Naturalist’s Notebook: Great Blue Heron Fends Off Gulls

23 December 2009
Isabella Reservoir
Kern County, California

I saw a remarkable interaction this morning as a lone Great Blue Heron and seven gulls—one juvenile Herring and the rest adult California Gulls—chased each other low over the water, well away from shore. At first I thought the gulls were mobbing a Bald Eagle until a diving gull caused the big bird to extend its long neck and head forward and simultaneously swerve sharply away from the attack. Then the heron suddenly wheeled around, singled out a gull, and began a determined pursuit, with all the other gulls falling in line behind them. After a minute or so of swerving this way and that, the roles switched, and the heron was once again being chased by the gull mob.

The role of pursuer and pursued switched several times as I watched. The heron usually became the aggressor when several gulls fell back to swoop at the water’s surface. I suspect the gulls were retrieving fish disgorged by the heron, though they were too far away for me to be certain.

In the final chase, the gulls broke off from their pursuit of the heron and started swooping over a small patch of water. The heron also rushed to the same place and, with its long legs dangling, eased down onto the water. For the next few minutes it floated in the deep water as easily as a duck, with its long neck fully extended up and forward. But I never saw the heron take anything from the water, probably because it had to fend off the attacking gulls.

The episode ended when a rapidly approaching American White Pelican prompted the heron to fly away. The pelican hit the water and skidded into the contested patch of water, no doubt expecting to find easy food. But even the gulls had lost interest and soon sailed away, leaving the pelican floating alone on the smooth waters.