Why Are Birds Migrating Early?

All over the world, birds migrate with the changing of the seasons. They often travel immense distances in order to find warmer climes and more abundant sources of food as the year progresses.

However, with manmade global warming playing havoc with regular climatic patterns, many birds are now being fooled into thinking that the seasons have changed earlier than normal. As a result, they are arriving at their breeding grounds earlier than usual, which is having a knock-on effect on the availability of nesting sites food sources and could lead to certain species diminishing in number.

Birds on the wing

The avian population of the Earth are a restless bunch. Swallows, for example, travel huge distances (from all over Britain to the tip of the Cape of Good Hope in South Africa, via the Pyrenees and the Sahara Desert) at incredible speeds. On a good day, a British swallow can reach speeds of up to 35mph, covering over 200 miles in 24 hours.

Its slightly smaller counterpart, the pied flycatcher, covers a similar distance, spending summers in the UK before holidaying in western Africa for the colder months of the year. Even those birds which don’t fly quite so far still get around. Lapwings and pied magtails rarely venture outside of the British Isles, but they do visit most parts of the country throughout the calendar year.

The birds undertake these great journeys to escape the onset of winter and to find plentiful sources of food in new breeding grounds.

Right place, wrong time

However, a new study conducted by the University of Edinburgh has found that manmade climate change might be having a disrupting effect on these patterns. As if dodging our fishing nets wasn’t bad enough, it now seems that birds are having to grapple with the colossal monster of global warming that we’ve created, too.

The study examined the flight patterns of British birds (including all of those named above) over the last 300 years, using any and all records the researchers could get their hands on. The investigation even included observations made by the esteemed 19^th century essayist and poet Henry David Thoreau.

It found that on average, birds are arriving one day earlier to their breeding grounds for every degree that the temperature is higher. While this discrepancy might seem small and inconsequential, it could have a major impact on certain avian species.

It’s all in the timing

If a bird fails to arrive at its destination by even just a day or two, they find themselves short of a nesting spot and scrabbling for food. This can have huge implications for the time that their eggs hatch, which threatens the survival of their young and the ongoing existence of their race as a whole.

Of course, such a hypothesis is little more than speculation at the moment, but lead author of the study Takuji Usui hopes that his work will lay the groundwork for a better understanding of the implications of these delayed arrivals in the future.

“Many plant and animal species are altering the timing of activities associated with the start of spring, such as flowering and breeding,” he explained.

“Now we have detailed insights into how the timing of migration is changing and how this change varies across species. These insights may help us predict how well migratory birds keep up with changing conditions on their breeding grounds.”