Each Spring, Something Remarkable Happens Inside the Brain

Updated: Apr 20

There is a moment each spring when the mornings suddenly become noisy again.

All winter the early hours are mostly quiet. Then, almost overnight, the trees seem to wake up again. Robins often begin singing nearly an hour before sunrise. Soon the familiar voices of sparrows, finches, and the cheerful Black-capped Chickadee join in. Then cardinals add their clear whistles from the treetops.

Within minutes the air fills with birdsong.

Inside many of those birds, something remarkable has already happened.

Purple crocus flowers emerging from snow

As daylight lengthens toward spring, hormones trigger growth in a part of the brain that controls song. Scientists call this region the HVC, the High Vocal Center.

In some species, this area can become 30 to 70 percent larger during the breeding season.

The temporary enlargement allows birds to produce longer and more elaborate songs, helping males attract mates and defend territory.

Researchers first noticed this seasonal brain change in birds such as the canary and the white-crowned sparrow. Similar patterns appear in many familiar backyard birds, including the bright red Northern Cardinal.

When the breeding season ends later in the year, hormone levels fall and the same brain region gradually shrinks again.

Birds that can see well in dim light tend to begin the dawn chorus first. As the sky slowly brightens, other species join in. In many places, robins are among the earliest singers, sometimes beginning well before sunrise. Soon chickadees and sparrows add their voices, followed by finches and other songbirds as the light grows stronger.

Early morning air helps as well. Before the ground warms and the air begins to stir, birdsong carries farther across the landscape.

The ability of birds to sense Earth’s magnetic field is well established. What scientists are now exploring is how widespread this hidden sense may be.

Evidence suggests humans may have a faint version of this ability as well.

You can read more about that surprising possibility here:

Could Humans Have a Hidden Magnetic Sense?