Migration is an important move that birds make when something in their brains tells them resources will soon be depleted as temperatures drop, wet weather arrives, and the wane of vital food triggers their flight. Currently, thousands of species across the world are now on their annual fall migration. However, this might not always be the case.
OUR CHANGING WORLD
Around 4,000 of the world’s bird species are migratory. But an increasing number of sobering voices are warning that this number will decrease in the coming years due to climate change. Extreme weather events, searing temperatures, and wildfires are some of the natural disasters birds face in addition to their food cycles being thrown off with fruit ripening too late and insects hatching too early, if at all.
A recent study looked at how birds rely on consistent environmental conditions for their survival. The study explored how species have been negotiating the upheaval in recent years caused by marine heatwaves, oceanic storms and other unpredictable and, more importantly, unfamiliar events. It found that smaller species like warblers were more at risk of dying on the journey as shifts in air temperature caused by storms or heat waves were overwhelming their bodies. Larger birds can regulate slight temperature differences more efficiently but smaller species like the Prothonotary warbler will not survive any more than a few degrees difference for sustained periods of time.
Climate change is already affecting when birds migrate. Some species are flying notably earlier or later than their usual departure dates, and others are changing their routes altogether to compensate for vital stopover sites that won’t be ready to provide the food and water they need to refuel on their way.
Richard’s pipits usually breed in Siberia and overwinter in Southern Asia, but they have been observed migrating on an east-west axis instead of heading south towards warmer latitudes. Researchers suspect that a warming climate has a role in establishing new routes. Similarly, Trans-Saharan migratory birds like the common cuckoo, the European turtle dove, and the common nightingale, who typically migrate from Europe to Africa in the winter, have been spending less time in their winter retreats and more time in their breeding grounds. If this trend continues, they may no longer overwinter in Africa at all if they can find food and habitat in Europe year-round.
The Arctic tern has held the record for longest migratory flight since records began, clocking a mind-blowing 24,000 miles each year as it travels between the North and South Pole. It starts from its breeding grounds in the Arctic Ocean as summer hits the Northern Hemisphere, then turning around again and heading back to the Southern Hemisphere, effectively living a life of endless summertime. Melting sea ice, the platform on which they congregate and breed, is making it difficult to find food and locations to raise their young.
However, some species are able to overcome these climate changes. Another study suggests that as Arctic terns cover such a vast geographical area, they may be resilient enough to adapt to these threats, seeking out alternative regions. Whilst this will mean they will have to fly for longer and further, the hope is that, due to the fact that they are accustomed to flying so much, it will be a crucial asset for their survival.
HOW WE CAN HELP
Information is power. Getting as much accurate information collected and into the right hands can be critical for research and emergency intervention. Citizen science plays a major part in collecting this data, as monitoring birds like tiny warblers is impossible for just a handful of researchers. You can help contribute towards essential datasets by installing a smart bird feeder in your yard, or submitting any bird encounters you have on eBird, as population demographics like this give a vital worldview of just where all the birds have gone.