Good to have on hand for your first aid preparedness. They are perfect for administering medications, supplements & formula type foods. Even for an adult bird, if they were to injure their beak or become very ill you might need to give formula or ground food. The size you need depends upon what you are going to administer as well as the size of your bird. If you don't have prior experience using these you DO want guidance from your avian vet or another experienced person. Incorrect use could cause aspiration!
*** NOTE *** As with many avian care topics, consider if your circumstance may warrant a trip to your certified avian vet!