Temporal and spatial variation of waterbirds at Sayula Lagoon, Jalisco, Mexico: a five-year winter season study

Waterbird surveys were conducted monthly over five winters, from October to March 2004-2007 and from October to March 2009-2011, as the migratory species are present in the study area in these months. Thirty (1 ha) permanent plots were randomly stratified using a numbered grid for each zone type. Each plot was located at a minimum distance of 500 m from each other in order to avoid double counts of the same individuals, following Ojasti and Dallmeier (2000). Plots were delimited with red and yellow sticks to allow their rapid location. Observations were made in the eight hours after sunrise. We recorded all the bird species seen and total abundance was also recorded. The block method (Howes and Bakewell, 1989) was used to estimate numbers whenever large flocks (> 300 birds) were present. The seasonal status of species was contrasted with those published in Howell and Webb (2001). The category of species risk was assigned using the Mexican Law (NOM-059-SEMARNAT-2010) and the IUCN Red List of Threatened Species. The on-line taxonomic Check-list of North American birds (AOU, 2015) was used.