Looking down at the ground, I noticed birch leaves,
and tasted a twig to confirm that it was a black birch (also known as sweet birch - click to see previous post on this species).
The fruiting catkins are mature; they're densely packed with papery seeds.
New female catkins will emerge in the spring out of the pointed buds. Male flower buds (in the upper left corner) are long, scaly, and rounded at the tip. In the spring, they will grow into yellow male catkins.