We have a large flock of blackbirds, mainly grackles swooping through the grassy dunes.
Probably well over 1,000 birds.
Grackles have a hard keel on the inside of the upper mandible that they use for sawing open acorns. Typically they score the outside of the narrow end, then bite the acorn open.
source - https://www.allaboutbirds.org/guide/Common_Grackle/lifehistory