Hans-Peter Plag
Published on May. 08, 2025, last updated May. 08, 2025.
It is well known that that bird populations are declining on a global scale. Efforts to tackle these declines in bird populations suffer from a limited availability of small-scale data useful to extract information about population change. There is a need for more spatially high-resolution data on population trends to better understand the causes and to guide conservation efforts. The paper by Johnston et al. (2025) utilizes crowed-sourced data from eBird to analyze population changes in 495 birds in North and Central America and the Caribbean. The results of the study revealed high spatial heterogeneity in trends. About 75% of species were found to declining overall, indicating a worsening situation for birds in the regions considered. 97% showed significantly increasing and decreasing populations in smaller-scale areas. For 97% of species there were areas with population increases and other areas with declines, the strongest declines were found for those areas with highest abundance of the species.
Figure 1: The Great Blue Heron is one of the species with significantly decreasing population in North America.
The paper does not speculate on the causes of the observed trends. It seems urgent to look at correlations between changes in light pollution, land use and land cover changes, use of pesticides, changes in insect populations, and other potential variables that could be related to the observed population trends. This could help to not only invest in conservation but also in prevention of loses.
