Annual Variation of Abundance and Composition in Forest Bird Assemblages on Navarino Island, Cape Horn Biosphere Reserve, Chile Page: 232
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IPPI ETAL.
southernmost forested ecosystems, found in the Cape Horn Biosphere Reserve, Chile (55S).
Combining data obtained through point-count surveys, mist-netting, and checklist methods, we recorded
a total of 34 bird species belonging to 20 families. Eighteen of these species were Passeriformes, and
the most abundant year-round resident species were Thorn-tailed Rayadito (Aphrastura spinicauda) and
Patagonian Sierra-Finch (Phrygilus patagonicus). The most abundant seasonal migrants species were
White-crested Elaenia (Elaenia albiceps) and Southern House Wren (Troglodytes musculus). Point-count
and mist-netting methods showed a reduction in species richness and abundance during winter, with one
third of the bird assemblage absent. This proportion was lower than that documented for more northern
Nothofagus forests. Additionally, our data provided no evidence that intra-annual patterns of avian
community structure were significantly affected by a recently implemented tourism trail through the
Omora Park. We believe that understanding seasonal patterns of richness, abundance, and migratory
status of Chilean temperate forests birds will help to better understand the world's southernmost forest
ecosystem, implement effective conservation, facilitate sustainable ecotourism, and lead to new
ecological and evolutionary research. Accepted 14 April 2009.
Key words: Forest birds, subantarctic forests, Chile, Cape Horn, point-count surveys.INTRODUCTION
The temperate forests of southwestern South
America extend from approximately 30-
560S along Chile and Argentina. The most
Austral portion of this biome, known as the
Magellanic subantarctic forest (48-560S), is
dominated by broadleaf trees from the genus
Nothofagus (Armesto et al. 1996). Compared to
the Northern Hemisphere, the avian commu-
nities that inhabit the southern temperate for-
ests are characterized by a higher degree of
endemism and relatively fewer migratory spe-
cies (Rozzi et al. 1996a), a combination that
arises from the region's biogeographic isola-
tion and the influence of glacial events that
reached their maxima 15,000 years ago (Ar-
mesto et al. 1996, Vuilleumier 1998). Follow-
ing the general rule of decreasing species
diversity with increasing latitude (Alekseev
1982, Gaston et al. 1995), bird species rich-
ness in the Magellanic subantarctic forests is
less than at lower latitudes farther north, such
as Chiloe Island (420S) (Rozzi et al. 1996b,
Anderson & Rozzi 2000).
Bird community structure, however, is
dynamic within and among years (Holmes et
al. 1986, Holmes 1988, Rozzi et al. 1996a), and
may vary among habitat types (Maia-Gouvea
et al. 2005), successional stages (Stiles 1980),or with the degree of anthropogenic distur-
bance (Newmark 2006). To detect and
describe the fluctuations and patterns of
avian diversity, long-term and year-round
studies are needed (Holmes 1988). Nonethe-
less, most ornithological field studies are con-
ducted over short time periods, usually in the
breeding season (Karr & Freemark 1983).
This pattern applies in the southern South
America temperate forest biome as well, and
even basic information is often lacking about
seasonal patterns of bird species occurrence,
abundance and diversity.
For the breeding season, short-term stud-
ies have described bird assemblages for South
American temperate forests at latitudes
extending from the Cape Horn Biosphere
Reserve (55-56S) to Fray Jorge National
Park (30S) (e.g., Sielfeld 1977, Venegas 1981,
1991, Jaksic & Feinsinger 1991, Willson et al.
1994, Rozzi et al. 1996b, Cofre 1999, Estades
& Temple 1999, Anderson & Rozzi 2000,
Anderson et al. 2002, Cornelius et al. 2000,
Figueroa Rojas et al. 2000, Reid et al. 2002,
Becerra Serial & Grigera 2005, Diaz 2005,
Diaz et al. 2005). While most of these studies
have been descriptive accounts of the breed-
ing season avifauna, some point-count sur-
veys have shown a reduction in abundance
and species diversity in winter (Garcia 1982,232
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Ippi, Silvina; Anderson, Christopher B.; Rozzi, Ricardo, 1960- & Elphick, Chris S. Annual Variation of Abundance and Composition in Forest Bird Assemblages on Navarino Island, Cape Horn Biosphere Reserve, Chile, article, 2009; [Caracas, Venezuela]. (https://digital.library.unt.edu/ark:/67531/metadc97951/m1/2/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT College of Arts and Sciences.