Edgar Amador

Colonies of Four Species of Terns and the Black Skimmer in Western Mexico

Abstract During the 2003 breeding season 367 historic, potential, and current nesting sites of larids (Fam. Laridae) along the coast of western Mexico were surveyed. In 2004 and 2005, three areas: Guerrero Negro, in Baja California Sur; Marismas Nacionales, in Nayarit-Sinaloa; and Laguna Cuyutlán, in Colima were surveyed more intensively. In 2003-2005, there were nine nesting sites and probably between 200 and 300 breeding pairs of Caspian Tern (Sterna caspia); eleven confirmed nesting sites and at least 13,000 breeding pairs of Royal Tern (S. maxima); two nesting sites, one of which included almost the entire population, and 90,000 breeding pairs of Elegant Tern (S. elegans); four nesting sites and about 20 breeding pairs of Forster’s Tern (S. forsteri); and 13 nesting sites and about 1,000 breeding pairs of Black Skimmer (Rynchops niger). Breeding of Caspian and Elegant Terns on the Pacific coast of Mexico is confined to the northern areas, whereas that of Royal Terns and Black Skimmers occurs at selected sites along most of the coast. Forster’s Terns nest in two widely separated areas, one in the northern section of the coast, and one in the southern section.

Waterbirds of the Lagoon Complex Magdalena Bay-Almejas, Baja California Sur, Mexico

Abstract The spatial distribution of avifauna was documented in Magdalena Bay, the largest coastal wetland on the Pacific coast of the Baja California peninsula. An inventory of waterbirds in the three wetland zones of Magdalena Bay-Almejas, Baja California Sur was conducted by boat. Composition, abundance, and distribution of species were determined in 12 coastal censuses conducted from February 2002 to February 2003. A total of 207,383 individuals of 80 species and 20 families were recorded. Seven listed species breed in the wetland. Only ten out of 80 species were very common, while the others were occasional along the coastline. Guilds with highest populations were pelicans and allies (54%), followed by shorebirds (23%), and gulls, terns and skimmers (14%). The highest richness of 63 species was recorded in the Santo Domingo Channel in autumn. In contrast, the highest abundance (50,082) was recorded in fall in Magdalena Bay. Migratory birds explained spatial and temporal changes in richness, while resident pelicans and allies explain abundance variations. The highest species richness was observed in mangrove zones, particularly in the Santo Domingo Channel. Therefore, this habitat together with breeding and gathering places used for other activities, should be primary targets for future management and conservation initiatives.

Population Status of American Oystercatchers (Haematopus palliatus frazari) Breeding in Northwest Mexico

Abstract. The western race of the American Oystercatcher (Haematopus palliatus frazari) is a resident and endangered shorebird of western Mexico. Its breeding population and conservation concerns are poorly known, but recent information indicates extremely low numbers and a discrete breeding distribution. Because of loss and degradation of sandy beaches by coastal development and disturbance from human recreational activities, the American Oystercatcher is a priority species in the Shorebird Conservation Plans of the United States and Mexico. Research on its distribution and abundance during the 2009 breeding season resulted in the identification of 2,286 adults in northwest Mexico. Although the population is higher than previous estimates, its distribution is more restricted than expected. It is distributed almost exclusively in northwest Mexico, and 80% of the total breeding population is found on the islands of Sinaloa and Baja California Sur. Based on these results, this species was officially federally listed on the Mexican List of Protected Species in 2010. This legal mechanism will promote the management and protection of this priority subspecies as well as other waterbirds occupying the same habitats.