First published March 18, 2025 | https://doi.org/10.1675/063.047.0405
AUTHORS
Thomas P. Ryan
Centro de Investigación Científica y de Educación Superior de Ensenada
Medardo Cruz López
Cornell Lab of Ornithology
Adriana Hernández Alvarez
Pronatura Noroeste
Brunilda Rebeca del Carmen Menares Parra
Organización para la Sustentabilidad y la Conservación del Medio Ambiente
Ángeles Yazmín Sánchez Cruz
Centro Intercultural de Estudios de Desiertos y Océanos
Eduardo Palacios
Centro de Investigación Científica y de Educación Superior de Ensenada
Lauren Dolinski
Prescott College Kino Bay Center for Cultural and Ecological Studies
Germán N. Leyva García
Centro de Investigación en Alimentación y Desarrollo
Manuel Muñoz Espinoza
Ejido Rodolfo Campodonico
Graciela Tiburcio Pintos
Organización para la Sustentabilidad y la Conservación del Medio Ambiente
Edgar Amador
Centro de Investigaciones Biológicas del Noroeste
Juanita Fonseca
Cornell Lab of Ornithology
Fransico Jaime Martínez Reyes
Prescott College Kino Bay Center for Cultural and Ecological Studies
Liliana Ortiz Serrato
Centro de Investigación Científica y de Educación Superior de Ensenada
ABSTRACT
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.
