摘要：The Western Kingbird (Tyrannus verticalis) has nested for six consecutive years in Arkansas since 1998. Eleven nests of this species were observed in the summer of 2003 in urban areas of Fort Smith (Sebastian Co.) and Van Buren (Crawford Co.). All nests were on human-made structures. Of the 11, seven (64%) were located on power stations and the remaining four (36%) were on light posts. Mean nest height was 7.92 m (n = 11nests) and the mean width of nest poles was 31.18 cm (n= 4). Nest building lasted 12 to 13 days (mean = 12.5 days, n = 2 nests). The attentive period of female parents (time spent on nest at a stretch during incubation) and their inattentive period were highly variable and averaged 11.97 minutes and 4.08 minutes respectively. The male stayed in close proximity of the nest throughout the nest building and incubation phases. Incubation period was estimated to be 17 days (n = 2 nests). Nesting success (percentage of nests that fledged young) was 72.7% (n = 11 nests). The average number of young fledged per successful nest was 3.37 (n =8) and the average number fledged over all nests was 2.45 (n = 11). In all nests, only the female participated in nest-building and incubation. Fledging occurred 13 to 14 days after hatching (mean =13.5 days, n = 2 nests).
