Territorial Behavior
Frenzied interactions, coupled with noisy squawking, loud bouts of birdsong or aggressive body language, such as flapping or posturing, can all signal the arrival of an unwelcome intruder to an individual bird’s territory.
Not all birds are as fiercely territorial, and some may tolerate visitors with no hostility. To find out more about the aggressive or defensive techniques some birds use to protect their patch, please read on.
Guardians of Their Realm
Territorial behavior is commonly observed in many different bird species, and relates to a bird’s instinct to defend a particular area for either breeding, feeding, nesting or roosting purposes.
Where food resources or suitable nesting locations are scarce, birds need to compete to claim their own space that is free from rivals and will allow them to raise young successfully and safely with sufficient food and appropriate shelter.
Not all bird species display territorial behavior, and in others, it becomes less evident once the breeding season ends, with birds becoming more sociable and less hostile to the presence of other birds on ‘their’ patch.
Birds that have access to abundant food resources or where nesting sites are readily available may coexist peacefully alongside others without needing to aggressively defend a territory.
Pictured: Rufous Hummingbirds battling over food sources
Understanding Territorial Behavior
In order to understand why some birds are so aggressive and hostile to others crossing territorial boundaries, it’s important to look at the reasons why this behavior has evolved and what forms it takes.
We’ll be taking a look at how birds vocally and physically assert a claim to a particular territory, and just how far some species go to defend their realm. Read on if this is something you’d like to know more about.
What is Territorial Behavior?
When arriving on breeding grounds early in the spring, the first thing that many male birds do is look for a suitable habitat that meets their needs for building a nest and ultimately finding enough food to successfully raise their young.
Particularly important might be access to fresh water, dense foliage cover for nesting the existence of cavities in tree trunks, and the absence of nearby threats from predators or human disturbance.
Once the perfect site has been identified, birds use vocalizations to establish and defend their new territory, making other nearby birds aware of their presence and warning them that a particular spot is now occupied and it would be wise to keep away.
As well as loud and distinctive calls and songs to mark their territories, some species may also use visual displays to communicate ownership of a particular area, for example showing colorful feathers, fluttering or posturing around the territorial boundaries or courtship displays to potential mates, alerting them that they have laid claim to the spot.
Birds may also patrol the boundaries of their territories, serving as a physical demonstration of where their land begins and ends.
Pictured: A Blue Grosbeak and Northern Cardinal in a dispute
Why Birds Establish Territories
Natural resources are not infinite, and during the breeding season, additional pressure is put on already stretched food supplies in many habitats.
In order to secure sufficient food to feed an incubating mate and several hungry young chicks (possibly twice or three times each year), it’s necessary for birds to guarantee a safe and steady supply that only they can access to give their breeding attempts the best chance of success.
Resource Protection
Finding the ideal nesting site, with plentiful foraging opportunities nearby and spots that offer protected, sheltered locations for raising young, is crucial to the survival of individual birds and their future offspring.
Young chicks often have intense feeding demands, and having these close at hand without competition from other birds is a huge benefit to parent birds.
When resources are not shared, they naturally last longer, meaning parents do not have to expend extra energy by traveling further afield.
Nesting materials are also a commodity that is not always in ready supply, and when territories are established, by limiting the competition for nesting cavities or sheltered tree forks, birds stand a higher chance of constructing a nest and keeping it safe from intruders.
Hummingbirds are particularly well-known for defending nectar-rich food sources, including wildflower meadows and backyard feeders. They display territoriality by chasing other hummingbirds away from the patch they have claimed as theirs and do not tolerate other birds nearby.
Woodpeckers are another species known for territorial behavior in response to limited resources, this time with regard to suitable nesting trees. They excavate cavities in tree trunks which they defend vocally and physically against other woodpeckers and cavity-nesting birds that might attempt to take over their hollows.
Owls, hawks, and eagles are highly territorial when it comes to feeding grounds, and require a large territory of their own to ensure they have access to enough prey, particularly small mammals or birds. They will use vocalizations and physically aggressive displays to make their claim to the ownership of an area heard loud and clear.
Pictured: A Hairy Woodpecker. Woodpeckers are another species known for territorial behavior in response to limited resources
The Great Horned Owl (pictured) is fearless, aggressive, and highly protective of its young
Mating and Reproduction
During the breeding season, territorial behavior reaches a peak, with birds at their most vigilant to deter predators and ensure the survival of their young.
Such behavior may begin with elaborate courtship displays where all the stops are pulled out to select a healthy mate with the highest chance of passing on strong genes.
Males show off their territories with chase displays, spiraling flights, or showcasing their colorful feathers, which passes on the message that they will be effective at defending a nest site against possible threats.
Red-winged blackbirds are known to associate in large flocks ahead of migration, and when foraging in the fall, but when breeding, there are fewer birds that display more territorial aggression. Male red-winged blackbirds arrive on their territories a couple of weeks ahead of females and use this time to scope out the perfect breeding ground to attract a mate.
Female Red-winged Blackbirds incubate eggs in nests concealed by dense foliage while males remain vigilant nearby, chasing off any other birds that dare to encroach on their territory and even dive-bombing cats, dogs, and humans that get too close.
Northern Mockingbirds are another species that exhibits fiercely territorial behavior when nesting, with extremely aggressive reactions to any potential threats, including other birds, animals, and even people. The song is also used as a territorial defense mechanism and can reach high volumes to get the message across.
In the UK, the seemingly cheerful European Robin is one of the most territorial garden birds, with violent clashes common when brave males stray into occupied territories.
What begins as a vocal affirmation that a patch has been claimed can quickly escalate into physical confrontation, and bolshy displays of their distinctive red breast in an attempt to intimidate intruders into leaving.
Red-winged Blackbird (male) showing territorial behavior
European Robin calls out to warn intruder
How Birds Defend Their Territories
Birds use a number of different techniques to announce their ownership of a territory and to defend it from threats.
Perhaps the most widely witnessed is the use of loud song, which gives a clear message to all within earshot that the area has been claimed and is occupied.
Displays of colorful plumage, chasing, and intimidating posturing are also widely used methods of driving away rivals.
Singing and Vocalizations
Vigorous singing is perhaps the most common signal that a particular spot has been claimed as home by a territorial male. Loud bursts of song, both during the day and night, can be heard reverberating from perches across the territory to reinforce the boundaries.
Complex songs are said to be more effective at deterring rivals from entering an occupied territory. Males may challenge each other by mimicry or by repeating a song quietly, to convey a calm authoritative claim to a territory.
Hermit Thrushes have a wide repertoire of songs heard in the breeding season, particularly in the early morning and early evening, reminding all birds in the neighborhood that they are alert and ready to see off any threats to the territory they have claimed.
The Gray Catbird is another distinctive vocalist who lays claim to its patch with loud, tuneful melodies, delivered from a high perch. A series of whistles, gurgles, and trills are interspersed with mechanical noises, and cat-like calls help to confuse and warn off any nearby birds and animals, not just other catbirds.
Displays and Aggression
Chasing other birds away from their territories is the most common form of physical defense, and can escalate quickly from a warning pursuit to a full-blown confrontation, which may involve antagonistic behaviors including hissing, bill snapping, and striking with bills and claws.
Sometimes, threats are averted before they reach this level, with birds taking advantage of their colorful plumage or distinctive crests or wing patches to intimidate intruders.
Bright feathers represent strong genes and fitness, a desirable quality for females in a potential mate as it equates to a capable defender of a territory and therefore improved chances of survival for future offspring.
The Hermit Thrush has a wide repertoire of songs heard in the breeding season
The Gray Catbird is a distinctive vocalist who lays claim to its patch with loud, tuneful melodies
Impact of Territorial Behavior on Bird Populations
In territorial bird species, an imbalance of breeding-age birds and available territories can lead to population declines as individuals are unable to establish a suitable patch of their own in which to raise their young.
Read on to learn more about the impacts of territorial behavior on population density and the survival of species.
Population Density and Territory Size
Generally speaking, as the population density of a bird species increases, territorial behavior will become more evident, as the birds need to defend feeding, nesting and roosting sites from other birds in the nearby habitat.
The higher the population density, the more competition exists for these limited resources, and territorial behavior will increase to maintain access to these sites.
One effect of territorial behavior in birds is population control, leading to stabilization of populations.
Where there are insufficient territories, only the dominant birds breed and other subordinate birds may delay breeding rather than put extra strain on resources that would not support additional populations.
Pictured: A Killdeer doing its 'broken-wing display' to ward-off any predators from its nest
Human Impact on Territorial Behavior
Human activity has had a largely detrimental effect on the territorial behavior of birds, both directly and indirectly.
Destruction of natural habitats through construction and development, urban sprawl, and changes in land use have led to a loss of feeding and nesting sites for many bird species, which in turn increases competition and territorial behavior among bird populations.
Construction of roads, buildings, and other infrastructure has led to fragmentation of some birds’ habitats, decreasing the size of territories or isolating birds into smaller than adequate land areas.
Additionally, the presence of traffic or industrial noise levels can drown out territorial song, which impacts bird communication and threatens a bird’s ability to successfully defend its home turf.
A further issue, introduced by humans is the presence of non-native species in the wild. These invasive species, for example, Ring-necked Parakeets across much of the southern UK, compete with local birds for resources and can disrupt natural ecosystems and reduce suitable habitats, causing conservation concerns and potential population declines.
Pictured: A Ring-necked Parakeet. By introducing non-native species into the wild, humans have contributed to these invasive birds competing for resources with the indigenous species
Summary
Particularly noticeable during the breeding season, the territorial behavior of birds takes many forms but serves the same purpose of protecting access to feeding, breeding, and roosting grounds.
Challenges to rival birds entering a claimed territory can take the form of song, displays, or physical interaction, all of which help to improve the chances of their own survival as well as that of their mate and their young.
Studying territorial behavior helps us understand wider aspects of the avian world, including migration patterns, the onset of breeding, and the consequences of habitat loss and insufficient availability of territories.