In April, the day starts early and with a bang, albeit a tuneful one. A male bird barely has time to yawn and stretch before he must start to fill the airwaves with his song, taking part in what we call the dawn chorus.
It’s an important and urgent chore, and no sleepy male bird can afford to be silent or drowned out. An individual’s spring fortunes can stand or fall on these vocal efforts at the break of day.
The dawn chorus is one of those natural phenomena that lap at the doorstep, and yet is rarely heard and appreciated in its fullness. In theory, it’s easy to rise in the pre-dawn darkness and hear a procession of birds singing over an hour or so – blackbirds and robins at first, using their large, light-sensitive eyes, then woodpigeons, great tits, dunnocks and wrens.
But few people bother. Sure, they hear sound from their beds, and might even curse the birds for their early morning impertinence, but they seldom get up to listen.
That’s a pity; the dawn chorus can delight and overwhelm you, even in the garden. And it is not really a chorus: much more a competition, weighty with consequence and full of intrigue.
The reasons behind song – the continual reminder to peers of territorial ownership, and the endless advertisement to females – are well understood, but the peak of song at dawn has long bothered scientists.
What is its purpose? There are plenty of theories.
Bright and early
For example, sound, for various atmospheric reasons, travels better at dawn than later in the day, and so it’s a good time to make a public statement, certainly better than competing with the mid-morning backdrop of suburban traffic, radios and lawnmowers.
Also, dawn is a poor time to feed: the half light makes searching difficult, and the normal insect prey is inactive in the relative cold. And so, if there’s nothing better to do, why not sing, and remind your neighbours that you’re there?
But there’s another theory for the dawn peak, and this one fits in rather better with April’s overwhelming drive. In this theory, the dawn chorus is all to do with tension between the sexes.
Female birds don’t sing, but many do lay eggs at dawn. Once they have finished, they are at their most fertile, requiring sperm as soon as possible to fertilise a further egg. Intoxicated by this need, they are particularly vulnerable to advances by any males, not just their mate’s.
And so, what’s a male to do if he wishes to protect his paternity? He rises early and floods his mate’s consciousness with song from the moment she wakes up. He is then available, hearty and ready for copulation as soon as she leaves the nest.
Any break in song or poor delivery could compromise his paternity by leaving his mate to the attentions and beguilement of others.
And so, if this is true, the need for a male to guard his nearest and dearest could be the trigger for April dawn’s tuneful, if rowdy, beginning.
It’s not just early in the day that April is ablaze with sexual tension among the birds in the garden. Many bird relationships are constantly strained by infidelity and by threatened infidelity.
Biologists once assumed that bird partners were solidly faithful in spring, but we now know that this is often not the case.
House sparrows, swallows, starlings and blue tits, for example, go behind their mate’s back at the drop of a hat and indulge in extra-pair copulation, simply because, in a male’s case, it is an easy way to increase his reproductive output, and in a female’s case, it’s a way to obtain the best genetic material.
The spring air is rife with hidden and deceitful liaisons, though we would be hard-pressed to detect these from our kitchen window.
No bird is more famous for its complicated sexual politics than the dunnock. Once considered to be a small, brown, inconsequential species, a bit of study has raised the dunnock’s profile considerably and engendered more smutty headlines than a bed-hopping soap star.
Essentially, the source of this intrigue is that the dunnock has formalised the practice of taking multiple mates. Though dunnocks are often monogamous, males regularly have more than one mate, and their mates, in turn, may also have more than one partner – turning your garden into the equivalent of a 1960s commune.
But even when this mate-sharing is out in the open, it doesn’t prevent conflict.
Rival male dunnocks, in particular, can often be seen chasing and ‘wing-waving’ in their relentless battle over access to a mate, particularly where two share one female. These males live in an uneasy world where one bird is dominant and the other subordinate.
The former should, by rights, have won sole access to the female, but he is up against the will of not only his subordinate but also his female. Females know that any male who copulates with her will subsequently help her feed the young, and so she actively seduces the subordinate as well as her dominant mate.
Though dunnocks play it liberal in the spring garden, starlings play it rotten. Extra-pair copulations are very common among these perky birds, but it’s not their only form of deceit: they also dump excess eggs on their neighbours.
A female, having laid her normal clutch of four to six eggs, enters another starling’s nest while the owners are elsewhere and lays an egg, cuckoo-like, among the latter’s brood. The neighbour becomes the unknowing foster-parent and the female has increased her productivity. In starlings, all kinds of relationships are unstable and movable.
It’s not just the starling that produces eggs during April; many other birds do, too, and it’s hard work. To make an egg requires plenty of fuel and effort, and the toil may render a female particularly vulnerable to predation and hunger for a while. And so, in many species, the male brings his mate regular extra rations.
All around the garden this ‘courtship feeding’ is common, and it is often confused with adults feeding fledglings. A male arrives, bill stuffed with worms or caterpillars, and delivers the offering to the fully-feathered female, who shivers her wings and begs as any baby bird would. In some species, the male delivers up to 50 food parcels a day – no little contribution.
Though a female in mid-clutch will always have several eggs inside on her production line on any given day, one is always well in advance of the others, and no bird lays more than one egg in each 24-hour period, usually at dawn.
This timing allows the post-natal female to move around relatively unencumbered, at least for a few hours, until the next egg reaches its final stage of production, usually at dusk.
Many a female, then, goes to roost on an April evening heavily pregnant and ready to lay next morning. Meanwhile, her mate, paranoid about his paternity, might yet still be fussing around her into the evening.
Male great tits have actually been observed escorting a mate to her roosting hole, watching her go in and only abandoning her once she has settled down. One can imagine his sigh of relief as he ‘sees her to bed’, safe from harm or temptation – at least, until dawn breaks the next day.