Birdseed is a mix of grains put out for garden birds. A bag of birdseed, scatter birdseed, refill with birdseed.
Cheap mixes are padded with wheat, which most garden birds throw on the ground looking for the sunflower seeds, so the cheap bag often costs more per bird fed. Feeding through the summer is now encouraged where it was once discouraged.
1nounbirdseedA mix of grains put out for garden birds.
“She filled the garden feeder with birdseed, and the sparrows soon arrived.”
birdseed is a food.
Bird plus seed, a plain compound from the nineteenth century.
From bird + seed.
Etymology from Wiktionary, CC BY-SA