Variable Seedeater

Taxobox
name = Variable Seedeater

---

image_width = 240px
image_caption = A male from near Panama City, Panama.
status = LC
status_system = iucn3.1
regnum = Animalia
phylum = Chordata
classis = Aves
ordo = Passeriformes
familia = Thraupidae
genus = "Sporophila"
species = "S. corvina "
binomial = "Sporophila corvina"
binomial_authority = (Sclater, 1860)
synonyms ="Sporophila aurita"
"Sporophila americana aurita"
"Sporophila americana corvina"

The Variable Seedeater, "Sporophila corvina", is a passerine bird which breeds from southern Mexico through Central America to the Chocó of north-western South America. The taxonomy is confusing, and it was formerly considered a subspecies of "Sporophila americana" ("see Taxonomy"). Even within the Variable Seedeater as presently defined, there are great variations in its plumage.

Description

The Variable Seedeater is a small, robust bird with a black conical bill. It is 10.5 cm (4 in) long and weighs 11 g (0.4 oz). There are four subspecies, which differ primarily in the plumage of the male:

* "S. c. corvina" (nominate): Found from southern Mexico and along the Caribbean slope from Belize south to Panama. Adult males are entirely black apart from a small white wing-speculum and white wing linings.
* "S. c. hoffmannii": Pacific slope in Costa Rica and Panama. Males resemble males "S. c. corvina", but with white half-collar, rump and belly (the rump often intermixed with grey and the flanks retain some black mottling or barring).
* "S. c. hicksii": Eastern Panama and adjacent north-western Colombia. Males resemble "S. c. hoffmannii", but, except for a small black chin and/or malar, the entire throat is white.
* "S. c. ophthalmica": South-western Colombia, western Ecuador, and far north-western Peru. Males are very similar to males of "S. c. hicksii", but black malar very fine or lacking, rump purer white, and show purer white flanks with little or no black mottling/barring.

Previously, additional subspecies have been recognized for the various hybrid populations found where the above mentioned subspecies meet ("see Taxonomy").

Females are olive-brown above, paler below, and have white wing linings like the male. The racial differences in the female plumages are minor, with "S. c. hoffmannii", "S. c. hicksii" and "S. c. ophthalmica" generally being paler and less brown than "S. c. corvina", and often with a faint yellow tinge below. Juveniles are like the adult female of their subspecies. Males may not acquire the full adult plumage in their first year, and may breed whilst still showing some immature features in their appearance.

A hypermelanic male was reported from Reserva Buenaventura in El Oro Province, Ecuador, in 2005. The bird had increased phaeomelanin; its white areas — except those of the wings — were bright tawny chestnut. A similar bird was collected along the "Pipeline Road" near Gamboa, Panama, in 1963. Such individuals seem to provide a glimpse at the circumstances of speciation: in the genera "Sporophila" and "Oryzoborus", several species exist which differ externally only by one having white areas, the other being hypermelanic just as the two Variable Seedeaters mentioned here. Of course, there must be some factor maintaining reproductive isolation, but the plumage differences between such seedeater species pairs probably had their origin in such a mutation becoming fixed in a founder population due to genetic drift. [Hosner & Lebbin (2006)]

Taxonomy

The taxonomy is highly confusing. "Sporophila corvina" was formerly considered a subspecies of "Sporophila americana" from north-eastern South America, in which case the combined species (also incl. "S. murallae" from western Amazonia) had the common name Variable Seedeater. They were split based mainly on the work by Stiles (1996), but the taxa east ("americana" group and "murallae") and west ("corvina" group) of the Andes had actually been considered separate species until they were merged into a single species by Meyer de Schauensee in 1952.

Following the split, additional confusion existed over the correct scientific name for present species. The name "Sporophila aurita" (Bonaparte, 1850) predates "S. corvina" by 10 years, and was widely believed to be the correct scientific name. However, the type for "S. aurita" has since disappeared and the original description was very vague, making it impossible to judge which population the name refers to. The name therefore becomes invalid, instead leading to "S. corvina" being the correct name.

Even after the split, the males of the remaining taxa have very different plumages, and the common name "Variable Seedeater" is fully deserved. The mainly black "S. c. corvina" has been considered a separate species, the Black Seedeater, from the remaining pied subspecies. As all subspecies hybridize freely whereever they meet, this is generally not recognized anymore. In large parts of Costa Rica and Panama it is impossible to clearly assign individuals to specific subspecies, where most instead show some level of intergradation between "S. c. corvina", "S. c. hoffmannii" and/or "S. c. hicksii". Some of these hybrid populations have in the past been recognized as separate subspecies, e.g. "semicollaris", "fortipes" and "collaris" from Panama alone.

Ecology

This seedeater is a common to abundant bird in lowlands and foothills up to 1,500 m altitude in semi-open areas such as forest edges, roadsides, low scrub and gardens. It also flocks with other species of seedeaters in pasture, weedy fields and other grassland.

This species feeds mainly on grass seeds, but also takes other seeds, berries and some insects.

The flimsy cup nest, built by the female, is made of coarse plant material and lined with a few finer fibres. It is placed in a tree 0.4 to 6 m up, occasionally higher, in the fork of a twig. The clutch is two or three brown-speckled pale grey eggs, which are incubated by the female alone for 12–14 days to hatching.

The Variable Seedeater has a harsh "chur" call. The male's song consists of a mixture of warbles, whistles, and twitters, and is more elaborate on the Pacific slope.

References

*|year=2004|id=61997|title=Sporophila corvina|downloaded=17 September 2007 Database entry includes justification for why this species is of least concern
* (2003): "Birds of Venezuela". Christopher Helm, London. ISBN 0-7136-6418-5
* (2006): Observations of plumage pigment aberrations of birds in Ecuador, including Ramphastidae. "Boletín de la Sociedad Antioqueña de Ornitología" 16(1): 30–42. [English with Spanish abstract] [http://www.sao.org.co/publicaciones/boletinsao/05Hosner&LebbinPlumage.pdf PDF fulltext]
* (1981): "The nature of variability in the Variable Seedeater of Panama (Sporophila americana; Emberizinae)." Proc. Biol. Soc. Wash. 94: 380–390.
* (2006). "Birds of Northern South America". Vol. 1 & 2. Helm, London. ISBN 0-7136-7242-0 (vol. 1); ISBN 0-7136-7243-9 (vol. 2).
* (2001). "The Birds of Ecuador - Field Guide". Cornell University Press. ISBN 0-8014-8721-8
* (1996): "When black plus white equals gray: The Nature of variation in the Variable Seedeater complex (Emberizinae: Sporophila)." Ornitologia Neotropical 7 (2): 75–107.
* (1989): "A guide to the birds of Costa Rica". Comistock, Ithaca. ISBN 0-8014-9600-4
* [http://www.museum.lsu.edu/~Remsen/SACCprop287.html Recognize four species of Sporophila within the Sporophila americana superspecies] – South American Classification Committee.

External links

* [http://ibc.hbw.com/ibc/phtml/especie.phtml?idEspecie=9421 Variable Seedeater videos] - Internet Bird Collection
* [http://mangoverde.com/birdsound/spec/spec202-103.html Photo gallery] - Mangoverde.
* [http://vireo.acnatsci.org/search.html?Form=Search&SEARCHBY=Common&KEYWORDS=variable+seedeater&showwhat=images&AGE=All&SEX=All&ACT=All&Search=Search&VIEW=All&ORIENTATION=All&RESULTS=24 Photo gallery] (OBS: Also includes a Wing-barred Seedeater) - VIREO
* [http://vireo.acnatsci.org/species_image.php?species=Sporophila+americana Photo of male] (listed as "S. americana [sic] ") - VIREO.
* [http://www.ontfin.com/Birds/displayimage.php?album=1030&pos=2 Photo of male] - STIVERphotos.
* [http://www.ontfin.com/Birds/displayimage.php?album=1030&pos=0 Photo of female] - STIVERphotos.