Climate Change Raises Grave Concerns about Bird Migration

Moneyless Travellers

Have you seen Black storks? Their legs and beak are long and red, belly and chest as white as chalk, and they are the apotheosis of bird beauty in this three-colour regalia. The scientific name is Ciconia Nigra. They are more world citizens than any of us, being born in Europe and flying off to Africa during winter, crossing Gibraltar and the countries of Israel and Turkey. They spend the cold winter days in Sub-Saharan Africa, feeding on fish found in the continent’s lakes, dancing behind the farmers' tractors to catch insects and worms unsettled from the tilled soil, and sleeping perched on buildings, branches of trees and even the ground. They see the world without spending a penny.

From Africa, they return to Poland for breeding. However, ornithologists were perplexed in 2018 when they found that the returning black storks were skipping the stopover in Poland but were continuing till they reached Israel. The reason was revealed soon. Poland’s summers were getting hotter than ever before.

The world is witnessing not only black storks but many migratory birds altering their flight routes owing to strange changes in the climate. Some return midway to where they started. Some other birds have stopped migrating at all. For example, some smaller birds that used to migrate from England to Spain, France, and North Africa in winter have stopped those wintering journeys all over. Somehow, these birds have sensed that the lakes and water bodies in those distant lands have dried up, and the forests there have become depleted and uninhabitable.

Erratic Bird Migration: The Unwanted Ripples in the Ecosystem

What will be the impact of a lifestyle shift of migratory birds into a sedentary life on both the native and the host ecosystems? Will the native ecosystems be able to support the birds if they stay for winter? The rats and insects that these birds would have rid the farmers of in those distant host ecosystems might be thriving, their predators choosing not to arrive.

The farmers there would have difficulty protecting their harvested grains from these pests. Trees and plants across the flight path would have their fruits eaten by these birds if the journey had commenced. What will happen to the species of trees whose seeds were to be propagated by these winged friends? The lack of seed propagation might cause the extinction of these trees.

When a link in the food chain is broken, the chain can collapse entirely. In the coming years, when climate change accelerates, what will happen to the around 50 billion migratory birds (of the total population of about 200-400 billion birds on the earth)? What will happen to the species that feed upon the migratory birds in host ecosystems? These questions together constitute a complex problem that evokes many forebodings.

Changes to Bird Migration in History

Recent research has proven that the ice age played a major role in the migratory behaviour of birds. What we are witnessing could be another moment of extreme climate change similar to the ice age. Once again, the bird migration instincts and patterns might be changing. The morphological and physiological features of birds, the very genetics encoded in them, govern their migratory behaviour.

Partial migration concerning immediate climate variations has been present in many bird species. Long spells of drought in their natural habitats during the breeding season aggravate this into absolute migrations. However, no drastic genetic change occurs along with these behavioural changes, and they would remain partial migrants. Their longer and full-fledged migrations are only an adaptive response to an immediate climate threat. When climate situations change, the total migration is reversed to a partial one. However, there is no consolation in this fact. New habits and habitat changes impart a heavy toll on the avian folk.

The Arrow Stork and the Discovery of Intercontinental Migration

In 1822, the people of the idyllic German village of Klütz bore witness to a bizarre sight. A white stork landed there with an arrow pierced across its neck. On further examination, it was revealed that the arrow was made of wood unique to Africa. People named this stork Pfeilstorch, meaning arrow-stork. That was the first in many events that prompted ornithologists to study bird migration more closely; the scale was hitherto unfathomed by human knowledge. The University of Rostock in Germany still has the original arrow stock stuffed and kept there. Further studies proved that the white storks from Africa make a round trip of 4000 miles from their natural habitat to Germany and back. Arctic Tern, another bird, travels 60000 miles from one pole to another in its journey of cross-continental migration.

The Flight of the Common Swift

The Common Swifts of Scandinavia fly to Sub-Saharan Africa and back, a voyage that takes about ten months, and throughout which, some of them never land but keep flying. They are found to be able to feed, mate, and sleep while flying. They are aptly called the “most mobile terrestrial birds in the world”. Their ability to constantly find food even as they keep flying is unbelievable.

They are chain migrators, where the first populations that arrive in a host ecosystem do not claim the territory they occupy. The late-arriving migrant populations also settle in and around the same location. This behaviour is in contrast to the leapfrog migration found in some other birds; one helps the first migrants to claim the territory as their own, and the late migrants move somewhere else.

In 2018, Patrick Barkham, an author at The Guardian, wrote, “Summer is a shadow of its former self with so few of these miraculous birds around”. He was talking about common swifts and lamenting how the English summers when these birds were supposed to go back. He felt vapid without them.

He cites the British Trust for Ornithology, which investigated the population decline of common swifts in the UK and found that between 1995 and 2017, the British swift population diminished by 57%. The study attributes this decline to climate change that results in habitat destruction.

Case Studies from around the Globe

The change in migration patterns of these birds is a sign. It suggests that the globe is reaching the nadir of livability. One alarming fact is that the bird populations are driven towards the mountains and polar regions.

Many bird species have shifted their habitats up-mountain in the last 80 years in the Sierra Nevada mountains. In the White Mountain National Forest in the US, the decline in the number of spruce-fir trees is associated with a fall in the population of bird species such as Bicknell’s Thrush that propagate their seeds.

When birds from lower elevations move up, the birds inhabiting higher elevations find the place too crowded in terms of space and food, and they, too, move upwards. These shifts result in all these species ending up in marginal habitats, which are habitats where they have only minimal means of sustenance.

The wintering birds (who migrate to avoid the winter cold) rather than breeding birds (who migrate for breeding) are more sensitive to climatic changes. The timing of migrations also manifests visible changes. A 2020 study published in Nature found that the birds leave earlier in spring and summer because of excess early warming in the atmosphere. The black-tailed godwits, a gorgeous bird species wintering in Spain and Portugal, started arriving two weeks early at the beginning of last decade. Unfortunately, it is observed that the bird species that fail to begin migrating early are facing a substantial decline in their population.

The mismatch between the timing of migration and the season of plenty in the host food ecosystems is a more dangerous and recent fallout. In this scenario, the birds arrive only to see that the season of food has ended in that place before their arrival. Earlier, if they used to find ripe fruits exactly at this time of the year, now the fruiting season has moved behind. The outcome is that the birds would starve in thousands. Scientists observe that this mismatch is growing.

Also, there is a growing discrepancy between the nesting time of breeding birds and the season of maximum food availability. Earlier, nesting was synchronised with the season when food was available at a maximum level, which is not the case anymore. Another unforeseen impact is on bird health; the birds retreating to locations where water is available sometimes makes them vulnerable to new viruses and diseases specific to those localities.

As the bird migration hiatus spreads globally, the onus to help the birds falls solely on us. We are at the causation end of the problem.