Sand Martin (Riparia riparia)
The sand martin is the smallest swallow that breeds in Europe. It measures only 12-13 cm beak to tail, that is about 5 inches. It breeds at elevations below 750 m or 2500 ft in North-America as well as Europe and Asia. It winters in South America as well as central and northwestern parts of Africa. Because of habitat loss it has become less common in Central Europe, where they can now only be found along the coast, a few river banks, and at the perimeter of gravel pits.
For nests the sand martins dig with beak and claws tubes at a slightly upward angle about 3 feet into the sandy or clay materials of a natural or man-made brim. At the end they expand the tube to accommodate the nest which is made more comfortable with feathers and grass or weed stems. Both parents breed for about 14-16 days and feed for 18-23 days, at which time the fledglings leave the nests to gather and live with the young-ones of other sand martins in a reed or a thicket along the shore. The now empty-nesters brood a second time.
The sand martin is not only the smallest but also the least conspicuous swallow we describe in this section. Like most of the other swallows its underparts are white, but alas the upperparts are just a simple brown, umber. The only 'embellishment' is a greyish neckband.
My Wings *
When air passes over an airfoil, forces arise which push it upwards. There’s a fairly complicated theory behind that, but I don’t want to bore you with it. The striking thing is that I can change the shape of my wing. I do it by erecting an extension of feathers on the front edge of my wing when I need to. This increases the lift. Naturally, this only happens when I am airborne. If the feathers were rigidly anchored to my wings, I could, of course, point them downward and thus obtain some lift. But then I’d nosedive because I would then have to lift my wing upwards, and this, in turn, would drive me downwards. My Creator took account of this and made sure that my feathers automatically twist somewhat whenever I lift my wings, so that they open like the slats of a Venetian blind, and the air can flow through. When I point my wings downwards, they close again, and I can soar high into the air. Since my wings also twist like an aeroplane propeller each time I beat them, they also propel me forwards.
The swallow continues: My Flying Expertise
* quotes from the book "If Animals Could Talk"
