A few years ago I received an email from someone in Hawaii wondering why so many pigeons on Maui were missing toes. I had no idea so I emailed the ornithologist at the University of Hawaii and she responded that with many people with long hair lying on the beaches leave bits of their tresses behind. Pigeons, with their shuffling gait, get the hairs tangled on their toes, and, unable to use their beak to remove the hairs, find them wrapping around the toes, constricting the blood flow and killing part of the toe.
Later I received another email with the same question; this one from a visitor to the Canary Islands. He asked whether there were predators that ate the toes of the pigeons, a disease, or if it was a genetic defect. I gave him the explanation of the hairs but he rejected my explanation and decided it was a genetic defect. (If he already knew, why did he ask?)
It’s not just beaches, though. The same thing has been noticed in Paris. “By observing 1,250 pigeons along 46 blocks in Paris, researchers at the Center for Ecology and Conservation Science in Paris found that 20% of the birds were missing at least one toe. Matching these numbers with data on human activity and pollution at the level of city blocks, the researchers found more missing-toe pigeons in areas with high concentrations of hairdressers as well as densely populated blocks with high air and noise pollution.” You can read the full study in the December issue of Biological Conservation.
Besides hair cutting off circulation, deformities of the feet are caused by disease and injury and are most noticeable among ground feeding birds, especially in towns and cities. Cuts to the feet can become infected which may result in swelling and lameness. Bumblefoot, or plantar pododermatitis, is caused by injuries to the foot, obesity, dependance on that foot because of injury to the other. A ulcer develops which is typically caused by bacteria such as Staphylococcus entering the skin through the cut or ulcer, followed by a swelling of the birds’ toes and pads of the foot. It mainly affects large birds such as crows and birds of prey, producing inflammation resulting in difficulties with perching and walking. This is more common in caged birds than wild ones. Avian pox, caused by a virus, can cause wart-like growths on the feet of birds.
Pigeons, inhabiting cities with all kinds of potential foot hazards like anti-pigeon spikes, wires, string, etc. seem to be most susceptible to foot injuries. The impact to their lifestyle can be dramatic. Birds missing a toe or two will not be able to groom themselves efficiently, especially if the toes are from the dominant foot (yes, they are right- or left-handed, so to speak). If their feathers get ruffled or become infected with lice and mites, they will be less able to stay insulated and waterproofed. Their aerodynamics are compromised but so is their attractiveness. A poorly groomed pigeon is not likely to attract a mate. So losing a toe or two is a serious matter.
By the way, I’m not sure why humans, especially young kids, sometimes are described as being pigeon-toed if their toes point inward.