Snail kite

The snail kite (''Rostrhamus sociabilis'') is a bird of prey within the family Accipitridae, which also includes the eagles, hawks, and Old World vultures. Its relative, the slender-billed kite, is now again placed in ''Helicolestes'', making the genus ''Rostrhamus'' monotypic. Usually, it is placed in the milvine kites, but the validity of that grouping is under investigation.

Description

Snail kites are long with a wingspan. They weigh from . There is very limited sexual dimorphism, with the female averaging only 3% larger than the male. They have long, broad, and rounded wings, which measure each. Its tail is long, at , with a white rump and undertail coverts. The dark, deeply hooked beak, measuring is an adaptation to its diet. The tarsus is relatively long as well, measuring .

The adult male has dark blue-gray plumage with darker flight feathers. The legs and cere are red. The adult female has dark brown upperparts and heavily streaked pale underparts. She has a whitish face with darker areas behind and above the eye. The legs and cere are yellow or orange. The juvenile is similar to an adult female, but the crown is streaked. Adults have red or orangish-brown irises, while juveniles have dark brown irises.

It flies slowly with its head facing downwards, looking for its main food, the large apple snails. For this reason, it is considered a molluscivore.

Taxonomy

Lerner and Mindell (2005) found ''R. sociabilis'' sister to '' Geranospiza caerulescens'', and that those two along with '' Ictinea plumbea'' were basal to both the ''Buteogallus'' and ''Buteo'' clades. They concluded that ''Rostrhamus'' belonged in Buteoninae (sensu stricto) and not in Milvinae, but noted that more investigation was needed.

Distribution

The snail kite breeds in tropical South America, the Caribbean, and central and southern Florida in the United States. It is resident all-year in most of its range, but the southernmost population migrates north in winter and the Caribbean birds disperse widely outside the breeding season.

Breeding

It nests in a bush or on the ground, laying three to four eggs.

Conservation

The snail kite is a locally endangered species in the Florida Everglades, with a population of less than 400 breeding pairs. Research has demonstrated that water-level control in the Everglades is depleting the population of apple snails. However, this species is not generally threatened over its extensive range.

In fact, it might be locally increasing in numbers, such as in Central America. In El Salvador, it was first recorded in 1996. Since then, it has been regularly sighted, including immature birds, suggesting a resident breeding population might already exist in that country. On the other hand, most records are outside the breeding season, more indicative of post-breeding dispersal. In El Salvador, the species can be observed during the winter months at Embalse Cerrón Grande, Laguna El Jocotal, and especially Lago de Güija. '' Pomacea flagellata'' apple snails were propagated in El Salvador between 1982 and 1986 as food for fish stocks, and it seems that the widespread presence of high numbers of these snails has not gone unnoticed by the snail kite.

Diet

This is a gregarious bird of freshwater wetlands, forming large winter roosts. Its diet consists almost exclusively of apple snails, (especially the species '' Pomacea paludosa'' in Florida).

Snail kites have been observed eating other prey items in Florida, including crayfish in the genus '' Procambarus'', crabs, black crappie, small turtles and rodents. It is believed that snail kites turn to these alternatives only when apple snails become scarce, such as during drought, but further study is needed. On 14 May 2007, a birdwatcher photographed a snail kite feeding at a red swamp crayfish farm in Clarendon County, South Carolina.

The presence of the large introduced '' Pomacea maculata'' in Florida has led the snail kites in North America to develop larger bodies and beaks to better eat the snail, a case of rapid evolution. These non-native snails provide a better food source over the smaller native snails and has had a positive effect on their populations.

References

External links

Snail Kite Information
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Great Florida Birding & Wildlife Trail
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{{Taxonbar, from=Q839657

snail kite
snail kite
Birds of Cuba
Birds of El Salvador
Birds of Mexico
Birds of South America
Native birds of the Southeastern United States
Birds of the Yucatán Peninsula
Higher-level bird taxa restricted to the Neotropics
snail kite
snail kite