TEMPORAL PATTERNS OF WITHIN-PAIR COPULATIONS, MALE MATE-GUARDING, AND EXTRA-PAIR EVENTS IN EASTERN RED-WINGED BLACKBIRDS (AGELAIUS-PHOENICEUS)

I studied the timing of within-pair and extra-pair behaviors in an eastern population of red-winged blackbirds. Within-pair activity was highest several days before egg-laying started and during the morning and evening hours. Extra-pair events also peaked just before egg-laying but showed no distinct diurnal pattern. Red-winged blackbird pairs on average copulated 21-22 times per clutch. Males followed their females more than the reverse, but spent only a third of the time within 10 m of their mates. Male presence on the territory deterred potential extra-pair events, and although males were on their territories for 94% of their day, they did leave, apparently to forage, on occasion. Extra-pair events involving these males' females were more likely during these departures than expected by chance. Apparently as a consequence, males went on fewer forays when their female was most fertilizable. Males did not copulate with their females more often than normal just before or after forays or intrusions. Pairs that copulated more often had fewer extra-pair fertilizations in their broods, but no other behaviors were correlated with paternity. These results have several important implications for understanding the effects of sperm competition of mating and parental behavior.