Picture courtesy of Ferran Pestana.
NATURE NOTES DRIVING back and forth along the Military Road this last week, I have been watching the last few swallows flying around and fattening up before setting off for warmer climes.
The end of October might seem quite late for these birds still to be here, but the IW Bird Report indicates that they can occasionally be seen well into November.
These are unlikely to be birds that have nested or spent the summer on the Island, but birds which are already on passage from further north. The swallow (or barn swallow) is one of the most widespread species of bird, occurring in Africa, Asia, Europe and the Americas, but is, nevertheless, considered to be a bird at risk in this country because of generally declining numbers.
The understanding of the migration of birds is only relatively recent, only proved as a fact by bird ringing in the late 19th century.
Prior to that, even such a renowned naturalist as Gilbert White (from Selbourne in Hampshire) believed that swallows hid themselves in the mud at the bottom of ponds throughout the winter. However, the truth of migration is almost as fantastic as the thought that they hibernated in mud for several months.
Swallows migrate at low altitudes, finding food on their way and flying at speeds of up to 35mph. Generally they fly more slowly, travelling up to 200 miles in a day.
The trip to their wintering grounds in Africa is 10,000 miles or so, and usually involves them flying over mountainous areas and, of course, the Sahara Desert.
Some swallows follow a more coastal route down the west coast of Africa to avoid the desert, but what they may gain by that is countered by the additional length of their journey. Some European birds winter further to the east, in the Indian sub-continent and the middle-east.
Despite taking time en route to feed and gain reserves of fat, swallows are vulnerable to starvation during the journey and many birds are lost each year.
Other hazards include storms and sheer exhaustion. The journey south may be assisted with favourable winds, but the journey north in the spring is more arduous.
Faced with more likelihood of flying into the wind, and also into areas where food may not be plentiful that early in the year, many more birds are lost on the spring migration than on the autumn one.
Swallow populations do fluctuate from year to year but there has been a persistent decline in numbers across Europe since the 1970s. This has been put down to a number of factors including climate change, not only in Europe but more significantly in Africa.
The expansion of the Sahara Desert is making the crossing even more of a barrier. Changes to farming practices in Europe have also contributed to a loss of nesting sites and a reduction in their food. The loss of grazing and the use of pesticides results in fewer insects.
Swallows and their nests benefit from protection under the Wildlife and Countryside Act 1981 and it is an offence to damage or destroy the nests while in use, or to injure any bird or nestling.
Most people are pleased to have swallows around in the summer, despite the mess they leave, sometimes going to extraordinary lengths to make them feel at home.
So when you wave goodbye to the last one this year, give some thought to whether or not you can provide a suitable nesting site next year, and share your summer with these graceful birds.