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Increased bird abundances over 30 years in an extensive commercial forest landscape

Published Article

Maine

Publication date: January 22, 2025

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Forest bird declines are widespread across North America, yet long‑term local patterns can differ. Replicating a study from 30 years ago, researchers surveyed a 238,000‑ha commercial forest landscape in northern Maine and found that most forest bird species increased or remained stable, contrasting sharply with continental Breeding Bird Survey trends. Population gains were driven by shifts in density within and across forest types, revealing greater habitat‑selection flexibility than previously recognized. The results suggest that Maine’s mosaic of commercial and preserved forests may serve as an important reservoir for breeding birds, partially offsetting declines at broader scales and informing regional conservation planning.

Subject Tags

  • Forest
  • Wildlife

Abstract

Habitat loss and degradation are considered the primary drivers of continental bird declines. We replicated an extensive study of forest bird populations conducted 30 years ago in a 238,000-ha commercial forest landscape in northern Maine (USA). The two study periods straddle a landscape-scale transition in forest ownership and management. We found that 55% of the 47 species we had sufficient data to evaluate showed increased landscape-scale abundances since 1993, while another 28% had not significantly changed. This is in stark contrast to trends reported in continental and regional Breeding Bird Survey data over the same period. Interestingly, abundance increases were driven primarily by changes in population densities within and across forest types, suggesting a greater role of flexible habitat selection than has been previously documented in this assemblage. The changes we observed suggest that the mosaic of commercial and preserved forest in northern Maine is providing an important reservoir of breeding bird habitat, and might be partially offsetting declines at broader spatial scales.

Citation

Levy, F. S., Reed, J. M., Mckinley, P. S., Gunn, J. S., Anderson, K., & Hagan, J. M. (2025). Increased bird abundances over 30 years in an extensive commercial forest landscape. Biological Conservation, 302, 110934. https://doi.org/10.1016/j.biocon.2024.110934

TNC Authors

  • John S. Gunn
    North America Natural Climate Solutions Science Director
    The Nature Conservancy
    Email: john.gunn@tnc.org