Not all birds join in with the dawn chorus
This depends on what you call ‘singing’. If you mean the jovial birdsong of the dawn chorus then no, not all birds are able to sing in this way. All birds can vocalise, but only a certain type of bird can make a melodic twitter – many others quack or squawk!
Songbirds are able to make these noises thanks to the syrinx, which is the bird voice box. The way that this is positioned in the chest provides songbirds with a huge range of vocal sounds. Singing is also mostly reserved for the males.
A song defends territory and shows females that the males are capable and strong. Song can also convey warnings and communication, but it’s not wise for females to sing loudly as this increases the risk of drawing the attention of predators to a nest.