Figure 3.

Figure 3. Changes in the isotopic composition of western white-winged dove diets through their stay in the Sonoran Desert. Points are means and bars are standard error. Means are from 6 to 10 birds. Note that starting in the middle of June the carbon isotopic composition of the doves approaches the composition of saguaro fruit (stippled bar). We used a two endpoint mixing model (see Wolf and Martínez del Rio 2000) to transform d13C values into percent of saguaro carbon incorporated into the doves' tissues. During July, at the peak of saguaro use, the carbon isotopic composition of the doves' tissues closely resembles that of saguaro.