Male birds sing to impress the ladies and scare away rivals. Birdwatcher Ranjit Lal compiles his top-of-the-pops. In the Express Eye magazine:
They sing early in the morning, because that’s when it’s usually very still so their song carries far. They also let the world know that they’re alive and well, and in possession of their territory and haven’t been taken by an owl or snake or cat during the night.
As for the girls — they’re born with specialised critical faculties. They listen and if they are impressed by what they hear, they accept their serenading suitor. If a guy can spend most of his time belting it out — and has a complicated repertoire too — it means he’s obviously living in clover and doesn’t need to spend too much of his time digging worms out of the ground. So he’s worth cozying up to, it’ll be good for the babies.
Some guys, of course, are admirable skanks. One magpie robin I met in Goa, sang different melodies from different perches within a certain area (including a swimming pool), pretending to be three different males, and so was in control of property far in excess of what he might have been able to control as a single fellow. Any prospecting male surveying the territory would have concluded that the area was fully occupied and would have moved on. I believe, the girls were either taken in or impressed by this display of underhand cunning. (Not all scientists, however, agree with this explanation.) Other especially talented Lotharios will win over one girlfriend; tuck her away safely in a nest and then serenade another! More:
Talking of birds…
This DIY birdbath that I (Shekhar Bhatia) set up in our small garden in Gulmohar Park, New Delhi, is a bundle of joy: