To save the Dull-Blue Flycatcher
By Buddhika Samaraweera
It is no secret that Sri Lanka’s biodiversity is second to none. Much of the flora and fauna that call it home are found nowhere else, and this can be attributed to its unique climatic, topographic and geological conditions.
One such unique habitat in the country is cloud forests, also known as montane rainforests. Wherever they are found in the world, these high-rainfall mountainous jungles host a variety of fascinating denizens, and Sri Lanka is no exception. For instance, highland endemic bird species have unique physical, biological and bio-geographical requirements that nowhere else can satisfy. These birds have evolved in tune with the specific high-altitudinal climate of the central hills of the island.
Among such bird species in Sri Lanka is the Dull-Blue Flycatcher, which inhabits the cloud forests of Horton Plains National Park (HPNP). With regard to this species, a long-term study has been conducted by the Faculty of Postgraduate Studies at the University of Sri Jayawardenapura (USJP), by Chathuranga Dharmarathne under the supervision of Senior Lecturer and Head of the USJP Department of Zoology, Prof. Dharshani Mahaulpatha.
These rare birds are only found in such cloud forests, where canopies have adapted to capture water from the clouds in a process known as cloud-stripping, which gives them far more water than they could obtain from rainfall.
Threatened with extinction
However, this species has been identified as ‘Near-Threatened’ (NT) by the International Union for Conservation of Nature (IUCN), meaning it faces the risk of extinction in the near future, even though it does not currently qualify for ‘Threatened’ status. The IUCN periodically re-evaluates the status of such NT species, making it a national responsibility to carry out provisional ecological studies on such critical species to ensure their conservation.
Certain researchers have already sounded the warning that Sri Lanka’s endemic highland birds are placed at risk by the reduction of suitable areas for them to live. The Sri Lankan Dull-blue Flycatcher, scientifically known as Eumyias sordidus, is an endemic, understory insectivorous bird that is restricted to a particular hill region (600m above sea level).
The species is unfortunately predicted to suffer an 80 per cent reduction in habitable area by 2080. Therefore, to ensure the conservation of this feathered treasure, we need to conduct more in-depth studies to understand the resilience of the highland forests and their present distribution, population, foraging ecology and other ecological aspects.
Dharmarathne's study highlighted how the lack of scientific data on avifauna poses a major problem to conserving bird species in Sri Lanka. Recent studies also revealed that insectivorous birds in the tropics face far more risk from habitat fragmentation than their cousins. The degradation, fragmentation and loss of habitat to human activity affect tropical biodiversity in all its forms, and the insectivorous bird species desperately require more understanding through informed study, considering that they are suffering a global decline due to reasons that are yet to be identified.
Dharmarathne’s research pointed out the numerous reasons why this species exclusively inhabits cloud forests, which include the canopy cover, ripened fruit, flowers, shrubs, ground and aerial insect availability, and wind speed. They may also be partial to the cloud forest habitat for the cover it provides from the South West Monsoon’s strong winds. It is also learned that there may be local migrations happening during the periods of harsh climate.
Dull-Blue Flycatchers hunt a wide range of invertebrate prey, including flying, ground and vegetation-dwelling species. With such a diverse range of prey, as well as the use of multiple foraging techniques, the Dull-Blue Flycatcher shows a very flexible diet. Current research shows that the species frequent the fruit of three plant species under the Rosaceae family, which is indigenous to montane cloud forests. Additionally, they prefer moderate forest cover over dense forests.
Diverse hunting methods that leave it vulnerable
Dharmarathne also noted that studies of the faecal samples of the Dull-Blue Flycatcher revealed remains of bees and wasps, dragonflies and damselflies, and adult lepidopterans and larvae, to a moderate level, while there have also been a few records of them capturing small amphibians to feed nestlings. The species also participates in mixed-species foraging flocks, which see different species of birds forming flocks to gather food together.
This behaviour shows that the Dull-Blue Flycatcher’s flexibility and range in diet can prove advantageous in the face of variable conditions (changes between habitats, seasons and years).
However, the wide range of invertebrate prey consumed by the Dull-Blue Flycatcher leaves it rather vulnerable to accumulating environmental toxins. Its prey includes strong-flying species (some bees, wasps, flies and dragonflies) which may come from relatively long distances away from the flycatcher’s sites. It also includes species of terrestrial and aquatic origin. Thus, pesticides and other potentially harmful compounds may be acquired from either of these resources.
Also, chemical toxins and exposure to pesticides and other harmful chemicals are particular threats at sites surrounded by intensive agriculture and along tea plantations, where this species was recorded in considerable numbers – a large number of pollinating insects in such grassland habitats are also a chief source of prey for the Dull-Blue Flycatcher.
This study provides valuable insight into the diet of endemic insectivores in tropical mountainous cloud forests. Combined with existing research, it also points out potential areas of concern and directions for the benefit of future researchers. According to Dharmarathne's findings, the Dull-Blue Flycatcher generally occupies road banks as their nesting sites. Unfortunately, several instances of roadkill were recorded during his study period, where fast-moving vehicles in the HPNP had collided with breeding individuals of the species, killing them in the process.
Dharmarathne pointed out that the April New Year season, during which a large number of local and foreign tourists visit the park, is the main breeding season for the Dull-Blue Flycatcher in this habitat. According to his findings, the overlap of these two factors results in severe negative effects on the Dull-Blue Flycatcher.
Field observations further prove that vehicles travel at considerably high speeds within the national park, result in the unfortunate deaths of any animal caught in their paths while returning to their nests for incubation or to feed their nestlings. Furthermore, fledglings are also directly impacted by these fast-moving vehicles, as nesting sites are often located beside the roads they frequent.
The study’s recommendations
Having identified that Dull-Blue Flycatchers are already a near-threatened species, Dharmarathne, in his study, suggests several recommendations and management implications for its conservation.
He noted that there are several white-coloured milestones beside the roads in the national park; these attract flying insects, as they strongly reflect sunlight. Dull-blue flycatchers were seen sallying around these milestones to catch such prey, which increases the risk of them ending up as roadkill. He therefore suggests that the colour of these mileposts be changed to something darker, which would prevent this from occurring and minimise such fatalities.
As the high speeds of vehicles within the park have been identified as a main disturbance to the Dull-Blue Flycatchers, Dharmarathne also suggests that a speed limit be enacted for vehicles inside the National Park and the areas surrounding the montane cloud forests to avoid damaging the flycatcher, as well as other endemic species.
Also, since this species prefers to use road banks as nesting sites, it was noted that these are often disturbed by visitors. He therefore suggests that wildlife viewing opportunities be provided at safe distances from the nesting sites to avoid, or at least minimise, disturbance by visitors. He also suggested that visitors and photographers be made aware about maintaining a safe distance from breeding sites as much as possible.
Dharmarathne was also able to record certain incidents of breeding individuals being disturbed by the practices of the HPNP’s management. For instance, road bank clearance activities by workers to widen the roads in the national park directly impact breeding individuals, disrupting their nesting habitats and removing their perching plants and shrubbery near their nesting sites.
Therefore, he suggests, all authorities concerned should pay attention to the matter, which would be of great benefit in preserving their natural nesting sites, especially if activities such as road bank clearances could be carried out at some time other than the breeding seasons of these birds.
There is a reason that such species cannot be found anywhere else: they have evolved over millennia to the specific environment they inhabit – in this case, the cloud forests of Horton Plains. We can study them as intensely as possible and marvel at the several particular features and habits they have developed to set them apart from the countless other more commonly-found species. However, we cannot wait further millennia for them to adapt to the careless destruction we leave in our wake; if so we will only be left with the memory of such unique creatures to remind us of our ignorance.
(Pix courtesy Chathuranga Dharmarathne)
Dull-Blue Flycatcher: Facts
* Found only in highlands of Sri Lanka where elevation from sea level is more than 600 metres
* Horton Plains National Park is one of the best places to see the Dull-Blue flycatcher
* A resident breeder whose breeding season is in March/April
* Usually builds nests on well-shaded rock ledges
* The nest is cup-shaped and made our of masses of moss
* In a normal clutch the female usually lays two to three brown spotted pink eggs
* A grown Dull-Blue Flycatcher is about 15 centimetres long and has a loud melodic song
* Adults are ashy blue, with a whitish belly and there is a black patch between the broad black bill and the eye, bordered with brighter blue above and below
* Both male and female birds look similar but females are slightly duller
* Juvenile birds are brown and heavily spotted on the head
* Feeds mainly on flying insects, beetles, caterpillars, and other insects, but also eats berries
* Relatively easy bird to spot
* Sri Lanka Dull-Blue Flycatcher is endemic to Sri Lanka
* An image of Sri Lanka Dull-Blue Flycatcher is seen on 50 rupee note