Figure 2

Roost aggregation size for seven species of bird. a. Temporal patterns of roost size for American robins, b. European starlings, and c. House sparrows. Roost sizes of individual American robins in panel 2a and house sparrows in panel 2c observed more than three times are represented by different open symbols. Closed circles show roost sizes for individuals observed less than three times. Points for American robins are jittered slightly to facilitate presentation. d. Mean roost size of for all species studied. Four species, Tufted titmouse, Northern cardinal, Gray catbird, and Mourning dove showed no significant variation over time; roost sizes for other species are estimated on the median date of the data in panels (a-c). Bold crossbars indicate the mean, boxes encompass ± 1 SE of the mean, and whisker lines represent 95% confidence bounds around the mean.