Starlings are small, dark birds that often gather in large flocks. They are an invasive species in North America, introduced from Europe in the 1800s. Since their introduction, starling populations have grown exponentially, raising questions about whether they should be considered a pest species.
What are starlings?
Starlings, scientific name Sturnus vulgaris, are songbirds about 8 inches long with short, triangular wings. Their feathers are dark with light speckles, and their bills are long and pointed. During the breeding season, their feathers become almost black and glossy with colorful markings. They produce a variety of vocalizations but are best known for their ability to mimic sounds, including other bird calls and even human speech.
Starlings are native to Europe, Asia, and North Africa. They were introduced to North America in the late 1800s when a group of 100 birds were released in New York City’s Central Park. The population grew rapidly and starlings had spread across the continent by the early 1900s. Today, their breeding range extends across most of the United States and Canada.
Starling diet and foraging behavior
Starlings are omnivorous birds that eat a wide variety of foods. Their diet includes both plant and animal material such as fruits, seeds, grains, insects, spiders, worms, and snails. They forage primarily on the ground, using their strong bills to probe for food. Starlings often forage in large flocks, descending on areas en masse in order to find food.
In urban and suburban areas, starlings take advantage of human-provided food sources such as trash bins, pet food bowls, bird feeders, livestock feed, and crops. Their ability to adapt to utilize human structures and food waste contributes to their success as an invasive species.
Foods starlings commonly eat:
- Cultivated grains such as wheat, corn, oats
- Fruit including cherries, grapes, apples
- Seeds and berries
- Household food waste from trash
- Livestock feed
- Invertebrates including insects, worms, snails
Negative impacts of starling populations
The large and growing populations of starlings in North America cause several types of damage and problems. As a result, they are considered pests by many agricultural operations, facilities managers, and homeowners.
Agricultural damage
Flocks of starlings can damage crops both through direct consumption and trampling/contamination. A study estimated they cause $800 million in damage to US agriculture annually. Some of the agricultural impacts include:
- Eat cultivated fruits and grains, reducing crop yield
- Trample plants and disrupt newly seeded fields
- Contaminate livestock feed and water with droppings
- Transmit diseases to livestock and crops
Nuisance issues
In urban and suburban areas, large flocks of starlings cause nuisance problems for homeowners and facilities managers:
- Roosting flocks create noise, smells, and messes from droppings
- Fouling structures and vehicles with droppings
- Competing with native bird species for nest sites
- Raiding and contaminating pet food/bird feeders
Their droppings are acidic and can accelerate corrosion and deterioration of infrastructure. At some sites such as warehouses or transmission towers, accumulations of starling excrement may create hazardous conditions for workers.
Health and safety issues
Large flocks of starlings pose some risks in terms of health and aviation hazards:
- Potential to transmit diseases to humans and livestock
- Bird strikes with aircraft, causing accidents
- Accumulated droppings may harbor bacteria or fungi that cause respiratory illnesses
Histoplasmosis, an infectious fungal disease, has been linked to the inhalation of dust contaminated with starling droppings which contains fungus spores.
Damage costs and summary
The wide array of damage caused by starlings comes at a high economic cost. The estimated damage and control costs associated with starlings in the United States includes:
- $800 million per year in crop losses and prevention costs to agriculture
- $2 million per year in repairs and cleaning from starling droppings at highway bridges
- $1 billion per year overall in pest control and repairs from starling damage
In summary, starling damage includes losses to agriculture, infrastructure repair costs, increased pest control expenses, and risks to aviation and human health. This high economic impact, coupled with starlings’ competition with native bird species, is why they are regarded as a pest species.
Positive aspects of starlings
Despite being considered a pest, starlings are an intelligent and engaging bird that provide some ecological benefits as well as enjoyment for bird enthusiasts.
Ecological importance
As an omnivorous bird, starlings help control populations of invertebrates like insects and snails. They also contribute to seed dispersal of some native plants when they consume the fruits. Additionally, starlings serve as an important prey species for certain native predators like falcons and hawks.
Positive interactions with humans
Many people enjoy seeing starlings visit their yards and observing their diverse vocalizations. Starlings are featured in literature and poetry for their vocal mimicry abilities. The starling’s small size and nesting habits provide recreational opportunities for birders and bird house enthusiasts in North America.
Intelligence and uniqueness
Beyond their adaptability, starlings exhibit intelligent behaviors such as problem-solving and mimicry. Each starling has unique vocalizations and feather patterning, making them distinguishable individuals for those who observe them closely.
So while they cause extensive damage, starlings do provide some ecological services and recreational enjoyment that adds nuance when debating their pest status.
Methods for controlling starling populations
A variety of methods are used to try to reduce starling population sizes or mitigate the damage they cause. However, their numbers remain high across most of North America.
Exclusion techniques
Physical exclusion seeks to block starlings from accessing roosting or feeding sites. Common techniques include:
- Netting to cover fruit crops, building ledges, rafters
- Porcupine wire to prevent roosting on ledges
- Closing gaps in building exteriors
While effective at specific sites, exclusion techniques are often costly and difficult to implement over large areas.
Population reduction techniques
Methods to directly reduce starling numbers include:
- Lethal control such as shooting or trapping
- Toxic perches using DRC-1339 avicide (where legal)
- Nest control to reduce productivity
- Sterilization techniques to prevent breeding
Lethal control is controversial and often faces public opposition. Sterilization and nest control techniques are experimental with small-scale field trials showing limited results so far.
Frightening techniques
Non-lethal frightening techniques can deter starlings from specific sites:
- Predator decoys (hawks, owls)
- Reflective tape
- Ultrasonic or other loud sounds
The effectiveness of frightening techniques is highly variable depending on timing and persistence of application. In many cases, birds eventually habituate to scary stimuli over time.
Summary of control challenges
Controlling starling populations is extremely difficult due to:
- Their extensive range and large numbers
- High reproductive potential
- Adaptability to exploit human structures and food sources
- Intelligence to overcome many frightening techniques
An integrated pest management plan using multiple exclusion, population reduction, and frightening techniques is required to have any meaningful impact on starling numbers.
Conclusion
After reviewing the evidence, starlings appear to meet the criteria for classification as a pest species in North America. While they have some positive impacts, the extensive economic and ecological damage caused by starlings outweighs these benefits.
Key supporting points for considering starlings a pest include:
- Cause substantial damage to agriculture through direct feeding and contamination
- Create messes, noise, and structural damage to urban infrastructure
- Spread of disease risks to humans and agriculture
- Compete with native cavity-nesting bird species
- Estimated control costs and damage exceeding $1 billion annually
Attempts to control starling populations have been largely ineffective so far. Developing an integrated management strategy across different environments is key to controlling starling numbers and mitigating their extensive damage as an invasive pest species.
