God speed to the godwits (and other autumn voyagers)
THIS weekend the recycled remnants of Hurricane Maria are upon us. In western regions expect heavy rains while readers elsewhere should be braced for winds of between 50 to 60mph. In short, it is far from ideal travelling weather. But travelling is what many species about us are currently preparing to do.
Autumn marks the final great migration of the year when animals are preparing for the cold months ahead by either storing up food or simply packing their bags for warmer climes.
Not just birds but butterflies, too. In 2009 scientists discovered that the Painted Lady migrated south each autumn as part of a 9,000 mile round trip from tropical Africa to the Arctic Circle. Remarkably, the whole journey is not undertaken by individual butterflies but in a series of steps completed by up to six successive generations in a hereditary relay race to the finish.
The weather can obviously be a massive help or hinder to migration – remember that Waitrose Christmas advert last year with the Scandinavian robin buffeted about by winter squalls?
Similarly, one would not recommend a Painted Lady setting off on its travels this weekend for fear it may get blown off course to the Faroes.
For larger birds the sun is best, heating up the land and causing warm air currents called “thermals” to spiral upwards enabling them to gain height without using precious energy and glide towards their destination.
For smaller species, a good breeze is crucial. According to the RSPB, in still conditions small birds fly at an average speed of 20mph and medium-sized ones at 30mph. However with the wind behind them, birds can easily cover 625 miles in just 24 hours. Bar-tailed godwits have been recorded migrating from Alaska to New Zealand – a distance of almost 6,800 miles – in just six days as a result of a favourable tailwind.
God speed to any godwits setting off over the next few days.
They will need it.