Using citizen science data in integrated population models to inform conservation

Analysis of animal population status and change are core elements of ecological research and critical for prioritizing conservation actions for at-risk species. Traditionally, count-based data from structured surveys have been the main source of information used to estimate trends and changes in populations. In the past decade, advances in integrated population models (IPMs) have allowed these data to be combined with other data sources (e.g., observations of marked individuals). IPMs have allowed researchers to determine the direction and magnitude of population trends and to identify underlying mechanisms contributing to population change. For many species, life-history characteristics (e.g., colonial breeding, low site-fidelity), low abundance and/or low detection probability make it difficult to collect sufficient data; thus, IPMs for these species are difficult to employ. Citizen science data may be useful in such situations and enable conservation biologists to combine data from many sources into robust estimates of population trajectories. IPM's represent a possible way of combining diverse data sources, but their practicality for incorporating citizen science data has not been investigated. Here, we used count data from eBird to estimate population trends for a species of conservation concern, the tricolored blackbird (Agelaius tricolor). We combined estimates of relative abundance with banding and nesting data. Our joint estimation of demographic rates allowed us to evaluate their individual contributions to the population growth rate. Our analysis suggests that the California tricolored blackbird population suffered a mean decline of 34% from 2007 to 2016. Mean annual adult survival ranged from 0.28 to 0.93 for females and 0.17 to 0.78 for males. Mean juvenile survival across years was 0.21 (95% CI = 0.0007–0.49), fecundity (as nestlings per nest) ranged from 0.46 to 1.27. We suggest that investments in increasing reproductive success and recruitment are the most likely conservation strategies to increase the population. Here, the extensive survey efforts of citizen scientists aided the employment of IPMs to inform conservation efforts for tricolored blackbirds.