2 research outputs found
Improving our understanding of demographic monitoring: avian breeding productivity in a tropical dry forest
The ratio of juvenile to adult birds in mistānet samples is used to monitor avian productivity, but whether it is a ātrueā estimate of per capita productivity or an index proportional to productivity depends on whether capture probability is not ageādependent (true estimate) or age difference in capture probability is consistent among years (index). Better understanding of the processes affecting ageā and yearāspecific capture probabilities is needed to advance the application of constantāeffort mistānetting for monitoring and conservation, particularly in many tropical settings where capture rates are often low. We ranked members of the avian community by capture frequencies, determined if temporary emigration influenced the availability of birds to be captured, and assessed the distribution of birds relative to mistānets and the parity between captureābased productivity estimates and number of fledglings in nest plots in a tropical dry forest in Puerto Rico in 2009 and 2010. Few captures characterized the community of 25 resident species and, when estimable, capture probabilities were low, particularly for juveniles (typically \u3c 0.1). Negative trends in capture probability, temporary emigration, and the distribution of birds suggest that avoidance of mistānets influenced capture rates in our study. Increasing mistānet coverage or moving mistānets between sampling periods could increase capture rates. The number of fledglings observed in nest plots (25 ha/plot) did not correlate well with captureāderived estimates (20 ha/net stations), suggesting the presence of immigrants or failure to find all nests. Our results suggest that indices of breeding productivity from mistānetting data may track temporal changes in productivity, but such data likely do not reflect ātrueā productivity in most cases unless ageāspecific differences in capture probability are incorporated into estimates. Pilot studies should be conducted to evaluate capture rates and the spatial extent sampled by mistānets to improve sampling design and inferences before informing decisions
Improving our understanding of demographic monitoring: avian breeding productivity in a tropical dry forest
The ratio of juvenile to adult birds in mistānet samples is used to monitor avian productivity, but whether it is a ātrueā estimate of per capita productivity or an index proportional to productivity depends on whether capture probability is not ageādependent (true estimate) or age difference in capture probability is consistent among years (index). Better understanding of the processes affecting ageā and yearāspecific capture probabilities is needed to advance the application of constantāeffort mistānetting for monitoring and conservation, particularly in many tropical settings where capture rates are often low. We ranked members of the avian community by capture frequencies, determined if temporary emigration influenced the availability of birds to be captured, and assessed the distribution of birds relative to mistānets and the parity between captureābased productivity estimates and number of fledglings in nest plots in a tropical dry forest in Puerto Rico in 2009 and 2010. Few captures characterized the community of 25 resident species and, when estimable, capture probabilities were low, particularly for juveniles (typically This article is published as Kornegay, M. Edye, Amber NM Wiewel, Jaime A. Collazo, James F. Saracco, and Stephen J. Dinsmore. "Improving our understanding of demographic monitoring: avian breeding productivity in a tropical dry forest." Journal of Field Ornithology 89, no. 3 (2018): 258-275. doi: 10.1111/jofo.12263.</p