Variable Seedeater
Encyclopedia
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
.
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
.
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 wherever 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.
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 insect
s.
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.
Passerine
A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...
bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
which breeds from southern Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
through Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...
to the Chocó of north-western South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. The taxonomy is confusing, and it was formerly considered a subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
of Sporophila americana (see Taxonomy). Even within the Variable Seedeater as presently defined, there are great variations in its plumage
Plumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
.
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 CaribbeanCaribbeanThe Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...
slope from BelizeBelizeBelize is a constitutional monarchy and the northernmost country in Central America. Belize has a diverse society, comprising many cultures and languages. Even though Kriol and Spanish are spoken among the population, Belize is the only country in Central America where English is the official...
south to PanamaPanamaPanama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. The...
. Adult males are entirely black apart from a small white wing-speculumSpeculum feathersThe speculum is a patch, often distinctly coloured, on the inner remiges of some birds.Examples of the colour of the speculum in a number of ducks are:* Common Teal and Green-winged Teal: Iridescent green edged with buff....
and white wing linings. - S. c. hoffmannii: Pacific slope in Costa RicaCosta RicaCosta Rica , officially the Republic of Costa Rica is a multilingual, multiethnic and multicultural country in Central America, bordered by Nicaragua to the north, Panama to the southeast, the Pacific Ocean to the west and the Caribbean Sea to the east....
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 ColombiaColombiaColombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...
. 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 EcuadorEcuadorEcuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...
, and far north-western PeruPeruPeru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
. 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
Juvenile (organism)
A juvenile is an individual organism that has not yet reached its adult form, sexual maturity or size. Juveniles sometimes look very different from the adult form, particularly in terms of their colour...
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
Melanism
Melanism is an undue development of dark-colored pigment in the skin or its appendages, and the opposite of albinism. It is also the medical term for black jaundice.The word is deduced from the , meaning black pigment....
male was reported from Reserva Buenaventura in El Oro Province
El Oro Province
El Oro province is the southernmost of Ecuador's coastal provinces. It was named for its historically important gold production. Today it is one of the world's major exporters of bananas. The capital is Machala.-Geography:To the north and east the province has borders with the provinces Guayas,...
, Ecuador
Ecuador
Ecuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...
, in 2005. The bird had increased phaeomelanin; its white areas — except those of the wings — were bright tawny chestnut
Chestnut (color)
Chestnut, also known as Indian red, is a color, a medium brownish shade of red, and is named after the nut of the chestnut tree.As Indian red, it is named after the red laterite soil found in India. It is thus an earth tone as well as a red. It is composed of naturally occurring iron oxides. Other...
. 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
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
: in the genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Sporophila
Sporophila
Sporophila is a genus of Neotropical birds in the Thraupidae family. The seed finches are sometimes also included in this genus.They are relatively small with stubby, conical bills adapted for feeding on seeds and alike...
and Oryzoborus
Oryzoborus
Oryzoborus is a genus of bird in the Thraupidae family. Sometimes classified in the bunting and American sparrow family Emberizidae, more recent studies have shown it to belong in the Thraupidae, and some have argued for merging it into Sporophila....
, 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
Reproductive isolation
The mechanisms of reproductive isolation or hybridization barriers are a collection of mechanisms, behaviors and physiological processes that prevent the members of two different species that cross or mate from producing offspring, or which ensure that any offspring that may be produced is not...
, but the plumage differences between such seedeater species pairs probably had their origin in such a mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
becoming fixed in a founder population due to genetic drift
Genetic drift
Genetic drift or allelic drift is the change in the frequency of a gene variant in a population due to random sampling.The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces...
.
Taxonomy
The taxonomyTaxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
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
Amazon Basin
The Amazon Basin is the part of South America drained by the Amazon River and its tributaries that drains an area of about , or roughly 40 percent of South America. The basin is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela...
) had the common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
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
Andes
The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...
had actually been considered separate species until they were merged into a single species by Meyer de Schauensee
Rodolphe Meyer de Schauensee
Rodolphe Meyer de Schauensee was an American ornithologist.He was born in Rome, and his family moved to the United States in 1913. He was curator of birds at the Academy of Natural Sciences in Philadelphia for nearly fifty years. He was particularly noted for his study of South American birds...
in 1952.
Charles Lucien Bonaparte
Charles Lucien Jules Laurent Bonaparte, 2nd Prince of Canino and Musignano was a French naturalist and ornithologist.-Biography:...
, 1850) predates S. corvina by 10 years, and was widely believed to be the correct scientific name. However, the type
Biological type
In biology, a type is one particular specimen of an organism to which the scientific name of that organism is formally attached...
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
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
"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 wherever 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
Cline (population genetics)
In biology, an ecocline or simply cline describes an ecotone in which a series of biocommunities display continuous gradient...
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 seedeaterSeedeater
The seedeaters are a form taxon of seed-eating passerine birds with a distinctively conical bill.Most are Central and South American birds that were formerly placed in the American sparrow family , but are now known to be tanagers closely related to Darwins finches...
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 insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s.
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.
External links
- Variable Seedeater videos - Internet Bird Collection
- Photo gallery - Mangoverde.
- Photo gallery (OBS: Also includes a Wing-barred SeedeaterWing-barred SeedeaterThe Wing-barred Seedeater is a passerine bird from coastal regions of north-eastern South America in north-eastern Venezuela, the Guianas, Amapá and north-eastern Pará , Brazil, and along the Amazon River upstream to around Manaus...
) - VIREO - Photo of male (listed as S. americana [sic]) - VIREO.
- Photo of male - STIVERphotos.
- Photo of female - STIVERphotos.