Effect of Epiphyte Removal on Common Bush-Tanagers and Golden-crowned Warblers

January 1, 2008 by Gregory Gough

Small yellow and olive bird

Tropical forests support more bird species than temperate forests. One of the differences that might account for part of the greater bird diversity is the presence of epiphytes, plants that grow on the branches of other plants (such as orchids and bromeliads).

To test how important epiphytes are to two common tropical birds, the common bush-tanager and golden-crowned warbler, scientists removed epiphytes from trees in one set of study plots and compared them to study plots with epiphytes left intact.

The study was done in a shade grown coffee farm in Xalapa, Mexico. Epiphyte removal is a common practice on coffee farms as it lets in more light for the coffee shrubs.

For common bush-tanagers, the loss of epiphytes made the forest seem uninviting. They were 5 times more likely to emigrate from non-epiphyte plots to those with epiphytes.

For golden-crowned warblers, the loss of epiphytes was met with a resounding "Meh!" They were equally at home in plots with or without epiphytes.

The difference in response between the tanager and the warbler is likely due to their different life histories. Golden-crowned warblers nest on the ground and spend much of their time near the forest floor eschewing the epiphyte-laden branches in the canopy. Common bush-tanagers, on the other hand, spend a lot of time looking for food in epiphytes and often build their nests in them.

This article summarizes the information in this scientific paper:

Cruz-Angon, Andrea, Sillett, Terence Scott and Greenberg, Russell S. 2008. An Experimental Study of Habitat Selection by Birds in a Coffee Plantation. Ecology, 89(4): 921-927.

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