Kerala researchers show impact of climate change on two migratory bird species

Even as climate change is being taken up as a major topic of discussion the world around, the impact of the environmental phenomenon is becoming quite evident as well. E R Sreekumr and Dr. P O Nameer, researchers from the wildlife department of Kerala University recently, conducted a study on the influence of the climate change on a couple of two migratory bird species has brought about results that were alarming and thought-provoking.

The study was conducted on two species of high-elevation dependant, restricted-range flycatchers: Black-and-orange Flycatcher (BOF) Ficedula nigrorufa (Jerdon, 1839) and Nilgiri Flycatcher (NIF) Eumyias albicaudatus (Jerdon, 1840), to determine how they respond to the predicted climate change scenarios. The researchers used 194 and 300 independent occurrence points for BOF and NIF to develop climate models and understand the species responses to climate change scenarios using MaxEnt algorithm.

The model predicted the current extent of occurrence of 6532 sq. km as suitable for BOF and 12,707 sq. km for NIF, within their ranges. However, only 27% and 24% of the existing suitable area of BOF and NIF respectively, falls within the protected area network in the Western Ghats. Future predictions suggest suitable area loss to the tune of 20–31% for BOF and 36–46% for NIF by 2050.

Climate change induced by human activities (anthropogenic) and increased environmental degradation have put millions of species at risk of extinction. According to a recent report of the Intergovernmental Panel for Climate Change (IPCC), anthropogenic activities will cause global temperature to rise by 1.2°C between 2030 and 2052 compared to pre-industrial levels. Erratic environmental conditions, decline in species abundances and widespread extinctions are some of the significant predicted effects of climate change, the study pointed out

The oscillating climate and unique floral structure in the montane ecosystems provide special microclimatic conditions and habitat for the species, and such montane ecosystems are known as ‘sky islands’. The Western Ghats (WG), considered as one of the 36 biodiversity hotspots in the world, is situated in southwest India and consists of such sky islands. Palakkad Gap is the major discontinuity in the entire stretch of the 1600 km long Western Ghats. Since 2012, Western Ghats is also a World Heritage Site13, and two hill ranges in the region (Nilgiri Hills and Agasthyamalai Hills) have been recognized as Biosphere Reserves by the United Nations Educational, Scientific and Cultural Organization (UNESCO), the study said.

The Western Ghats mountain range exhibits high endemism with several species restricted to a narrow elevational range16. This specialized habitat is now deteriorating due to changing climatic conditions and anthropogenic activities17–19. Under the looming threat of global warming and climate change-driven habitat loss, it is vital to assess the fate of habitat specialists of Westers Ghats, so that remedial conservation strategies can be planned, the report said,

Black-and-orange Flycatcher and Nilgiri Flycatcher are monotypic species endemic to the southern Western Ghats and confined to higher elevations. BOF prefers the understorey of shola forests, especially Strobilanthes and bamboo thickets, among the stunted evergreen forest patches in the sky islands of Western Ghats and distributed above 700 m altitude, but more common around 1500 m and above. The NIF is also found above 600 m elevation but more frequently above 1200 m.

Degraded forests and plantations of timber, tea, coffee and cardamom adjacent to the forest areas are also considered suitable habitats. NIF mainly feeds on invertebrates; however, it also consumes fruits and berries of Vaccinium spp., Syzygium spp., Cestrum spp., etc. Both these flycatchers are categorized as ‘Least Concern’ (LC) according to the IUCN Redlist and fall under ‘moderate’ conservation concern according to the current state of India’s Birds report.

It is essential to recognize the effect of climate change on endemic species because of their restricted distribution and specific habitat requirements26.

Species distribution models (SDMs) are practical tools to understand the relationship between species occurrence and environmental factors. SDMs also help determine the previously unknown areas of a species from the known species occurrence points and predictor variables.

The study predicted suitable locations along the high-altitude regions for two species of restricted distributed flycatchers in Western Ghats. Among the two, NIF has more widely distributed suitable areas available in South Western Ghats. BOF is restricted to the high-elevation pockets and is more isolated in distribution than NIF. Few occurrence data are available in the Brahmagiri Hills for both species. In the case of NIF, the model predicts additional suitable areas in BR Hills, but the species may not be found there because of the unavailability of montane habitat. Also, NIF is not a long-distance migrant and such predicted suitable areas are 50–100 km away from the known range of the species. Regions within the Agasthyamalai Hills, Pandalam Hills, Anamalai Hills and Nilgiri Hills are the core habitats for both species of flycatchers. Both BOF and NIF have a high preference for montane habitats, the report said.

The findings of the study have been published in the latest edition of the prominent science journal Current Science. The study was carried out as part of E R Sreekumar's Ph. D research.