Mexican Jay
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 Mexican Jay from Texas,
Aphelocoma ultramarina couchii. Note unmarked throat. |
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| Aphelocoma ultramarina (Bonaparte, 1825) |
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The Mexican Jay, Aphelocoma ultramarina,[1] also known as the Gray-breasted Jay, is a New World scrub-jay native to the Sierra Madre Oriental and Sierra Madre Occidental mountains of Mexico, north to southeast Arizona, southwest New Mexico and westernmost Texas in the United States. Its preferred habitat is montane pine-oak forest in mountains.
It is a medium-large passerine similar in size to most other jays, with a blue head, blue-gray mantle, blue wings and tail, and pale gray breast and underparts. The sexes are similar, and juveniles differ only in the blue being grayer and less intense. The bill, eye and legs are black, except for juveniles, which may show a yellow base to the bill (see below). It is most readily distinguished from the similar Western Scrub-jay by the plain (unstreaked) throat and breast, and the mantle contrasting less with the head and wings. Its range somewhat overlaps with the inland Western Scrub-Jays. In the arid habitat in the north of the zone of overlap, individuals of both species are fairly washed-out-looking birds according to Gloger's Rule, but they seem to show ecological and morphological character displacement (Curry et al. 2002).
The Mexican Jay's diet consists mainly of acorns and pine nuts, which are stored in the autumn for use through the following winter and spring. Excess stored seeds often germinate, thus perpetuating the bird's preferred habitat. Other food includes a wide variety of plant and animal matter, the latter including invertebrates, small amphibians and reptiles, and birds' eggs and nestlings.
It has a cooperative breeding system similar to that of the related Florida Scrub Jay, with several birds helping at a nest; these 'helpers' are usually immature offspring of the dominant pair from the previous 1-2 years, but also include apparently unrelated flock members.
[edit] Systematics
The Mexican Jay represents an old isolate among the living Aphelocoma. As regards its relationship to the other species, nothing can be said with certainty beyond it being very distinct from all of them (Rice et al. 2003).
There are seven described subspecies that extend from the southern US into central Mexico. They are divided into three main groups. The northern populations occupy a continuous, U-shaped area throughout the highlands of the Sierra Madres Occidental and Oriental, and intergrade on the Mexican plateau. The southern range is throughout the Trans-Mexican volcanic belt. This forms a W-E line with apparently no significant gene flow between it and the U due to interspersed valley and lowland areas. The Eastern group also overlaps with the southeastern arm of the Western Scrub-jay's distribution. Southernmost individuals of this species ("Sumichrasti Jays") are recognizable by their crisply demarked coloration; they are found south of the volcanic belt (Rice et al. 2003). The situation situation in S Texas/NE Mexico birds is more complex.(Brown 1992, Madge & Burn 1992)
Color variation is not very pronounced and generally follows Gloger's Rule.
Southern group
Trans-Mexican volcanic belt of central Mexico. Juveniles have a yellow base to the beak. Adults are larger and longer-tailed but shorter-billed than those in the northern groups. Apparently geographically isolated and likely more differentiated, but localized taxa colimae and gracilis deserve further study.
- Aphelocoma ultramarina ultramarina Bonaparte, 1825
- Aphelocoma ultramarina colimae
- NW of ultramarina, but very local: west and central Jalisco to NE Colima
Western group
Sierra Madre Occidental to Arizona and New Mexico. Intergrades with Eastern group on the Mexican plateau (Guanajuato, Aguascalientes, and surroundings), limits in Jalisco deserve further study. Juveniles have a yellow base to the beak for up to two years. More complex social system and more cooperative breeding behaviour than the eastern races.
- Aphelocoma ultramarina gracilis
- E Nayarit and N Jalisco
- Small
- Aphelocoma ultramarina wollweberi
- W Mexico
- Intermediate
- Aphelocoma ultramarina arizonae
- NW Mexico north to Arizona and New Mexico, USA
- Large. Uniformly pale green eggs without speckles.
Eastern group
Sierra Madre Oriental north to Texas. Intergrades with Western group as described above, does not contact Southern group. Juveniles have an all-black beak. Apparently, both are territorial and generally monogamous.
- Aphelocoma ultramarina potosina
- East-central Mexico
- Larger
- Aphelocoma ultramarina couchii
- S Nuevo León and W Tamaulipas north to SW Texas (Chisos Mountains)
- Smaller than preceding. Much similar to Western Scrub-jay. Population of latter species distinguishable by more contrasting markings and ecological preferences (lowland birds). Egg color may range from plain blue to nile blue with pale brownish speckling, most heavy on blunt half. Gives rattle call, apparently in territorial defence, similar to Cyanocitta and Western Scrub-jays.
mtDNA NADH dehydrogenase subunit 2 sequence data (Rice et al. 2003) of a 2 specimens each of ultramarina, wollweberi, and potosina indicated gene flow between the latter two, with the first being more isolated, as per the biogeographical expectations.
[edit] References
- BirdLife International (2004). Aphelocoma ultramarina. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 09 May 2006. Database entry includes justification for why this species is of least concern
- Brown, J.L. (1994): Mexican Jay (Aphelocoma ultramarina). In: Poole, A. & Gill, F. (eds.): The Birds of North America 118. Academy of Natural Sciences, Philadelphia, PA & American Ornithologists' Union, Washington, D.C. Online version, retrieved 2007-FEB-25. DOI:10.2173/bna.118 (requires subscription)
- Curry, Robert L.; Peterson, A. Townsend & Langen, T.A. (2002): Western Scrub-Jay (Aphelocoma californica). In: Poole, A. & Gill, F. (eds.): The Birds of North America 712. Academy of Natural Sciences, Philadelphia, PA & American Ornithologists' Union, Washington, D.C. Online version, retrieved 2007-FEB-25. DOI:10.2173/bna.712 (requires subscription)
- Madge, Steve & Burn, Hilary (1994): Crows and jays: a guide to the crows, jays and magpies of the world. A&C Black, London. ISBN 0-7136-3999-7
- Pitelka, Frank A. (1951): Speciation and ecological distribution in American jays of the genus Aphelocoma. University of California Publications in Zoology 50: 195-464.
- Rice, Nathan H.; Martínez-Meyer, Enrique & Peterson, A. Townsend (2003): Ecological niche differentiation in the Aphelocoma jays: a phylogenetic perspective. Biol. J. Linn. Soc. 80(3): 369–383. DOI:10.1046/j.1095-8312.2003.00242.x PDF fulltext
[edit] Footnotes
- ^ Etymology: Aphelocoma, from Latinized Ancient Greek aphelo-, "soft" (Ancient Greek: apalos, απαλός) + Latin coma "hair", in reference to the smooth plumage of birds of this genus compared to other corvids. ultramarina, New Latin: "colored ultramarine blue".
