Glossary
House Wren
The House Wren, Troglodytes aedon, is a very small songbird of the wren family, Troglodytidae. It occurs from Canada to southernmost South America, and in most suburban areas in its range it is the single most common wren. Its taxonomy is highly complex and some subspecies groups are often considered separate species.
Description
Though living about 5,600 miles (9,000 km) away, southern house wrens in S?o Paulo (Brazil) differ from their northern relatives in voice more than in looks.
Adults are 11-13 cm long and weigh about 12 g. The subspecies vary greatly, with upperparts ranging from dull greyish-brown to rich rufescent-brown, and the underparts ranging from brown, over buff and pale grey, to pure white. All subspecies have blackish barring to the wings and tail, and some also to the flanks. All subspecies show a faint eye-ring and eye-brow and have a long, thin bill with a blackish upper mandible, and a black-tipped yellowish or pale grey lower mandible. The legs are pinkish or grey. The short tail is typically held cocked.
This bird's rich bubbly song is commonly heard during the nesting season but rarely afterwards. There is marked geographical variation in its song, though somewhat more gradual than in the birds' outward appearance which can strikingly differ e.g. on neighboring islands in the Caribbean.
The House Wren is usually divided into three distinct subspecies groups and one or several distinct island-endemic subspecies. Some or all of these are often considered distinct species.
It has also been suggested that the taxa from the Lesser Antilles represent one or more separate species, but there is less agreement as to their subdivision, because as far as they have been studied to date, there is little clear biogeographical structure among these populations.
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In North America, the House Wren is thought to achieve the highest density in floodplain forests in the western great plains where it uses woodpecker holes as nesting sites. In South and Central American it can be found in virtually any habitat and is, as indicated by its common name, often associated with humans. North American birds migrate to the southern United States and Mexico for winter. Most return to the breeding grounds in late April to May, and leave for winter quarters again around September to early October[2]. These birds forage actively in vegetation. They mainly eat insects such as butterfly larvae, also spiders and snails. Southern house wrens rarely attend mixed-species feeding flocks.
Reproduction
The nesting habits do not seem to differ significantly between the Northern and Southern House Wrens at least. They usually construct a large cup nest in various sorts of cavities, taking about a week to build. The nest is made from small dry sticks and is usually lined with a variety of different materials. These include: feather, hair, wool, spider cocoons, strips of bark, rootlets, moss, and trash. The male wren finds dry sticks, which he adds to the nest. Once he is done, the female inspects at the nest; but if she does not approve of the construction, she will throw any unwanted sticks to the ground. After this process, the female lines the nest. Nest cavities are usually a few meters above ground at most, but occasionally on cliffs as high up as 15 meters and more at least in southern populations[verification needed]; they may be natural or man-made, often using bird houses.
House Wrens are feisty and pugnacious animals considering their tiny size. They are known to occasionally destroy the eggs of other birds nesting in their territory by puncturing the eggshell. They are also known to fill up other birds' nests within its territory with sticks to make them unusable.
Depending on the exact population, the House Wrens' clutch is usually between two and eight red-blotched cream-white eggs, weighing about 1.4 grams each and measuring c.17 and 13.4 mm at the widest points. Only the female incubates these, for around 12-19 days, and she will every now and then leave the nest for various reasons. When on the nest, the male provisions her with food. The young, which like all passerines hatch almost naked and helpless, take another 15-19 days or so to fledge[citation needed]. They are being fed by both parents, and need plenty of food given their tiny size (see also Bergmann's Rule). As the young near fledging, the parents spend much of their time procuring food for them. Brood loss due to predation was found to be light in the Southern Andean Yungas, with predation of nestling young being almost insignificant.
Migrant populations are nesting within 6 weeks of returning from winter quarters, leaving theoretically time for a second brood. In the subtropical montane forest of northwestern Argentina and similar habitat, the Southern House Wren breeds in the rainy summer months from late October to late December.
In Washington, D.C. area, House Wren parents made significantly more feeding trips per hour in suburban backyards compared to rural backyards. Yet rural nestlings grew at a faster rate than their suburban counterparts. In addition, suburban parents spent less time brooding (sitting on the nest) compared to rural parents. Such results suggest that suburban backyard habitats offer House Wrens food for nestlings that is inferior in either quality or quantity to what rural habitats offer. Food items may, for example, be smaller in suburban habitats, and force adults to make more trips to the box.
Conservation status
The House Wren may have been displaced somewhat in some northern parts of its range by the introduction of the House Sparrow, but is still common and widespread throughout most of the Americas. It is not considered threatened by the IUCN[8], though this would certainly not hold true for several of the island population if they turn out to be good species.
Some taxa, especially from the Lesser Antilles, are rare and highly endangered or possibly already extinct. Several factors seem to have contributed to a varying degree to the decline of these birds, namely habitat destruction, predation by introduced mongooses, and hurricanes:
* Martinique Wren, Troglodytes aedon martinicensis) ? Martinique, apparently extinct (c.1890)
* Guadeloupe Wren, Troglodytes aedon guadeloupensis ? Guadeloupe, possibly extinct (late 20th century?)
* Saint Lucia Wren, Troglodytes aedon mesoleucus ? Saint Lucia, believed extinct by 1970s, subsequently rediscovered but still precariously rare
The Saint Vincent Wren (Troglodytes aedon musicus) of Saint Vincent was close to extinction in the mid-late 20th century; it has since recovered and today is not uncommon
As remarked above, these are variously placed in T. musculus if that is considered distinct, or as one or several distinct species.
House Wrens and humans
Its diminutive size and seemingly overconfident and bold behavior make the House Wren a well-liked bird to many Americans. House Wrens can be encouraged to nest in gardens in their range by offering nest boxes with hole small enough to prevent competitive cavity nesters.
King Friday XIII, a protagonist of the PBS children's educational program Mister Rogers' Neighborhood, had a wooden wren upon a stick that he often played with as a cherished toy. This bird was referred to as House Wren when the King composed and sang a song about his toy, mentioning the scientific name Troglodytes aedon.
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