Red-winged Blackbirds
Pen and Ink
Tony Angell,
1985?
Collection of the artist

This illustration shows a sexual chase in which several male red-wings temporarily violate territorial boundaries. Female choosiness in mate selection is well-documented in the literature. It may depend on the "attractiveness" of the male's territory or the quality of his sexual advertisements. Male choice is more mysterious. Female red-wings who arrive on the nesting grounds early are chased more vigorously than late-arrivals. Chasing may test female flight skill and hence potential foraging success, a key to successful parenting. As harem size increases with the season, however, male selectivity (and hence chasing) decreases.

Early violations aside, territories are staunchly defended and not just against other red-wings. On the trail along Lake Lagunita the vigor of red-wing territorial defense is readily apparent as 'trespassing' joggers can attest.