(WHTM) — Those little hummingbirds that you sometimes see flying around gardens or hummingbird feeders will be migrating south in just a few short weeks.

We know when they migrate back down south, but how do these little creatures know how to fly south?

According to Journey North Hummingbirds, scientists are still learning how hummingbirds can know when it’s time, but they have conducted research on other birds. Because of this, scientists now believe that hummingbirds know when to migrate home for a few reasons.

Scientists believe that the little birds respond to the photoperiod. This is a fancy term for the number of hours that sunlight is available. This changes throughout the year and can release hormones that can signal to hummers that it’s time to fly.

Another possible way for the birds to know when to fly back is by using the sun as a compass. They use the position of the sun in the sky to stay on course. Scientists believe that the bird’s pineal gland on top of the hummingbird’s brain is sensitive to light.

Scientists even believe that birds notice and recall major “landmarks” such as mountain ranges, rivers, and coastlines. Because of this, you may even see the same hummingbirds every single year in your garden.

Hummingbirds can live between three and four years, so it is possible that if you see a hummingbird calling your garden or backyard home, it may return to the same spot the following year.

There is still plenty of research to be done, but scientists are getting closer to figuring out how exactly these birds know where to go, and when to go.