Monitoring winter shorebird populations in the Bay of Panama: 2013–2017

The wetlands of the Bay of Panama are composed of mangroves, mudflats, marshes, and sandy or rocky beaches extending for over 200 km along the Pacific coast of Panama. This area is one of the most important sites for migratory shorebirds in the Western Hemisphere. As part of a wider shorebird monitoring project along the western flyway, the Panama Audubon Society has conducted an annual winter ground-based shorebird census from 2013 to 2017 over three sites which include 21.2 linear km of the wetlands most heavily used by shorebirds. Eight species, out of 23 recorded over the five years, comprised 99.5% of all shorebirds counted and their census numbers provide a baseline against which to measure any future changes in winter population or habitat usage. Four of these species had the highest linear density at the site closest to the city and which had experienced a significant increase in mangrove growth coincident with substantial
urban growth over the previous two decades. Three smaller, but much more abundant, species preferred the coast farthest from the urban area with no mangroves. Recognition of the  importance of the wetlands of the Bay of Panama for shorebirds is based in part on an aerial survey in January 1993 (Morrison et al. 1998). Our results show that the winter populations of several species are substantially higher than the 1993 survey, either because of a difference in methodology or an actual increase in their winter populations. Regardless of the underlying cause, our study shows that these wetlands have more shorebirds than previously thought.