'find' leaks a file descriptor for the working directory specified by the -execdir option.

Lets limit the maximum number of open file descriptors to 30.
$ ulimit -n 30

and create a tmp directory with >100 files:
$ mkdir tmp; cd tmp
$ mkdir one two
$ for i in $(seq 1 100); do touch $i one/$i two/$i; done

If I execute find with execdir option, it aborts complaining about too many files:
$ ../find . -execdir ls '{}' \; > /dev/null
../find: Failed to save working directory in order to run a command on '89': Too many open files

Apparently, find uses up *a lot* of file descriptors.