Do bird perching structures elevate seed rain and seedling establishment in abandoned tropical pasture?

  • Published source details Holl K.D. (1998) Do bird perching structures elevate seed rain and seedling establishment in abandoned tropical pasture?. Restoration Ecology, 253-261.


Lack of seed dispersal may limit tropical forest recovery in abandoned pasture land. This study determined whether providing bird perches enhanced seed dispersal and tree seedling establishment in an abandoned pasture by the Las Alturas Biological Station, southern Costa Rica.

In May 1995, 12 perches (six each of two types) were installed in the pasture. Crossbar perches comprised a 6 m post with two horizontal crossbars 2.2 m long at the top. Branch perches (5.8 to 7 m) comprised a branch of Inga spp. The perches were dug into the soil to 1 m depth, thus height was approximately 5 m. Perches were installed in pairs (one of each type) each 10 m apart. Three pairs were erected at about 25 m and three pairs at 250 m from the forest-pasture edge. From June 1995 to March 1996 bird perch use was recorded (total 72 hours observation time), including periods when bananas were provided during baiting trials.

Seed rain and tree/shrub seedling establishment was measured below perches and in plots in the open pasture from 1 June 1995 to 31 May 1996.

Three bird species were observed on crossbar perches and 10 on branch perches. Bird visitation rates were low but significantly higher on branch than on crossbar perches (0.41 and 0.12 visits per hour on branch and crossbar perches, respectively). The number of animal-dispersed seeds was significantly higher below branch perches than below crossbar perches or in open pasture. Despite differences in seed rain, cover of animal-dispersed plants and the number of seedlings of such plant species were similar below both perch types and in open pasture. Baiting perches with bananas did not increase bird visitation rates or seed rain. Results suggest that, although perching structures increase seed dispersal, they do not overcome barriers to forest recovery such as seed predation and low seed germination.

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