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Accession Number 5003440

Title The hormonal control and the effects of endocrine-active contaminants on avian

secondary sex characteristics

Project Description Measuring the effects of endocrine-active chemicals (EACs) on wildlife is a challenge that is made

complicated by the complexity of the endocrine system and the wide variety of reproductive

patterns seen in nature. Biomarkers with some utility in the field to assess the effects of exposure

to EACs will be an important tool for the wildlife biologist to evaluate the impact of these

compounds on populations under their management. Morphological secondary sexual

characteristics of birds are features that have promise as biomarkers for EACs: they are readily

visible, measurements can be made without killing the bird, aspects of plumage (coloration and

pattern) and the color of soft parts are under some degree of hormonal control and often these

characters are crucial to reproductive success through courtship and mating. There is useful

information extant on the hormonal control of molting schedules in many bird species, and

important but less extensive information on the control of color and patterning of plumage and bills

and other dermal structures. More information on the degree of hormonal control of avian

secondary sexual characteristics, and the sensitivity to known EDCs is needed before these can

be useful biomarkers in birds. This project will develop measures for plumage, soft parts (bill and

dermal structures) color and pattern in American kestrels (Falco sparverius). In addition,

experiments will characterize the effects of both steroid hormones and EACs on plumage and soft

parts in species from two different groups of birds: one that develops secondary sexual

characteristics in advance of breeding (i.e. has an alternate plumage) and one that does not (i.e.

has only a basic plumage). These two groups of birds differ in the hormonal control of their


Keywords birds, contaminants, endocrine disruptors, human impacts, kestrels, toxicology,

Principal John B French, USGS Patuxent Wildlife Research Center:;


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