WHAT THE EVIDENCE SAYS
Bird communities across 24 urban green-space patches were analyzed against a composite urbanization gradient. Species richness declined consistently; two-dimensional functional space occupied by the community also contracted, especially for larger-bodied, higher hand-wing-index and aquatic-associated traits. Functional richness declined too, but that result was sensitive to how residual spatial structure was modeled. Water-body cover, vegetation cover and foliage-height diversity were associated with different functional groups.
WHY IT MATTERS / OUR READ
Urban biodiversity design should not treat every green polygon as equivalent. Water, vertical vegetation structure and blue–green connectivity can retain different parts of the avian trait space, while a single richness score may not reveal which ecological functions are disappearing.
CAVEATS / UNCERTAINTY
The study is cross-sectional and limited to 24 patches in one city. Trait–habitat relationships are associations rather than experimental treatment effects, and the functional-richness result is explicitly model-sensitive.
SOURCE
Journal of Applied Ecology — primary study
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