Por Eduardo Palacios y Antonieta Valenzuela 

The black brant (Branta bernicla nigricans) is a goose that travels long distances to spend the winter and spring almost exclusively in the west coast of the United States and northwestern Mexico, mainly in Baja California.

Nearly 85% of the black brant population winters in four coastal lagoons of Baja California: San Quintín Bay, Ojo de Liebre Lagoon in Guerrero Negro, San Ignacio Lagoon and Magdalena Bay. The rest winters along the west coast of Mexico, from the Colorado River Delta in Sonora to Santa María Bay in Sinaloa.

Since the black brant is a priority migratory species, it is legally protected in Mexico under the Official Mexican Standard NOM-059-SEMARNAT-2010, where it is classified as a threatened species.

Pacific Brant arrive at their wintering grounds in the fall after migrating from their staging areas in Izembek Lagoon, Alaska (Ward et al. 1994) and then pass the winter and spring in traditional coastal lagoons on the Pacific coast of US and northwestern Mexico.

Brant depend on eelgrass (Zostera marina) as their primary food source and are, therefore, very vulnerable to changes in the quality and quantity of this seagrass in their overwintering sites. The decline in eelgrass, which was first detected in the 1980s and 1990s, appears to be linked to climate change issues (increasing air and water temperatures, changes in nutrient availability, and episodic flooding events) in the southern temperate Pacific.

Black brant count

In mid-January 2016, Eduardo Palacios PhD, together with a team of researchers and volunteers, carried out black brant ground surveys with the purpose of calculating the size and distribution of the population of this species.

By the end of the project, it was estimated that a population of 72,390 black brant was wintering in northwestern Mexico. This number represents 46% of the total black brant population in western North America, which is about 159,000 brant.

In the Baja California peninsula, 55,066 brant were counted, including 19,694 estimated in the San Quintín Bay and only 317 in Punta Banda, Ensenada.

	2014	2015	2016
Northwestern Mexico	97 142	68 432	72 390
Baja California	68 290	44 533	55 066
San Quintín	14 344	18 807	19 694
Punta Banda	350	750	317

The population wintering in northwestern Mexico was 3.958% larger than in 2015; it increased by a 24% in the wetlands of Baja California (especially in three small wetlands in Ojo de Liebre Lagoon and San Ignacio Lagoon), whereas it decreased by a 28% in mainland Mexico.

In 2016, the wetlands in the Baja California peninsula were home to 76% of the black brant population in northwestern Mexico; the remaining 24% was found at seven locations in the coast of mainland Mexico, predominantly in Sonora.

The black brant count was carried out in a 14-day period and the ground surveys were conducted in 21 traditional wintering sites, including 11 locations on the Pacific coast of Baja California and 10 in the mainland coast of the Gulf of California.

This Project was funded by the U.S. Fish and Wildlife Service (Division of Migratory Bird Management) and Terra Peninsular, A.C. provided administrative support.