Abstract
In this paper, we report the number of core and transient bird species in an Amazonian savanna site and assess their ecological differences. We conducted our study at Campo Experimental do Cerrado (CEC) da Embrapa–Amapa, 48 km north of Macapa (0 2'5 N / 51 2'2 W), Amapa, Brazil. Forty points were monitored on a monthly basis over the course of one year, using the unlimited-distance point counts in a plot of 360 hectares of well-preserved and relatively homogeneous upland savanna from September 2006 to August 2007. Species were classified in core (recorded in the area in nine or more months), transient (recorded in the area in four or less months) and intermediate (the ones recorded between five and eight months). Species were also classified according to feeding guilds and habitat preferences. Statistical analyses were made to compare core and transient species. We recorded 72 species in the plot, of which 36 were transients, 12 were intermediates, and 22 were core. Core species have higher abundances than transient species. Core species are found mostly in the savanna while transient species also occur in other habitats within the landscape. Both core and transient groups presented well-marked seasonal variation in abundance. Recruitment explains abundance variation for core species, while differences in the availability of food resources in the site explains variation of the abundance in transient species. We predict that plot-level (not more than 500 hectares) bird assemblages in South American savannas will be composed of a small number of abundant and habitat-restricted species that occupy the site almost year round, combined with a high number of low abundant transient species that are habitat generalists and use the plot only during limited periods of their annual life cycle.
Highlights
The most common approach to biodiversity conservation is to identify and protect natural features such as ecosystems and threatened species, whose distributions can be mapped and targeted through conservation management activities (Watson et al 2011)
Core and transient species are very different in their habitat use (G = 27.2, df = 1, p < 0.0001) because most of the core species (68.2%) are found only in savannas, whereas most of the transient species (94.4%) occur in two or more habitats (Table 1)
Species’ richness in the site is mostly dominated by transient species, abundance is dominated by core species
Summary
The most common approach to biodiversity conservation is to identify and protect natural features such as ecosystems and threatened species, whose distributions can be mapped and targeted through conservation management activities (Watson et al 2011). While such an approach is important, the conservation of species and ecosystems cannot be achieved unless the ecological and evolutionary processes that sustain them are understood and maintained (Cowling et al 1999, Fuller et al 2001). A thorough understanding of the major patterns of biological movements from the local to the regional scales is a critical step towards the design of conservation systems that maintain ecological flows and enable the resilience of populations against the effects of global changes (Watson et al 2011)
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