Using citizen science to parse climatic and land cover influences on bird occupancy in a tropical biodiversity hotspot

Abstract

Disentangling associations between species occupancy and its environmental drivers –– climate and land cover –– along tropical mountains is imperative to predict species distributional changes in the future. Previous studies have primarily focused on identifying such associations in temperate mountain systems. Using 1.29 million robustly processed citizen science observations contributed to eBird between 2013 and 2021, we examined the role of climatic and landscape variables and its association with bird species occurrence within a tropical biodiversity hotspot, the southern Western Ghats in India. Using an occupancy modeling framework, we found that temperature seasonality, precipitation seasonality, and the proportion of evergreen forests were significantly associated with species‐specific probabilities of occupancy for 78% (n=43 birds), 38% (n=21 birds), and 27% (n=15 birds) of bird species examined, respectively. Our study shows that several forest birds (n=18 species) were negatively associated with temperature seasonality, highlighting narrow thermal niches for such species. The probability of occupancy of six forest species and eight generalist species was positively associated with precipitation seasonality, indicating potential associations between rainfall and resource availability, and thereby, species occurrence. A smaller number of largely generalist species (n=9 birds) were positively associated with human‐modified land cover types –– including the proportion of agriculture/settlements and plantations. Our study shows that rigorously filtered citizen science observations can be used to identify associations between environmental drivers and species occupancy on tropical mountains. Though current distributions of tropical montane birds of the Western Ghats are strongly associated with climatic factors (mainly, temperature seasonality), naturally occurring land cover types (forests) are critical to sustaining montane avifauna across human‐modified landscapes in the long run.

Forest bird decline and community change over 19 years in long-isolated South Asian tropical rainforest fragments

“…Our study also identifies greater changes in species composition over wider time windows and with greater habitat structural change as indexed by ΔPC scores, with larger fragment areas tending to support more stable communities, particularly of rainforest and restricted-range birds (Table 2, Figure 2). These results provide a first look into decadal bird community dynamics in the rainforests of South Asia and corroborate observations on regional declines and interactive land-use and climate change impacts on rainforest birds from citizen science in the Western Ghats (SoIB 2020, Ramesh et al 2022) as well as comprehensive bird community change elsewhere in the tropics and around the world (Şekercioğlu et al 2019, Hendershot et al 2020, Campos-Cerqueira et al 2021, Tinoco et al 2021, Williams & Fuente 2021).…”

“…However, poorer habitat quality favoured density and richness (marginally so) of matrix-derived open-country birds, indicating lower redundancy (Figure 2). Citizen-science data corroborates this pattern at scale: poorer habitat ‘quality’ (or habitat complexity) correlates with lower occupancy of rainforest-adapted species (Ramesh et al 2022). Rising temperatures can increase the fraction of edge habitat, pushing rainforest birds off their thermal optima while benefitting open-country birds.…”

“…Monsoon rains in the southern Western Ghats have steadily declined in the past century (Varikoden et al 2019) while post-monsoon cyclonic events in the Bay of Bengal have increased in frequency and intensity (Balaguru et al 2014). Unless birds and the vegetation they depend on rapidly acclimate (Martin & Mouton 2020) or adapt (Van Buskirk et al 2010) to such shifts in climate, both the density and diversity of bird assemblages may decline (Ramesh et al 2022). (Ramesh et al 2022)Species with restricted ranges (Robin et al 2015) and narrower extant habitat and climatic envelops are likely to be especially sensitive to such climate change (Şekercioğlu et al 2012).…”

“…Unless birds and the vegetation they depend on rapidly acclimate (Martin & Mouton 2020) or adapt (Van Buskirk et al 2010) to such shifts in climate, both the density and diversity of bird assemblages may decline (Ramesh et al 2022). (Ramesh et al 2022)Species with restricted ranges (Robin et al 2015) and narrower extant habitat and climatic envelops are likely to be especially sensitive to such climate change (Şekercioğlu et al 2012). Any change in bird communities through time would be modulated by habitat: fragments in our study system have idiosyncrasies specific to each fragment, including higher than average secondary disturbance (for instance, invasive understory shrubs (Joshi et al 2009), preferential extraction of pole-sized trees (Mudappa & Raman 2007), or active or passive restoration (Osuri et al 2019) – all of which can alter understory structure over two decades.…”

Taxonomic and functional components of avian metacommunity structure along an urban gradient

“…The eBird database is a citizen science project whose data have demonstrated to be effective for describing patterns of diversity at multiple spatial scales and to be comparable to more standardized data sets [23]. To limit the inherent biases associated with eBird data, we followed methods of Callaghan et al [24] and Ramesh et al [25]. We removed the following kinds of checklists: (1) those that did not report all observed species, (2) those that were duplicates from multiple observers who participated in the same sampling event, or (3) those where the observer traveled greater than 5 km or covered more than 500 ha so as to stay within our sampling locations.…”