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COPYRIGHT 2005 Wilson Ornithological Society
Jabirus (Jabiru mycteria) breed locally from southern Mexico (Campeche, Tabasco) through the lowlands of Central America and east of the Andes to northern Argentina (Bent 1926, Blake 1977, Knoder et al. 1980, Hancock et al. 1992, Antas and Nascimento 1997). They favor extensive inland and shallow wetland habitats for feeding, but prefer nearby wooded areas for roosting and nesting (Hancock et al. 1992, Stotz et al. 1996, Antas and Nascimento 1997; DW pers. obs.). Jabirus are distributed widely but are not abundant anywhere in their breeding range. They are considered regionally threatened, although not endangered (Luthin 1984, 1987; Stotz et al. 1996). In southeastern Brazil, however, they have been extirpated from the basins of the Paraiba do Sul, Tiete and Grande rivers, and there are only a few remnant populations restricted to the Sgo Francisco River valley in the state of Minas Gerais (Antas and Nascimento 1997: 17).
Comprehensive information on numbers and population trends of Jabirus are limited, especially in Central America. Luthin (1987), however, observed Jabirus throughout their breeding range and concluded that there are three distinct populations: Central American, northern South American, and south-central South American. He suggested that research on the ecology and status of Jabirus be undertaken for each distinct population to develop a global conservation strategy for the species. DW (in Scott and Carbonell 1986) reported on the status of wetlands and conservation of waterbirds in Belize, referencing known Jabiru nesting areas. Recently, Frederick et al. (1997) documented previously unrecorded populations of Jabirus breeding in coastal wetlands of Nicaragua and Honduras, (Miskito Coast and La Mosquitia, respectively) during aerial strip-censuses of breeding waterbirds.
Kahl (1971, 1973), Thomas (1981, 1985), and Poveda (2003) described behavior and comparative ethology of Jabirus in Argentina, Venezuela, and Costa Rica, respectively, and Antas and Nascimento (1997) studied the ecology of Jabirus on the Pantanal of Brazil. Breeding and egg-laying dates have been published for some populations of Jabirus (Table 1). Breeding dates are variable across the range and seem to be influenced largely by seasonal rainfall patterns. Two published reports provide quantitative data on Jabiru breeding biology: Gonzalez (1996a) and Anas and Nascimento (1997) for Venezuela and Brazil, respectively.
In Belize, the Belize Audubon Society (BAS) has published much anecdotal information on Jabiru nesting and sightings since 1969, but no comprehensive report exists for its breeding biology. From 1969 to 1987, DW and the late WFY collected information on nest locations and breeding activities of Jabirus in Belize, where the species has been officially protected since 1973. Our objective was to synthesize published and unpublished information from reliable sources and compile representative data for Jabirus in Belize. We then present an analysis of the breeding biology of Jabirus in Belize based on those sources.
METHODS
Study area.--Most Jabiru nests for our study were located in the northern and central sections of Belize (17[degrees] 10'-18[degrees] 10' N; 89[degrees] 15'-88[degrees] 12'W; Fig. 1). Mean monthly temperatures range from 16 to 17[degrees]C in the winter wet season and from 24 to 25[degrees]C in the summer dry season. On average, the northern coastal plains (Corozal District) receive about one third the rainfall (1,347 mm) of the south (4,526 mm, Toledo District). Seasonal effects are greatest in the central and northern regions, where January through April or May are dry (<100 mm per month). In south-central regions, the dry season (February to April) is shorter. A minor, less rainy period usually occurs in August (Hartshorn et al. 1984, Central Statistical Office 2000).
[FIGURE 1 OMITTED]
Data sources.--Data for this study were gathered from four main sources: the unpublished field notes of DW (1968-1987), personal communications with DW from 2001 to 2003, 44 reports published in the Belize Audubon Society Bulletin from 1969 through 1987, and several letters written by WFY to Charles S. Luthin summarizing the results of nine census flights conducted between 1985 and 1986. C. S. Luthin worked for the Brehm Fund for International Bird Conservation and was chairman of the World Working Group on Storks, Ibises, and Spoonbills (WWG-SIS). We also included several recent 2003 personal observations from Belizean ornithologist, O. A. Figueroa.
Jabiru survey flights can be divided into two time periods: 1968-1981 and 1983-1987 (Table 2). Between 1968 and 1981, we confirmed 30 flights (~22.0 hr) by WFY (Young 1998). Flights were conducted in a single-engine aircraft and based out of Belize City Municipal Airport. These were low-altitude flights, often below 800 m, when nest contents were being observed. Nest locations (Appendix, Fig. 1) are approximate. To locate nest sites, we referred to the aerial-flight (Fig. 2) and nest-location maps developed by WFY and DW from the WWG-SIS flights (1983-1986) and DW's notes. WFY had become personally interested in Jabirus and periodically took flights to confirm nest sightings reported by charter pilots and the public. He also owned a real estate business and often located nests when flying clients. Flights between 1969 and 1981 that were not real-estate related were highly targeted and covered central and northern Belize almost exclusively. After Jabirus gained protected status in 1973, public radio announcements were made to increase awareness and to encourage reports of nest sightings and Jabirus to the BAS. Flights that were conducted between 1968 and 1982 were systematic, in that they covered areas and habitats where previous sightings had been reported.
[FIGURE 2 OMITTED]
From 1983 to 1987, 12 of 15 flights (26.6 hr) were financed by WWG-SIS and flown by J. Fuller in a Cessna 172, V3-HEJ. These flights covered predetermined routes (Fig. 2), but also included...
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