They are looking for mates!
Birds sing in the spring to attract mates.
They don't but for many birds good looks help to attract mates!
They usually don't, they only call women birds
no some humans do
yes i beleve so
whales use echolocation to find each other and birds... i think to attract mates.
Bowerbird
No. Most birds make sounds which communicate to other birds - for example warning sounds and songs to attract mates. Some birds (such as parrots and Mynas) can mimic human talking.
Bright colors and unusual plumages are helpful in attracting mates.
Some have very ornate tails, used in attracting mates.
As with most birds the males are brightly colored to attract the females.