Abstract
1. Accurately estimating the likelihood of occurrence of threatened species is essential for effective impact assessments at development sites. Current survey guidelines often rely on coarse, static species distribution maps, risking misalignment for migratory birds present only seasonally.
2. We evaluated 70 wind farms in eastern Australia to assess the alignment between survey timing and seasonal occurrence of four migratory species. Using eBird-based relative abundance models, we classified recommended and actual survey periods as optimal, suboptimal or poorly timed.
3. Approximately half of all surveys were not optimal, and one fifth missed the species' potential temporal window of presence altogether. Field detections mostly occurred within modelled optimal or suboptimal windows, validating the effectiveness of our modelling approach for identifying suitable survey timing.
4. Likelihood of occurrence conclusions presented in the reviewed impact assessments were significantly lower at sites with suboptimal or poorly timed surveys compared to those with optimal timing, suggesting that poor survey timing can lead to systematic underestimation of species presence.
5. Synthesis and applications: Current guidance and approaches to surveying migratory birds at windfarm developments in Australia are insufficient. Evidence-based alignment with seasonal presence is needed to improve biodiversity assessment standards, ensuring renewable energy expansion proceeds in a way that better safeguards migratory species and supports global biodiversity and sustainability goals