California wildlife officials this year have been urging the public to get rid of their bird baths and feeders.
The reason? Rising concerns that non-native pigeons are spreading an infectious disease (avian trichomoniasis) believed to be killing band-tailed pigeons, the state's only native pigeon species.
Elsewhere, bird flu is a rising concern. The U.S. government this month confirmed a case of bird flu — the H5N2 strain — in Arkansas, noting that the disease is threatening the poultry industry in the Southeast. The H7N9 strain, which may cause illness in humans, was found in Canada earlier this year. Additionally, the U.S. Department of Agriculture confirmed H5N1 in wild duck in Washington state in January — the nation's first confirmed case in a bird.
Concerns associated with pigeons extend into Arizona, where the region's non-native species descended from the African rock dove and also may pose a threat.
While the World Health Organization reports that the rate at which people contract avian influenza viruses is low, contact with pigeons still can lead to infection, disease and death.
"There is constantly a new H-something, N-something emerging to threaten human health because the influenza A virus is a common cause of zoonotic infection," said Dawn H. Gouge, a University of Arizona entomologist and integrated pest management specialist in the College of Agriculture and Life Sciences.
"These are infections that transfer from animals to humans, and exist in the vertebrates that surround us, including those in our own backyard," Gouge said. "The biggest concern is whether an avian flu strain could potentially generate a highly pathogenic human flu."
With ongoing public health concerns associated with avian flu, Gouge answered some questions associated with non-native pigeons and ways to reduce animal and public health risks.
Q: Why are pigeons so ubiquitous, especially in urban areas?
A: People are used to pigeons. If I throw a cockroach at you, what would you do? You wouldn't have the same reaction toward a pigeon landing nearby.
It really is a pest we volunteer for. Pigeons love to live with and around us. They thrive wherever we are. The million-dollar question is "Why?" There are three things we do for them: We provide irrigation water and bird baths; we provide lots of food options in the waste that we discard, and we even put out seed for wild birds, which they love to dine upon; also, we provide harborage sites, and great habitat they can utilize. We treat them more like pets than pests. So pigeon management is in part people management, because it is people who support the pest that we then complain about.
Q: Provided that there is a small chance that pigeons could transfer avian flu to humans, what are some of the other public health concerns?
A: There is also the risk of allergies and fungal infections that people can acquire. If you have pigeons, you may find mites and a number of bird ectoparasites associated with their nests. Mites in particular can generate problems, as they will move into homes if birds die or leave, where they will bite and irritate people. Pigeons nesting on or near commercial air exchange units should be removed, as air drawn into buildings will carry allergens, which can trigger allergy and asthma symptoms in sensitive individuals. Anyone given the job of clearing up significant amounts of pigeon poop should be aware that the poop may contain a fungus called histoplasma. The fungus lives in the environment, and particularly in soil that contains large amounts of bird or bat poop. The fungus is less prevalent in Arizona compared to Eastern states, but precautions should be taken to avoid breathing in the spores.
Photo credit: The University of Arizona
Q: Why does it seem that we so rarely see squabs (baby pigeons) or pigeons nesting?
A: They like roof areas, holes, and will recess within protective areas. Pigeons will find window ledges, rooftops, bridges and warehouses, all ideal substitutes to the natural ledges and cliff sites (hence, the name "rock dove") used for roosting and nesting. They will even nest on flat roofs. The good news is that there are some simple things that people can do to keep pigeons off buildings.
Q: What are the humane and preventative measures people can do to help reduce health risks?
A: Avoid feeding, watering and providing harborage sites by:
- Limiting or reducing access to bird baths and pooled irrigation water.
- Using feeders that are more selective. Be prepared to manage or clean up the overspill under bird feeders.
- Excluding pigeons form nesting sites using bird exclusion mesh, bird spikes and sloping surfaces. Spikes may discourage them from landing on some ledges but in some situations can provide nesting habitat for other birds.
Pigeons prefer perches 8 or 9 feet above the ground, often under the eaves of roofs where netting can be used to exclude them. While pigeons are good parents, they are poor home builders and will balance loose nests on flat surfaces and perches. The flatter the surface, the easier they can manage to utilize it as a nesting site. Careful thought when planning buildings or adding 45-to-60-degree slopes after construction can help reduce nesting opportunities.
Pigeons in Arizona breed year-round and can produce more than a dozen offspring in a year. If you just remove their eggs and chase them off, they will continue to come back to lay more eggs. Also, pigeons are seed feeders but will forage on discarded human food remnants happily. Dispose of food waste carefully, keep trash-can and dumpster lids closed. This will also reduce rodent activity.
Q: What should you do if you find a dead bird?
A: Wear disposable gloves to carefully collect, double-bag and dispose of dead birds in exterior dumpsters as soon as possible. Do not attempt to cuddle sick birds.
Q: In some ways, pigeons do have a beloved history. For example, homing pigeons were used as messenger carriers during World Wars I and II. Also, some train pigeons for racing, and the National Pigeon Association hosts shows across the nation. What is so interesting about this bird?
A: They are truly fascinating birds. They are very good parents, pairs will mate for life, and they rear the young together, with both the males and females feeding the offspring. They are highly proficient fliers, have strong site fidelity and have adapted to live around the globe in all but the coldest and driest areas.
UA entomologist Dawn H. Gouge is an integrated pest management expert based in Maricopa, Arizona. She serves as an associate professor within the UA Department of Entomology, which is housed within the College of Agriculture and Life Sciences, and as an associate specialist in urban entomology with UA Cooperative Extension. For pigeon population control, Gouge does not recommend – either because of inefficiency or risk – the use of Avitrol, a highly toxic product, and polybutene gels, which can harm other animals. She also does not suggest using ultrasonic or bird-frightening sounds, or even statues, as the birds tend to habituate to them. For long-term, area-wide pigeon management, Ovocontrol is a birth-control option.