were shorter during incubation than during egg laying. Males continued to follow females beyond the e xpected fertile period. Possible explanations for continued mate follo wing include: males guard their mates against predators, males guard t heir paternity for future nesting attempts, and males respond to extra -pair male intrusions, which continue during incubation.