Giant Cowbird
Encyclopedia
The Giant Cowbird, Molothrus oryzivorus, is a large passerine
bird
in the New World
family Icteridae. It breeds from southern Mexico
south to northern Argentina
, and on Trinidad
and Tobago
. It may have relatively recently colonised the latter island.
It is associated with open woodland and cultivation with large trees, but is also the only cowbird
that is found in deep forest. It is a quiet bird, particularly for an icterid, but the male has an unpleasant screeched whistle, shweeaa-tpic-tpic. The call is a sharp chek-chik. They are also very adept mimics.
Like other cowbirds, it is a brood parasite
, laying its eggs in the nests of oropendola
s and caciques
. The eggs are of two types, either whitish and unspotted, or pale blue or green with dark spots and blotches. The host’s eggs and chicks are not destroyed, but there is considerable doubt about the theory that the young Giant Cowbirds benefit the host’s chick by removing and eating parasitic flies.
Their icterid hosts breed colonially, and defend their nests vigorously, so even a large, bold and aggressive species like the Giant Cowbird has to cover an extensive territory to find sufficient egg-laying opportunities. Several Giant Cowbird eggs may be laid in one host nest.
The male Giant Cowbird is 36 cm (14.2 in) long, weighs 180 g (6.3 oz) and is iridescent black, with a long tail, long bill, small head, and a neck ruff which is expanded in display. The female is smaller, averaging 28 cm (11 in) long and weighing 135 g (4.8 oz). She is less iridescent than the male, and the absence of the neck ruff makes her look less small-headed. Juvenile males are similar to the adult male, but browner, and with a pale, not black, bill.
This gregarious bird feeds mainly on insect
s, and some seeds, including rice
, and forages on the ground or in trees. It rarely perches on cattle
, unlike some of its relatives, but in Brazil
it will ride on Capybara
s as it removes horse flies
.
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...
in the New World
New World
The New World is one of the names used for the Western Hemisphere, specifically America and sometimes Oceania . The term originated in the late 15th century, when America had been recently discovered by European explorers, expanding the geographical horizon of the people of the European middle...
family Icteridae. It 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...
south to northern Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
, and on Trinidad
Trinidad
Trinidad is the larger and more populous of the two major islands and numerous landforms which make up the island nation of Trinidad and Tobago. It is the southernmost island in the Caribbean and lies just off the northeastern coast of Venezuela. With an area of it is also the fifth largest in...
and Tobago
Tobago
Tobago is the smaller of the two main islands that make up the Republic of Trinidad and Tobago. It is located in the southern Caribbean, northeast of the island of Trinidad and southeast of Grenada. The island lies outside the hurricane belt...
. It may have relatively recently colonised the latter island.
It is associated with open woodland and cultivation with large trees, but is also the only cowbird
Cowbird
Cowbirds are birds belonging to the genus Molothrus in the family Icteridae. They are brood parasitic New World birds which are unrelated to the Old World cuckoos, one of which, the Common Cuckoo, is the best-known brood parasitic bird....
that is found in deep forest. It is a quiet bird, particularly for an icterid, but the male has an unpleasant screeched whistle, shweeaa-tpic-tpic. The call is a sharp chek-chik. They are also very adept mimics.
Like other cowbirds, it is a brood parasite
Brood parasite
Brood parasites are organisms that use the strategy of brood parasitism, a kind of kleptoparasitism found among birds, fish or insects, involving the manipulation and use of host individuals either of the same or different species to raise the young of the brood-parasite...
, laying its eggs in the nests of oropendola
Oropendola
The oropendolas comprise two or three genera of South and Central American passerine birds in the New World blackbird family.All the oropendolas are large birds with pointed bills, and long tails which are always at least partially bright yellow...
s and caciques
Cacique (bird)
The caciques are passerine birds in the New World blackbird family. Members of the family are resident breeders in tropical South America and north to Mexico. All of the group are in the genus Cacicus, except the aberrant Yellow-billed Cacique , which constitutes a monotypic genus...
. The eggs are of two types, either whitish and unspotted, or pale blue or green with dark spots and blotches. The host’s eggs and chicks are not destroyed, but there is considerable doubt about the theory that the young Giant Cowbirds benefit the host’s chick by removing and eating parasitic flies.
Their icterid hosts breed colonially, and defend their nests vigorously, so even a large, bold and aggressive species like the Giant Cowbird has to cover an extensive territory to find sufficient egg-laying opportunities. Several Giant Cowbird eggs may be laid in one host nest.
The male Giant Cowbird is 36 cm (14.2 in) long, weighs 180 g (6.3 oz) and is iridescent black, with a long tail, long bill, small head, and a neck ruff which is expanded in display. The female is smaller, averaging 28 cm (11 in) long and weighing 135 g (4.8 oz). She is less iridescent than the male, and the absence of the neck ruff makes her look less small-headed. Juvenile males are similar to the adult male, but browner, and with a pale, not black, bill.
This gregarious bird feeds mainly on 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, and some seeds, including rice
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...
, and forages on the ground or in trees. It rarely perches on cattle
Cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
, unlike some of its relatives, but in Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
it will ride on Capybara
Capybara
The capybara , also known as capivara in Portuguese, and capibara, chigüire in Venezuela, Colombia, and Ecuador ronsoco in Peru, chigüiro, and carpincho in Spanish, is the largest living rodent in the world. Its closest relatives are agouti, chinchillas, coyphillas, and guinea pigs...
s as it removes horse flies
Horse-fly
Insects in the order Diptera, family Tabanidae, are commonly called horse flies. Often considered pests for the bites that many inflict, they are among the world's largest true flies. They are known to be extremely noisy during flight. They are also important pollinators of flowers, especially in...
.
External links
- Giant Cowbird videos on the Internet Bird Collection
- Stamps (for MexicoMexicoThe 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...
) with RangeMap - Giant Cowbird photo gallery VIREO Photo-High Res
- Photo; Article geometer–"Brazil Birds"
