ESTIMATION OF THE Charadrius montanus J. K. Townsend, 1837 POPULATION IN THE NORTHEASTERN MEXICO

Abstract

Charadrius montanus nests, mainly, in the desert grassland of western United States of America and spend the winter at the north of Mexico. The aim of this research was to monitor their populations in the El Tokio region, located at the northeast of the Mexican territory. A counting of all individuals was made during the summers and winters from 2003 a 2006 in eight sites, in the states of Coahuila, Nuevo León and San Luis Potosí, at least once during each season. The number and length of transects were determined from the size of the colony to be assessed. Density and population size were calculated for each sampling. The estimations were made with the Distance Beta 5.0 program Bird annual density was significantly different in the years of study (Kruskal-Wallis ANOVA, H = 41.13, P < 0.0001), and that of birds varied significantly among sites (F = 2.647; P = 0.0007). During winter, the density in the La Soledad, NL, was significantly higher (t0.05, 3= 4.235, p = 0.024) than that recorded in the other localities; and in this time of the year it was greater than that estimated for summer, which reflects that the migratory populations mix with the residents. However, it is still unknown if the summer birds remain in the area during the cold time. The estimated winter population represents around 8 % of the total number of birds of the species, while that of fall adds 3 to 6 percent to it.