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Article Excerpt
Chaetocercus (Trochilidae) is presently considered to comprise six species (C. mulsant, White-bellied Woodstar; C. bombus, Little Woodstar; C. heliodor, Gorgeted Woodstar; C. astreans, Santa Marta Woodstar; C. berlepschi, Esmeraldas Woodstar; and C. jourdanii, Rufous-shafted Woodstar) which inhabit semiarid to humid forest and woodland in northern and western South America from to 4,000 m above sea level (Graves 1986, Schuchmann 1999). Four of the six species are generally rare to uncommon, three (C. bombus, C. berlepschi, and C. astreans) have restricted ranges, and two are globally threatened (C. bombus, Vulnerable; C. berlepschi, Endangered) (Schuchmann 1999; BirdLife International 2000, 2008a, b). Chaetocercus woodstars are difficult to detect in the field because of their small body size and inconspicuous behavior outside of the breeding season. Their small size makes collection and specimen preparation challenging and, coupled with a reduction in collecting effort, has resulted in a dearth of specimens for some species (Freymann and Schuchmann 2005). The great majority of specimens that exist were collected before 1960 (Freymann and Schuchmann 2005).
Female Chaetocercus woodstars are similar to each other in plumage and are, at times, considered to be inseparable in the field (Hilty and Brown 1986, Hilty 2003). These factors have combined to make the genus poorly known as evidenced by few recent records of several species and a paucity of detailed breeding biology information for any (Schuchmann 1999). All species except C. jourdanii were formerly placed in the genus Acestrura but most recent authors and checklists follow Schuchmann (1999) in merging these species into Chaetocercus because there was insufficient morphological justification for their separation (e.g., Dickinson 2003, Restall et al. 2006, Remsen et al. 2008).
One of the least-known Chaetocercus is the localized Ecuadorian endemic Esmeraldas Woodstar (Simon 1889). This hummingbird inhabits semi-deciduous to evergreen moist forest (~1,500 mm annual rainfall) along the Pacific coast of western Ecuador from near sea level to 750 m elevation (Becker et al. 2000, Ridgely and Greenfield 200l, Agreda 2007) (Fig. 1). The vast majority of records come from the rainy season, mid October to late May. The species is found along a gradient from low elevation (0-250 m), partially disturbed areas (Becker et al. 2000, Ridgely and Greenfield 2001) to more intact, higher elevation (250-750 m), misty garua forest in the hills of the Cordillera Chongon-Colonche (Agreda 2007). Contrary to Mata et al. (2006), C. berlepschi is not known from subtropical or temperate forests. The species seems to breed in lower elevation, disturbed areas along the central Ecuadorian coast and move to northwestern Ecuador for the non-breeding season (MEJ, pers. obs.; C. D. Becker, pers. comm.). Data are still limited because movements and breeding biology of the species remain poorly known. Before this study, C. berlepschi had been recorded from 11 localities but was only regularly observed at two: Rio Ayampe (01[degrees] 41' S, 80[degrees] 48' W; Manabi Province), and Reserva Ecologica Loma Alta (Loma Alta; 1[degrees] 50' S, 80[degrees] 39' W; Santa Elena Province) (Collar et al. 1992, Ridgely and Greenfield 2001, Agreda 2007).
C. berlepschi is sympatric with C. bombus, and accurate identification of either species depends on careful consideration of the other. C. berlepschi males are characterized by green upperparts with a faint bluish sheen and white underparts with a narrow green chest band. They have a purple gorget (Purple 1, Smithe 1975), and a forked tail with a short and rounded rectrix 1 (R1), a longer and narrower pointed R2, and long, distinctive R3-5 reduced nearly to shafts (Ridgely and Greenfield 2001: Frontispiece). Males of C. bombus have a ruby-pink gorget, more extensive green on the underparts, a cinnamon-buff pectoral collar, and usually display bronzier green upperparts (Schuchmann 1999, Ridgely and Greenfield 2001, Gurney 2006, Mata et al. 2006, Restall et al. 2006, Schulenberg et al. 2007). Published works illustrate C. berlepschi females as white below with a white postocular stripe, and a buff-tinged throat (Meyer de Schauensee 1970, Schuchmann 1999, Ridgely and Greenfield 2001, Mata et al. 2006, Restall et al. 2006). The central rectrices of the female are green and R2-5 are cinnamon with a black subterminal band and white tips. Depictions of female C. bombus vary but all suggest that its cinnamon-buff underparts and postocular stripe are the main identifying features (Schuchmann 1999, Ridgely and Greenfield 2001, Gurney 2006, Mata et al. 2006, Restall et al. 2006, Schulenberg et al. 2007). The tail is shown as cinnamon with a black subterminal band (the tips are also cinnamon) and green is at times shown on the central rectrices. The short and narrow cheekstripe (extension of the auriculars) is also a diagnostic feature of female C. bombus (Gurney 2006).
Much of the lowland humid forest in western Ecuador has been cleared, threatening numerous species including C. berlepschi (Dodson and Gentry 1991, Best and Kessler 1995), and the species is considered rare to uncommon (Becker et al. 2000, Ridgely and Greenfield 2001). The combination of these factors has led to the perception that the species is Endangered with an estimated population size of 250-999 individuals (Collar et al. 1992; BirdLife International 2000, 2008a) and should perhaps even be treated as Critically Endangered (Ridgely and Greenfield 2001).
The Esmeraldas Woodstar has received little research attention despite its restricted range and Endangered status, and little was known of its reproductive biology. The objectives of our study were to: (1) gather fundamental natural history and distributional information on the species, (2) assess its conservation status, and (3) recommend possible conservation actions.
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METHODS
We searched for and observed C. berlepschi from October 2007 to April 2008 in Manabi and Santa Elena provinces, western Ecuador. We searched for the species at Ayampe in October and November and documented the arrival date of male and female C. berlepschi. We continued our searches from December 2007 to April 2008 along the coast from San Jose (1[degrees] 45' S, 80[degrees] 45' W; 30 m; Santa Elena Province) north to Cabo Pasado (0[degrees] 24' S, 80[degrees] 29' W; 25 m; Manabi Province; Figs. 1,2). We surveyed areas <20 km from the coast from to 700 m elevation that varied from arid to humid. We were based in Ayampe and data were collected from that site across all months of the study. We also documented the location and elevation of each C. berlepschi nest to obtain information on which areas are important for reproduction. We complemented breeding season observations with intensive searches in August and September 2008 that attempted to locate non-breeding localities. We searched along the coast from Ayampe to San Lorenzo (1[degrees] 4' S, 80[degrees] 53' W: Manabi Province) to Bilsa Biological Station (0[degrees] 22' N, 79[degrees] 45' W; Esmeraldas Province) from 3 to 20 August 2008. We also surveyed the northern and central Cordillera Chongon-Colonche in Manabi Province (0 to 700 m elevation) from 22 August to 9 September 2008. We searched from Agua Blanca (1[degrees] 32' S, 80[degrees] 44' W) to Pedro Pablo Gomez (1[degrees] 37' S, 80[degrees] 33' W) to Puerto Cayo (1[degrees] 21' S, 80[degrees] 44' W) to above Galan (1[degrees]...
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