Farms of various types are impacted by the waste and potential disease transmission posed by congregations of invasive birds, particularly house sparrows (Passer domesticus), European starlings (Sturnus vulgaris), and pigeons (Columba livia). Fortunately, the blueprint for how to reduce these birds is well known. For instance, due in large part to a reduction in open stores of grain around animal-feeding operations, the house sparrow is much less numerous now in Iowa than it was 100 years ago. In this way, we can continue to shrink their numbers by further limiting their access to food. If you cut down on the amount of grain for them to reach, whether by thoroughly cleaning up spills or sealing entrances to grain bins, there will be fewer House Sparrows to contend with. But no matter how well we keep a watchful eye on spills these problematic, invasive birds are still likely to use our farm buildings for nesting (in pairs) and roosting (in bigger flocks). This means exclusion is key.
All birds in Iowa are protected by state laws and most are also afforded protections through federal legislation. However, these three species -- house sparrows, pigeons, and European starlings -- are all exempt from state and federal protections because they are exotic species and considered nuisances. Please consult with a wildlife conservation officer if you different species of protected birds are causing problems around your home or farm.
Basic Life-history information
Habitat and distribution: The house sparrow was originally an inhabitant of Europe, Asia, and northern Africa. Because of introductions by humans around the world, this aggressive songbird now occupies every continent except Antarctica. These aggressive birds thrive in human-altered habitats, such as farms (particularly if livestock and/or grain are present), towns, and urban areas. In North America, climatic tolerance ranges from sea level to about 10,000 feet and from hot, dry desert landscapes to cool, rainy coastal areas. The primary requirement in any of these settings is an abundance of artificial structures for nesting and roosting and a nearby food resource. Thus, both rural and urban/suburban landscapes of Iowa provide ample habitat for house sparrows.
Diet: House sparrows eat seeds throughout the year and supplement with insects and grubs during the warmer months. House sparrows in Iowa are especially fond of corn, which they obtain at bird feeders and on feedlots, grain elevators, grain bins, and nearby agricultural fields. They prefer to forage within a short distance of buildings or dense shrubs. At livestock operations, fly larvae taken from dung are a summertime staple for adults and young birds. Weed seeds, small grains (e.g., oats), leftover food around restaurants, and large flying insects (including those attracted to lights at night) round out the house sparrow’s diet.
Nesting: From mid spring to late summer, the House Sparrow typically places its bulky, untidy nest in cavities of solid structures, such as houses, barns, grain elevators, bird boxes, and bridges. However, it will also build a nest within tangled vines on buildings and occasionally within the fork of a dense tree or shrub. Whatever the spot, House Sparrows will do their best to fill the sheltered space with a haphazard accumulation of dried plant fibers, which they typically adorn with random bits of feathers, string, paper, plastic bags, and other refuse. Conversely, the native songbirds found in the same type of habitats generally construct nests that are much tidier.
Group behavior: Outside the nesting season, House Sparrows congregate in flocks to feed on the ground and roost on buildings, vines, or dense shrubbery. These groups can number from just a few birds to many dozens at sites with abundant food and thick cover.
Habitat and distribution: Much like the House Sparrow, the European starling originally inhabited Eurasia and northern Africa, but it now persists on six continents due to releases by humans. A mere 100 individuals released in New York City during the 1890's gave rise to a current census of over 200 million starlings across much North America, stretching from the tree limit in Canada to tropical climates of northern Mexico and the Caribbean. In Iowa, the starling was first noted in 1922 and had established itself in all 99 counties by the 1930's. Early wide-scale efforts to eradicate this invader from the state were unsuccessful, and starlings continue to thrive in human-altered habitats across Iowa.
Diet: The starling’s diet is diverse and varies among regions and season, but it generally includes a mix of invertebrates, seeds, and fruits. Midwestern birds feed extensively on insects pulled from the open ground of lawns, feedlots, pastures, and fields – or caught in the air. Starlings also target abundant, concentrated resources. As such, spilled grain (especially corn), livestock feed (particularly protein supplements), and seed at bird feeders are often quickly decimated by starling flocks. Likewise, starlings can make quick work of fruit in orchards and on ornamental trees.
Nesting: The European Starling nests in natural tree cavities, competing with beneficial native birds in the process. However, it readily occupies nooks and crannies of artificial structures, including houses, barns, office buildings, and traffic lights. Nest boxes intended for Purple Martin and Eastern Bluebird are also a favored dwelling; starlings notoriously drive off adults of these species to usurp nesting spots. From April to August starling pairs fill their nesting cavity with a messy mass of plant fibers (stems, husks, etc.), which surround a more neatly woven cup of thin grasses and feathers. Two broods are typically raised per year in Iowa.
Group behavior: Although mostly found in pairs, family groups, and small flocks during the nesting season, starling numbers in fall/winter grow to thousands (even hundreds of thousands) in a single flock. Buildings and nearby trees in urban areas, large farmsteads, and windbreaks provide warm, safe roosting sites for starlings during the colder months. Flocks tend to remain faithful to particular roosting sites in a given winter – and often return there in successive years. Such sites are sometimes located a considerable distance from preferred feeding areas. Both at roosts and feeding areas, these nuisance flocks generate considerable problems with their noise and droppings.
Habitat and distribution: Having been adapted to nesting around humans since the early phases of civilization, the Rock Pigeon first greatly expanded its range across Europe, Asia, and northern Africa via the buildings constructed during the Roman Empire. Over a thousand years later, after its arrival to the New World, the Rock Pigeon followed the spread of European colonization westward across North America. It remains common to this day around cities, towns, and farms across Iowa.
Diet: In rural areas, rock pigeons mostly eat seeds, plus small amounts of fruit and insects. Not surprisingly, pigeons are especially attracted to corn, which has been shown to account for over 90% of their diet in scientific studies of wild birds. Thus, abundant sources of corn at livestock facilities and grain elevators, as well spills along farm fields, attract flocks of pigeons. In urban areas, they consume a wide variety of starchy and grain-based items like popcorn, peanut butter, and bread.
Nesting: Rock pigeons build their nests on a solid, flat structure that is sheltered from the elements overhead. Such sites are selected in the alcoves of barns, silos, chicken coops, bridges, billboards, and urban high-rises. In this way, pigeons find places to match characteristics used by cliff-nesting birds in western North America, the Ozarks, and Appalachia. Inside the nest space, a pigeon pair makes a cluttered pile of plant stems, twigs, roots, and straw. Nails and other pieces of metal are sometimes included in the base of the nest.
Group behavior: Rock pigeons move about singly or in flocks reaching the hundreds when roosting, feeding, and flying in Iowa. Generally, the more extensive the habitat, the larger the flocks become, along with the health hazards that they bring. Similarly, pigeons congregate in greater numbers around abundant food resources.
Damage caused by invasive birds
All three of these invasive birds damage structures and present health hazards to humans and livestock, as well as crowding out or driving off beneficial native birds. Identifying the specific problems caused by each species can lead to better prevention.
- Consume and contaminate grain at farms, storage facilities, and nearby fields
- Create unsanitary conditions in and around buildings where nesting, roosting, & feeding
- Build nests that are highly flammable, posing a threat to buildings
- Produce constant, loud chatter at roosting sites in early morning and evening
- Roost in enormous flocks numbering in the dozens to thousands (especially in fall/winter), leaving behind droppings that cause health and sanitation hazards, corrode buildings, and befoul sidewalks and automobiles.
- Compete with beneficial native birds for nest sites (ex: Purple Martin and Eastern Bluebird) and drive off desirable birds at feeders (ex: Northern Cardinal and American Goldfinch)
- Harbor ectoparasites (fleas, mites, lice) that can spread to poultry and occasionally bite humans
Preventing and limiting damage of nuisance birds
Many preventative measures and eviction techniques work for all three invasive birds. However, each species’ differing size and habits may necessitate specific efforts.
- Place wire mesh or netting across outer walls and eaves, and on the underside of rafters and overhangs inside buildings to discourage roosting and nesting. Nylon netting can also be used to cover fruit trees to prevent birds from eating the berries.
- Remove vines on building walls or dense ornamental shrubbery that attracts flocks of roosting/resting sparrows; place plastic mesh or nylon netting over vines and shrubs that you’d like to keep
- Increase the angle of ledges to 45 degrees by adding sheet metal, plexiglass, or wood blocks to make them less suitable for perching.
- Hang long, flexible, 4-6 inch wide strips of plastic around food storage; birds will see these as impenetrable barriers
- Close all openings greater than ¾ of an inch on buildings to limit house sparrow access for nesting, roosting, and feeding. Make sure any mesh used to cover larger openings, like old window spaces on chicken coops, does not haves holes exceeding this ¾-inch threshold.
- Use porcupine wires to prevent pigeons from landing on surfaces such as roof peaks and ledges.
- Follow strict specifications when designing bluebird boxes to keep starlings from entering; for instance, the nest hole should be exactly 1 ½ inches in diameter
- Thinning of windbreaks and woodlots: in Iowa and much of the Midwest, starlings prefer to roost in dense clusters of trees; thinning a stand by one-third will disperse large flocks of starlings while helping to improve timber growth and quality
Note: Repellants and scare tactics (explosive noises like air cannons) typically only have a short-term effect. The time, money, and effort nearly always outweigh the results.
- Promptly remove any nest materials and eggs from cavities on buildings or from bird boxes. Dispose of materials to prevent reuse. Many nuisance birds are persistent, so the process will need to be repeated every two weeks throughout a nesting season.
- Trapping: place traps where the nuisance birds congregate to feed or roost. Putting seed or grain out for a few days prior to placing traps can help increase likelihood that birds will go into the traps once they are set up. It is often necessary to vary the location and presentation of the traps throughout the year, especially for house sparrows, so the birds don’t become trap shy. Checking traps regularly is important to ensure non-target species are released unharmed.
- Funnel traps and automatic "elevator" traps can be used to capture house sparrows.
- Decoy traps can be highly effective in capturing large numbers of starlings.
- There are multiple experts that can assist with nuisance birds on the farm. Contact information for someone in your area can be found on our wildlife conflict resolution page.
This article is an update of "Managing Iowa Wildlife: Problem birds around homes and farmsteads" (PM-1302d) originally authored by Georgia Bryan and James Pease.