Methodology for shorebird monitoring in Mexico and Central and South America

In Mexico there have been few efforts to develop monitoring programs to systematically track changes in shorebird populations. Therefore the object of this study was to develop and validate a methodology to implement such a program for any wintering site. This was developed using shorebird count data from one of Mexico’s most important shorebird wintering sites, the Guerrero Negro Wetland Complex.

We carried out monthly shorebird counts at Guerrero Negro between July 2006 and June 2007 to identify the sites where the greatest numbers occurred. For this purpose, we divided the study area into 45 zones, based on the type of substrate (mud, sand, dunes and marshes) and origin (natural and artificial). We selected 24 of the zones (based on abundance and geographic relevance) in which 73% of the aggregate number of shorebirds was counted. We found that the abundance of shorebirds in these zones allowed us to predict the total abundance of shorebirds in the whole 45 zones with 98% confidence. If only the 24 zones had been counted there would have been a reduction in effort of about 53%. A validation exercise undertaken in a portion of the lagoon complex allowed us to conclude that the monitoring model proposed predicts abundance with 95% confidence.

Important wintering sites such as Guerrero Negro are key for developing monitoring programs because they allow sampling trials at different scales. It is also valuable to focus studies on such sites because they can support large proportions of biogeographic populations; e.g. Guerrero Negro hosts >30% of the population of three shorebird species or subspecies.

The methodology we propose is for the establishment of a common shorebird monitoring plan for wintering sites in Mexico, Central and South America that is simple to perform, reliable and efficient. Applying the same method will allow the integration of shorebird monitoring efforts at regional, national and international scales in a way that will greatly improve our ability to determine shorebirds population trends.