We assessed bird guild species richness and composition on 274 point-counts with different stand age ranging from 3 to 70 years old [we excluded two point-counts from the total of 276 plots because they were in recently abandoned (<1 year) milpa]. Point-counts were located in the same location as for the vegetation sampling (see Sect. 11.2.4). The bird survey was carried out during the reproductive season (May 2009 and May 2010) and migratory season (November 2008 and November 2009). We used a modified double-observer method (Nichols et al. 2000; for full description see Leyequien et al. 2007), registering all birds seen or heard for a period of 12 min within a fixed radius of 60 m. Minimum distance among plots was 200 m to avoid double counting. The total sampling time was 203.2 h.
All birds were classified into feeding guilds based on their primary food source and their foraging strata using existing literature and field observations (Milesi et al. 2002; Gray et al. 2007; MacKinnon and Wood 2009, personal communication). We excluded some guilds based on the following criteria: (1) carnivores and full aerial birds were excluded because of their low number of records, and (2) omnivores were excluded because they are highly resilient (insensitive) to habitat disturbance and forest succession. We used only nine feeding guilds for the analysis (Appendix 11.1). Although we are aware that various species in the selected feeding guilds are facultative species that could shift to secondary resources depending on ad hoc conditions, we grouped bird species into one exclusive feeding guild to maintain sufficiently large sample sizes for each guild class (see review by Philpott et al. 2008; Sekercioglu et al. 2004).