Yellow Billed Magpie mating and reproduction

Yellow-billed magpies breed in loose colonies. Extrapair courtship is frequent, and a comparison (1) between two adjacent areas with different inter-nest distances, and (2) with solitary, territorial European black-billed magpies, indicates that either an aggregated distribution of nests, or a relatively loose territorial system in yellow-billed magpies increases opportunities for extrapair behavior. Male yellow-billed magpies guard their partner by closely following them from five days before the first egg is laid. Pair copulations were infrequent, occurring 3 or 4 times per clutch, and mainly over days -5 to -3. Territoriality, which is most pronounced during the female's fertile period, may enable the male to guard his partner while simultaneously foraging to provide her with food.marginally significant evidence of female mate preference based on body mass, wing length, wing loading index, or age