updated: May 28, 2011

go fujita
ecology, animal behavior & conservation

my study

Habitat selection of birds in patchy agricultural landscape

Agricultural landscapes are highly patchy, as you know. Light brown of a wheat field is often adjacent to fresh green of a meadow. Shining water of a rice paddy is edged with green grass ridges or footpaths.

Paddy fields before planting (Boso, Japan)

Thanks to numerous efforts made by conservation biologists, we do know now these human made landscapes do not only produce foods for human beings, but also sustain biodiversity, at least, as alternative habitats of natural grasslands or wetlands.

I consider the agricultural landscape a model system to study decision making on patch choice or habitat selection of animals. If the landscape is perfectly even, patch choice is no longer problem. An individual can gain the same benefit from anywhere it settles in. Patch choice can be an issue under the heterogeneous landscape only and, of course, the world is heterogeneous more or less. I believe that the agricultural landscape is a clear-cut example of various habitats in the world.

In addition, it is easy to measure what patch animals use within the landscapes. These mosaic structures are likely to generate spatial structures of populations that might govern dynamics of the populations.

barn swallows aggregating in open fields

Farmlands in Satsuma peninsula, the southernmost of mainland Japan, are dominated by potato fields and tea bushes. Within the fields, barn swallows, a summer visitor, aggregate into particular sites from early August to late September, between just after the nesting periods and before the migration season of the swallows.

In this area, I carried out field studies on spatial patterns of swallows, and represented the following results (Fujita and Higuchi 2005b):
  • Most swallows aggregated into poultry farms that are scattered within the fields
  • Numbers of swallows aggregated were ranged from around 20 to more than 2,000
  • Swallows aggregated into the farms repeated foraging primarily on soldier flies above tea bush leaves and resting on electric wires
  • High densities of soldier flies distributed only near, within 100 m, from the farms
  • Numbers of swallows aggregated were stable during the daytime
  • The greater amounts of flies near the farms, the larger numbers of swallows there
According to these facts, I concluded that, during the daytime after the nesting periods, swallows aggregated into poultry farms to forage soldier flies that emerged from feeds of the farms. I believe that this swallow-fly system in an agricultural landscape should be a suitable subject to study on foraging patch choice by animals at large scales. So far, among numerous studies dealt with spatial patterns of animals, limited studies treated relationship between prey amounts and predator distributions at large scales in natural system.

and now..

I focus on ecological process generating the variations of swallow numbers aggregating poultry farms at large scales in Satsuma peninsula, south Japan.

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