Trends in bird abundance differ among protected forests but not bird guilds

Area of Science:

• Ecology
• Conservation Biology
• Statistical Modeling

Background:

• Effective monitoring of bird populations, especially rare species, is vital for conservation across large regions.
• Understanding population trends requires robust inferential tools for accurate management decisions.

Purpose of the Study:

• To assess abundance trends for 106 bird species in eight northeastern US national parks from 2006 to 2019.
• To develop and apply a novel hierarchical model for improved inference on rare species and sparsely sampled areas.
• To evaluate the influence of local forest structure on bird abundance trends.

Main Methods:

• A multispecies, multiregion, removal-sampling hierarchical model was developed to share information across species and parks.
• The model enabled uncertainty-quantified estimates of bird abundance at multiple geographical and taxonomic levels.
• Data were collected from a network of eight forested national parks in the northeastern United States.

Main Results:

• Bird abundance trends varied significantly across parks, but species within parks showed similar trends.
• Three parks experienced overall decreases in bird abundance, while three others showed increases.
• Bird abundance was highest with medium basal area, high percent forest, and high forest regeneration, with percent forest being the most influential factor.

Conclusions:

• Local forest conditions appear to have a consistent, broad effect on entire bird communities within parks.
• Further research is recommended for parks with declining bird abundance to identify specific drivers of these trends.
• Understanding bird community responses to forest structure and other stressors is essential for effective conservation management.