Effects of Edge Habitat and Nest Characteristics on Depredation of Artificial Nests in Fragmented Australian Tropical Rainforest |
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Authors: | Franziska?Hausmann Email author" target="_blank">Carla P?CatterallEmail author Scott D?Piper |
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Institution: | (1) Rainforest Co-operative Research Centre and Faculty of Environmental Sciences, Griffith University, Nathan, Qld, 4111, Australia |
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Abstract: | Variation in nest predation levels associated with rainforest fragmentation (edge effects) was assessed in Australia's Wet
Tropics bioregion. Artificial nests were placed in the forest understorey at seven edge sites where continuous forest adjoined
pasture, seven interiors (about 1 km from the edge), and six linear riparian forest remnants (50–100 m wide) that were connected
to continuous forest. Four nest types were also compared, representing different combinations of two factors; height (ground,
shrub) and shape (open, domed). At each site, four nests of each type, containing one quail egg and two model plasticine eggs,
were interspersed about 15 m apart within a 160 m transect during September–October 2001. Predators were identified from marks
on the plasticine eggs. The overall depredation rate was 66.5% of 320 nests' contents damaged over a three-day period. Large
rodents, especially the rat Uromys caudimaculatus, and birds, especially the spotted catbird Ailuroedus melanotis, were the main predators. Mammals comprised 56.5% and birds 31.0% of predators, with 12.5% of unknown identity. The depredation
rate did not vary among site-types, or between open and domed nests, and there were no statistically significant interactions.
Nest height strongly affected depredation rates by particular types of predator; depredation rates by mammals were highest
at ground nests, whereas attacks by birds were most frequent at shrub nests. These effects counterbalanced so that overall
there was little net effect of nest height. Mammals accounted for 78.4% of depredated ground nests and birds for at least
47.4% of shrub nests (and possibly up to 70.1%). The main predators were species characteristic of rainforest, rather than
habitat generalists, open-country or edge specialists. For birds that nest in the tropical rainforest understorey of the study
region, it is unlikely that edges and linear remnants presently function as ecological population sinks due to mortality associated
with increased nest predation. |
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Keywords: | Bird Edge Forest Fragmentation Nest shape Nest predation Nest height Rodent |
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