Abstract
Abstract Urbanisation can limit species persistence and bias composition of functional guilds with serious consequences for ecosystem functioning and conservation planning. Standardised biodiversity surveys are missing at most tropical urban cities where biodiversity levels are high alongside rapidly increasing rates of urbanisation. We explored the utility of time-bound surveys to document winter birds at ponds (wetlands ≤ 5 ha) in Delhi, India at two different times of the day (morning and evening) and in areas with varying extents of wetlands. Systematic surveys at 39 ponds during January–March 2020 yielded an estimated 173 ± 22 bird species (∼37% of Delhi’s birds). The total bird species assemblage at ponds did not vary significantly with time of day, but β-diversity increased marginally with increasing extent of wetlands. Total bird abundance and species richness varied substantially with time of day, with differences apparent across several species rich functional feeding and habitat guilds. Abundance and species richness of some guilds, including species-poor guilds, varied in ponds located in areas with differing extent of wetlands. Reliable and comparable measures of species abundance and species richness (both total and across functional guilds)— metrics commonly used to set research and conservation priorities—in urban habitats can be obtained after appropriately standardising field effort. Such standardised efforts can help underscore the importance of maintaining and improving erstwhile-ignored habitats such as unprotected ponds that are providing refugia to hundreds of bird species in mega-cities like Delhi.
Highlights
Urbanisation is on the increase throughout the world and so is ecological research in urban areas (McDonnell 2011)
Metrics using full bird assemblages showed that species compositions did not vary with time of day or extent of wetlands but b-diversity increased with extent of wetlands
Bird abundances and species richness were higher during morning surveys with effects spilling over to the most speciesrich guilds
Summary
Urbanisation is on the increase throughout the world and so is ecological research in urban areas (McDonnell 2011). Research in urbanised areas is currently biased towards birds and is mostly carried out in cities in developed countries. Biased geographical coverage of research in cities is leading to three fundamental problems. Majority of the understanding in urban ecology is coming from relatively species-poor temperate countries with limited understanding from cities in areas with much higher species richness (Botzat et al 2016; Mcdonald et al 2020).
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