Figure 3. Geographic variation in the seasonal patterns of warbler and sparrow flight calls.

Average seasonal pattern in warbler (solid line) and sparrow (dashed line) nocturnal flight call (NFC) detections during fall in 2010 and 2011 at eight coastal sites in southern Rhode Island, USA (see Figure 1): (A–B) two sites on the mainland coast, (C) one on Aquidneck Island, and (D–H) five on Block Island. Seasonal patterns were estimated with generalized additive models; the seasonal trend of the linear predictor (and 95% confidence interval) is illustrated with other variables held at their mean value. All plots share the same vertical scale to facilitate comparisons of NFC detections among locations. Note that each unit change in the linear predictor represents nearly a tripling of NFC detections.