Post-Fledging Parental Care in Tree-Nesting Double-Crested Cormorants (Nannopterum auritum)

Post-fledging parental care occurs in a wide range of colonial waterbird species but data on the behavior are limited. The behavior is hypothesized to contribute towards offspring survivorship, but opportunities for post-fledging parental care are constrained for migratory species. Two datasets were used to examine the behavior in a Great Lakes tree-nesting Double-crested Cormorant (Nannopterum auritum) colony: annual monitoring of nest success, and focal observations of successful nests. For eight nesting seasons (2012–2019) a total of 631 sample nests were tracked for nest success, fledge date, number of chicks fledged, and post-fledging adult attendance at the nest site. During the post-fledging period, 52.2% of successful nests (n = 425) had adult attendance. Fledge date was a predictor of post-fledging adult attendance (earlier nests more likely to have the behavior) but not number of chicks fledged or year of observation. Post-fledging adult attendance was estimated to average 15.9 days in length. Focal observations confirmed that fledglings visited a nest and were fed if a parent was present (10/11 times). These findings confirmed post-fledging parental care in tree-nesting Double-crested Cormorants, but late nesting birds have reduced opportunity to provision after fledging.