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Icterus oberi

Montserrat Oriole

  • Order: Passeriformes
  • Family: Icteridae
  • Monotypic

Authors: Oppel, Steffen, Andrew Cassini, James Daley and Calvin Fenton

Identification

Summary

A slim oriole with a moderately-sized, triangular beak, unlikely to be confused with any other resident forest bird on Montserrat. Male is black with yellowish-orange underparts and rump, female is mostly olive green above and yellowish-green below. Juvenile is similar to female plumage but has a duller overall appearance. Song can be delivered by both sexes and consists of a series of loud, well-spaced whistles. Contact and alarm calls are harsh 'chuck' notes.

Similar Species

No similar species are resident on Montserrat. Casual vagrants include Orchard Oriole (Icterus spurius) and Baltimore Oriole (Icterus galbula), both of which can be distinguished by light colored wing bars along the margins of the median and greater coverts.

Vocalizations

Adapted from Jaramillo and Burke (1999):

Song is a loud series of melodious whistles, but slow and methodical. Single notes given are given every 2 - 3 seconds. Notes are composed of single syllables, or two syllables, usually short, sharp whistles or lower pitched gurgled whistles. One predominant note is a sharply descending whistled 'tseew'. Song mostly heard during breeding season, but does not sing consistently at high rate. Both sexes can produce song.

Call is similar to other orioles, a harsh and sharp chic or chuck note, often repeated incessantly when bird is alarmed. The call is the easiest way to detect the presence of this species.

Additional audio recordings of vocalizations of Montserrat Oriole can be heard at xeno-canto.

Nonvocal Sounds

No nonvocal sounds are known from this species.

Detailed Description (appearance)

The male Montserrat Oriole has a full black hood, with black eye and silver-black bill. The black reaches to the middle of the breast, leaving the appearance of a small yellow spur near the wing. The wings are all black with no wing bars and the tail is all black as well. The belly, flanks and rump are rich yellowish-orange. The legs are blackish gray. The female Montserrat Oriole has an overall greenish olive drab appearance. The head has a greenish yellow appearance, with the back and tail being more green. The wings are greenish brown with a yellow leading edge. The belly, flanks, breast and throat are a uniform greenish yellow. Juveniles are very similar to females, but have an overall duller appearance. Young males will begin to transition to adult plumage and can show prominent patches of black feathers around the eyes and face.

Bare Parts

Iris: black

Bill: silvery black

Measurements

The following measurements are averages from data collected by A. Cassini using consistent morphometric measurements in 2011 and 2012. In parentheses are mean, minimum, and maximum measurements reported by Garrido et al. (2005). Note that differences in tarsus measurements are most likely due to different measuring techniques.

MALE (n = 37 individuals):
Tail length: 97.1 mm (96.1; range 92.4-99.8) ; bill length: 21.9 mm (22.1; range 20.5-24.2); wing chord: 91.0 mm (91.5; range 87.1-94.0); tarsus length: 22.0 mm (25.8; range 24.9-26.4); body mass: 36.6 g 38.0, range 36.0-39.0).

FEMALE (n = 11 individuals):
Tail length: 94.1 mm (94.0, range 84.2-95.0); bill length: 20.6 mm (20.6, range 19.5-25.3); wing chord: 83.9 mm (81.7, range 75.1-85.3); tarsus length: 20.9 mm (24.3, range 22.0-27.2); body mass: 33.6 g (33.7, range 31.5-35.4).

JUVENILE (n = 25 individuals of both sexes):
Tail length: 94.8 mm; bill length: 20.9 mm; wing chord: 84.1 mm; tarsus length: 20.9 mm; body mass: 34.3 g.

Molts

No detailed information on molt is available for this species.

Geographic Variation

Monotypic. The species is endemic to a single island, where two small sub-populations exist, that have been separated by 5 km of inhospitable habitat since 1997. Prior to the volcanic eruption, the population inhabited contiguous forest, and it is currently unknown whether the recently separated forest fragments are genetically isolated and whether geographic variation exists. No apparent plumage or call variation between the Centre and the South Soufriere Hills is known.

Systematics

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Recommended Citation

Oppel, Steffen, Andrew Cassini, James Daley and Calvin Fenton. 2012. Montserrat Oriole (Icterus oberi), Neotropical Birds Online (T. S. Schulenberg, Editor). Ithaca: Cornell Lab of Ornithology; retrieved from Neotropical Birds Online: http://neotropical.birds.cornell.edu/portal/species/overview?p_p_spp=673516