Scale dependence of bird diversity in London

Abstract Context Understanding drivers of biodiversity in cities can be mutually beneficial for ecosystems and people. Crowd-sourced bird observations provide an opportunity to assess how patterns of bird diversity change across observation scales and suggest driving processes. Objectives We assessed the scale dependence of bird diversity within a 128 × 128 km extent over London’s urban–rural gradient to suggest scales at which key drivers may be operating. Methods We quantified scale variance of bird diversity across scales from 500 m to 64,000 m for three groups of species (All, Passeriformes, and Anseriformes and Charadriiformes combined). We estimated diversity by aggregating observations into a series of grids and computed comparable diversity estimates within each cell using interpolation and rarefaction. We calculated the variance explained by each scale for common diversity metrics. Results The results show that bird diversity patterns around London vary by scale, and that the location of high variance shifts across the study area depending on both scale and species group. The variance of Passeriformes diversity gradually shifted from the urban core to the periphery, while variance of Anseriformes and Charadriiformes diversity occurred near water features. Conclusions The results suggest that the urban–rural gradient and location of water are two properties of the study extent around London influencing the scale dependance of bird diversity that could be used to ground scale considerations of further modeling efforts.