Vitelline warbler  (Dendroica vitellina)

The vitelline warbler is classified as Least Concern on the IUCN Red List (1). 

The vitelline warbler (Dendroica vitellina) is a rare songbird found only on the Cayman Islands and the Swan Islands in the western Caribbean. The taxonomy of this species has been the subject of some debate, as it is extremely similar in body size, plumage colour and facial markings to the prairie warbler (Dendroica discolor), a close relative (2). 

Like the prairie warbler, the vitelline warbler has olive-green upperparts and entirely yellow underparts, with some white on the tail, and middle wing-coverts which are broadly tipped with yellow (3) (4). There is also a yellow stripe above the eye that is bordered by a black stripe below. The key features in distinguishing the vitelline warbler from the prairie warbler are that the vitelline warbler lacks any chestnut on the back or streaking on the underparts, and its facial markings tend to be fainter (3). 

The female vitelline warbler is paler than the male, and the juvenile has very little yellow. The vitelline warbler may be further identified by its call, which is a wheezy “Zu-zu-zweee” or “Zu-zu-zwee-zu” (3).

With a total range of less than 270 square kilometres, the vitelline warbler is found only on the Cayman Islands and the Swan Islands in the western Caribbean (5). It is the only breeding passerine found on the Swan Islands (6). 

Three subspecies of the vitelline warbler are currently recognised. Dendroica vitellina vitellina is found on Grand Cayman, Dendroica vitellina crawfordi occurs on Cayman Brac and Little Cayman, and Dendroica vitellina nelsoni is found on the Swan Islands (5).

The vitelline warbler is most common in low scrubby woodland, but is also found in arid mixed woodland, clearings, coastal scrub and thickets, mangroves, and even urban areas (2) (5).

A little-studied species, there is very little information available on the biology or behaviour of the vitelline warbler. However, most warblers in the family Parulidae, also known as the New World warblers, feed largely on insects, with warblers of the genus Dendroica preferring caterpillars, particularly during the breeding season. New World warblers use a variety of foraging strategies to catch prey, often moving rapidly through the foliage of bushes or trees to glean insects off leaves and stems (7). 

During the breeding season, New World warblers tend to be fiercely territorial, with non-migratory species such as the vitelline warbler defending territories from other warblers all year round. Monogamous pairs are typically formed, but the female may mate with several males in a single breeding season. The female does most of the nest construction and incubation of the eggs, but both adults feed the nestlings and fledglings (7).

Although the vitelline warbler is thought to be fairly common, it has an extremely small range. Furthermore, only half of this area contains suitable habitat for this species. The vitelline warbler is therefore at risk from habitat degradation and loss, with proposed habitat conversion and land development threatening populations on the Cayman Islands (5). 

It is also vulnerable to the destructive effects of hurricanes, which are a frequent occurrence in the Caribbean region. Hurricanes can cause serious damage to habitats used by birds, such as by felling trees and destroying mangroves (2).

The vitelline warbler has not been the target of any known conservation measures. However, it is afforded a degree of protection in a number of reserves, including the Salina and Mastic Reserves in the Cayman Islands. As the vitelline warbler is in decline, future conservation measures for this species may include monitoring its numbers (5).

ARKive is supported by OTEP, a joint programme of funding from the UK FCO and DFID which provides support to address priority environmental issues in the Overseas Territories, and Defra

More information on conservation on the Cayman Islands:

• Cayman Islands National Trust:
  http://www.nationaltrust.org.ky/index.html

More information on the vitelline warbler and other bird species:

• BirdLife International:
  http://www.birdlife.org/datazone/speciesfactsheet.php?id=9116&m=0