The IMBD 2004 artwork by Ram Papish depicts a variety of birds that nest colonially. The two sides of the piece roughly portray "northern" and "southern" groups of birds.

Birds of a feather…nesting together. Congregatory nesting behavior has been a successful strategy evolutionarily for 1 in 8 species of bird worldwide. Many colonial-nesting species are aquatic birds, such as frigatebirds, herons, egrets, gulls, terns, and puffins, but several landbirds such as swallows and blackbirds are also colonial. [See Fact Sheet] Colony sites take many forms: mud nests plastered on vertical surfaces; burrows riddling a seaside cliff, a stretch of depressions in a sandy beach, or bulky stick nests forming a woodland rookery; what defines them is the close proximity and social behavior of the colony members.

Why do birds gather together to nest? It is believed that coloniality evolved in response to shortages in suitable, safe nesting sites within range of food sources. Birds nesting in colonies may enjoy “safety in numbers,” for example, when colony members cooperate to chase off predators. Also, colonial nesters may learn about spotty and scattered food supplies from observing their neighbors. Congregatory nesting behavior does have disadvantages: colonies may actually attract predators, foster higher rates of disease or parasitism, and members may experience increased competition for nest materials and food.

Coloniality also increases population risks by concentrating birds in a limited area. In other words, a single event or incident can affect the nesting success of a large number of birds. There have always been natural threats to colonies such as storms and predators, but human activities have brought many new threats to colonies. The introduction of exotic species to breeding areas, disturbance of colonies, and outright loss of breeding habitat threaten many species of colonial birds.

Fortunately, colonial birds and their colonies are often highly visible and impressive, and thus can garner positive public attention and support. Join other IMBD celebrants in 2004 as we help the public get to know colonial-nesting birds and the ways people can help them survive!