Bonaparte’s Gulls Feeding

Bonaparte’s Gulls are a small “Black headed” gull found throughout much of North America. They can be found breeding in Alaska and Canada, migrating though the middle of the continent and wintering in the southeast and along all coasts. These small gulls can be found in coastal Texas during the winter on any wetland environment both freshwater and marine.

Bonaparte’s Gulls feeding methods are diverse, taking fish and invertebrates mainly by aerial or surface dipping. They also feed by patrolling shorelines and tidal pools. A recent outing to Galveston Bay on the Upper Texas coast revealed an interesting strategy employed by these successful hunters. – Social Parasitism
Social Parasitism is defined as an interspecies relationship based on exploiting interactions between members of differing species.

Large numbers of Red-breasted Mergansers gather in Texas Bays during late winter. Recently, I observed a large group of Bonaparte’s Gulls (about 75 individuals), actively feeding over and among a huge raft of Red-breasted Mergansers. An estimated 300 Red-breasted Mergansers were actively diving and pursuing prey along the Texas City Dike in Galveston Bay.

The strategy employed by the gulls depends on the Merganser’s ability to dive and drive concentrations of prey to the surface. The Bonaparte’s either swim with or fly above the Merganser raft, picking off panicky bait fish. These small gulls are very agile and maneuver with surprising ease in tight quarters. The Mergansers were in constant pursuit with the Bonaparte’s in tow for at least 30 minutes.

Along with the Bonaparte’s, I observed several Herring Gulls and a few Laughing Gulls also foraging. They were very few in numbers compared to the Bonaparte’s, however.

If you come across an interaction between Bonaparte’s and a diving species, take the time to observe and enjoy. Its quite a show put on by this successful predator.