If you've ever buried your head under a pillow to drown out the sounds of birds loudly singing their familiar songs before the crack of dawn, you're probably not alone. Birds have a way of making their presence known even before the sun rises each day, and in the spring especially they can create quite a racket.

The birds aren't just greeting the new day with a cheerful good morning, and it doesn't have anything to do with the early bird getting the worm, either. Most of the songs we hear in the dawn chorus are the work of male birds, and they are looking to attract a mate and establish a territory, according to Wild Birds Unlimited.

When you think about it, the predawn hours are a good time for birds to be singing loudly and proudly. The darkness of early morning makes it too difficult to spend time searching for food, and at the same time it's also too dark for many predators to be on the prowl, the Woodland Trust reports. Plus there's not as much noise being generated from other activity — traffic and the like — so a bird's song can carry as much as 20 times as far as it might later in the day. 

Researchers at one time believed birds were also taking advantage of the cooler, drier air in the morning to allow their notes to carry a little farther, but research has shown that's not the case. Their notes actually carry as far — or even farther — at midday than in the predawn hours thanks to their early-morning warmup, according to a study conducted by a team of researchers from Duke University.

The Duke researchers hypothesized that songbirds' early morning concert is a warmup so they can perform vocally later in the day, and they tested their theory by studying the behavior of a group of male swamp sparrows between 2 a.m. and noon for two to three mornings per bird. In all, they analyzed more than 1,500 swamp sparrow songs, and they found that the birds' vocal ability improves as the day goes on, allowing them to sing more complicated notes and songs as the day progresses. While the study demonstrated a clear improvement in singing ability after the birds' early-morning warmup, researchers aren't certain what causes their singing to improve.

Does the chorus of birds seem to start hours before the sun rises in your neighborhood? That could be because of where you live. The dawn chorus typically begins shortly before sunrise, but it starts earlier in cities, WGN reports. This may be because artificial light makes it seem like the day is starting even before the sun comes up. In addition, cloud cover and other weather conditions can more easily allow light to be reflected back to the ground in urban areas. 

A strong singing voice is important for male birds because it is a sign of health and strength, which are qualities potential mates are looking for, the American Bird Conservancy reports. Breeding season — spring and summer for most songbirds — is prime singing season, but hearing birds sing at other times of year is not uncommon because some species also sing to warn off predators or intruders on their territory or simply communicate with other birds.

And while males are the primary crooners in the bird world, some female songbirds sing too. Both male and female cardinals carry a tune, for example. Other female singers include eastern phoebes, purple martins, barn swallows, black-capped chickadees, gray catbirds, European starlings, eastern towhees, song sparrows and house finches, according to the Cornell Lab of Ornithology. Female birds sing for the same reason as males: to defend their territory and communicate.