Northern parula

The northern parula (Setophaga americana) is a small New World warbler. It breeds in eastern North America from southern Canada to Florida.

Description
The northern parula is one of the smaller North American migratory warblers, often being one of the smallest birds in a mixed feeding flock besides kinglets or gnatcatchers. Length is 10.8 to 12.4 cm, wingspan is 16 to 18 cm and body mass is 5 to 11 g. Among standard measurements, the wing chord is 5.1 to 6.5 cm, the tail is 3.7 to 4.5 cm, the bill is 0.8 to 1.1 cm and the tarsus is 1.5 to 1.8 cm. This species has mainly blue-gray upper parts, with a greenish back patch and two white wing bars. The breast is yellowish shading into the white belly. The summer male has bluish and rufous breast bands and prominent white eye crescents. At the end of the breeding season, individuals molt into a duller version of the breeding plumage. Females are similar-looking but tend to be duller and lack the breast bands. The unique breastband fades in males and may disappear altogether in females.

Its song is a click-like trill or buzz, zeeeeee-yip and the call is a soft chip.

Etymology
"Parula" ultimately derives from Latin parrula, Tit (bird). The genus name Setophaga is from Ancient Greek ses, "moth", and phagos, "eating", and the specific americana is Latin for "American".

Distribution
This species is migratory, wintering in southern Florida, northern Central America, the West Indies and most of the Lesser Antilles. This species is a very rare vagrant to western Europe.

While the species is still common as a breeder across most of eastern North America, there are conspicuous gaps in their breeding range that were likely once breeding grounds. They have been extirpated as a breeder from much of the Midwest as well as from many areas in Massachusetts, New Jersey, Connecticut, New York, Rhode Island and Vermont. Explanations for the disappearance may be changes in habitat or increasing air pollution, which limited the growth of epiphytes on trees that the warbler depended on for nesting. A further explanation is the clear-cutting and bog draining that have significantly reduced the amount of suitable habitat in eastern North America.

Habitat
The northern parula inhabits various habitats depending on season and location. This is primarily a forest-dwelling species, but the northern and southern breeding populations select different habitats. In general, abundance of this species has been found to be positively correlated with increased tree species diversity, canopy height, and percent canopy cover. Northern populations breed in mature, moist coniferous forests. This species constructs its pendulum nests in hanging vegetation and so it is often attracted to suspended clumps of moss or coniferous twigs that are more abundant in moist spruce bogs or hemlock swamps. Southern populations breed in mature, moist, bottomland forest where Spanish moss is prevalent. Outside of the breeding season, the northern parula becomes more of a habitat generalist and may be found in a wide variety of habitats during migration and winter. These habitats may include: pastures; moist, dry or wet forests; and agricultural fields or plantations.

Ecology
The northern parula is considered a monogamous species; however, a few cases of polygamy have been reported. Southern populations can start breeding as soon as March but in the north of the range, the species does not nest until May. The breeding habitat is humid woodland with growths of Old Man's Beard lichen or Spanish moss. Northern parulas nest in trees in clumps of these fungi (Old Man's Beard; Usnea) or plants (Spanish moss; Tillandsia usneoides), laying 3–7 eggs in a scantily lined cup nest. Sites located near water sources are preferred and many nests are found at the end of branches suspended over water. Due to their longer breeding season, southern parulas frequently raise two broods, as opposed to northern ones who raise only one. The female hollows out a clump of vegetation in the moss and proceeds to fill the cavity with vegetation fibers, animal hair, grass, or pine needles. These nests average 7 cm in outside diameter. The incubation period typically lasts 12-14 days and the young fledge at 10-11 days. Breeding maturity is attained the following year.

The northern parula forages mostly or entirely on terrestrial invertebrates. Prey items include spiders, damselflies, locusts, bugs, grasshoppers, aphids, beetles, caterpillars, flies, wasps, bees, and ants. Regardless of season, caterpillars and spiders are consumed most often. During the winter, the northern parula consumes more beetles and occasionally forages on berries, seeds, and nectar. This species primarily captures prey from vegetation by a hover-glean method, however this species is versatile in using a variety of foraging methods. It may make short flights from a perch to snatch prey in mid-flight or even hang upside-down to forage. It is most often seen foraging in the mid- to upper canopy levels of vegetation. Though most foraging activity occurs in arboreal vegetation, this species occasionally forages on or around the ground as well.

A northern parula from Augusta, Georgia was found to be a host of an intestinal acanthocephalan worm, Apororhynchus amphistomi.

Northern parulas will occasionally hybridize with yellow-throated warblers, resulting in a hybrid species known as Sutton's warblers.

Thesis

 * Baltz ME. Ph.D. (2000). The nonbreeding season ecology of neotropical migratory birds in the dry zone of Puerto Rico. University of Missouri - Columbia, United States, Missouri.
 * Barrow WC, Jr. Ph.D. (1990). Ecology of small insectivorous birds in a bottomland hardwood forest. Louisiana State University and Agricultural & Mechanical College, United States, Louisiana.
 * Moorman CE. Ph.D. (1999). Relationships between artificially created gaps and breeding birds in a southeastern bottomland forest. Clemson University, United States, South Carolina.

Articles
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 * Bay MD. (1999). A review of the behavior and ecology of the Northern Parula (Parula americana) with notes from Oklahoma and Texas. Proceedings of the Oklahoma Academy of Science. vol 79, p. 33-40.
 * Bay MD. (1999). The type B song of the Northern Parula: Structure and geographic variation along proposed sub-species boundaries. Wilson Bulletin. vol 111, no 4. p. 505-514.
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 * Conner RN & Dickson JG. (1997). Relationships between bird communities and forest age, structure, species composition and fragmentation in the West Gulf Coastal Plain. Texas Journal of Science. vol 49, no 3 SUPPL. p. 123-138.
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 * Moorman CE & Guynn DC, Jr. (2001). Effects of group-selection opening size on breeding bird habitat use in a bottomland forest. Ecological Applications. vol 11, no 6. p. 1680-1691.
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 * Morse DH. (1989). Song Patterns of Warblers at Dawn and Dusk. Wilson Bulletin. vol 101, no 1. p. 26-35.
 * Pashley DN. (1988). Warblers of the West Indies Ii. the Western Caribbean. Caribbean Journal of Science. vol 24, no 3-4. p. 112-126.
 * Pashley DN & Hamilton RB. (1990). Warblers of the West Indies Iii. the Lesser Antilles. Caribbean Journal of Science. vol 26, no 3-4. p. 75-97.
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 * Ports MA. (1981). Miscellaneous Summer Records of Birds from Southwestern Kansas USA. Transactions of the Kansas Academy of Science. vol 84, no 2. p. 109-114.
 * Regelski DJ & Moldenhauer RR. (1996). Discrimination between regional song forms in the Northern Parula. Wilson Bulletin. vol 108, no 2. p. 335-341.
 * Staicer CA. (1992). Social Behavior of the Northern Parula Cape May Warbler and Prairie Warbler Wintering in Second-Growth Forest in Southwestern Puerto Rico. In Hagan, J M Iii and D W Johnston (Ed) Ecology and Conservation of Neotropical Migrant Landbirds; Symposium, Woods Hole, Massachusetts, USA, December 6-9, 1989 Xiii+609p Smithsonian Institution Press: Washington, DC, USA; London, England, Uk Illus Maps 308-320, 1992.
 * Torres AR & Leberg PL. (1996). Initial changes in habitat and abundance of cavity-nesting birds and the Northern Parula following Hurricane Andrew. Condor. vol 98, no 3. p. 483-490.