Besides male Cardinals and Turkey Tail Fungus, the most reliable source of winter color in Columbus Park is Staghorn Sumac:

Do the tips of those branches remind you a bit of male deer (or stag) antlers? Read on for another reason why this small tree is called "Staghorn Sumac".
Looking closer, the red parts are clusters of fuzzy fruits:

Staghorn Sumac fruits provide one of the few bright colors in Columbus Park in winter.
All winter long the squirrels have left these fruits alone. Then, just yesterday, I caught a Gray Squirrel hauling off a sumac fruit:

After leaving the fruits alone all winter, this squirrel bit off a fruit cluster and climbed off with it.
Maybe squirrels know that sumac fruits are a good source of vitamin C. There can’t be much of that in Columbus Park in winter. Or maybe it just ran out of other things to eat. It seems that birds eat sumac only as a last resort.
One more thing about this tree. The name “staghorn” mostly comes from the fuzzy coating on the twigs, which reminds folks of the “velvet” that covers deer antlers as they grow:

Staghorn Sumac is the plant we love to pet.
So, while enjoying the colorful fruits, we also like to pet the fuzzy twigs. Staghorn Sumac adds both color and texture to the winter woods.
(But if you are allergic to cashews, you might think twice about petting this plant!)
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Note added April 17, 2009. Most sumac fruits stayed on the trees until mid April, when woodpeckers attacked! Go here to read about it (near the bottom of the post).
Wonderful site you have here and great post!