Some seeds currently don't work with the birdhouses on Fossil island. My suggestion would be to make them work there. This would make the seeds gathered from bird nests, farming contracts useful, that otherwise use up valuable bank space.
I tried to see what low-level seeds currently don't work with birdhouses. These are my results:
cabbage seed
sweetcorn seed
onion seed
potato seed
tomato seed
strawberry seed
apple tree seed
banana tree seed
orange tree seed
curry tree seed
dwellberry seed
rosemary seed
redberry seed
poison ivy seed
marigold seed
mushroom spore
belladonna seed
cactus seed
woad seed
acorn
nasturtium seed
cadavaberry seed