Wrens, Dippers and Thrashers by David Brewer

Author:David Brewer
Language: eng
Format: epub
Tags: ebook, book
ISBN: 9781408135525
Publisher: Bloomsbury Publishing
Published: 2019-11-23T00:00:00+00:00

STATUS AND DISTRIBUTION Over most of its wide range common or abundant in suitable habitat; however, since it is not found in unbroken forest the actual overall density in, for example, much of Amazonia may be quite small. Readily adapts to modified habitat and has hence probably increased in recent times. Over most of its range sedentary; however, the extreme southern populations are highly migratory. The winter range of the race chilensis, from Tierra del Fuego, extends at least 800km north of the breeding range.

The situation of the endemic populations in the West Indies is, however, quite different. On Dominica it is common, in Grenada common in some areas, on St Vincent uncommon. On Martinique it probably became extinct about 1900; on Guadeloupe it was believed to be extinct since about 1914, but small populations were rediscovered in 1969 and 1973 (Barlow 1978), but it has not been seen since (Raffaele et al. 1998). On St Lucia a tiny population remained in 1984 (Graves 1985). In all of these locations the cause of decline or extinction seems to be the usual ones of habitat destruction and introduced predators, especially mongooses.

BREEDING The nest is essentially similar to that of the Northern House Wren; situated in a cavity, frequently an artificial one such as niches in outbuildings. Takes very readily to nestboxes. The base of the nest is a mass of coarse twigs, gradually becoming finer further up. The base is largely made by the male while most of the finishing is done by the female; the male may continue to drop larger twigs into the cavity during this stage, which are then removed by the female. In Colombia, nest sites from 0.5–11m above the ground have been recorded, but the majority are about 2–3m up (Alvarez-López et al. 1984). For a tropical wren, the Southern House Wren is unusually fecund; clutches in Colombia are two to four, most commonly three, with an average of 3.2; one female laid seven clutches, to a total of 20 eggs, in 17 months (in contrast to, for example, the wood wrens whose clutches seem invariably to consist of two eggs only); in Costa Rica, clutches usually four eggs, very rarely five, questionably two (Skutch 1953); in Trinidad four or five (Belcher & Smooker 1937). Eggs whitish, densely flecked all over with fine markings of brown, reddish-brown or cinnamon (Skutch 1953); rarely white (Kattan 1993). Incubation by female only, 14.5–15.5 days, rarely 17. Young fed by both sexes, but as the fledging period progresses, increasingly by the female; young fledge in 18–19 days, rarely 17–20. Pairs appear to remain faithful through several broods, in contrast to the situation in Northern House Wren, where mate switching is rampant in some populations (Drilling & Thompson 1991). Again in contrast to the Northern House Wren, polygamy in Southern House Wrens is rare. It was not noted in a detailed study in Colombia (Alvarez-Lopéz et al. 1984), although in Panama several instances were observed (Freed 1986). In this instance both

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