River otters kill dozens of brown pelicans at Point Reyes, birds begin fleeing

Field biologists Terence Carroll and Megan Isadore of the River Otter Ecology Project conducted shoreline walks at Abbotts Lagoon every 7-10 days from June through November 2023, mapping and marking dead brown pelicans to avoid double counting. Their effort uncovered 73 fresh pelican deaths on 17 of 19 visits, with up to 11 birds found in a single survey, and they identified otter predation by the characteristic removal of heads and necks.

Data from eBird indicated that mortality peaked when larger pelican flocks arrived, exposing lone individuals along the water's edge. Although no water-quality problems were detected, the researchers suggest that cold-water swimming drives otters to target the energy-rich, slow-moving birds. By late summer 2024, observations showed pelicans fleeing as otters approached, hinting at learned avoidance.

The study, published in the IUCN Otter Specialist Group Bulletin, notes that otter leftovers provide carrion for terrestrial scavengers like coyotes, creating a new nutrient pathway between lagoon and land. Despite the high local death toll, overall pelican numbers at Point Reyes remain stable, making the phenomenon a notable but not population-threatening ecological development.