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J.J. Armesto et al.
(Myrtaceae), and Nothofagus dombeyi (Fagaceae) . Shrubs include
Berberis darwinii, B. buxifolia (Berberidaceae), and Gaultheria phillyreifolia (Ericaceae). Primary forests are dominated by Amomyrtus luma
and Laurelia philippiana (Monimiaceae) (Armesto & Figueroa, 1987).
These rainforests are representative of the Valdivian rainforest type,
which is widespread over most of south-central Chile, particularly on the
coastal range (Veblen, Schlegel, & Oltremari, 1983). These forests grow
in a maritime climate, characterized by low temperature fluctuations and
high humidity year-round (Alaback, 1991; Arroyo, Armesto, Squeo, &
Gutierrez, 1993). Average annual rainfall exceeds 2000mm; and average
monthly maximum (February) and minimum (August) temperatures at
sea level are 20.7°C and 3°C respectively. More details on the vegetation,
climate, and soils of the study area are given by Holdgate (1961), Villagran
(1985), and Armesto and Rozzi (1989).
Methods
We surveyed bird populations by mist-net captures and sight/sound censuses during the fruitinglflowering seasons of 1988, 1990, and 1991. Bird
censuses were conducted in the first 3 hours after sunrise, along a fixedstrip transect 800m long and 15 m wide. Avian densities reported here are
the average of five transects surveyed on five consecutive days during
January each year. Black mist nets, 12m long and 2m wide, with a mesh
size of 25 mm, were set at four different locations in the second-growth
forest during daylight hours for a period of 5 to 10 days every summer.
Mist nets are known to provide biased estimates of bird densities (Karr,
1981) and, therefore, they were used only as a complement of transect
surveys and for collecting samples of birds' gut contents.
Consumption of fruit by birds was determined by examining feces
obtained from mist-net captured birds placed in paper sacks for 2 to
10min (d. Herrera, 1984). Voided seeds were identified to species later
in the laboratory. Over a 3-year period, we examined the gut contents of
a total of 351 birds. For one species of bird, the ground-dweller Scelorchi/us rubecula, data on fruit consumption are those reported by Correa
et al. (1990).
At monthly intervals (bimonthly during the winter of 1988) during 1987
and 1988, we recorded the phenology of 61 species of trees, shrubs, and
woody vines and epiphytes occurring in both old-growth and secondary
forests between 200 m and 500 m elevation. Flower and ripe fruit stages
were distinguished (Smith-Ramfrez & Armesto , 1994). An average of 7
individuals (range 4-14) per species was considered.
Hummingbird visitation was assessed by recording visits to all the
flowering plants bearing red (or pink) tubular corollas in the study area in
February, June, and November of 1989 (Smith-Ramirez, 1993).
J.J. Armesto et al.
(Myrtaceae), and Nothofagus dombeyi (Fagaceae) . Shrubs include
Berberis darwinii, B. buxifolia (Berberidaceae), and Gaultheria phillyreifolia (Ericaceae). Primary forests are dominated by Amomyrtus luma
and Laurelia philippiana (Monimiaceae) (Armesto & Figueroa, 1987).
These rainforests are representative of the Valdivian rainforest type,
which is widespread over most of south-central Chile, particularly on the
coastal range (Veblen, Schlegel, & Oltremari, 1983). These forests grow
in a maritime climate, characterized by low temperature fluctuations and
high humidity year-round (Alaback, 1991; Arroyo, Armesto, Squeo, &
Gutierrez, 1993). Average annual rainfall exceeds 2000mm; and average
monthly maximum (February) and minimum (August) temperatures at
sea level are 20.7°C and 3°C respectively. More details on the vegetation,
climate, and soils of the study area are given by Holdgate (1961), Villagran
(1985), and Armesto and Rozzi (1989).
Methods
We surveyed bird populations by mist-net captures and sight/sound censuses during the fruitinglflowering seasons of 1988, 1990, and 1991. Bird
censuses were conducted in the first 3 hours after sunrise, along a fixedstrip transect 800m long and 15 m wide. Avian densities reported here are
the average of five transects surveyed on five consecutive days during
January each year. Black mist nets, 12m long and 2m wide, with a mesh
size of 25 mm, were set at four different locations in the second-growth
forest during daylight hours for a period of 5 to 10 days every summer.
Mist nets are known to provide biased estimates of bird densities (Karr,
1981) and, therefore, they were used only as a complement of transect
surveys and for collecting samples of birds' gut contents.
Consumption of fruit by birds was determined by examining feces
obtained from mist-net captured birds placed in paper sacks for 2 to
10min (d. Herrera, 1984). Voided seeds were identified to species later
in the laboratory. Over a 3-year period, we examined the gut contents of
a total of 351 birds. For one species of bird, the ground-dweller Scelorchi/us rubecula, data on fruit consumption are those reported by Correa
et al. (1990).
At monthly intervals (bimonthly during the winter of 1988) during 1987
and 1988, we recorded the phenology of 61 species of trees, shrubs, and
woody vines and epiphytes occurring in both old-growth and secondary
forests between 200 m and 500 m elevation. Flower and ripe fruit stages
were distinguished (Smith-Ramfrez & Armesto , 1994). An average of 7
individuals (range 4-14) per species was considered.
Hummingbird visitation was assessed by recording visits to all the
flowering plants bearing red (or pink) tubular corollas in the study area in
February, June, and November of 1989 (Smith-Ramirez, 1993).