The Turkish filbert, or Turkish hazel, (Corylus colurna) is in the Birch family. All members of the family have male and female catkins on the same tree. Here are the filbert's male catkins. They will hang on all winter and mature in the spring.
The leaves are cordate at the base and have double-serrate margins.
The corky outer bark is grey, but when it exfoliates, reveals reddish-brown inner bark.
The tree has a pyramidal form with most limbs perpendicular to the trunk.
The nuts are encased in a stiff, bristly husk called an involucre. They come in clusters, the involucres joined at the base.
Here are some nuts still on the tree in late summer.
And here's one of the filbert's guests. All of its visitors are harmless; the filbert is not susceptible to any major diseases or pests.