Squirrel nests.
http://www.ofnc.ca/fletcher/our_animals/squirrels/Red-Squirrel-nest.jpg

They are usually a blend of grass and leaves. The red squirrels try to use more grass, grey squirrels like to use more leaves.
They are usually too high to reach, but not always.
If you can reach one it is a pile of dry leaves or grass that will fill a wheel barrow and there is a nest of finer fiber in the middle.
Red squirrels seem to like building in spruce trees more than the grey squirrels which seem to like nesting in maples and oaks more.