| Snail kite | |
|---|---|
 | |
| Adult male | |
_female.jpg) | |
| Adult female, Panama | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Accipitriformes |
| Family: | Accipitridae |
| Subfamily: | Buteoninae |
| Genus: | Rostrhamus Lesson, 1830 |
| Species: | R. sociabilis |
| Binomial name | |
| Rostrhamus sociabilis (Vieillot, 1817) | |
| Subspecies[2] | |
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| Range ofR. sociabilis All-year resident Breeding only range Area of breeding and vagrancy | |
Thesnail kite (Rostrhamus sociabilis) is abird of prey within the familyAccipitridae, which also includes theeagles,hawks, andOld World vultures. Its relative, theslender-billed kite, is now again placed inHelicolestes, making thegenusRostrhamusmonotypic. Usually, it is placed in theMilvine kites, but the validity of that grouping is under investigation.
Snail kites are 36 to 48 cm (14 to 19 in) long with a 99–120 cm (39–47 in) wingspan. They weigh from 300 to 570 g (11 to 20 oz).[3][4] 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 29–33 cm (11–13 in) each. Its tail is long, at 16–21 cm (6.3–8.3 in), with a white rump and undertail coverts. The dark, deeply hooked beak, measuring 2.9–4 cm (1.1–1.6 in) is an adaptation to its diet. Thetarsus is relatively long as well, measuring 3.6–5.7 cm (1.4–2.2 in).[4]
The adult male has dark blue-grayplumage with darkerflight feathers. The legs andcere 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.[5]
It flies slowly with its head facing downwards, looking for its main food, the largeapple snails. For this reason, it is considered amolluscivore.
Lerner and Mindell (2005) foundR. sociabilis sister toGeranospiza caerulescens, and that those two along withIctinea plumbea were basal to both theButeogallus andButeo clades. They concluded thatRostrhamus belonged inButeoninae (sensu stricto) and not inMilvinae, but noted that more investigation was needed.[6]
The snail kite breeds in tropicalSouth America, theCaribbean, and central and southernFlorida in theUnited States. It is resident all-year round in most of its range, but the southernmost population migrates north in winter and the Caribbean birds disperse widely outside the breeding season.
It nests in abush or on the ground, laying three to foureggs.
The snail kite is a locally endangered species in the FloridaEverglades, with a population of less than 400 breeding pairs. Research has demonstrated thatwater-level control in the Everglades is depleting the population of apple snails.[7] However, thisspecies is not generally threatened over its extensive range.
In fact, it might be locally increasing in numbers, such as inCentral America. InEl 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 atEmbalse Cerrón Grande, Laguna El Jocotal, and especiallyLago 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.[8]
Due to thedrainage and habitat destruction of the Everglades, they were one of the first species put on theUS Fish and Wildlife Service'sendangered species list[9] on 11 March 1967.[10] The snail kite continued to decline, reaching a population of less than 800 in 2007. One factor for the decline in the 2000s was the introduction of the invasiveSouth American snailPomacea maculata, which were five times bigger than the nativePomacea paludosa species, and most kites could not eat the new snails.[11] However, the kites quicklyevolved to be 12% bigger toadapt to the new food source.[12][13] This population gradually rebounded, reaching a count of 3,000 snail kites in 2022. Everglades conservation efforts over the course of 30 years and costing over US$20 billion also contributed to restoring native vegetation of the snail kites' habitats and flow of water in marshes.[9]
This is a gregarious bird of freshwaterwetlands, forming large winter roosts. Its diet consists almost exclusively ofapple snails, especially the speciesPomacea diffusa,P. maculata andP. paludosa in Florida, other species ofPomacea (P. doliodes) elsewhere in its range, and species of the genusMarisa (M. cornuarietis).[14][15][16]
Snail kites have been observed eating other prey items in Florida, including otherfreshwater snail species (such as thebanded mystery snail),crayfish in the genusProcambarus,crabs in the generaDilocarcinus andPoppiana (P. dentata),black crappie,ring-necked snakes, smallturtles (including thecommon musk turtle,striped mud turtle,coastal plain cooter,Florida red-bellied cooter,Florida softshell turtle, and other unidentified species),rodents andcarcasses (based only on a single reported case of a deadAmerican coot).[17][15][14][18] It is believed that snail kites turn to these alternatives only when apple snails become scarce, such as during drought,[19] but further study is needed. On 14 May 2007, abirder photographed a snail kite feeding at ared swamp crayfish farm inClarendon County, South Carolina.[20][21]
The presence of the largeintroducedPomacea 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 rapidevolution.[22] These non-native snails provide a better food source than the smaller native snails and have had a positive effect on the kites' populations.[23]
In Florida, snail kites may be eaten by some growth stage of invasive snakes such asBurmese pythons,reticulated pythons,Southern African rock pythons,Central African rock pythons,boa constrictors,yellow anacondas,Bolivian anacondas,dark-spotted anacondas, andgreen anacondas.[24]
Media related toRostrhamus sociabilis at Wikimedia Commons
Data related toRostrhamus sociabilis at Wikispecies
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