Why should you sprinkle coffee grounds around your bird feeder?

Sprinkling coffee grounds around your bird feeder is suggested for several reasons related to pest deterrence and garden health, though its effectiveness varies. The main reason people do it is to deter squirrels, rats, and mice from approaching the feeder, because coffee grounds have a strong bitter smell and taste that rodents dislike and they contain caffeine which can be irritating to small mammals, causing them to avoid areas where grounds are spread. Coffee grounds may also help deter ants and slugs from climbing feeder poles, though results are inconsistent. Another reason is that coffee grounds are a natural fertilizer, they contain nitrogen, potassium, and other nutrients that enrich soil and can benefit plants and grass beneath the feeder, and they improve soil drainage. They also help mask the scent of fallen bird seed that attracts rodents. Additionally, coffee grounds may help repel some insects. However, you should use used, dry grounds in a thin layer and not in thick clumps that mold, keep them away from direct contact with bird seed because caffeine is not healthy for birds if ingested in large amounts, and do not rely on coffee grounds alone to stop squirrels which are very determined. Effective squirrel proofing requires baffles, proper feeder placement, and sealed seed storage more than coffee grounds.