What do pigeons hate the smell of?

Pigeons have a relatively poor sense of smell compared to many animals, but they do dislike certain strong, pungent odors that irritate their nasal passages, though smell alone is not an effective long-term deterrent if food and shelter remain. What pigeons hate the smell of most includes strong spices and essential oils like cayenne pepper and chili pepper with capsaicin that irritates, black pepper, cinnamon, and peppermint oil and eucalyptus oil with strong menthol scents that overwhelm their senses. They dislike the smell of vinegar with its strong acidic odor, garlic and onion in strong concentrations, and mothballs which contain naphthalene, though mothballs are toxic to humans, pets, and wildlife and are not recommended and illegal to use outdoors in many areas. Some people use predator urine or ammonia, but these have only short-term effects. Pigeons also dislike the smell of rotting or strong chemical cleaners. However, because pigeons have a weak sense of smell, scent repellents have very limited effectiveness and pigeons quickly habituate if highly motivated by food like bird seed, trash, and pet food left outside. Pest control experts consider scent repellents minor supplemental measures. The most effective way to deter pigeons is exclusion and sanitation, using bird spikes, netting, and wire over ledges and entry points, sealing food sources, and cleaning up droppings, rather than relying on smells.