Evaluating Assumptions of the North American Marsh Bird Monitoring Protocol

The standardized North American Marsh Bird Monitoring Program has been used over the past decade to increase detection probability of secretive marsh birds across North America. This survey has greatly improved researchers understanding of secretive marsh bird habitat use and the impact of wetland management on these important species. This survey is frequently done across 3 survey periods, defined roughly by latitude, which are supposed to encapsulate the end of migration and pre-nesting period. A pattern observed across many studies using these methods is a decline in detections from the first to the last survey period, which begs the question of why this pattern is observed, and what influence it may have on our inference and understanding of existing marsh bird survey data. We examined several possible explanations for this decline using data simulation, and several existing datasets, as well as data specifically collected to better quantify the detection process.