Birds facing impossibly longer migratory trek

The trials and challenges facing migratory birds are highlighted by the famous Monty Python Holy Grail skit about crossing the Bridge of Death, but this was made at a time when the migration habits of birds were so reliable that Monty Python could make a joke out of it.

However the ravages of climate changes are no laughing matter.

Recent investigations have concluded that the annual journey north for some species could grow by 400 kilometres.

A change of that magnitude could be devastating for some birds.

Studies on one typical species, European Sylvia Warblers, seem to indicate that while the southern wintering grounds for most species will stay pretty much as they are, the northern breeding and feeding grounds will fluctuate dramatically.

Many bird species have adapted quite specifically for the current migration routes.

To get ready for the long and arduous haul, they need to load up on fat energy stores, many doubling their weight.

There are even bird species that annually shrink their internal organs to get maximum aerodynamic performance over routes of thousands of kilometres.

There are species that weigh as little as nine grams (or a third of an ounce).

They push the envelope in terms of sheer endurance.

Add a few hundred kilometres extra to a the trip and it could well be fatal.

Around 500 million birds of seventeen different species make the flight out of Africa each year.

Some of them cross the vast Sahara desert, and some tough it out all the way over the Mediterranean sea after having crossed the Sahara, without touching down.

Other species choose to take a break in North Africa before flying on northward to their breeding grounds.

Simulation data, published in the Journal of Biogeography, predicts that by the end of this century over half of the 17 species that migrate will be facing much longer, tougher flights.

Some exceptional birds, such as the Blackcap, have already developed major behaviour change and now spend winter in Britain rather than making the flight to Africa.

The Chiffchaff also chooses to winter in the UK rather than fly to Iberia.

So while we cannot definitively answer Monty Python’s questions, we can be reasonably certain that an extra 9 percent fuel fat store and 5 percent lean body mass will be required by migratory birds in decades to come.