First documented instance of cannibalism in the Critically Endangered Madagascar Fish Eagle <i>Icthyophaga vociferoides</i>

Cannibalism is rarely documented in raptorial birds, despite the widespread occurrence of siblicide. This study focused on this phenomenon in the Critically Endangered Madagascar Fish Eagle Icthyophaga vociferoides (family Accipitridae) within the Tsimembo Manambolomaty Complex Protected Area (TMC-PA). During the 2023 breeding season, camera traps were installed at two nests containing two nestlings each. A review of 3 490 images from both nests and 394 video recordings from one of them revealed that siblicide occurred between 7 and 10 days after the hatching of the second nestling in both nests. The older sibling killed the younger through intermittent pecking, averaging 32.6 ± 3.7 pecks per day over a three-day period in both nests, inflicting a bloody wound that led to death. The day after siblicide in both nests, camera trap footage captured a cannibalistic event involving the adult female. She approached the deceased nestling, dissected abdominal and thoracic regions, and consumed portions herself. She then fed smaller fragments to the surviving nestling. This provisioning behaviour lasted 30 minutes, alternating between self-consumption and feeding. This is the first documented case of cannibalism in the Madagascar Fish Eagle. We suggest that resource constraints are unlikely to explain this phenomenon. However, further studies with a larger sample size are needed to clarify the underlying causes.