Birdseed, in moderation, is fine for rabbits. If it was not the Angora rabbit industry would be in a lot of trouble. Mine ... the rabbitry is a nice sized Angora rabbitry and one of the top in the country ... get various seeds with each meal. It is built in from the day they can eat with mommy. Bird seeds not only provide nutrients for the animals, but roughage to keep the wool/fur from building up in the intestional tract. My formula was built off of the top rabbitry's many years ago. Rabbits in the wild are foragers. They eat seeds, grasses, anything that is in the ground area...even tree bark. Check your trees in the spring for the tell-tale signs of rabbits around the trunk! As with all things we feed, it is the amount. All things in moderation and noting overdone at first.