Do urban gardens restored with native shrubs contribute towards conservation of birds? Portland, Oregon, is a mid-sized city with many restored yard habitats and nearby regional natural areas, with yards varying in the degree of native plantings and the sizes and groupings of the yards involved. We studied several of the purported ecological benefits attributed to these widespread, but small-scale, urban gardens. We measured the relative success of yard habitats in contributing to diversity and abundance of forest-habitat birds. We studied how the abundance and diversity of shrubs, arthropods, and birds were related. We compared two neighborhoods; one having high, native tree cover, and the second having lower, non-native tree cover. Both neighborhoods had nearby greenspaces. We selected 6 replicate yards in each neighborhood, each with at least a minimum number of native shrubs. We also measured bird species richness using citizen science data.
The abundance of arthropods significantly predicted the bird species richness. Both the amount of regional and local tree cover had a stronger statistical signal than shrub cover. The presence of native species of shrubs in these yards was not a good predictor for abundance of arthropods.