Integrating general and targeted biodiversity monitoring through parallel survey designs to improve indicator robustness

Francesc Sardà-Palomera, Manel Puigcerver, Irene Peña de la Cruz, Marc Anton, José Domingo Rodríguez Teijeiro

Breeding Bird Monitoring Schemes (BMS) provide large-scale, long-term data essential for biodiversity assessment and conservation decision-making. However, their multispecies design can generate species-specific detectability biases, particularly for taxa whose behavioral or ecological traits deviate from standardized count assumptions, potentially affecting abundance estimates and population indicators. We propose a structured integration framework linking general monitoring schemes with species-specific high-detection surveys through parallel designs and ecological modeling. The approach involves (1) implementing temporally matched general and targeted surveys, (2) modeling the relationship between survey outputs while incorporating ecological covariates influencing detectability differences, and (3) projecting the calibrated relationship onto broader BMS datasets to improve abundance indices and trend estimation.

We apply this framework to the Common Quail (Coturnix coturnix), a farmland game species with context-dependent detectability under standardized protocols. Parallel surveys revealed marked discrepancies between monitoring methods across habitat conditions. Incorporating habitat information into the calibration reduced detectability-related variability and improved the consistency of long-term trend estimates.

By formally linking general and targeted systems, this framework enhances the reliability and policy relevance of biodiversity indicators while retaining the spatial and temporal scalability of existing monitoring programs.