Animal of the Week April 4, 2011 -- One does not a summer make

Malene Thyssen

Taking a step back from what I've got in my garden this week... I've not yet seen a single one of this week's animal in my garden, although it is only a matter of time before I see Hirundo rustica (barn swallow) if not in the tiny space out back, then skimming over the top of the gardens or flitting inches from the ground in Regents Park or Hampstead Heath.

Swallows are one of those species of impressively aerial birds including martins and swifts that arrive in spring to feast on the emerging flying insects as they raise their families. One way to tell the birds apart is the place in the air column they choose to feed. Sickle-winged swifts fly high overhead, house martins swoop around above rooftops, swallows often feed inches above the grass of meadows or the surface waters of rivers and lakes their buoyant graceful flight bringing them impossibly close to crashing in pursuit of supper. Close to, swallows are easily distinguished by their oily blue back and their red throats.

I saw swallows a month ago in Seville, bouncing off the surface of the Guadalquivir, and it seems that now they have caught up with me and made it to the UK, with the Wildfowl and Wetlands Trust twitter feed telling me they've arrived at the Barnes Wetlands Centre in south west London.

The barn swallow is one of the most widespread birds in the world, with few countries where they are not to be seen at some point during the year. The birds follow the spring north, nesting from north Africa, Mexico, and northern India all the way up to the arctic circle. Then, as the nights draw in in the north, they head back south to Central and South America, sub-Saharan Africa, south Asia and northern Australia. Birds arriving in England now may have come all the way from Cape Town.

Individual birds cover over 11 000 km in their migration each year. And the estimated worldwide population of 190 million has a range that covers 51 million square-kilometres, which is more than a third of the total land surface area of the earth.

Sorry Aristotle, perhaps one does not a summer make, but all over the world 190 million swallows do.