Avian species richness and tropical urbanization gradients: Effects of woodland retention and human disturbance

Abstract

Urbanization is a major driver of tropical biodiversity loss. In temperate regions avian species richness-urbanization intensity relationships typically exhibit unimodal patterns, with peak richness at intermediate urbanization levels. In tropical regions, the form of such relationships and the extent to which they are moderated by patches of seminatural habitat are unclear. We address these questions in Bangkok, Thailand (one of the largest and most rapidly expanding tropical mega-cities) and generate conservation recommendations for tropical biodiversity in urban locations. We use repeated point count surveys at a random location, and the largest available woodland patch, in 150 1 km  1 km grid cells selected along the urbanization gradient. Woodland patches support higher species richness compared with randomized locations (except for non-natives), and avian species richness declines linearly with increasing urbanization. The contrast with unimodal patterns in temperate regions is probably driven by divergent patterns of habitat heterogeneity along tropical and temperate urbanization gradients. Moreover, we provide novel evidence that retaining patches of urban woodland moderates adverse impacts of urbanization on avian species richness. For most species groups, the benefits of woodland increase as urbanization intensifies, despite such woodland patches being very small (mean of 0.38 ha). Avian species richness in woodland patches is maximized, and community composition less similar to that in randomized locations, when woodland patches are larger and visited by fewer people. Assemblages of forest-dependent species (which provide additional ecological functions) have higher richness, and are less similar to those in randomized locations, in patches of woodland with higher tree species richness and biomass. Finally, species richness in randomized sites is greatest when they are closer to woodland patches, and such assemblages more closely resemble those of woodland sites. Our work highlights four strategies for tropical urban bird conservation: (1) conserving woodland patches across the urbanization gradient regardless of patch size, (2) improving the quality of existing woodland by increasing tree biomass and diversity, (3) creating additional woodland that is well distributed throughout the urban area to

Squirrel and tree‐shrew responses along an urbanisation gradient in a tropical mega‐city – reduced biodiversity, increased hybridisation of Callosciurus squirrels, and effects of habitat quality

“…Our survey design, field methods and analytical approach are based on Thaweepworadej & Evans (2022). Our focal study region consists of a 70 km × 80 km rectangle (5,600 km 2 ), centred on central Bangkok and covering parts of the surrounding provinces (Fig S1).…”

“…Grid cells with ≥25% impervious surface cover that were isolated from the main urban region or had <25% impervious surface cover were considered to be part of other urban settlements and not classified as part of urban Bangkok, (b) the % cover of greenspace in 1 km × 1 km grid cells across the study region; grid cells outlined in black represent the 150 sampling cells selected using random stratification across each of the greenspace % cover categories (15 sampling grid cells for each of the ten categories). This Figure is modified from Thaweepworadej and Evans (2022). [Color figure can be viewed at wileyonlinelibrary.com]…”

“…Predators that are capable of predating squirrels within urban Bangkok are primarily free‐ranging cats Felis catus and dogs Canis lupus familiaris . Other mammalian predators are largely absent and diurnal avian predators are rare and localised (see Thaweepworadej & Evans, 2022). Whilst some owl species are reported to be widespread, for example, Collared scops owl Otus lettia (Round & Gardner, 2008), these have a predominately invertebrate based diet (Wilman et al ., 2014).…”

Decomposing the Spatial and Temporal Effects of Climate and Habitat on a Hazel Grouse (Tetrastes bonasia) Population in Northeastern Chinese Mountains

“…Human disturbances are critical factors influencing population distributions and species diversity [ 31 , 32 , 33 ]. Nature reserves and national parks have been established in the mountainous areas of northeastern China in recent years, which have largely relieved the destruction of forest habitats by human activity.…”

An efficient acoustic classifier for high‐priority avian species in the southern Great Plains using convolutional neural networks

“…acoustic, autonomous recording unit, Bell's vireo, convolutional neural network, dickcissel, eastern meadowlark, grassland birds, northern bobwhite, painted bunting, template matching Population declines have been reported worldwide across a wide range of avian species (Thomas et al 2004, Szabo et al 2012, Sauer et al 2013, resulting from a variety of factors, including climate change (Northrup et al 2019, Stewart et al 2022, urbanization and land use change (Sol et al 2020, Thaweepworadej andEvans 2022), and the spread of invasive species and disease (Ishtiaq 2021). One particular biome at great risk of conversion is grasslands, which would result in a substantial loss of biodiversity (Newbold et al 2016, Roberts et al 2022, Wilcox et al 2022.…”