The poet Ted Hughes famously wrote how,when the swifts arrived back in Britain in springtime then he knew that the world 'was working again'.

My first sighting this year occured on 3rd May when a lone bird flew fast and direct northwards to some far off El Dorado.

My local swifts began filtering back on 5th May,screaming 'scree-scree'above the garden,one pair at first then as the week progressed more joined them but briefly flew miles away again to avoid low pressure.

We welcome four swept back wing species to grace our skies for the summer namely swift,swallow,house and sand martin.All look superficially similar at first glance but there are marked shape and colour differences.Most elegant are swallows sporting long streamer tails whereas tails of martins and swifts are shorter and less forked.Martins are by comparison rather dumpy with shorter less angled wings.Swifts,belonging to a different family are larger with long sickle-shaped wings and appear darker in colour.All four specied feed on the wing catching insects and spiderlings.

One location where all four species can be seen is at the London Wetland Centre.A purpose- built sandbank drilled with holes has been constructed for sand martins which nest in colonies raising two broods.The other species nest elsewhere but martins,swifts and the occasional swallow can be seen skimming the numerous water bodies hunting for prey at the centre.

Much fun can be had testing our identification skills as we sit in a bird hide and watch the birds flash by at speed.