Reinita Gorginaranja/Blackburnian Warbler/Setophaga fusca

Nombre en español: Reinita Gorginaranja

Nombre en inglés: Blackburnian Warbler

Nombre científico: Setophaga fusca

Familia: Parulidae

Canto: Andrew Spencer

La reinita gorjinaranja (Setophaga fusca), también denominada reinita de fuego, reinita pechinaranja, reinita de Blackburn y cigüita del frío, es una especie de ave paseriforme de la familia Parulidae. Se reproduce en el este de América del Norte, desde el sur de Canadá a Carolina del Norte. Las reinitas de garganta naranja son migratorias y pasan el invierno en el sur de América Central y en Sudamérica.

Descripción

Son de 11,5 cm de largo y pesan 8,5 g . En el verano, el macho hace alarde de su lomo gris oscuro y dobles franjas blancas en las alas, con pecho amarillento y coronilla chocolate oscuro. Las partes inferiores de esta ave son blancas, y matizadas con amarillo y mechones negros. La cabeza es bastante colorida amarilla y negro, con una garganta de color anaranjado.

Otros plumajes son versiones descoloridas del macho del verano, y tienen una carencia en particular en el diseño de la cabeza, amarilla y gris pálido, en vez de negro.

Comportamiento

Los hábitats de cría de estas aves son bosques de coníferas maduros o los bosques mixtos, especialmente aquellos que contienen piceas y tsugas del Canadá. Esos aves ponen de 4 a 5 huevos en un nido en forma de taza en el que se coloca generalmente de 2 a 38 m de altura, en una rama horizontal.

Estos pájaros son insectívoros, pero incluyen fresas en su dieta en la temporada de invierno. Usualmente están en búsqueda de insectos en las copas de los árboles.

Los cantos son unas simples series de notas altas swi, que a menudo suben de tono. Su reclamo es un sip alto.

Blackburnian warbler

The Blackburnian warbler (Setophaga fusca [formerly Dendroica fusca]) is a small New World warbler. They breed in eastern North America, from southern Canada, westwards to the southern Canadian Prairies, the Great Lakes region and New England, to North Carolina.

Blackburnian warblers are migratory, wintering in southern Central America and in South America, and are very rare vagrants to western Europe.

Etymology

The genus name Setophaga is from Ancient Greek ses, «moth», and phagos, «eating», and the specific fusca is Latin for brown.

These birds were named after Anna Blackburne, an English botanist.

Description

Blackburnian warblers are small passerines and average-sized wood-warblers. They measure around 11 to 13 cm (4.3 to 5.1 in) long, with a 20 to 22 cm (7.9 to 8.7 in) wingspan, and weigh 8 to 13 g (0.28 to 0.46 oz). The average mass of an adult bird is 9.7 g (0.34 oz), although is slightly higher in fall due to fat reserves, averaging 10.2–10.4 g (0.36–0.37 oz). Among standard measurements, the wing chord is 6.3 to 7.3 cm (2.5 to 2.9 in), the tail is 4.2 to 5 cm (1.7 to 2.0 in), the bill is 0.9 to 1 cm (0.35 to 0.39 in) and the tarsus is 1.6 to 1.8 cm (0.63 to 0.71 in). In summer, male Blackburnian warblers display dark gray backs and double white wing bars, with yellowish rumps and dark brown crowns. The underparts of these birds are white, and are tinged with yellow and streaked black. The head is strongly patterned in yellow and black, with a flaming-orange throat. It is the only North American warbler with this striking plumage. Other plumages, including the fall male and adult female, are washed-out versions of the summer male, and in particular lack the bright colors and strong head pattern. The Blackburnian warbler is practically unmistakable if seen well, even the female due her dull-yellow supercilium, contrasting with greyish cheeks and yellow throat contrasting with the dark streaky sides and back. The only other wood-warbler with an orange throat is the flame-throated warbler of Central America and is very distinctive, lacking the contrasting blackish streaking about the head and whitish underside of a male Blackburnian. Basic plumages show weaker yellows and gray in place of black in the breeding male. Blackburnian warblers’ songs are a simple series of high swi notes, which often ascend in pitch. Transliterations have included zip zip zip zip zip zip zip zip, titititi tseeeeee or teetsa teetsa teetsa teetsa. Their call is a high sip. Genetic research has shown that their closed living relative is the bay-breasted warbler, the latter species perhaps specialized to forage in the same coniferous trees at lower levels. Hybridization in the wild has been recorded once each with a bay-breasted warbler (in West Virginia, with a black-and-white warbler (in Pennsylvania) and possibly a wintering hybrid with a Kirtland’s warbler (in Hispaniola).

Ecology

Blackburnian warblers are solitary during winter and highly territorial on their breeding grounds and do not mix with other passerine species outside of the migratory period. However, during migration, they often join local mixed foraging flocks of species such as chickadees, kinglets and nuthatches. Similarly, in the tropics they were found to be fairly social while engaging in migration but solitary from other passerines while wintering. These birds are basically insectivorous, but will include berries in their diets in wintertime. They usually forage by searching for insects or spiders in treetops. Their breeding season diet is dominated by the larvae of Lepidoptera, i.e. moths and butterflies. They may help control the spruce budworm (often considered a harmful pest) when breakouts occur, at the local if not at epidemic level. In one study from Ontario, 98% of the diet was made of insects, the remaining 2% being spiders. Among the migratory Setophaga warblers, it is considered one of the specialist at foraging in the micro-habitat of the tree’s top canopy.

The breeding habitats of these birds are mature coniferous woodlands, the central part of their breeding range being in the southeastern portion of Canada’s boreal forest. However, their distribution as a breeding species continues broadly down much of New England and the Appalachian Mountains, from New York to northernmost Georgia, in elevated mixed woodlands, especially ones containing spruce and hemlocks. Hemlocks in particular are most likely to host Blackburnian warblers in mixed forests. It typically winters in tropical montane forests, from roughly 600 to 2,500 m (2,000 to 8,200 ft), mainly from Colombia to Peru, more sporadically in Panama and the Amazon region.

Blackburnian warblers begin their first clutches in mid-May to early June in the contiguous United States and about 1 to 2 weeks later in Quebec. This species build a nest consisting of an open cup of twigs, bark, plant fibers, and rootlets held to branch with spider web and lined with lichens, moss, hair, and dead pine needles that’s placed near the end of a branch. Although typically only laying one brood per year, if a nest is destroyed they are capable of producing a second or even third brood. Three to five whitish eggs are laid in its nest which is usually placed 2–38 m (6.6–124.7 ft) above the ground, on a horizontal branch. Nests usually constructed outwardly with twigs, bark, plant fibers, and rootlets; lined with lichens, mosses, fine grasses, hair, dead pine needles, and even occasionally such exotic substances as string, willow cotton, horsehair, and cattail down. Only the female broods and spends about 80% day actively brooding, with the male usually helping bring food to the nest. Among warblers, they are relatively rarely parasitized at the nest by brown-headed cowbirds, most likely due to the cowbirds lack of success in dense pine-dominated forests. Blue jays and American red squirrels have been verified to prey on nestlings and new fledglings, while a merlin was recorded killing a brooding adult female. Sharp-shinned hawks and Cooper’s hawks are likely, but not confirmed, predators of adult Blackburnian warblers.^[16] By far the greatest threat faced by this species is destruction of forest habitat, which some predict could cause the Blackburnian warbler to lose up more than 30% of its wintering or breeding habitat. However, currently this species continues to occur over a large range and can appear in stable numbers where habitat is appropriate.

The Blackburnian Warbler is a brilliantly colored Nearctic-Neotropical migrant and one of a group of Setophaga wood warblers that coexist during the breeding season in the northeastern coniferous forests of North America. Birds of this group are so similar structurally that early students of bird foraging and niche partitioning wondered how they coexisted. They are now known to separate ecologically by foraging areas (Macarthur 1958, Morse 1968a), the Blackburnian Warbler exploiting a treetop niche.

Although the Blackburnian Warbler is morphologically similar to many of its congeners that share these forests, it differs strikingly from them in coloration. Breeding males are characterized by blazing orange plumage over much of the anterior part of their body, a color not shared by other Setophaga species.

In common with some other Setophaga wood warblers, the range of the Blackburnian Warbler extends both to the northwest in Canada and to the southeast along the Appalachian Mountains. In the southern part of its breeding range, this species specializes on hemlock (Tsuga canadensis), although like the Black-throated Green Warbler (Setophaga virens) it sometimes inhabits deciduous forests as well. Throughout its breeding grounds, this insectivorous species appears to feed primarily on lepidopteran larvae, which it gleans from small branches high in trees. It nearly always builds its nest in conifers, on small limbs well out from the trunk.

Populations of this species are vulnerable owing to the loss of preferred winter forest habitat in northern South America, although Breeding Bird Survey data suggest that their numbers have been stable to moderately increasing in recent decades. The Blackburnian Warbler is a forest-interior species and numbers decline in forest fragments. Southerly populations breeding in eastern hemlock and Fraser fir are at risk as a result of wooly adelgids responsible for heavy mortality of these trees.

Some aspects of the Blackburnian Warbler’s breeding biology are relatively well known, including foraging (Macarthur 1958, Morse 1968a), population dynamics (Morse 1976b), interspecific interactions (Morse 1976a), habitat selection (Morse 1976b), and singing behavior (Morse 1967c). Some ecological studies have been performed on their wintering grounds in Colombia (Chipley 1980, Lerner and Stauffer 1998). Recent studies have focused on the effect of silvicultural practices on this and other species (e. g., Hagen et al. 1996, Meiklejohn and Hughes 1999, Hobson and Bayne 2000b, Cumming and Diamond 2002). However, information on many aspects of the species’ life cycle is rudimentary. Little is known of its migratory ecology. Many aspects of its breeding ecology remain largely or completely unknown, in part a consequence of its treetop existence in northern forests.