eWestern Birds

Loosely Colonial Nesting by Western Kingbirds in Northwestern Texas

Carroll D. Littlefield

ABSTRACT: The number of Western Kingbirds (Tyrannus verticalis) breeding on a farmstead in northwestern Texas increased from four pairs in 1990 to 13 pairs in 2001. In most cases, nests were located in large planted shade trees at this 0.6-ha farmstead. The earliest resident birds arrived on the mean date of 20 April (n = 12 years), and earliest observed nest building was on 10 May 2000; the first fledglings were noted on the mean date of 6 July (n = 11 years). Most clutch and nestling losses resulted from nest displacement (n = 7) caused by strong winds, with only two from other causes. Ten fledglings died, all from weather events. During the 1990–2001 study period, seven adults were known to have died. Territorial defense of only a small space surrounding the nest and dispersed foraging may have permitted such a large number of pairs to breed successfully in an area where nest sites were limited.

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