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14 ARTICULOSselective logging but was not observed in thenational park. Nests of diuca (Diuca diuca, 6),rara (Phytotoma rara, 10), diucón (Xolmis pyrope,6), and chincol (Zonotrichia capensis, 13) werefound only in shrubby habitat or near forest edges;nests of cometocino (Phrygilus patagonicus, 10)and tordo (Curaeus curaeus, n = 3) occurred inboth shrub and forest fragments.Nest survival in forest and shrub habitats.Daily nest survival of all nests in forest (0.964 ±0.003, n = 256, 3363 exposure days) was marginallyhigher (c 2 = 3.72, P < 0.06) than in the shrub habitat2of roadsides, fencerows, and pastures (0.945 ±0.009, n = 60, 604 exposure days). Estimated nestsuccess (Mayfield) in forest habitat was 21% for S.sephanoides (1919 exposure days), 20% for T.falcklandii (444 exposure days), and 27% for E.albiceps (658 exposure days). Predation accountedfor 71% of 122 known nest failures in forest, butjust 42% of 33 failed nests in fencerows, roadsides,and pastures, where brood parasitism accounted for39% of failures.Brood parasites (mirlo, Molothrusbonariensis) affected three species in shrubbyhabitats. Parasitism rates for host species werefairly high (46% of 13 Z. capensis nests, 50% of 6D. diuca nests, 57% of 7 P. patagonicus nests).Brood parasitism often decreased the probabilityof nest success: one nest fledged the cowbirdyoung, but the host (Z. capensis) eggs did nothatch; eleven nests were abandoned by hosts (3nests of D. diuca; 3 nests of P. patagonicus; 5 nestsof Z. capensis) after being parasitized, and one nestwas depredated after hatching both the cowbird andhost (P. patagonicus) eggs; the remaining nestsfledged at least one chick. Although X. pyrope isa documented cowbird host (Johnson 1967, Mason1985, Johnsgard 1997), none of the nests we foundwas affected.Nest survival in fragments and edges.Apparent nest success of S. sephanoides and T.falcklandii differed only slightly between edge andinterior or between fragments and the national park(Table 1). In contrast, apparent nest success of E.albiceps was markedly lower in fragments (21% of24 nests) than in the park (39% of 13 nests) and lowerin forest edges than interior (Table 1).Nest survival and nesting phase.Considering all forest nests (with known outcomeand placement relative to edges), only 5% (of 40nests) in the national park were depredated duringthe nestling period, compared with 33% during theincubation period. In contrast, predation during theegg and nestling stages was similar in forest edges(25% of 64 nests during incubation, 27% duringnestling stage) and the interior forest of fragments(22% of 92 nests during incubation, 20% duringnestling stage).DISCUSSIONWe found marked edge effects only for someopen-cup nesting species (and none for natural cavitynests; De Santoet al. 2002), confirming that case-by-case dataare necessary to obtain information usable forconservation and management purposes (Flaspohler etal. 2000). Nest success of open-cup nests was far lowerthan that of cavity nests in this rainforest (De Santoet al. 2002), a result that is commonly recordedbut seldom based on studies conducted in the sametime and place (Martin and Li 1992). We also notedlower predation of nestlings than eggs in the interiorforest of the national park, but not within forest edgesor the interior forest of fragments. The observeddifferences in patterns of nest predation may be relatedto the behavior and abundance of predators or toinherent vulnerability of nests in each habitat.Although several nest predators have been documentedin our study area (Willson et al. 2001), relatively littleis known about their habits or behaviors.Molothrus bonariensis has been reportedto parasitize the nests of several species (Johnson1967, Mason 1985, Johnsgard 1997); this broodparasite occurs on Chiloé despite its commonomission from distribution maps (Ridgely andTudor 1994, Johnsgard 1997, Peña and Rumboll2001) and depresses the nest success of its hosts.We found cowbird eggs in the nests of two of thethree previously documented species (D. diuca andZ. capensis, but not X. pyrope) as well as in nestsof P. patagonicus, a species not previously reportedto be a host. As more and more forest is clearedfor agriculture, however, an increase in suitablehabitat is expected to lead to increased populationsof potential hosts and of this brood parasite, andbrood parasitism may even expand to additionalspecies and habitats.The three most common species in oursample (E. albiceps, S. sephanoides, T. falcklandii)
ARTICULOS15are all important mutualists with plants in our studyarea (Armesto et al. 1987, 1996; Smith-Ramírez1993; Willson et al. 1994, 1996b). Previous workshowed that population densities of all three arerelatively high in forest fragments; indeed, E.albiceps was the most frequently detected bird inmany study sites (Willson et al. 1994, Rozzi et al.1996). The low nest success (20-30%), togetherwith a small clutch size (usually 2 or 3 eggs),suggests that populations might have difficultymaintaining current levels (in the absence ofimmigration to fragments), and interactions withnative plants may ultimately be impaired. However,additional information on demographic traits (e.g.,juvenile and adult survival, number of nestingattempts per year) of these birds is needed in orderto assess this risk properly.It is becoming clear that general rules aboutthe effects of habitat fragment size and edge effectsare difficult to formulate. Many factors contributeto the observed variation, including landscapecontext (degree of fragmentation, structure of thematrix, Castellón and Sieving 2006, Tewksbury etal. 2006), regional differences in abundance,distribution, and identity of predators and broodparasites, and differing responses of the nesting birdsthemselves (e.g., Friesen et al. 1999, Morse andRobinson 1999, De Santo and Willson 2001).Achievement of conservation goals for at-riskbreeding birds therefore requires knowledge of localrisk patterns and will commonly requireexamination on a case-by-case basis.ACKNOWLEDGMENTSWe thank Corporación Nacional Forestal forlogistical support, numerous field assistants for theirintensive work, and many Chilote landowners fortheir gracious permission to work in their forests. K.Hyer and T. Max assisted with statistical analyses.Comments from C. Estades, E. Lance, and J.Morrison improved the manuscript. This work wassupported by National Science Foundation-International Programs (grant number 96-02917),National Geographic Society Committee for Researchand Exploration (grant 5457-95), and the PacificNorthwest Research Station. Collaboration of MWFand JJA during manuscript preparation was supportedby Conicyt grant 1501-0001 to the Center forAdvanced Studies in Ecology and Biodiversity(CASEB). This manuscript is a contribution fromCASEB and the research program of EstaciónBiológica Senda Darwin in Chiloé.LITERATURE CITEDARMESTO, J. J. & J. FIGUEROA. 1987. Standstructure and dynamics in the temperate rainforests of Chiloé Archipelago, Chile. Journalof Biogeography 14:367-376.ARMESTO, J. J., R. ROZZI, P. MIRANDA, & C.SABAG. 1987. Plant/frugivore interactionsin South American temperate forests. RevistaChilena de Historia Natural 60:321-326.ARMESTO, J. J., C. SMITH-RAMÍREZ, & C.SABAG. 1996. The importance of plantbirdmutualism in the temperate rainforest ofsouthern South America. Pp. 248-265 in InR.G. Lawford, P.B. Alaback, & E. Fuentes[eds.], High-latitude rainforests andassociated ecosystems of the west coast ofthe Americas: climate, hydrology, ecology,and conservation. Springer-Verlag, Berlin.ASKINS, R. A. 1995. Hostile landscapes and thedecline of migratory songbirds. Science3267:1956-1957.BALMFORD, A. & A. LONG. 1994. Avianendemism and forest loss. Nature 372:623-624.BÖHNING-GAESE, K., B. HALBE, N. LEMOINE,& R. OBERATH. 2000. Factors influencingthe clutch size, number of broods and annualfecundity of North American and Europeanland birds. Evolutionary Ecology Research2: 823-839.CASTELLÓN, T. D. and K. E. SIEVING. 2006. Anexperimental test of matrix permeability andcorridor use by an endemic understory bird.Conservation Biology 20: 135-145.CORNELIUS, C., H. COFRE, & P. A. MARQUET.2000. Effects of habitat fragmentation on birdspecies in a relict temperate forest in semiaridChile. Conservation Biology 14:534-543.DE SANTO, T. L. & M. F. WILLSON. 2001.Predator abundance and predation of artificialnests in natural and anthropogenicconiferous forest edges in southeast Alaska.Journal of Field Ornithology 72:136-149.
Page 1 and 2: Boletín Chileno de OrnitologíaNú
Page 3 and 4: ARTICULOS3ABSTRACTAt “El Morado
Page 5 and 6: ARTICULOS5RESULTADOSEn el sector en
Page 7 and 8: ARTICULOS7AGRADECIMIENTOSA la Corpo
Page 9 and 10: ARTICULOS9CONTINUACIÓN ANEXO 1PERI
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Page 13: ARTICULOS13also monitored nests in
Page 17 and 18: ARTICULOS17SAUER, J. R. & B. K. WIL
Page 19 and 20: ARTICULOS19La comunidad de aves que
Page 21 and 22: ARTICULOS21Este trabajo muestra que
Page 27 and 28: CONTRIBUCIONES BREVES27sandivicensi
Page 31 and 32: CONTRIBUCIONES BREVES31Cuadro 1: Da
Page 33 and 34: NOTAS33alimentaban en la entrada de
Page 35 and 36: NOTAS35Presencia de cisne coscoroba

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