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Extramural Research

Grantee Research Project Results

Grantee Research Project Results

A Multitrophic Interaction Involving Scale Insects and Birds in Humid, Montane Forests of Mexico

EPA Grant Number: U916078
Title: A Multitrophic Interaction Involving Scale Insects and Birds in Humid, Montane Forests of Mexico
Investigators: Gamper, Heather A.
Institution: Florida International University
EPA Project Officer: Just, Theodore J.
Project Period: January 1, 2002 through January 1, 2004
Project Amount: $53,844
RFA: Minority Academic Institutions (MAI) Fellowships for Graduate Environmental Study (2002)
Research Category: Ecological Indicators/Assessment/Restoration , Academic Fellowships , Fellowship - Environmental Science and Engineering



The objective of this research project is to investigate the use of a sugar solution, honeydew, by birds in highland forests near Xalapa, Mexico.


Honeydew, a sugar solution produced as waste by scale insects and other phloem-feeding insects, is commonly a prized food for many species of ants. The relationship between ants and scale insects is well documented in the literature. Less frequently reported than these ant-scale insect interactions is the use of honeydew by birds. A honeydew-producing scale insect (family Margarodidae, tribe Xylococcini, Stigmacoccus garmilleri), has been found to be associated with oak trees (Quercus spp.) in highland forests more than 2,000 meters in elevation near Xalapa, Mexico. At the study site, trees in both pasture and forest support locally dense populations of Margarodidae. Resident and migratory birds were observed foraging on honeydew, and Audubon's warblers (Dendroica coronata auduboni) actively defended the honeydew resource. Data from 160 hours of observation at 40 focal trees suggest that honeydew may be an important component of the diet of Audubon's warblers and other species of birds. Ants also were observed feeding on honeydew, but the incidence of consumption did not approach that of avian species. Scale-insect densities and honeydew sugar concentration were recorded to investigate changes in seasonality, time of day, temperature, humidity, habitat type, and elevation. Data collected from focal trees in pasture and forested areas also were used to analyze similarities and/or differences in description of this system between these two dissimilar habitat types.

Supplemental Keywords:

fellowship, honeydew, avian, multitrophic, birds, Audubon warblers, avian species, ants, scale insects, Mexico, highland forests.

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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