Who are migratory birds?
Avian migration is a natural process, whereby different birds fly over distances of hundreds and thousands of kilometers in order to find the best ecological conditions and habitats for feeding, breeding, and raising their young. Arctic tern, Blackpoll warbler, Greater flamingo, Great white pelican, Red knot, and Common cuckoo are a few examples of migratory birds.
Most birds migrate in flocks. When larger birds fly as flocks it reduces their energy cost. Additionally, this provides safety in numbers since each individual is less likely to be attacked by a predator than if it were traveling alone. Some such as Geese and Cranes travel in their family groups inside larger flocks. The V-shaped formation that Geese use when migrating serves two important purposes. First, it conserves their energy. Secondly, each bird flies slightly above the bird in front of them resulting in the reduction of wind resistance.
Some birds also fly while sleeping with one-half of their brain. Frigate birds fly for months over the ocean and can engage in both regular sleep and use half their brain at a time to sleep during soaring or gliding flight.
The Red Knot has one of the longest total migration routes of any bird, traveling up to 16,000 kilometers twice a year. It breeds in Siberia and overwinters on the west coast of Africa, some even going down to the tip of South Africa.
It is truly amazing how migratory birds can navigate with pinpoint accuracy. Exactly how migrating birds find their flyways is not fully understood. It has been shown that they are able to orientate by the sun during the day, by the stars at night, and by the geomagnetic field at any time. Some species can even detect polarized light, which many migrating birds may use for navigation at night.
Threats they face
Migration is a perilous journey and involves a wide range of threats, often caused by human activities. And as diverse as people and their habits in different countries are, so are the threats the birds face. As migratory birds depend on a range of sites along their distribution area, the loss of wintering and stopover sites could have a dramatic impact on the birds’ chances of survival. Some of the threats faced by migratory birds include threats from predators like owls or hawks, dehydration, starvation, oil drilling rigs in the ocean, windmills, power stations, and drastic climate changes.
Light pollution is a significant and growing threat to wildlife including many species of migratory birds. Every year, light pollution contributes to the death of millions of birds. Attracted by artificial light at night, particularly when there is low cloud, fog, or rain or when flying at lower altitudes, migrating birds become disoriented and may end up circulating in illuminated areas. Depleted energy reserves put them at risk of exhaustion, predation, and often fatal collision with buildings.
Plastic waste enters the world’s oceans each year. Once in the water, it often leads to lethal cases of ingestion and entanglement. In certain cases, plastic waste can be mistakenly understood as crabs, eggs, fish, and other prey and therefore due to biomagnification and bioaccumulation through food webs, this has become a serious threat.
Also when pesticides and heavy metals leak into water bodies eutrophication takes place and as a result, algal mats are built. These could entangle migratory birds.
World Migratory Bird Day
World Migratory Bird Day (WMBD) is an annual awareness-raising campaign highlighting the need for the conservation of migratory birds and their habitats. It has a global outreach and is an effective tool to help raise global awareness of the threats faced by migratory birds, their ecological importance, and the need for international cooperation to conserve them.
World Migratory Bird Day was initiated in 2006 by the Secretariat of the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) in collaboration with the Secretariat of the Convention on the Conservation of Migratory Species of Wild Animals (CMS).
Countries or regions observe the peaks of migrations at different times therefore the main days for the international celebrations are on the second Saturday in May and in October.
World migratory bird day is celebrated annually under a specific theme. In 2023 the migratory bird day campaign will focus on the topic of water and its importance for migratory birds and identify key actions for protecting water resources and aquatic ecosystems. The migratory birds rely on water and associated habitats and lakes, rivers, streams, and ponds all inland and coastal wetlands for feeding, drinking, or nesting and also as places to rest and refuel during their long journeys. Unfortunately, aquatic ecosystems are becoming increasingly threatened around the world and so are the migratory birds that depend on them. The increasing human demand for water, as well as pollution and climate change, are having a direct impact on the availability of clean water and the conservation status of many migratory birds.
“Dim the lights for birds at night” was the theme of World Migratory Bird Day in 2022, focusing on the topic of light pollution and its impact on migratory birds. “Sing, fly, soar – Like a bird” was the theme for WMBD 2021, focusing on the phenomena of “bird song” and “bird flight”. “Birds connect our world” was the theme for WMBD 2020. Connectivity is essential for migratory species and important for a wide variety of ecological functions. It describes the natural and necessary movement of species and the flow of natural processes that sustain life on Earth.
Migratory birds in Sri Lanka
Sri Lanka rests at the furthest southern point away from the southmost point of India with no other land mass until the south pole, the migrating birds end their long journey on the island making it a regular wintering ground. Some of the migrants include Open Bill, Ibis, Heron, Egrets, Pelicans, and water cock. Bundala national park rests on the Southern tip of the bird migratory root and also happens to be one of the significant birding grounds for flocks of flamingoes, herons, and storks. It is an internationally important wintering ground for migratory water birds in Sri Lanka.
The Field Ornithology Group of Sri Lanka, an affiliate of bird life international, organizes “Migrant Watch”, an opportunity for bird lovers to observe and study migratory birds.
Let us focus on the prevention of water pollution this year since water is a major resource not only for migratory birds but also for all living animals on Earth. Migratory birds help keep the ecological balance and add color to nature.
2nd Year Undergraduate,
Biological Science Stream,
Faculty of Science,
University of Colombo.
- World Migratory Bird Day 2023 to Focus on Water | World Migratory Bird Day. (n.d.). https://www.worldmigratorybirdday.org/news/2022/world-migratory-bird-day-2023-focus-water
- Lockhart, J. (2023, February 21). 9 Awesome Facts About Bird Migration. Audubon. https://www.audubon.org/news/9-awesome-facts-about-bird-migration