Cooperative Breeding Behaviors in the Hawaiian Stilt (Himantopus mexicanus knudseni)

Cooperative breeding, which is commonly characterized by non-breeding individuals that assist others with reproduction, is common in avian species. However, few accounts have been reported in Charadriiformes, particularly island-nesting species. We present observations of cooperative breeding behaviors in Hawaiian Stilts during the 2012-2020 nesting seasons on the Hawaiian islands of O‘ahu and Moloka‘i. We describe three different behaviors that indicate cooperative breeding: (1) nest sharing; (2) helper at the nest; (3) cooperative chick rearing. Our observations suggest an ideal opportunity to examine the evolution of cooperative breeding behaviors in the order Charadriiformes.