The Dawn Chorus

My monthly 'Nature Notes' column for the month to come . . .

The other morning I woke quite early, and decided just to open my window and let the dawn chorus wash over me. It was absolutely lovely - but why does it happen?

As I wrote last month, birds sing and for many different reasons, but the spring songs of songbirds or passerines, some 50% of the world’s nine thousand odd species of bird, are principally tied in to the important business of finding a mate and establishing and defending a territory.

But why sing in the early morning? Some people think that in the cool freshness of early morning sound carries further (it’s also true that this early in the day there are fewer other sounds), so to sing then is more effective - the sound goes further. You could put this another way round, of course: since birdsong is competitive, each (generally male) bird will be inspired to sing when hearing the songs of others.

A loud and lusty song advertises the presence of a healthy and active potential mate, and perhaps the fact that singing is the first thing a cock bird will do at - or even a bit before - daybreak may be linked to, firstly, a need just to say, very clearly, “I’m still here!” - I’ve survived the night; secondly, the fact that females are often at their most fertile in the early part of the day; and thirdly that to be able to sing well even before the first meal of the day is one way of making it clear that here is a male in the peak of condition.  A decent burst of singing is a more effective way of competing than, for example, physical scraps - though it seems to me that male blackbirds, to name but one species, are more than ready to do both!

It’s at just this time of the year that birds have the time to engage in competitive singing; the dawn chorus tends to tail off later in the breeding season when there are demanding young chicks to be fed. Then singing more of less stops completely by early July, when the breeding season is over and the moult begins. But at its peak this month the chorus can begin as early as 4 am, building up gradually and then continuing at full blast until perhaps about seven, when things get a bit quieter, and when other noises start to intrude. It may very simply be, of course, that since birds can’t easily feed in the half light of early morning they might just as well sing to pass the time! Then, when the proverbial early bird leaves off singing to get his worm, that starts a process of quietening things down.

Anyway, there is still a bit of mystery about this thing called the dawn chorus. It happens, but no-one quite knows why. It may be that all the possible reasons set out above have some grain of the truth in them. Maybe the most important thing is that at this quiet time birds are encouraged to sing by the singing of others (a bit like one dog barking in a yard setting off all the others in the street!). But it’s a glorious and special sound, whatever the reason - get up early one day this month, and listen!