What is the filthiest bird?

There is no official filthiest bird, because cleanliness is subjective and birds have different habits, but some birds are perceived as filthier due to their nesting, feeding, or scavenging behavior and association with human waste. Vultures are often considered filthy because they eat carrion, dead animals, and have bald heads adapted for scavenging, though they are actually very clean in terms of disease control as their stomach acid kills bacteria. Pigeons are often called filthy in cities because their droppings stain buildings and sidewalks, but they are actually clean birds that groom frequently and the droppings problem is due to human feeding and poor waste management. Crows and ravens are sometimes considered dirty because they scavenge trash. Seagulls are considered filthy in coastal cities because they steal food and leave droppings. Among nesting habits, some birds like starlings and house sparrows build messy nests with droppings around. The bird with the most unhygienic nesting habit is often considered to be the Hoatzin chick which has claws and drops into water to escape predators and has messy nests, or the swiftlet that builds nests with saliva. In terms of disease, birds that carry many parasites like pigeons can be considered filthy by some. However, no bird is truly filthy, as all birds groom and preen regularly, and perceptions of filthiness often stem from human created problems like trash and feeding.