I found upwards of a dozen of these secured lengthwise like this to the little twigs of a marcescent sapling near an evergreen-lined lake in the middle of a large deciduous woods. I'm pretty sure the sapling was hop-hornbeam, but hard to tell for certain at that age, in winter. All but a couple of the cases were empty (the other two were enclosed but I didn't open them to check the contents). Most appeared sheared off at the end, like the first photo here. I found one that seemed to have a trap-door type of exit. A woman's (my) forefinger for scale.

Anyone have any guesses as to the owner?