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The masked yellowthroat (''Geothlypis aequinoctialis'') is a New World warbler. It has a number of separate resident breeding populations in Central and South America, some of which may be considered to form separate species. The breeding habitat is marshes and other wet areas with dense low vegetation. The masked yellowthroat may also be found in other areas with dense shrub, but is less common in drier habitats. Two white eggs with reddish-brown markings are laid in a lined cup nest low in grass or rank vegetation. The masked yellowthroat is 13.2 cm long and weighs 13 g. It has yellow-green upperparts, bright yellow underparts, and a mainly black bill. The adult male has a black facemask, bordered above with a gray band. The female is similar, but lacks the black mask. She is slightly duller, has variable amounts of gray to the head (often virtually none), a yellowish eye ring and a yellowish stripe from the bill to the eye. There are significant racial variations in the male plumage (''see Taxonomy''). This species is easily distinguished from wintering common yellowthroat by its uniform yellow underparts, whereas the North American bird has a white belly. The masked yellowthroat is usually seen in pairs, and does not associate with other species. It is often skulking, but may pop up occasionally, especially to sing. It feeds on insects, including caterpillars, which are usually captured in dense vegetation. The call is a fast chattering, quite unlike that of other yellowthroat species, and a more typical sharp ''chip''. This species may be spreading in Central America due to deforestation. ==Taxonomy== There are five subspecies of the masked yellowthroat, differing in size, male head pattern and song. The Central American subspecies is sometimes considered a separate species, and the two Pacific subspecies together are also often treated as a species. Recent genetic evidence suggests that the southern South American subspecies may also merit specific status. The populations are as follows: *The nominate race, ''G. a. aequinoctialis'', described above, breeds from central Colombia, through northern Venezuela, Trinidad, the Guianas, to the regions near the Amazon River in Brazil. The song is a warbled ''tee-chee-chee teecheweet teecheweet''. *''G. (a). velata'', southern yellowthroat, breeds in central South America from south-eastern Peru and adjacent parts of Brazil, through Bolivia, Paraguay, Uruguay and southern Brazil, to central Argentina. It is slightly smaller than ''aequinoctialis'', and the male has a narrower black mask, with a broader gray band which extends onto the nape and neck sides. The song is longer, faster and more warbled than that of the northern race. *''G. (a). auriculata'' and ''G. a. peruviana'', black-lored yellowthroat, breeds in western Ecuador and western Peru. The male has the black mask restricted to the area from the bill back to the eye and a narrow band on the forehead. The subspecies ''peruviana'', which is found in the Marañón valley, is similar in size to ''aequinoctialis'', but ''auriculata'' is noticeably smaller. The song of is a cheerful ''wee wee wee weeyou weeyou''. *''G. (a). chiriquensis'', Chiriqui yellowthroat, occurs in western Panama and Costa Rica. It is another small form, but the male has the broadest black mask of all the races, extending on to the forecrown. The song is similar to ''auriculata'', but repeated many times, becoming faster, higher and weaker before a final flourish, and it may be given in flight. It is likely that the range of this species was once continuous, perhaps in the cooler conditions of the last ice age, but the populations are now separated by the dense sections of wet lowland forests of the Amazon and Chocó. The ''auriculata'' and ''chiriquensis'' groups are further separated from the nominate and ''velata'' groups by the Andes Mountains. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Masked yellowthroat」の詳細全文を読む スポンサード リンク
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