Breeding ecology of the Welcome swallow, Hirundo tahitica neoxena Gould, in southern Wairarapa, New zealand

Abstract

The breeding ecology of the Welcome Swallow, Hirundo tahitica neoxena Gould, in the vicinity of Lake Wairarapa, in southern Wairarapa, was studied from September 1992 to the end of February 1994, to determine if any changes in breeding success have occurred during at least 34 years of colonization and breeding in New Zealand. The breeding season extended from early August to late February. Mean clutch-size per month increased from 3.7 in August, to reach a peak of 4.2 - 4.5 in November / December, and then declined to 3.6 - 3.9 in January. The overall mean clutch-size was 4.0. The length of the incubation period, from the day that the last egg was laid, ranged from 14 to 19 days with a mean of 15.6 days. The eggs did not necessarily hatch in the order in which they were laid. At least some of the hatching occurred throughout the daylight hours. Evidently four clutches and broods can be successfully hatched and raised during a single breeding season. This is a rare occurrence, however, due to predation of eggs and nestlings. During the 1993-94 breeding season, the number of clutches attempted per nest-site ranged from one to six, with three attempts being the most common. For the one and a half breeding seasons studied, from 322 clutches attempted, at least 1285 eggs were laid, 760 eggs hatched (59.1 %), and 657 chicks fledged (51.1 % of the eggs laid resulted in a chick fledging; 86.4 % of the hatched chicks fledged). 16.9 % of the eggs and 6.1 % of the nestlings were lost through predation, but only two broods were evidently destroyed by mammalian predation; most predation was avian. At least three eggs and at least three nestlings survived attack by avian predators. A further 4.9 % of the eggs and 3.7 % of the nestlings were destroyed by the nest breaking or becoming detached from the supporting wall of the bridge or culvert. 7.4 % of the eggs failed to hatch due to infertility, incomplete embryo development, or failure of the chick to break out of the eggshell. The most common lengths of the nestling period were 21 and 22 days; growth rates were measured by nestling weights and the extent of feather development. The information recorded was compared with published data from New Zealand and Australia.