Changing Seasons, Changing Birds

 

Changing Seasons, Changing Birds

By Jenna Atma 

As summer comes to a close, a lot of things begin to change. The weather starts to get cooler, the leaves start to change colors, but something that not everyone may notice is that many birds also change their colors as well.

Take these male Scarlet Tanagers, for example. During the summer, we often observe them in the Tennessee region with their bright red-and-black plumage—a very bold and striking appearance. However, if we saw this same bird as they made their way south for the winter during migration, we might notice a change—his feathers will have changed from that bright red to more greenish-yellow color!

Scarlet Tanager male, breeding plumage (Nashville, Tennessee)

Scarlet Tanager male, non-breeding plumage (Madre de Dios, Peru)

So why do some birds change their colors?

Birds undergo a post-breeding season molt; in other words, they replace their worn-out feathers from the summer with fresh ones for the winter. During this transition from the old set of feathers to the new, many bird species will conserve their energy and put less effort into creating the bright and colorful feathers often used to attract mates, such as the red of the Summer Tanager. The end of the summer’s breeding season gives these birds enough time to complete their full-body molt, where they shed all of their feathers in around a month and replace them with brand new feathers, a process that requires ample food and energy. You can see in the photo above that this male Scarlet Tanager, seen on his wintering grounds in the Peruvian Amazon, is beginning to molt out of his non-breeding plumage (known as “basic” plumage) back into his breeding plumage (known as “alternate” plumage) with the dotting of fresh red feathers.

Many species go through plumage changes between seasons. Warblers are a great example of this; some go through more drastic color changes (such as the Bay-breasted Warbler), whereas other species’ molts result in a more subtle appearance change (like the Yellow-rumped Warbler).

Yellow-rumped Warblers

Breeding plumage (top), non-breeding plumage (bottom)

Bay-breasted Warbler, breeding plumage (Nashville, Tennessee)

Bay-breasted Warbler, non-breeding plumage (banded at Warner Park’s bird-banding station)

So next time you spot a bird out in the wild, I encourage you to notice its colors—are they bright or dull? What time of year is it? How are they behaving? We can often learn a lot about our little feathered friends by observing features as simple as these!

Here at Warner Parks, year-round bird banding is one of the many research projects conducted by the BIRD Program.  Banding sessions are open to the public and dates and times are published in our seasonal program schedule and on the Friends of Warner Parks events calendar.