The California Least Tern (Sternula antillarum browni) population is declining in California, U.S.A., but little is known about the Least Tern population breeding in the Gulf of California, México. Because of this decline in California, it is important to determine current distribution, population trends, and movements in the nearby Gulf of California. Emigration from coastal California to the Gulf of California is one possible reason for the decline. We analyzed Least Tern colony counts to provide an overview of its current breeding distribution, abundance trends, and connectivity in the Gulf of California. We documented 84 nesting sites, including 61 extant, 10 historic, and 13 sites of unknown status. We estimated the Gulf of California population to be 2,400–3,500 adults, breeding in the 61 extant colonies. Colonies here were small, averaging 49 adults/colony. Most colonies occurred in the Upper Gulf, Gulf Entrance, and on the southern end of the Baja California Peninsula. We estimated a significant negative trend for the population of the Gulf of California. We found no marked individuals in the Gulf of California nesting colonies banded in California or the Baja California peninsula, indicating no regular movement away from coastal California.
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18 March 2025
The Current Status and Distribution of the Least Tern Breeding in the Gulf of California, México
Thomas P. Ryan,
Eduardo Palacios,
Edgar Amador,
Medardo Cruz Lopez,
Lauren Dolinski,
Juanita Fonseca,
Adriana Hernández Alvarez,
Germán N. Leyva García,
Francisco Jaime Martínez Reyes,
Brunilda Rebeca Del Carmen Menares Parra,
Manuel Muñoz Espinoza,
Liliana Ortiz Serrato,
Ángeles Yazmín Sánchez Cruz,
Graciela Tiburcio Pintos
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Waterbirds
Vol. 47 • No. 4
February 2025
Vol. 47 • No. 4
February 2025
colonies
connectivity
conservation
decline
distribution
Gulf of California
Least Tern
