The bird that sings at 4am is the American robin bird and is the first bird to sing in the dawn chorus.
American robin are known for their melodic songs and the dawn chorus or singing starts with robins, blackbirds and thrushes.
Then as daylight emerges more birds join in on the singing.
The reason why birds sing and are so loud at 4am is because the early morning hours allow for the best conditions for their sounds or songs to carry further and be heard by other birds due to less background noise.
The cooler air and the stillness at 4am or early morning is great for the bird to attract mates and defend their territory.
When birds are loud in the morning it means that the birds are participating in a dawn chorus which is where male birds will sing loudly in the morning to attract mates or communicate with other birds or defend their territory.
The birds take advantage of the quiet morning air which carries the birds song further with less background noise and is most prominent during the birds breeding season.
The birds that start singing first in the morning are song thrushes, robins and blackbirds.
Song thrushes, robins and blackbirds start their singing when it's still dark and the air is cool.
Birds will sing in the morning to defend territory, attract mates and to raise their young.
Male birds will often sing in the morning to show that they are healthy, fit and have a good territory with lots of food available.
Most birds will start singing first in the morning or in the morning from March to July and the peak of the birds singing is in May and June.
The dawn singing chorus from birds is the loudest and the clearest during the spring breeding season.
Some other birds will also join in with the singing at dawn.
These birds that will also join in with the birds singing in the morning or at dawn include.
Wrens.
Warblers like Willow Warblers, Blackcaps, Chiffchaffs.
The song thrush bird is also known for it's many short fluty phrases which is repeated a few times after a pause.
The house sparrow is also know for it's chirp in the morning.