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COPYRIGHT 2005 Wilson Ornithological Society
Habitat fragmentation has affected a multitude of taxa worldwide (e.g., Saunders et al. 1991, Turner 1996) by disrupting forest dynamics (Laurance et al. 1998) and adversely affecting floras and faunas (Alzen and Feinsinger 1994, Dale et al. 1994). Surprisingly, few studies have examined the effects of fragmentation on large frugivorous birds such as parrots, hornbills, and toucans. These birds are among the most threatened in the world (BirdLife International 2000) and often disappear from small fragments (e.g., Willis 1979). On the other hand, many are also highly mobile, which may allow them to disperse to areas within fragmented landscapes (e.g., Rowley 1983, McNally and Horrocks 2000).
The ability of a given species to use the mosaic of different habitats found outside of reserves (extra-reserve landscape) may affect its future survival, which makes this an important topic for research. Agro-ecosystems cover the vast majority of land outside protected areas (Western and Pearl 1989), which could have important influences on species ecology (Mesquita et al. 1999, Bentley et al. 2000) and survival (Laurance 1991, Gascon et al. 1999). A species' ability to use the extra-reserve landscape may be especially important around protected areas or other habitat fragments, as dispersal into the extra-reserve landscape might boost local populations (e.g., Ricketts et al. 2000). In the case of large avian frugivores, which tend to occur at low population densities (e.g., Marsden 1999), it is unknown whether protected areas can support viable populations of some taxa, especially in small reserves (e.g., Gurd et al. 2001). Examination of landscapes adjacent to reserves or other "key patches" (Verboom et al. 2001), and improving extra-reserve habitat suitability for threatened taxa, may be a first step toward enhancing populations in and around protected areas, or at least buffering within-reserve populations from negative outside influences (e.g., Gotmark et al. 2000).
The problem of forest fragmentation is acute in Brazil's Atlantic Forest, where remaining forest cover is ~7.5% of the original 1 million [km.sup.2] (Morellato and Haddad 2000, Myers et al. 2000). Deforestation has been particularly intense in the interior of Sao Paulo state; aside from the relatively large Morro do Diabo State Park, the few small fragments of forest that remain are isolated by vast areas of sugar cane and other agricultural land (e.g., Cullen et al. 2001). One of these fragments is the Caetetus Reserve (2,179 ha), situated near Garca. The reserve is surrounded by an extra-reserve landscape dominated by pasturelands and coffee plantations, but which also contains small areas of remnant and degraded forest, along with plantations of Eucalyptus spp. and citrus fruits. The reserve holds Sao Paulo's largest remaining population of the Blue-winged Macaw (Primolius maracana; formerly placed within Ara or Propyrrhura but now assigned to Primolius, Tavares et al. 2004), a species classified as "Vulnerable" (BirdLife International 2000). This species (body length = 39 cm) has disappeared from many of the protected areas in the southern part of its range (M. F. Nunes unpubl. data). Six other parrot species survive in the area (body lengths from Juniper and Parr 1998): White-eyed Parakeet (Aratinga leucophthalmus), 32 cm; Maroon-bellied Parakeet (Pyrrhura frontalis), 25-28 cm; Blue-winged Parrotlet (Forpus xanthopterygius), 12 cm; Canary-winged Parakeet (Brotogeris versicolurus), 25 cm; Scaly-headed Parrot (Pionus maximiliani), 27 cm; and Blue-fronted Parrot (Amazona aestiva), 37 cm.
Our objectives were to (1) estimate population sizes of Blue-winged Macaws and other parrot species within the reserve, (2) examine parrot use of the extra-reserve landscape, and (3) determine which features of the extra-reserve landscape influence parrot use. We then used these results to make a preliminary assessment of the likely viability of parrot populations in the area and to suggest which features of the landscape should be preserved or enhanced to protect parrots.
METHODS
Study area.--The study was based in and around Caetetus Ecological Station, Sao Paulo state, Brazil (22[degrees] 24' S, 49[degrees] 42' W; Fig. 1). The reserve covers 2,179 ha and consists mainly of mature, semi-deciduous forest (the area has been protected from major logging for ~30 years) and some areas of more recently disturbed secondary forest. Additionally, there are much smaller areas dominated by stands of bamboo and palmito (Euterpe edulis), and some small artificial lakes (Fig. 1). Annual precipitation averages 1,260 mm (Cullen et al. 200l). The study was conducted toward the end of the dry, cool season (May to September) in the plateau region of Sao Paulo. The landscape surrounding Caetetus is dominated by pasturelands and coffee plantations (Table 1), although fragments of degraded and regenerating forest and riverine forest also occur outside the reserve.
[FIGURE 1 OMITTED]
Within-reserve study.--We censused parrots in July and August 2001. The identification of parrot species, by both sight and call, and estimation of their distances from census points, was practiced for 10 days before starting the study. We established 90 parrot census points at 200-m intervals along nine transects. Caetetus has an existing network of narrow "research" trails covering much of the reserve and...
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