Aggregation is a common strategy among waterfowl that can enhance foraging efficiency and reduce predation risk for individuals within the group. When foraging in flocks, individual behavior may vary depending on position within the group, with outer-edge individuals often exhibiting more vigilance and reduced foraging compared to those in the interior. While these patterns are known for some waterfowl species, it remains unknown whether flock position impacts foraging behavior in American Coots (Fulica americana). We investigated this question by observing multiple, different sized, flocks of American Coots across numerous sites in the Willamette Valley of Oregon. We hypothesized that coots on the edge of a flock would dive less frequently and spend less time underwater per dive than those in the center, regardless of flock identity. We also predicted that individual dive frequency would increase with flock size, independent of flock position. Our results showed that outer-edge coots dove significantly less frequently than inner coots, but that this pattern was dependent on flock size. Overall dive frequency and dive time decreased with increasing flock size, but the difference in diving frequency between inner and outer flock coots was more pronounced in larger flocks. We discuss potential explanations for these findings, suggesting that these patterns may reflect context-dependent anti-predator or predator-avoidance strategies.
