Heterogeneity, Productivity, and Migration Drive Continental Evenness Patterns of Bird Assemblages
This study across the contiguous United States examines how productivity, habitat heterogeneity, and migration interact to shape weekly patterns of bird assemblage evenness. Using eBird data and mixed‑effects models, we show that evenness rises in productive, heterogeneous landscapes and shifts seasonally with migrant presence and dominance.
Subject Tags
- Land management
- Wildlife
- Habitat restoration
Abstract
This study examines how productivity, habitat heterogeneity, and migration interact to shape evenness patterns in bird assemblages across the contiguous United States. Using weekly eBird‑derived relative abundance maps for 613 species and generalized linear mixed‑effects models, the research evaluates how NDVI‑based productivity, land‑cover heterogeneity, and migratory dominance influence evenness. Results show that productivity increases evenness only in high‑heterogeneity landscapes, while seasonal peaks in evenness occur during pre‑breeding and breeding periods due to low‑abundance migrants. However, strong dominance by migratory species reduces overall evenness and weakens productivity–evenness relationships. These findings highlight the joint roles of energy availability, niche partitioning, and migration dynamics in shaping continental bird community structure.
Citation
Gilbert, N. A., Queally, N., Cooper, J. C., Eyster, H. N., & Williams, P. J. (2026). Heterogeneity, Productivity, and Migration Drive Continental Evenness Patterns of Bird Assemblages. Global Ecology and Biogeography, 35(2), e70205.
TNC Authors
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Harold N. Eyster
Climate and Land Use Analyst. Colorado
The Nature Conservancy
Email: harold.eyster@tnc.org