(adjective) The term colonial describes bird species that nest and breed in close proximity as a group, often sharing communal behaviors for the benefit of the entire group, including both adults and chicks. The size of the colony can vary from just a few breeding pairs to hundreds or thousands of birds depending on the species and the availability of resources.
(rhymes with ceremonial, matrimonial and testimonial)
About Colonial Nest Sites
While many birds are very isolated and secretive when nesting in order to protect their offspring, colonial birds are just the opposite. A colonial nesting ground may have hundreds or thousands of nests in a small area, and different pairs of birds may nest within a few feet or even a few inches of one another. The better the nesting ground - with suitable nest sites and abundant food sources - the more birds will take advantage of it. In most cases nesting colonies are just a single species, though some other bird species may casually nest nearby or along the colonies fringes to take advantage of mutual benefits.
The most popular nesting colony sites are often those that are relatively inaccessible to predators and other intruders. Rocky coastal islands, steep cliffs and large trees in open areas are often popular nesting sites for colonial birds. The same birds may return to those nesting areas for many years, even reusing nests or nesting materials each year.
Nesting colonies can be very loud and filled with the vigorous activity of courting adults, begging chicks, nest repair and the normal comings and goings of birds. Feces, feathers and nest debris can accumulate rapidly, and some bird species, such as several types of penguins, will use that material for future nesting.
With so many birds in one place, it may seem impossible for birds to recognize their mates or chicks. Adults in the colony often distinguish their own nests and young through subtle visual clues as well as distinct sounds.
Benefits of Colonial Nesting
Being colonial has many benefits for nesting birds and their chicks, including:
- Safety in numbers as a larger colony has more mature birds to guard against predators or to keep a lookout for potential threats and raise the alarm right away
- Sharing of parental duties for growing chicks, including gathering food, monitoring chicks or even sharing incubation or brooding duties if needed
- Easy opportunities to find replacement mates in the event of a bird divorce or a mate's death so the nesting season may not be lost or wasted
- Better chances for offspring survival as predators may be satiated by an abundance of chicks or other prey, so the remaining chicks are safe
Problems in Nesting Colonies
At the same time, being colonial also has disadvantages, some of which can be truly devastating. Common problems in nesting colonies include:
- Depletion of local food sources, making it difficult for birds to find sufficient food to feed their offspring if many birds are breeding at once
- Sheer numbers of birds in a breeding colony attract multiple predators, leading to higher levels of predation and a continual risk of attacks
- An infectious disease or parasite can quickly spread throughout the colony, which can be especially problematic among vulnerable chicks
- A natural disaster can quickly decimate an entire breeding population and destroy nesting areas that have been built up for generations
While these problems are severe enough, they are even more traumatic when a colonial species may be threatened or endangered. In these extreme cases, one bad event could dramatically impact the entire species, and it may take years for the breeding population to recover to its previous levels. Several years of difficulties could wipe out a nesting area entirely as no new birds are able to mature to begin nesting themselves.
Colonial Bird Species
Birds that are gregarious year-round are often colonial breeders, including herons, egrets, flamingos, albatrosses, penguins, cormorants and swallows. Tropical species such as oropendulas and weaverbirds are also colonial, as are many different shorebirds and seabirds. In total, more than 10 percent of the world's bird species, or approximately 1,000-1,300 different bird species, are considered colonial.
Birders, nature photographers, wildlife researchers and ornithologists may arrange special trips to these colonies to study or observe the birds. Many breeding colonies for endangered birds are protected against human disruptions, though limited studies or closely monitored visits may be permitted with proper authorization.
Also Known As:
Bird Colony (noun), Nesting Colony (noun), Breeding Colony (noun), Rookery (noun)