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COPYRIGHT 2006 Wilson Ornithological Society
The genus Sporophila (Emberizidae) comprises a diverse group of small finches widely distributed in the Neotropics. The greatest diversity is reached in interior South America, where most species inhabit grassy semi-open areas (Ridgely and Tudor 1994, Sick 1997). However, detailed information on breeding biology is lacking for most of these species. Furthermore, the melodious songs of these seedeaters make them vulnerable to pursuit for the illegal pet trade. As a result, many species have been locally extirpated, and some are severely threatened (Collar et al. 1992, Willis and Oniki 1992, Ridgely and Tudor 1994, Sick 1997, Willis 2003).
The Double-collared Seedeater (S. caerulescens) is the most common seedeater in southern South America. It inhabits grasslands and agricultural areas (Ridgely and Tudor 1994), commonly near populated locations. Recently, it has expanded its distribution in response to the destruction of forested areas and the consequent spread of exotic grass species (Sick 1997). Although not endangered, entire populations of the Double-collared Seedeater have been lost to the illegal pet trade, being one of the most popular cage birds in Brazil. Information on its breeding biology is limited to descriptions of nests and eggs (Euler 1900, Ihering 1900, Pereyra 1956, De La Pena 1981, Alabarce 1987) and the length of the nestling period--obtained from a single nest observed in Argentina (Pereyra 1956). More information on the species' ecology is needed before meaningful conservation objectives can be developed for the species. Herein, I describe the reproductive biology of the Double-collared Seedeater in southeastern Brazil. Phenology and duration of the breeding season, length of incubation and nestling periods, egg mass, nest success, and information on parental care are reported.
METHODS
Study area.--I conducted my study on the campus of Sat Carlos Federal University, located in the central region of Sao Paulo state, southeastern Brazil (21[degrees] 58' S, 47[degrees] 52' W). The campus is subdivided into a semi-urbanized portion and an adjacent non-urbanized, disturbed cerrado area (savanna that ranges from open grasslands to forested areas, such as gallery forests that grow alongside water-courses; Eiten 1972). The semi-urbanized area totals 187 ha, and is composed of extensive lawns, orchards, gardens, and Eucalyptus spp. and Pinus spp., with regenerating cerrado undergrowth. Buildings and streets are widely spaced and compose only 23 ha (12%). The non-urbanized area is a 529.6-ha mosaic composed of sensu lato cerrado (125 ha), gallery forest (3.6 ha), regenerating cerrado (84 ha), an abandoned Eucalyptus spp. plantation with regenerating cerrado undergrowth (94 ha), and active Eucalyptus spp. silviculture (223 ha) (Paese 1997). The climate in this region is tropical, with two well-marked seasons: a humid, hot season from October through March and a dry, cold season from April through September. In both the semi-urbanized and non-urbanized areas, grass seeds are abundant during the wet season.
During seven breeding seasons (1997-2003), I conducted nest searches from early November, when males started to sing and defend territories, to May, when males stopped singing. All habitats were searched for nests. Although I conducted nest searches weekly, the number of habitats covered and...
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