Starlings are a species of small songbird that are found across North America, Europe, Asia, and parts of Africa. They have been incredibly successful at adapting to human-altered environments and expanding their range dramatically over the past century. There are several key factors that help explain why starlings thrive in diverse habitats.
Ability to Learn Vocalizations
One of the most important reasons starlings do well is their ability to learn vocalizations. Starlings have a complex system of bird calls and songs that they use to communicate with each other. Young starlings develop these vocalizations by listening to adult birds and then practicing and mimicking those sounds. This ability to learn different calls allows starlings to adjust quickly to new environments. If they colonize a new area, they can pick up on the local dialect of bird calls which helps them blend in.
Omnivorous and Opportunistic Diet
Starlings are omnivores that eat a wide variety of different foods. Their diverse diet includes insects, earthworms, berries, seeds, nectar, and even human trash and food scraps. Because starlings eat so many different things, they can find plenty of food sources no matter what environment they are in. Starlings have adapted to forage on farms, in cities, in woodlands, grasslands, and all kinds of habitats. Their flexible, omnivorous diet allows them to thrive and take advantage of many different food resources.
Tolerance of Disturbed Environments
Unlike many bird species that prefer pristine natural areas, starlings are highly tolerant of human disturbed environments. They do well near farms, urban areas, suburbs, and anywhere there are open grassy areas mixed with trees. Starlings are able to nest in cavities found in human structures like building crevices, vents, nest boxes, and holes in trees. They also will flock to large open grassy spaces like fields, pastures, and lawns to forage. Their ability to tolerate disturbance and human activity enables starlings to exploit these human-created habitats.
Aggressive Territorial Behavior
Starlings are aggressive birds that defend their nesting and foraging territories from other birds. They will attack much larger birds to try and displace them from an area. Their aggressive behavior gives them an advantage over other species when competing for nesting cavities and food resources. Once starlings take over a nesting site, they will fiercely guard it throughout the breeding season. Additionally, large flocks of starlings will often displace other bird species from favorable foraging areas.
Rapid Reproduction Rate
Starlings have a rapid reproductive rate, with females capable of raising two or even three broods per breeding season. Each brood will contain 4-6 eggs on average. This high reproductive potential allows starling populations to grow quickly and expand their range swiftly. Even when population numbers take a hit from severe winter weather, their high reproduction rate enables them to quickly bounce back or recolonize areas the following spring.
Highly Social and Form Large Flocks
Starlings are highly social birds that gather in extremely large flocks, especially during winter and the non-breeding season. Flocks numbering hundreds of thousands and even millions of birds are not uncommon. There are many benefits to these huge flocks, including better foraging success, predator protection, and information sharing. Roosting and flying together in massive groups enables starlings to survive and thrive in a variety of environments.
Rapid Flight Speed
Starlings are swift, agile fliers. Their rapid flight speed allows them to evade predators, chase down prey, and cover large distances efficiently when traveling or foraging. They use their speed and adept flying abilities to exploit fragmented habitats with scattered food sources. Starlings can quickly move from place to place to take advantage of seasonal food supplies spread over wide areas.
Highly Intelligent and Innovative
Starlings display highly intelligent behavior and problem-solving abilities. They are innovative foragers and constantly coming up with new techniques to exploit food sources. Starlings are known for learning how to open milk bottles, eat larvae within snails by cracking open shells, and even pull levers for food rewards in laboratory experiments. Their intelligence and innovation enables starlings to discover and take advantage of new opportunities, especially in human-altered environments.
Strong Immune System
Research shows that starlings have a robust immune system that helps them withstand diseases and parasites. This gives them added protection in areas where they encounter novel diseases or high pathogen loads, such as around farms and livestock production. Their hardy immune function likely evolved to handle the bacteria and other microbes encountered when probing soil and rotting matter while foraging.
Key Trait | How It Helps Starlings Thrive |
---|---|
Ability to learn vocalizations | Allows them to adapt calls to new environments |
Omnivorous, opportunistic diet | Can eat a wide variety of food items |
Tolerance of disturbed areas | Can live near human sites like cities and farms |
Aggressive behavior | Can displace other species from nest sites and food resources |
High reproduction rate | Populations can grow and expand quickly |
Highly social, form big flocks | Flocks improve foraging, offer predator protection |
Rapid flight ability | Helps them efficiently find and exploit food sources |
High intelligence and innovation | Enables learning and problem-solving |
Robust immune system | Protects them from diseases and parasites |
This combination of physical, behavioral, and life history traits allows starlings to thrive across diverse habitats. Their intelligence and adaptability, willingness to live near humans, aggressive social behavior, and high reproduction rate enable them to successfully colonize and dominate new areas. Starlings are likely to continue their spread and success in the future as they are well equipped to exploit human-altered environments.
Starling Diet and Foraging
Starlings are omnivores and opportunistic foragers. They will eat a wide assortment of different foods depending on availability. Their diverse diet includes:
- Insects – beetles, flies, ants, caterpillars, moths, crickets
- Earthworms
- Berries – elderberries, blackberries, currants, grapes, etc
- Seeds and grains
- Nectar from flowers
- Tree fruits – cherries, apples, peaches, plums, etc
- Livestock feed from troughs
- Garden fruits and vegetables
- Scraps from garbage or compost piles
- Bird food from feeders
Starlings forage primarily on the ground. They walk or run over grassy areas probing the soil for insects and worms. Their sharp eyes also spot food items on the surface. Flocks will aggressively displace other species to gain access to the best feeding areas.
Foraging Behavior
Some key aspects of starling foraging behavior include:
- Probing grassy soil for invertebrates
- Rapidly spearing prey from surface
- Prying apart rotting wood or dung to uncover insects and larva
- Pulling earthworms out of the ground
- Balancing while walking to detect worms underground
- Flipping over leaves, debris, or animal dung to find food underneath
- Perching on fruit trees and aggressively chasing other birds away
- Flocking together to overwhelm competitors at food sources
- Foraging aerially for flying insects
- Raiding gardens, orchards, and agricultural fields for fruits, grains, and vegetables
This varied foraging behavior allows starlings to exploit many different food sources. It provides them with a flexible, omnivorous diet that fuels their energetic needs and population growth.
Starling Nesting and Reproduction
Starlings build nests in cavities, holes, crevices, and other enclosed spaces. They do not construct an open cup nest like many songbirds. Favorite nesting sites include:
- Tree cavities – natural hollows or old woodpecker holes
- Nest boxes put up for native cavity nesters
- Spaces under bridges, highway overpasses, and eaves
- Holes in building walls, roofs, vents, and gutters
- Natural crevices in cliffs, rock outcrops, and ledges
- Old woodpecker nests
- Burrows in earth banks
Starlings are aggressive about defending nest sites. They will fight off other starlings, evict other cavity nesting birds, and even destroy eggs or kill young of competitors.
Nesting Materials
The nest itself is made up of a jumble of various materials wedged into the cavity space including:
- Twigs
- Grass
- Feathers
- Plastic
- Paper
- Dry leaves
- Pine needles
- Bits of fabric, string, and yarn
- Anything else the birds can stuff into the nesting space
Eggs and Young
Female starlings lay one egg per day until the clutch is complete. Clutch size ranges from 4-6 eggs and is usually 5. The eggs are pale blue or greenish-blue. Both parents take turns incubating the eggs for about 11 days before they hatch.
The chicks are altricial, meaning they hatch helpless and require extensive parental care. Both parents feed the chicks by regurgitating food into their mouths. Initially the chicks are brooded almost constantly to keep them warm. They fledge the nest at around 21-23 days but remain dependent on the parents for an addition 2-3 weeks. Starlings have a relatively short nesting cycle of just under two months from egg laying to independence.
Number of Broods
Starlings are capable of raising more than one brood per breeding season. Typically they will raise two broods, but some pairs may manage to raise three broods in a long summer. The female begins laying a new clutch right after the first brood fledges the nest. This repeated nesting contributes to starling’s rapid population growth and expansion.
Nesting Behavior | Description |
---|---|
Nest placement | Cavities in trees, buildings, bridges; nest boxes |
Nest construction | Messy accumulation of grasses, twigs, feathers inside cavity |
Clutch size | Typically 5 eggs |
Incubation period | 11 days |
Fledging period | 21-23 days |
Broods per season | Often 2, sometimes 3 |
Starling Migration and Winter Behavior
Starlings are resident year-round across most of their range. However, populations at northern latitudes migrate south for the winter. Some details about starling migration include:
- Northern populations migrate starting in mid-October through November.
- They gather in enormous flocks numbering hundreds of thousands of birds on migration.
- They travel during the day and roost together in huge nighttime flocks.
- Most migrate to the southern U.S. but some go as far as Mexico and Central America.
- They return north again in March and April.
In winter, starlings form massive communal roosts at night that provide protection from predators and help them share information about food resources. During the day they break off into smaller foraging flocks. Points about winter flocks include:
- Roosts are often found in urban areas and can cause noise and mess issues.
- Winter flocks help starlings find inconsistent food sources and exploit temporary abundances.
- Flocking behavior is important to winter survival and energy conservation.
- Foraging flocks will fly to agricultural fields, orchards, livestock facilities, etc to find food.
- Flocks aggressively displace other bird species from good foraging sites.
Migration and Winter Behavior | Description |
---|---|
Migration timing | October-November and March-April |
Migration flocks | Hundreds of thousands of birds |
Winter night roosts | Gather by the tens or hundreds of thousands in urban roosts |
Winter foraging | Break into large flocks that cover territory to find food |
Problems Caused by Starlings
While starlings are remarkably successful birds, they also cause a variety of problems, especially from an agricultural and ecological perspective. Some of the issues associated with starlings include:
- Displace native cavity nesting birds – They take over nest sites needed by native birds.
- Consume cultivated fruits and grains – Large flocks infest orchards and farms causing economic loss.
- Spread invasive plants – Their droppings spread undigested seeds of exotic plants.
- Damage structures – Nesting and roosting starlings corrode steel, block gutters, and dirty outdoor areas with droppings.
- Risk of disease – They can spread pathogens to people, pets, livestock and native birds through their droppings.
- Collision hazard – Large flocks pose an aircraft collision risk, especially during migration.
- Noise and odor issues – Noisy night roosts near urban areas and the smell from droppings.
Despite these problems, starlings are so well established across North America and much of the world that completely eliminating them is unrealistic. Management methods aim to control local nuisance populations and limit damage. Methods include disturbing or removing roosts, use of repellents and toxins, exclusion techniques, trapping, and reducing habitat attractiveness.
Conclusion
In summary, starlings owe their incredible success to a suite of physical and behavioral adaptations. They are aggressive, omnivorous, highly social, intelligent, and rapid breeders. Starlings thrive in close association with humans and are able to exploit disturbed areas and seasonal food abundances very effectively. They pose significant problems from an economic and ecological perspective due to their impacts on agriculture and competition with native species. Their abundance speaks to their ability to flourish in human-altered environments and dominate areas where they are introduced.