Novel Estimates of Bird Migration Traffic at the Continental Scale Using Participatory Science Data

Abstract

Aim Quantifying movement patterns of migratory birds throughout their annual cycles is critical for effective conservation planning. The BirdFlow project uses eBird participatory science data products to model species‐level migratory trajectories across entire ranges. However, BirdFlow trajectory models are not readily compatible with location‐based monitoring technologies such as weather radar. We develop a scalable, species‐level measurement of nocturnal bird migration traffic and assess its utility for integration with radar monitoring. Innovation We introduce the BirdFlow migration traffic rate (BMTR), a location‐based metric of migratory passage for individual species derived from BirdFlow models. BMTR quantifies the weekly proportion of a species' population passing over a transect, can be calculated across a species' entire range and can be converted to absolute numbers using population estimates. We applied this framework to 312 nocturnal migratory bird species in North America. Aggregating all species' migration activities, we compared them with average weekly nocturnal migration traffic detected by 152 NEXRAD weather surveillance radars over 28 years. We further evaluated the use of BMTR to disaggregate radar‐derived migration traffic into species‐level estimates. Main Conclusions BirdFlow‐ and radar‐derived migration traffic showed strong agreement ( r = 0.784), particularly along the Mississippi and Atlantic Flyways, with models incorporating demographic adjustments performing best. Annual nocturnal migration traffic estimated by BirdFlow and radar was closely aligned, with BirdFlow estimates averaging 33.3% higher. BMTR effectively captured major flyways, high‐traffic routes and seasonal migration dynamics. It also enabled disaggregation of radar traffic into species‐level contributions, revealing dominant species at specific locations. BMTR provides a new methodological bridge between trajectory‐based BirdFlow movement models and location‐based monitoring approaches. It offers a scalable, species‐specific tool for migration ecology and conservation, supports monitoring in areas without radar coverage and enables new opportunities for public engagement through visualisation of near real‐time, species‐level migration.

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