Urban parks serve as indispensable bastions of biodiversity within the increasingly paved and concrete landscapes of modern cities. Yet, despite their recognized importance, understanding the precise environmental features that sustain and promote avian diversity remains a complex puzzle. The latest comprehensive study by La Sorte, Fournier, Clark, and colleagues dives deep into this issue, analyzing bird occurrence data collected from an impressive 935 parks across 186 U.S. cities, encompassing a wide geographic and climatic spectrum. Their findings unravel some of the nuanced relationships among park characteristics, seasonal variations, and three critical dimensions of bird diversity: species richness, phylogenetic diversity, and functional diversity.
At the core of this research lies the quantification of avian diversity through three complementary lenses. Species richness, simply the count of distinct bird species observed, provides a straightforward measure of biodiversity. However, species counts alone often fail to capture the evolutionary and ecological complexity embedded in bird communities. To address this, the authors incorporated phylogenetic diversity, which reflects the breadth of shared evolutionary history among species present in a park, offering insights into the conservation value of protecting lineages that have diverged deeply over time. Equally crucial is functional diversity, representing the range of ecological roles and traits birds fulfill—such as diet specialization, nesting habits, and foraging strategies—which directly influences ecosystem function and resilience.
One of the standout revelations from the study is the consistent positive relationship between park area and species richness across seasons and regions. Larger parks inherently provide more habitat heterogeneity and resources, supporting a greater number of species. This foundational biodiversity principle underscores the need for maintaining and expanding substantial green spaces within urban matrices. However, the story becomes far more intricate when examining phylogenetic and functional diversity, which do not necessarily follow the same patterns as species richness.
Intriguingly, parks situated closer to urban boundaries—areas where city landscapes transition into less developed or natural environments—harbor higher phylogenetic diversity. This spatial gradient suggests that edge parks may serve as critical refugia supporting a wide array of evolutionary lineages, possibly due to increased habitat connectivity with regional biomes or the availability of unique niches less prevalent in the urban core. Such findings argue for strategic park placements and conservation efforts that capitalize on these boundary zones to maximize evolutionary heritage conservation.
The relationship between habitat heterogeneity and functional diversity unveiled a somewhat unexpected pattern. Contrary to the intuitive assumption that more heterogeneous habitats necessarily bolster functional trait diversity among birds, the data revealed that parks with lower habitat heterogeneity contained higher functional diversity. This counterintuitive result may arise because more uniform habitats favor a set of functionally complementary species that efficiently exploit available resources, whereas patchier environments might be dominated by specialists reducing overall functional complementarity. This nuanced understanding invites reconsideration of habitat management practices aimed at maximizing functional attributes critical for ecosystem services like pest control and pollination within urban contexts.
Water features emerged as a major driver of select diversity dimensions. Parks incorporating water bodies consistently exhibited increased species richness and phylogenetic diversity but did not show a parallel rise in functional diversity. Water bodies likely provide essential resources such as drinking sites, foraging grounds, and habitat for aquatic-associated species, thereby enhancing the number and evolutionary spread of birds. However, the lack of impact on functional diversity suggests that water-associated species may be functionally similar or that water features support a narrower range of ecological roles than terrestrial habitat components.
Perhaps the most complex and geographically variable finding related to tree canopy cover highlights the intricate interplay between urban form, biogeography, and biodiversity. In the Intermountain West, tree canopy cover positively influenced both species richness and phylogenetic diversity. This arid and open landscape region may rely heavily on shaded, cooler microhabitats provided by tree cover, which attract diverse birds from varied lineages. Conversely, in eastern cities characterized by older, more forested landscapes, increased tree canopy cover was surprisingly associated with reductions in species richness and phylogenetic diversity, though functional diversity increased. These contrasting trends underscore the necessity of tailoring urban park management strategies to regional ecological contexts rather than applying blanket prescriptions.
Seasonality further complicates the relationships between park features and bird diversity metrics. Birds’ life history stages, migratory patterns, and resource availability fluctuate dramatically through the year, influencing the assemblage and diversity present in parks. Although the study did not focus explicitly on seasonal breakdowns of each driver, the overarching conclusion is clear: no single park configuration optimizes all aspects of avian diversity year-round. Instead, habitats must be diversified spatially and temporally to accommodate the shifting needs of bird communities.
The comprehensive spatial scale of the study lends high confidence to the generality of the findings. Covering nearly a thousand parks in nearly two hundred cities affords wide geographic representation, spanning deserts, forests, mountains, and urban cores. This broad sampling enhances the applicability of recommendations to a majority of U.S. urban contexts and highlights the importance of incorporating regional variations into urban biodiversity planning.
From a conservation perspective, the insights emphasize the vital role of multiple parks with a mosaic of varying features to collectively support biodiversity. A network approach that integrates large parks near urban boundaries with smaller, strategically designed green spaces featuring water bodies and variable canopy coverage emerges as the winning formula. Such diversity in park features ensures a robust representation of species, evolutionary history, and ecological functions, promoting resilient urban ecosystems.
Moreover, the study’s findings have profound implications for urban planners and policymakers seeking to balance urban expansion with biodiversity conservation. As cities continue to grow, pressures on existing parks intensify, and the creation of new green spaces often faces spatial constraints. Recognizing which park attributes maximize critical facets of bird diversity guides efficient allocation of resources and informs innovative urban design solutions, such as green corridors connecting parks and integrating water features within dense urban fabrics.
The research also paves pathways for future investigation. Questions remain regarding the mechanisms through which specific park features differentially influence phylogenetic and functional diversity, particularly the surprising negative association between habitat heterogeneity and functional diversity. Longitudinal studies tracking bird communities’ responses to park management interventions across seasons could illuminate causative pathways and inform adaptive management.
Finally, this work serves as a clarion call emphasizing urban parks not merely as recreational amenities but as vital arenas for sustaining biodiversity and ecosystem services in human-dominated landscapes. Integrating ecological knowledge into urban design, grounded in rigorous science and bolstered by extensive datasets such as this, promises to transform cities into havens for birds and other wildlife while enriching human quality of life.
In sum, promoting avian diversity in cities is a multifaceted endeavor requiring nuanced understanding of how diverse park features interact with regional contexts and seasonal dynamics. The study by La Sorte and colleagues equips urban biodiversity advocates with robust empirical evidence to develop multi-scaled, variable-feature park networks that nurture species richness, safeguard evolutionary heritage, and sustain ecological functions, ultimately fostering vibrant and resilient urban ecosystems in an ever-urbanizing world.
Subject of Research: Urban avian diversity and its environmental drivers across seasons and regions within U.S. city parks
Article Title: Promoting avian diversity in cities requires multiple parks with variable features
Article References:
La Sorte, F.A., Fournier, B., Clark, J.A.G. et al. Promoting avian diversity in cities requires multiple parks with variable features. Nat Cities 3, 155–166 (2026). https://doi.org/10.1038/s44284-025-00385-w
Image Credits: AI Generated
DOI: February 2026
