Abundance and phenology of Red Knots in the Guerrero Negro–Ojo de Liebre coastal lagoon complex, Baja California Sur, Mexico
10 – 15
1 April 08
Roberto Carmona, Nallely Arce, Victor Ayala-Pérez, Gustavo D. Danemann
Marine Biology Department, Universidad Autónoma de Baja California Sur. Apartado postal 19-B, La Paz, Baja California Sur, CP 23000 Mexico.
To determine the spatial and temporal distribution of Red Knots Calidris canutus roselaari in the Guerrero Negro–Ojo de Liebre coastal lagoon complex, including the Guerrero Negro Saltworks, we carried out a monthly census from July 2006 to June 2007. The aggregate total of the twelve monthly counts was 32,059, and the maximum count of 6,458 was made in September 2006. The Red Knots arrived in July and August and their numbers were high until October, decreased in November and increased again in December (to 4,595), but then declined constantly until March; in April there was a notable increase to 4,647. We suggest two hypotheses to explain the fluctuations in numbers: (1) that there is onward migration with birds departing in late autumn and more birds arriving for the winter or (2) that Guerrero Negro is the terminus of the migration and numbers vary because of local movements to and fro other sites within a 200 km radius. Seventy-seven per cent of all knots counted occurred in 11 of the 45 zones into which we divided the study area. We classified the 11 zones into four sections according to their seasonal use by the knots: Los Medanitos was important in autumn; Estero Norte in spring; Guerrero Negro was consistent and with regular abundance throughout the year; and Salitrales showed large fluctuations. We conclude that the abundance of knots in these four sections can be used to estimate the total number in the entire lagoon/saltworks complex (r2= 0.94).