Methods

To fill critical information gaps about where, when and why birds stopover on migration, the Neotropical Flyways Project employs a three-stage hierarchical methodology. The three main steps undertaken in each of the countries of interest are:

Country-wide occupancy and visible migration surveys to define broad-scale patterns of use during fall and spring migration
Establish constant effort mist-netting stations at potential stopover sites identified through occupancy surveys to understand the energetic contribution of a stopover
Employ tracking technologies, such as nano-tags (radiotransmitters), to determine stopover duration and onward migration strategies in focal species

Below, we describe the methodology employed in stage one, namely that behind the occupancy surveys that underlie the maps of stopover use presented here (see Maps by species on the home page).

Study sites (occupancy surveys)

In each country, a series of study sites are established in order to cover the main gradients of elevation and precipitation, as well as key habitat types, such as mangrove, tropical dry forest, montane forest etc. Sites are also selected to cover the geography of any given country, bearing in mind where migratory birds would be expected to arrive or be concentrated by local geography. To date, sites have been established in Colombia, Panama, Costa Rica, Nicaragua, Honduras and Guatemala, and how their location relative to precipitation and elevation gradients, as well as forested regions is shown in the maps below.

At each study site, the methodologies described in the five boxes below are undertaken by in-country observers following an initial training period. The two main survey periods run from mid-March to mid-May (Spring) and late August to early November (Fall).