Improving Detectability Studies in Avian Tropical Cloud Forest Communities

In tropical cloud forest systems a lack of systematic programs and infrastructure result in avian population demographics, trends and ranges that are less well known than temperate systems. Few long term study sites currently exist to collect this vital data. Since 2007, Operational Wallacea (Opwall) has led conservation research through the recruitment of ecologists to conduct fieldwork in tandem with teaching tropical ecology techniques to volunteers operating in the Honduran cloud forest. Opwall’s initial protocol required point counts three times per transect per season and mist-netting twice per transect per season along 28 transects of varying lengths. First season results were scrutinized by Martin et al. [Ornitologia Neotropical, 21 (2010)] to determine effectiveness leading to methodological changes for subsequent seasons. There had been a need for increased effort on point-counts, but mist-netting efforts were sufficient and could be scaled back. These recommendations resulted in revised protocols that consisted of point counts along each transects thrice per season, and mist-net operations to be conducted six times per camp per season. This protocol has been implemented since 2011. I re-examine the revised protocols for point counts and mist-netting to make further recommendations using the same methodology. Using 2015 data, point count species accumulation curves saturate at ~67% effort while mist-net operations never achieve saturation. I believe the discrepancy is the product of increased effort: 208 additional point counts were conducted in 2015 and net-meter-hours increased from 9,360 to 22,200. Recognizing that increased effort leading to decreased detection is counter-intuitive, I propose that a combination of net-shyness and oversampling of six sites (down from 26 sites) limited mist netting effectiveness to detect diversity. Avian cloud forest diversity detection efforts should ensure mist-netting operations are spread throughout the research sites and not concentrated as they often are at temperate migratory banding stations.