Avian Indicators of Climate Change Based on the North American Breeding Bird Survey
Appropriate ecological indicators of climate change can be used to measure concurrent changes in ecological systems, inform management decisions, and potentially to project the consequences of climate change. However, many of the available indicators for North American birds do not account for imperfect observation. We proposed to use correlated-detection occupancy models to develop indicators from the North American Breeding Bird Survey data. The indicators were used to test hypotheses regarding changes in range and distribution of breeding birds. The results will support the Northeast Climate Science Center’s Science Agenda, including the science priority: researching ecological vulnerability and species response to climate variability and change.
- Estimating indices of range shifts in birds using dynamic models when detection is imperfect (not open access)
- There is intense interest in basic and applied ecology about the effect of global change on current and future species distributions. Projections based on widely used static modeling methods implicitly assume that species are in equilibrium with the environment and that detection during surveys is perfect. We used multiseason correlated detection occupancy models, which avoid these assumptions, to relate climate data to distributional shifts of Louisiana Waterthrush in the North American Breeding Bird Survey (BBS) data. We summarized these shifts with indices of range size and position and compared them to the same indices obtained using more basic modeling approaches. Detection rates during point counts in BBS surveys were low, and models that ignored imperfect detection severely underestimated the proportion of area occupied and slightly overestimated mean latitude. Static models indicated Louisiana Waterthrush distribution was most closely associated with moderate temperatures, while dynamic occupancy models indicated that initial occupancy was associated with diurnal temperature ranges and colonization of sites was associated with moderate precipitation. Overall, the proportion of area occupied and mean latitude changed little during the 1997–2013 study period. Near-term forecasts of species distribution generated by dynamic models were more similar to subsequently observed distributions than forecasts from static models. Occupancy models incorporating a finite mixture model on detection – a new extension to correlated detection occupancy models – were better supported and may reduce bias associated with detection heterogeneity. We argue that replacing phenomenological static models with more mechanistic dynamic models can improve projections of future species distributions. In turn, better projections can improve biodiversity forecasts, management decisions, and understanding of global change biology.