Starlings are a species of small passerine birds that are native to Europe, Asia, and northern Africa. They are very social birds that often gather and roost in large flocks numbering in the thousands. Starlings were introduced to North America, Australia, New Zealand, and South Africa in the late 19th and early 20th centuries where they have multiplied and spread rapidly. There has been much debate about whether starlings are simply invasive pests or whether they cause real ecological or economic harm in areas where they have been introduced.
Quick summary
In short, while starlings are considered an invasive pest species, they do have some major negative impacts primarily related to agricultural damage and risks to human health and aviation. Their massive roosting flocks can also cause property damage and sanitation issues. However, some of their potential impacts are complex and not entirely detrimental. Overall, their high reproductive rate, aggressiveness, and ability to thrive in human-altered environments allow them to outcompete many native bird species which is why they are generally regarded as destructive invaders.
Do starlings cause damage to crops and agriculture?
Yes, starlings are known to cause significant damage to agricultural crops and facilities. Some of the major ways starlings negatively impact agriculture include:
- Eating planted seeds and seedlings – Starlings will flock to freshly planted fields and eat newly planted seeds and germinating seedlings of many crops.
- Grazing in orchards and vineyards – Large flocks will descend on orchards and vineyards and graze on ripening fruit, olives, and grapes.
- Raiding livestock facilities – Starlings will eat grain and livestock feed at farms, dairies, and cattle feedlots. Their droppings also contaminate animal food and water.
According to a report by the USDA, starlings cause around $800 million in damage to agricultural industries each year in the United States. The main crops impacted include corn, wheat, sorghum, ripening fruits, and grapes. Starlings compete directly with domestic livestock for feed and contaminate food supplies with their droppings which can transmit diseases.
Methods used to control starlings in agriculture
Some methods used to try to control starling damage at agricultural facilities include:
- Noise makers such as propane cannons, distress calls, exploders
- Visual deterrents like hawk kites, eye-spot balloons, shiny tape, and lasers
- Netting or covering crops and feed bins
- Toxic perches with chemical repellents
- Trapping and culling methods
However, most non-lethal methods provide only temporary relief from the large and persistent flocks. Lethal control through trapping, shooting, and poisoning is considered more effective for reducing starling populations but these methods can be labor intensive, regulated, and controversial.
Do starlings pose risks to human health and infrastructure?
Yes, large flocks of starlings can cause a few different risks and problems for humans, pets, and infrastructure including:
- Disease transmission – Starlings can spread diseases to humans and livestock through their droppings. Diseases include histoplasmosis, salmonella, transmissible gastroenteritis (TGE), and avian cholera. Their droppings also encourages growth of toxic fungus.
- Sewage contamination – Large roosts can overload and block drainage systems causing sewage backups and overflows.
- Aviation hazards – Starlings are a significant hazard to aircraft as flocks can get sucked into jet engines causing engine failure and crashes. From 1990 to 2015, starlings were involved in over 2000 aircraft strike incidents reported to the FAA. Over 250 people have died as a result.
- Property damage – Their acidic droppings corrode and degrade buildings, statues, cars, and other structures. Roosting birds can damage trees and landscaping as well.
In addition to economic losses from damage and disease, large roosts can become a public nuisance due to noise, odor, and excrement issues. However, potential health risks from dense roosts near populated areas is considered the most serious impact.
Methods to control urban starling populations
Control methods used in cities and populated areas include:
- Dispersal and harassment techniques using loud noises, pyrotechnics, flashing lights
- Roost nest disruption or removal of nesting cavities
- Trapping and lethal control (shooting, poisoning)
- Use of chemical repellents on roost surfaces
The main goal of most urban control programs is to break up the roost and disperse or deter birds from reforming at a problematic site. However, controls usually have to be continued over a period of time to keep large flocks from returning and re-establishing roosts. Complete elimination of starlings from an urban area is very difficult to achieve.
Do starlings compete with native bird species?
Starlings are very aggressive birds that compete strongly for food and nesting sites with native bird species. Their large, dense flocks allow them to easily outcompete most other birds at feeders and nesting cavities. Research shows starlings have detrimental effects on the abundance and reproductive success of many native bird species including:
- Bluebirds – Starlings take over nest boxes and evict bluebird eggs and young. Bluebird populations declined in parallel with starling introductions. Installing starling-resistant nest boxes has helped bluebird recovery.
- Woodpeckers – Starlings compete for nest cavities and may kill adult woodpeckers. Occupied starling nests prevent woodpeckers from re-using cavities.
- Other cavity nesters – Starlings reduce breeding success and populations of tree swallows, purple martins, flickers, and other cavity nesting birds by taking over nest sites.
- Native insectivores – Declines in native insect-eaters like flycatchers, swallows, and warblers have been attributed to competition with starlings for insects.
However, some research also indicates that starlings may facilitate other species in certain habitats by providing additional nesting cavities, removing botfly larvae, and alarming when predators approach. So their competitive effects seem complex and context dependent.
How starlings outcompete other cavity nesting birds
Starlings are so effective at displacing native cavity nesting birds because of their:
- Aggression and territorial behavior – They aggressively defend nest sites from other birds.
- Early spring arrival – Starlings get a head start to claim the best nesting sites.
- Larger colony size – Allows them to dominate resources and displace competitors.
- Flexible nesting habits – They nest in a wider variety of sites and cavities than most species.
- Brood parasitism – Female starlings lay eggs in other active bird nests, reducing their breeding success.
Providing more nest boxes designed to exclude starlings has been a key strategy used by conservation programs to help recover declining populations of native cavity nesting birds like bluebirds and tree swallows.
Do starlings help control insect pests?
Starlings consume large quantities of insects and other invertebrates, especially during the breeding season when they are feeding nestlings. Some research indicates they can help suppress populations of harmful agricultural and forest pests. However, their overall impact is debated:
- Benefits: Starlings eat many crop pest insects including cutworms, corn earworm, scale insects, grasshoppers, ants, and others. This may provide some natural biocontrol of harmful outbreaks.
- Drawbacks: Their diverse diet means they also eat many beneficial predator insects. Starlings damage fruits and grains directly so this likely outweighs any pest control benefits.
More research is still needed, but current evidence suggests starlings are more of an agricultural pest overall despite eating some insect pests. In forests, they may disrupt native insectivore bird communities more than suppress harmful insects.
Do starlings help control Lyme disease?
There is some evidence that starlings help reduce Lyme disease risk by eating Ixodes ticks that transmit the bacteria that causes Lyme. Studies in New England found areas with more starlings had lower Lyme infection rates. Starlings groom themselves frequently and may be good at removing ticks before they can transmit the Lyme bacteria. However, starlings also contribute to Lyme disease risk by spreading ticks over wider geographic areas. Overall their impact on Lyme disease ecology is likely small and complex.
Conclusion
In summary, while starlings are an aggressive invasive species, they do provide some benefits and their total harm is debatable. But the overall consensus by wildlife managers and agriculture specialists is that starlings have predominantly negative economic and ecological impacts in regions where they have been introduced. Their extreme adaptability, rapid spread, and ability to thrive among humans allows them to outcompete most native birds. Continued population control is recommended to reduce their damage, and habitat modification can make the environment less suitable for starlings while still supporting native species. But completely eliminating them is unlikely to succeed.
References
Here are some references used as sources for this article:
- Linz, G.M., Homan, H.J., Gaulker, S.M., Penry, L.B., and Bleier, W.J. (2007). European Starlings: A Review of an Invasive Species with Far-Reaching Impacts. USDA National Wildlife Research Center – Staff Publications. 778.
- Peoples, A.D. and Apostolou, A. (1967). The Present Status of the European Starling in California and Recommendations for Its Control. Vertebrate Pest Control Conference Proceedings collection. 7.
- Kessel, B. (1953). Distribution and Migration of the European Starling in North America. The Condor, 55(2), 49-67.
- Koenig, W.D. (2003). European Starlings and Their Effect on Native Cavity-Nesting Birds. Conservation Biology, 17: 1134-1140.
- Pimentel, D., Zuniga, R., and Morrison, D. (2005). Update on the environmental and economic costs associated with alien-invasive species in the United States. Ecological Economics, 52(3): 273-288.
