The birds who never forget a face – and have sex lives that’ll ruffle a few feathers
EVER since our caveman ancestors first gazed up into the sky, human beings have tried to fathom the extraordinary talents of birds. How can a swallow weighing less than an ounce travel thousands of miles to its winter home in Africa, and then return the following spring to the very same place it was born? How does a nightingale improvise its legendary song, choosing from up to 300 phrases like a feathered jazz musician? And how do swifts — those incredible creatures that pelt t helter- skelter across our city skylines every y summer — manage to sleep on the wing?
For centuries ornithologists couldn’t understand r- birds’ more bizarre sensory abilities, such h as their ability to see ultraviolet light or to use e the Earth’s magnetic field to navigate accurately y across the surface of the globe. But these and other questions about the extraaordinary abilities of birds may have e been answered in a new book, Bird d Sense, by Tim Birkhead, professor of behaviour and evolution at the e University of Sheffield.
Professor Birkhead has spent a lifetime - studying birds — not in some e ivory tower, but out there in the field. d.
He recalls that as a young student t he once visited a gull colony and had d the unfortunate experience of one of these huge seabirds simultaneously y defecating and vomiting on his head d at the same time. But this certainly y didn’t put him off, and since then he e has travelled the world studying the e different aspects of bird behaviour.
He points out that many of their r extraordinary abilities have evolved d simply so they can pursue their prey.
The great grey owl of North America, northern Europe and Asia is able to hunt mice and voles hidden beneath a thick layer of snow by using its round face, which is lined by stiff feathers, to magnify the sound of its prey’s movements and channel them towards its ears.
The owl’s ears are also at different heights on the sides of its head, helping it to pinpoint the exact direction the sound is coming from. It then plummets down to catch the rodent with its razor-sharp talons.
The kiwi, New Zealand’s national bird, is similarly well-adapted: in its case, to a mainly nocturnal existence.
It suffers from terrible eyesight and can hardly see more than a few inches in front of its beak.
But it makes up for this deficiency with highly developed senses of smell and touch, which it relies on when finding food. A kiwi can detect the scent of an earthworm buried six inches in the soil, and then use its long, probing bill to root it out.
As well as being singularly welladapted, birds are more similar to humans than you might imagine.
The guillemot — a black and white seabird — locates its mate amid the spectacle and cacophony of its breeding colony by using more or less the same technique you and I might use to pick out our partner in a crowded room — by scanning faces and listening for their calls.
BUT there is one crucial difference — we can recognise a familiar face or voice in a group of a few dozen people; the guillemot does so among tens of thousands of birds. This is not the only way in which birds outstrip humans. The dawn chorus — which, as we move into spring, is beginning in woods, hedgerows and gardens — is a display of musicality far beyond the greatest virtuoso’s reach. It gives humans much pleasure, but for the birds it serves a much more serious purpose.
When a male bird sings he is sending out two messages at the same time.
To rival males, he is issuing a warning: don’t come into my territory or there’ll be trouble!
And to listening females, birdsong is an invitation to join the songster in the most important event in any bird’s life: the annual race to reproduce.
And what is truly amazing is how persistent the singing males can be: during the breeding season, a song thrush can sing for several hours a day, every day for three months or more. By the time his brood of chicks have safely fledged and left the nest, he may have sung more than one million separate phrases of song.
For some species, the need to call as loudly as possible gives rise to a problem: how can they do so without deafening themselves?
This is particularly tricky for the corncrake, an elusive little farmland bird whose call can reach an earsplitting 100 decibels — the same as a personal stereo at full volume.
THE corncrake has found an elegant solution. Every time he calls he momentarily muffles his own hearing, thus avoiding damage to his ears. When it comes to the thorny subject of birds’ sexual behaviour, things get really interesting. Professor Tim Birkhead’s daughters once jokingly called him ‘the professor of promiscuity’, and he has certainly discovered extraordinary things about the sex lives of birds.
For a long time scientists assumed that birds get little or no pleasure from the sexual act; partly because in many species it lasts only a fraction of a second. But some birds may be enjoying it more than we thought.
Careful observation of the mating habits of the red-billed buffalo weaver has revealed that at the moment of climax the male bird shudders intensely and momentarily tightens his grip on his mate.
Birds can also display a range of emotions. The great American ornithologist Alexander Skutch once wrote a book entitled The Minds Of Birds, which examined whether they share any of our human feelings such as grief, joy or a sense of fun. It’s a controversial question, and one we may never be able to answer.
Yet anyone who, like Professor Birkhead, has spent a lifetime watching birds, can’t fail to notice instances when they appear to show feelings.
Take our largest seabird, the gannet — male and female gannets pair for life, but often spend long periods apart.
One biologist studying these birds at Yorkshire’s Bempton Cliffs observed a female gannet returning to her mate after a five-week absence.
After she landed, the pair spent almost 20 minutes greeting each other by pointing their beaks towards the sky, stretching out their wings and calling noisily.
It was hard to avoid the comparison with any devoted human couple, joyfully hugging and kissing one another after a long separation.
BIRD Sense: What It’s Like To Be A Bird by Tim Birkhead (Bloomsbury, £16.99).