• A look into the migratory birds’ behaviour and the threats they face

Migratory birds have a certain allure to them, and their behaviours and movement are definitely one of the wonders of nature. Sri Lanka sees its fair share of such migratory birds, among which are barn swallows. The Daily Morning Brunch recently received images of hundreds of birds gathering in Balangoda.

This piqued our interest, and we reached out to environmentalists to learn more about this species. Gayomini Panagoda, a PhD candidate and researcher in bird migration ecology, avian sciences and conservation at Colombo University’s Department of Zoology and Environment Sciences took the time to answer our questions about the barn swallows in Balangoda.

While extending a special thank you to Colombo University’s Prof. Sampath Seneviratne, Panagoda said that information shared by Prof. Seneviratne indicated a 60% drop in the number of barn swallows and insectivorous birds that migrate to Sri Lanka over the last 25 years.

Regarding the birds in Balangoda, can you tell us a bit more about the species? Where do they come from and what’s the reason they visit Sri Lanka?

They are barn swallows (scientific name – Hirundo rustica). In fact, it is the most widespread species of swallow in the world. It builds a cup nest from mud pellets in barns or similar structures and feeds on insects caught in flight. This species lives in close association with humans, and its insect-eating habits mean that it is tolerated by humans.

They are migratory birds that breed in Europe, Asia, and North America and spend their winters in Africa, South America, and parts of Asia. The barn swallows that visit Sri Lanka are likely to be from the breeding populations in Central Asia and India.

During their annual migration, barn swallows fly over long distances, covering thousands of kilometres, and use various routes and stopover sites along the way. They visit Sri Lanka and other tropical countries in lower latitudes looking for suitable conditions for survival during the harsh winter months in higher latitudes.

In higher latitudes, winter brings extreme cold temperatures, frozen water sources, and reduced food availability, which can make survival very challenging for many bird species. By moving to lower latitudes during winter, birds can find milder climates with more available food and water resources, which increases their chances of survival. Another reason why birds migrate to lower latitudes is to take advantage of longer daylight hours, which provide more time for foraging. In higher latitudes during winter, the days are shorter and the temperatures are colder, which limits the time and energy that birds can devote to these activities.

What are some unique or interesting details about this occurrence?

Swallows gather in large numbers at night for several reasons, including:

To reduce heat loss: Swallows are small, lightweight birds that lose heat rapidly in cold temperatures. By huddling together in large groups, they can conserve heat and reduce the amount of energy needed to maintain their body temperature

To reduce predation risk: At night, swallows are more vulnerable to predators such as owls and bats. By gathering in large groups, they can reduce their risk of predation. With more eyes and ears available, there is a greater chance that predators will be spotted and the group can react quickly to avoid danger

To communicate: Swallows are social birds that use vocalisations to communicate with each other. By gathering in large groups at night, they can communicate with each other and coordinate their movements. This helps them to stay together and maintain their group cohesion

To share information: Swallows are also able to share information about food sources and potential dangers. By gathering in large groups, they can share information and benefit from the collective knowledge of the group

Overall, gathering in large groups at night allows swallows to conserve heat, reduce predation risk, communicate with each other, and share information. This behaviour is particularly important during the non-breeding season, when swallows must navigate unfamiliar environments and cope with the challenges of migration and survival.

During which time of the year can we see this occurrence in Balangoda? Do these birds visit other areas of the island as well?

This occurs throughout the migratory season which spans from August/September to April the following year.

The other areas where such large gatherings of barn swallows occur in Sri Lanka include Rathnapura, Matugama, Baduraliya, Deniyaya, etc. They often gather in towns on overhanging wires. In the said locations, their numbers can go up to 10,000-40,000.

When co-existing in the same environment as these birds, is there anything we should keep in mind?

When co-existing with barn swallows, it's important to keep in mind a few things to help promote their conservation and wellbeing.

Limit pesticide use: Pesticides can be harmful to barn swallows and their food sources, which include insects. Limit the use of pesticides, especially around areas where barn swallows are known to roost. If you need to use pesticides, try to use them sparingly and use non-toxic alternatives if possible

Promote insect habitat: Barn Swallows rely heavily on insects for food, so promoting insect habitat can help provide a reliable food source for them. This can include avoiding the use of insecticides and planting native plants that attract insects

These steps will not just promote the wellbeing of barn swallows but a whole lot of other insectivorous birds and wildlife in general who share the same space as us.

Do they face any threats, whether by nature or by man? How can we address these?

Barn swallows face various threats, almost all are human-induced. Some of the threats they face include:

Habitat loss and degradation: Barn swallows rely on suitable habitats for breeding and foraging, but their habitats are often destroyed or degraded by human activities, such as agriculture, urbanisation, and deforestation

Climate change: Climate change can affect the timing and availability of food resources that barn swallows rely on, which can impact their breeding success and survival

Pesticides: Pesticides used in agriculture and other human activities can reduce the availability of insect prey for barn swallows, which can negatively impact their survival

To address these threats, several conservation measures can be taken, including:

Habitat conservation and restoration: Protecting and restoring barn swallow habitats can help ensure their survival. This includes preserving natural habitats

Reduction of pesticide use: Reducing the use of pesticides can help ensure an adequate supply of insect prey for barn swallows

Climate change mitigation: Reducing greenhouse gas emissions and addressing the impacts of climate change can help ensure the availability of food resources for barn swallows

Public education and outreach: Educating the public about the importance of barn swallows and their conservation needs can help raise awareness and support for their protection. Insectivorous birds including barn swallows play an important role in maintaining the balance of natural ecosystems and provide valuable services for humans, including pest control, pollination, and maintaining biodiversity