b. Cultural importance

  i. Calendar birds

Bird migration has long been the subject of human fascination, and has become an important aspect of some cultural traditions. The predictable arrival or departure of some birds, the so-called calendar birds, has come to symbolise the turn of the seasons. The return date of some birds can almost be predicted to the day: the first redshank arrived in Helsinki between the 1st and the 8th of May every year over a period of 24 years! Such regularity is made possible by an internal clock, which records day length: the most reliable indicator of season in temperate climes1. The oldest written poem in the English language is about the cuckoo, heralding the arrival of summer and begins:

"Swifts", by Anne Stevenson (b. 1933), celebrates the birds' return:

Spring comes little, a little. All April it rains.The new leaves stick in their fists. New ferns, still fiddleheads. But one day the swifts are back. Face to the sun like a childYou shout, The swifts are back!

ii. Free as a bird

Bird migration has also come to symbolise freedom.
Free as a bird. Free because they fly - over national boundaries, through changing climates, across lines of latitude and longitude, through war and peace. We envy birds' flight because we are grounded: they are symbols of freedom, encompassing the ability to move apparently effortlessly between places (S. Norris, The Poetry of Birds). In "The Wild Swans at Coole", WB Yeats marvels at swans' ability to wander where they will, as he remains earthbound:

Unwearied still, lover by lover, They paddle in the cold
Companionable streams or climb the air;
Their hearts have not grown old;
Passion or conquest, wander where they will,
Attend upon them still.