How does Climate Change Affect Migratory Birds?

Bird migration or aviation migration is a natural process. Birds travel a long distance, more than hundreds or thousands of miles annually, for migration. They fly over countries, islands, oceans, and continents for months. So, migration is risky and grueling for small animals like birds. Regardless, they migrate every year.

Bird migration is when some birds travel from areas of low or decreasing ecological conditions to areas of high or increasing ecological conditions. Accordingly, they are migrating due to a need for more convenient ecological conditions such as food, optimal weather conditions, and nesting locations for their annual lifestyle.

Not all birds, but some of them in countries with cold weather, travel to tropical countries to escape the cold winter season. It is different from every bird migrates in the same season and duration. The migratory bird patterns can change from bird species to species.

Click here to read more details on daily bird migration and bird forecasts.

The map below shows the global route of migratory birds, which can also be accessed here. There are 8 main flyway paths in the world, and Sri Lanka belongs to Central Asia flyway. Therefore, Sri Lanka is a destination country in that pathway.

Most bird species complete their annual migration at night when wind currents are smoother, and the moon and stars guide their way. There are further indications that birds sense the earth’s magnetic field and use it to direct them in flying to their desired destination. They do not fly as individuals during migration. They can always be found as flocks. It offers foraging benefits as well as protection from predators while migrating.

Siberian cranes and greater flamingos are the best examples of migratory birds. These birds migrate to India in the winter season usually. In addition, blue-tailed bee-eater, barn swallow, Indian pitta, Indian paradise flycatcher, and common redshank are some common examples of migratory birds found in Sri Lanka.

Do climate changes impact bird migration?

Climate change is a significant crisis in the world these days. Within a few decades, the climate in the world has shifted into a more vulnerable place.

With these climate changes, most wild animals have been affected, and migratory birds are one of the major victim groups of this crisis.

Bird’s life cycle is based on seasonal changes. Especially migratory birds have a particular schedule for their lifestyle according to seasonal changes. Not only are locations scheduled, but their appetite style, breeding, and every basic need are also based on seasonal changes. You can read more about the migratory bird lifestyle and seasonal changes here   Archived.

With temperature variations and climate change, unexpected seasons have occurred. Just one change in this can significantly impact migratory birds’ life cycles. Changes in seasonal patterns can disturb the lifestyle of migratory birds. While this sometimes leads to birds adapting to climate changes, it can mostly threaten a whole species. This causes a change in the migratory period of many bird species.

For example, with the temperature rise in the world, the spring season usually starts earlier. As a result, the migratory birds start migrating for spring sooner than they did before. Though these false springs made birds migrate earlier, their destinations may still have less than optimum temperatures for birds’ ecological conditions. There can be fewer food stocks and nesting locations, and it may be hard to survive even after avoiding the peak time of winter after traveling a long distance.

With this mismatch of bird behavior and environment, some migratory birds change their routes and shorten or cancel their journey due to changing temperatures. But that is not very beneficial for birds and their exergy. Therefore, the migratory birds that become victims of the negative impacts of climate change can be put in danger of being forced to survive in unacceptable ecological conditions and situations.

The bird distribution, which had been in the world for a long time, has changed with the impact of climate change. Also, the bird flyways have the same threat of changing.
Though birds migrate on their regular schedule, even under global warming and its side effects, their ordinary ecological communities can be changed completely. Food and nesting materials are their essential needs. Climate change can cause the reduction or disappearance of predators, parasites, competitors, and prey which used to exist in the ecosystem. It will take time for migratory birds to adapt to these new conditions and cause changes in the populations. Additionally, this can threaten the migratory birds’ endurance.
As a result, migratory birds are on the decisive line in the threat of extinction.

Some scientists think that, pretty soon, birds might not even migrate with these disturbances due to the impacts of climate changes on their time migration schedule.

Thermoregulation in migratory mammals

Compared to mammals, birds have high basal metabolic rates, use energy at higher speeds, and have higher body temperatures. Generally, birds’ body temperatures range from about 38 °C to 44 °C. Body temperatures of large flightless birds (Eg: emu and ostrich) and some aquatic birds (Eg: penguins) are at the lower end of this range and within the range of mammals. For example, the house sparrow has a body temperature of 43.5 °C.

Maintaining temperature within the thermoneutral zone requires energy, which is a precious resource for most organisms. Migratory birds, in particular, have tight energy budgets; to cover long distances without food means that migrating birds need to assimilate and conserve energy as much as possible before and during migration. The birds should avoid both heat and cold stress, as these use the energy needed for flight, and they do so in several different ways. In cases where individuals travel long distances without drinking – for example, when crossing oceans or deserts – both thermoregulatory and osmoregulatory (water regulation) adjustments are required to conserve energy and water. Before migration, birds increase food intake, sometimes doubling their mass (pre-migratory fattening)
Read more about thermoregulation here  Archived.
 
Migratory birds in Sri Lanka

Sri Lanka is a biodiversity hotspot in the world, with tropical climate conditions and natural habitats for birds. So, Sri Lanka is an island that attracts more migratory birds.
Climate Fact Checks group contacted Professor W A D Mahaulpatha, Senior lecturer at the Department of Zoology, the University of Sri Jayewardenepura, regarding the topic. Professor WAD Mahaulpatha commented on the threats to migratory birds in Sri Lanka.
“The main two migratory bird categories in Sri Lanka are coastal and wetland birds. But with climatic change, Sri Lanka has faced serious matters of irregular rainfall patterns. For example, due to changes in periodicity of rainfall, Anavilundawa RAMSAR wetland turned into an arid area in a season, while the other season has extreme rainfall.”
She commented that the birds who target the Anavilundawa wetland as their final destination have a threat of losing their habitat with good conditions due to climate change.
Also, Professor Mahaulpatha mentioned that with global warming, glaziers and the ice layer in the world have melted, which increases the sea level. Therefore, it may cause the coastal areas to minimize favorable conditions, such as food for coastal migratory birds around the island. This is a major challenge for coastal migratory birds.
 
How to save migratory birds from Climate Change

The director of wildlife health at the Department of Wildlife Conservation, Dr. Tharaka Prasad, was contacted to learn the methods for conserving migratory birds.
“Legally, we have protected every animal, including migratory birds, through the ‘Flora and Fauna Protection Ordinance,’ to live and peregrinate freely. And also, inter boundary protection has been provided for them with mutual understanding within every range state by the Bonn conversation (Convention on the Conservation of Migratory Species and Wild Animals).”

Dr. Tharaka Prasad also said that climate change had affected the migrations of birds to Sri Lanka. Bird migration is always aimed at escaping from extreme weather conditions. But with global warming, migratory birds change their pattern of migration. Sometimes they may not want to travel far like before, and they will find a closer place to spend their winter.
We also asked about the changes in the number of migratory birds in Sri Lanka. But he said there has yet to be a noticeable difference in Sri Lanka. This is because changes in the annual numbers of migratory birds are minimal in number in Sri Lanka and are not found due to climatic changes.
As individual human beings, we should do our best to protect and conserve these migratory birds from climate change and prevent human-induced global warming to our best capacity.

( With inputs from Mihiri Saparamadu )