SPRING 2002/VOLUME 16, NUMBER 2

In 2001, participants of The Birdhouse Network (TBN) reported that 26 percent of nest boxes were exposed to pesticides within 100 feet. The data were collected for a pilot study on the effects of pesticides on the breeding success of cavity-nesting birds. For the study, conducted in partnership with the American Bird Conservancy, participants answered questions about pesticide use near their nest boxes, in addition to providing the nest-box monitoring data they normally submit. TBN also recruited some participants to collect data and test protocols on golf courses.

Figure 1. Percentage of reported nest attempts in 2001 that were exposed to pesticides within 100 feet. Species with fewer than 25 nesting attempts were excluded. Total number of nest attempts reported for each species is indicated in parentheses.

We received pesticide data for about 3,400 of the 6,800 nest boxes reported. Of these, 26 percent were exposed to pesticides applied within 100 feet of the box. For most species, the percentage ranged from 20 to 30 percent (Figure 1). Only Mountain Bluebird and House Sparrow nests were exposed to pesticides more than 40 percent of the time. Fewer than 10 percent of Carolina Chickadee nests were exposed.

Habitat type probably explains some of this variation. Pesticide exposure was highest on golf courses, with more than 60 percent of boxes exposed. Surprisingly, participants reported fewer than 20 percent of boxes exposed to pesticides in agricultural fields. New questions this year will help reveal whether this low figure resulted from a reporting bias in cases where participants did not verify pesticide use with landowners.

Figure 2. Percentage of pesticides used within 100 feet of next boxes, singly and in combination with other pesticides.

Figure 2 shows the types and proportions of pesticides applied within 100 feet of nest boxes. Herbicides were used most often (84 percent of nest-box sites exposed to pesticides), followed by fungicides (35 percent) and insecticides (32 percent).

In the coming months, we will use the 2001 data to examine the relationships among habitat, pesticide exposure, and breeding success of cavity-nesters. To our knowledge, no other repository of continentwide data incorporates these very important factors. We'd like to thank everyone who contributed data and encourage your participation during 2002, because understanding complex questions about the effects of pesticides on the breeding success of birds will require several years of data collection and analysis.