Every fall, millions of migratory birds leave their nesting grounds and head south to the tropics. Scientists wondered how this might affect the resident tropical birds.
Researchers set up a study site on a shade coffee farm in Mexico. Shade coffee, coffee shrubs grown under a canopy of trees, is excellent habitat for both resident and migratory birds.
A small resident bird, the rufous-capped warbler (pictured at right), was followed year-round to see if its behavior changed when migratory birds moved in.
When migrants were absent, during the wet season, the rufous-capped warbler spent equal time in the tree canopy and in the coffee shrub layer, although it was more successful in catching its insect prey in the canopy layer.
But during the dry season, when the migrants moved in, the rufous-capped warblers spent 80 percent of their time in the shrub layer while the migrants spent the majority of their time in the canopy.
This article summarizes the information in this scientific paper:
Jedlicka, J., Greenberg, Russell S., Perfecto, I., Philpott, S. and Dietsch, Thomas Victor 2006. Seasonal foraging niche shifts of tropical avian residents: resource competition at work? Journal of Tropical Ecology, 22: 385-395.
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