MATE GUARDING IN THE MAGPIE PICA-PICA

Data were collected to test the idea that male magpies guard their mates during the fertile period (i.e. when a female can be fertilized) from mating attempts by other males. During the fertile period males remained closer and followed their mates more than before. Each sex responded differently to male and female intruders. A caged female in a territory elicited aggression from the female, and from male and female when both birds approached together. Lone males courted the caged female. Non-breeding males were probably the greatest risk to mated males. The adaptive significance of different copulation frequencies in birds, in relation to cuckoldry, is discussed. © 1979.