Breeding biology and natural history notes for White-collared Swift Streptoprocne zonaris in Costa Rica

摘要

The breeding biology of White-collared Swift Streptoprocne zonaris was studied in Costa Rica. Eggs were laid between mid April and mid May, and fledging occurred between late June and mid July. There are three clear nesting patterns for this wide-ranging species, which can be termed 'northern', 'central' and 'southern', all associated with the onset of the rainy season. My study was consistent with the breeding pattern elsewhere in the Northern Hemisphere. All nests were placed in sites with high humidity and were from 10 cm to 30 m or more above ground or water level. Nests were reused in subsequent seasons, and one nest was in use for at least 13 years. All observed clutches had two eggs and mean egg mass was 9.9 g. Egg (n = 23) were dull white and sub-elliptical (39%), long sub-elliptical (35%), short sub-elliptical (17%) or short oval (8%) in shape. Incubation period was 26 (25-27) days. Mean hatching mass was 8.8 g, and max. mass was reached at age 33 days (127% of adult size), thereafter it declined slightly. Fledging occurred at 47 (43-51) days. The growth constant k = 0.225 and T period was 19.5 days. Most mortality occurred at the egg stage or in the early days of a nestling's life. The major cause of nest failure was weather-related: flooding and starvation, but egg infertility and predation also occurred. Adult primary feather moult started in tandem with egg laying and lasted 6-7 months.