In dogs and cats, alopecia often appears as bald patches, thinning fur, or areas of broken hair. Common causes include flea allergy dermatitis, ringworm, hypothyroidism, and Cushing's disease. Birds may pluck feathers due to boredom, illness, or nutritional deficits. A veterinary exam with skin scraping, bloodwork, or biopsy helps identify the root cause. Treatment depends on the diagnosis and may include parasite control, dietary changes, hormone therapy, or environmental enrichment to reduce stress.