It may sound like nature’s creatures living harmoniously amongst each other, but what you can actually hear are hundreds of tiny spats going on between males. They are doing two things – defending their territories and competitively trying to attract a mate.
We may break into a tune when we’re feeling relaxed, but for songbirds singing requires a huge amount of energy. Therefore, those male songbirds who have the strongest and most complex songs are deemed the fittest. Singing well, especially after a long night without food, is a sign a male’s generally well-fed with a fruitful territory! This wards off weaker males and attracts females.
There are several theories as to why birdsong happens mostly at dawn. During the main part of the day, the sun’s radiation heats the air near the ground, causing it to rise and displace the air above it which sinks downwards, creating turbulent conditions. At dawn though, with much less sunlight, the stiller air means that sound can travel up to twenty times further than at midday! Also, the birds save their food searching energy for the main part of the day when the visibility has improved, spending the morning trying to attract a mate when they can’t do much else. Finally, as singing makes birds more obvious to predators, it’s best to do it before their whereabouts is revealed by full sunlight!
The dawn choruses begin in March with our native species like robins, blackbirds and song thrushes. As spring ticks on, many migratory species return to the UK to breed – chiff chaffs, blackcaps and cuckoos join the spectacle, bringing the dawn chorus to its crescendo, giving us International Dawn Chorus Day on the first Sunday of May! As the birds couple up, the males no longer need to make such an effort and the chorus quietens by July.
One of the earliest risers is the skylark which you may see on open grassland. Males rise into the air (heights of 1000 feet have been recorded!), hovering and singing to advertise their territories to females before parachuting back down. Skylarks create nests on the ground lined with grasses, leaves and hair.
The robin usually sings from more concealed locations like bushes and trees so you’re more likely to hear them in wooded areas. Their nests are small and cup-shaped, lined with moss, leaves and hair and can be found in a variety of near-ground locations like tree roots, log piles and even old boots!
Arriving in the UK in April and joining the dawn chorus is the cuckoo. If you’re lucky you might hear it in woodland habitats, particularly at the woodland edge. The cuckoo doesn’t build a nest at all – it doesn’t even need to raise its young. It lays an egg in the nest of another bird. Believing the egg is its own, the nest owner incubates it and feeds it once it hatches, despite the cuckoo chick being several times its size. The cuckoo chick pushes the other chicks out of the nest, feeding as much as it can from the exhausted adoptive parent before disappearing off to Africa around July. Amazingly, the juvenile cuckoos achieve this journey without an adult guide. In fact, they never even meet their biological parent – this remains one of nature’s great mysteries!
To hear our spring birds in the dawn chorus, set yourself up in a park, woodland or area with lots of gardens about an hour before sunrise. Alternatively, come and join some of our bird experts on a dawn chorus walk (next one is 24th March). Visit www.avonwildlifetrust.org.uk/events for more details.