Collections of small urban parks consistently support higher species richness but not higher phylogenetic or functional diversity

When prioritizing regions for conservation protection, decisions are often based on the principle that a single large (SL) reserve should support more species than several small (SS) reserves of the same total area (SLOSS). This principle remains a central paradigm in conservation planning despite conflicting empirical evidence and methodological concerns. In urban areas where small parks tend to dominate and policies to promote biodiversity are becoming increasingly popular, determining the most appropriate prioritization method is critical. Here, we document the role of SLOSS in defining the seasonal diversity of birds in 475 parks in 21 US cities. Collections of small parks were consistently associated with higher species richness, spatial turnover, and rarity. Collections of both small and large parks were associated with higher phylogenetic and functional diversity whose patterns varied across seasons and cities. Thus, collections of small parks are a reliable source of species ric..., , , # Collections of small urban parks consistently support higher species richness but not higher phylogenetic or functional diversity

Three CSV files containing city and urban park information, bird occurrence data, and five avian diversity metrics.

## Description of the data and file structure

**urban-park-id-area.csv**

The names of the 21 cities and 475 urban parks and each park's identification number (POLYFID) and surface area in square meters.

**species-composition.csv**

Species composition of bird assemblages in 475 urban parks (POLYFID) during four seasons: (1) nonbreeding, (2) spring migration, (3) breeding, and (4) autumn migration.

**diversity-metrics.csv**

Five diversity metrics calculated for bird assemblages in 475 urban parks (POLYFID) during four seasons: (1) nonbreeding, (2) spring migration, (3) breeding, and (4) autumn migration. The diversity metrics include: species richness (S), phylogenetic diversity (PD), mean pairwise distance (MPD), mean nearest taxon di...