Belding's Yellowthroat Geothlypis beldingi Scientific name definitions

The Belding’s Yellowthroat is a marsh-loving warbler endemic to the Baja California Peninsula in Mexico. It differs from the more northern Common Yellowthroat (Geothlypis trichas) in being extensively yellow below, and showing a yellow surround to the black mask instead of a white one. The Belding’s Yellowthroat is otherwise a typical yellowthroat, living in and breeding in fresh-water marsh. It takes Scirpus reeds or Typha cattail, and presumably only requires that emergent vegetation be thick and relatively tall. As it is found in a largely desert region of the world, its distribution is spotty and fragmented; this is a common species where the right habitat exists, but in world terms it is a relatively rare species. Quite curiously molecular work shows it to be reasonably distinct, but sister to the western populations of the Common Yellowthroat. In fact it is more closely related to the western Common Yellowthroat, than the western Common is to the eastern Common! This suggests that there may be a species level distinction between eastern and western Common Yellowthroats, or something equally interesting in the history of the Belding’s Yellowthroat. Molecular data, voice, and plumage all argue strongly that the Belding’s Yellowthroat is a good species. It is Endangered.

14 cm; 13·8–17·7 g. Male nominate race has black mask from forehead back through and below eye to side of neck, bordered above and at rear by broad yellow band; crown to nape and upperparts  olive, throat  and underparts  rich yellow; iris dark; bill black; legs dull pinkish. Differs from very similar G. trichas in larger size and longer, heavier bill, and yellow (not greyish) fore­crown band. Female lacks male's head pattern, has crown and ear-coverts olive, crown washed with warm brown, pale olive-yellow super­cilium (indistinct) and broken eyering; underparts paler than male's, often whitish on belly and washed olive-brown on flanks. Juvenile  has brownish-olive head and upperparts, obscure pale cinnamon wingbars on greater and median upperwing-coverts, and greyish-buff underparts. Race goldmani differs from nominate in having forecrown band greyish-white (not yellow), upperparts slightly greyer, underparts paler, especially on belly, which is yellowish-white.

Editor's Note: This article requires further editing work to merge existing content into the appropriate Subspecies sections. Please bear with us while this update takes place.

Editor's Note: Additional distribution information for this taxon can be found in the 'Subspecies' article above. In the future we will develop a range-wide distribution article.

Freshwater marshes  containing extensive reed  , cat-tail (Typha) or hard-stemmed bulrush (Schoenoplectus acutus), often along marshy river edges; may also occur in brackish coastal marshes and mangroves fringing coastal estuaries.

Little known. Feeds on insects and other invertebrates, foraging mainly by gleaning low in marsh vegetation.

Song transcribed as "wi te-wich-uh", similar to that of G. trichas but fuller, deeper and more powerful, sometimes with buzzy notes admixed, and phrasing slightly different. Usual call  a dry "djip", slightly fuller and deeper than that of G. trichas; also gives a dry rattle  .

VULNERABLE. Previously considered Critically Endangered. Restricted-range species: present in Baja California EBA. Global population no more than a few thousand at very most. Total area of occupied habitat very small; suitable habitat severely fragmented, and species recently extirpated from at least one site. In recent surveys, found to be present at a total of at least 26 sites. N race goldmani found at twelve localities, and appears to be common at most of these; total population last estimated to number 1100 individuals, but current total probably higher than that, e.g. estimated population 537–648 individuals at one locality (San Ignacio) in 2007; extent of suitable habitat, however, likely to be very small. Nominate race known from at least 20 (1 Erickson, R.A., Hamilton, R.A. and Mlodinow, S.G. (2008). Status review of Belding’s Yellowthroat Geothlypis beldingi, and implications for its conservation. Bird Conservation International. 18(3): 219–228. Close ) sites, with main concentrations at Estero de San José del Cabo (487–700 adults in 2009), Santiago (up to 150 birds), Todos Santos (120 individuals)#R and Punta San Pedro (70); last count of this race produced figure of c. 550 individuals, most of which were in a single population (at San José del Cabo). Although the global population size has not been precisely estimated, it is placed in the band 1000–2500 mature individuals#R. Species was formerly locally common in Baja California, where it inhabited lowland freshwater marsh, but populations have collapsed in the past owing to destruction of habitat; this a result largely of human activity, but also of natural events such as droughts and hurricanes. However, dispersal abilities appear to be better than previously thought (1 Erickson, R.A., Hamilton, R.A. and Mlodinow, S.G. (2008). Status review of Belding’s Yellowthroat Geothlypis beldingi, and implications for its conservation. Bird Conservation International. 18(3): 219–228. Close ) and areas are recolonised. One of main sites, Estero de San José del Cabo (a 42-ha freshwater coastal lagoon at S tip of Baja California), was designated a Ramsar site in 2008; two small local groups in adjacent town have traditionally taken an active interest in conservation of area. Current conservation initiatives include development of a "Conservation Area Plan", whereby main threats identified and a conservation strategy set up, and continuation of research and monitoring to ascertain present status of and threats to this species in Estero de San José del Cabo Ecological Reserve and at other historically important sites; also, erection of information boards planned at this reserve and material to be distributed to local schools. By end of 2008, more than 80 local bird guides had been trained; these will attempt to raise the profile of this yellowthroat and reinforce ties between local economic practices and conservation of this species. Presently, main threats are continued destruction of habitat during housing and tourist developments, drainage of wetlands for agriculture, and drying-out of reedbeds during droughts and fires; natural events can also have serious adverse effect on such a small and fragmented population, hurricanes frequently destroying areas of reeds. Brood parasitism by Brown-headed Cowbird (Molothrus ater) not recorded, but could become a problem if numbers of this parasite increase in S Baja California. It is legally designated as "Threatened" in Mexico (2 SEMARNAT (2010) Norma Oficial Mexicana NOM-23759-SEMARNAT-22371237, Protección ambiental-Especies nativas de México de flora y fauna silvestres-Categorías de riesgo y especificaciones para su inclusión, exclusión o cambio-Lista de especies en riesgo. Diario Oficial de la Federación, jueves 30 de diciembre de 2010. Gobierno de los Estados Unidos Mexicanos, Mexico D.F. Close ).