Bird colony
A bird colony is a large congregation of individuals of one or more
Variations on colonial nesting in birds
Approximately 13% of all bird species nest colonially.[2] Nesting colonies are very common among seabirds on cliffs and islands. Nearly 95% of seabirds are colonial,[3] leading to the usage, seabird colony, sometimes called a rookery. Many species of terns nest in colonies on the ground. Herons, egrets, storks, and other large waterfowl also nest communally in what are called heronries. Colony nesting may be an evolutionary response to a shortage of safe nesting sites and abundance or unpredictable food sources which are far away from the nest sites.[4] Colony-nesting birds often show synchrony in their breeding, meaning that chicks all hatch at once, with the implication that any predator coming along at that time would find more prey items than it could possibly eat.[2][5]
What exactly constitutes a colony is a matter of definition.
Some seabird colonies host thousands of nesting pairs of various species. Triangle Island, for example, the largest seabird colony in British Columbia, Canada, is home to auks, gulls, cormorants, shorebirds, and other birds, as well as some marine mammals.[7] Many seabirds show remarkable site fidelity, returning to the same burrow, nest or site for many years, and they will defend that site from rivals with great vigour. This increases breeding success, provides a place for returning mates to reunite, and reduces the costs of prospecting for a new site. Young adults breeding for the first time usually return to their natal colony, and often nest very close to where they hatched. Individual nesting sites at seabird colonies can be widely spaced, as in an albatross colony, or densely packed like an auk colony. In most seabird colonies several different species will nest on the same colony, often exhibiting some niche separation. Seabirds can nest in trees (if any are available), on the ground (with or without nests), on cliffs, in burrows under the ground and in rocky crevices. Colony size is a major aspect of the social environment of colonial birds.
Some birds are known to nest alone when conditions are suitable, but not sometimes. The white-winged dove of southwestern North America was known to nest in large colonies when foraging areas could support such numbers. In 1978, in Tamaulipas, Mexico, researchers counted 22 breeding colonies of white-winged doves with a collective population size of more than eight million birds. But as habitat was transformed through urbanization or agriculture, the doves apparently spread out into smaller, less long-lived colonies. Today, these doves are observed to nest singlyin both urban and not urban areas.[11][12]
The term colony has also been applied, perhaps misleadingly, to smaller nesting groups, such as forest-dwelling species that nest socially in a suitable stand of trees. The
Ecological functions
The habit of nesting in groups is believed to provide better survival against predators in several ways. Many colonies are situated in locations that are naturally free of predators. In other cases, the presence of many birds means there are more individuals available for defense. Also, synchronized breeding leads to such an abundance of offspring as to satiate predators.
For seabirds, colonies on islands have an obvious advantage over mainland colonies when it comes to protection from terrestrial predators. Other situations can also be found where bird colonies avoid predation. A study of yellow-rumped caciques in Peru found that the birds, which build enclosed, pouch-like nests in colonies of up to one hundred active nests, situate themselves near wasp nests, which provide some protection from tree-dwelling predators such as monkeys.[15] When other birds came to rob the nests, the caciques would cooperatively defend the colony by mobbing the invader. Mobbing, clearly a group effort, is well-known behavior, not limited to colonial species; the more birds participating in the mobbing, the more effective it is at driving off the predator.[2] Therefore, it has been theorized that the larger number of individuals available for vigilance and defense makes the colony a safer place for the individual birds nesting there. More pairs of eyes and ears are available to raise the alarm and rise to the occasion.
Another suggestion is that colonies act as information centers and birds that have not found good foraging sites are able to follow others, who have fared better, to find food.[16] This makes sense for foragers because the food source is one that can be locally abundant. This hypothesis would explain why the lesser kestrel, which feeds on insects, breeds in colonies, while the related common kestrel, which feeds on larger prey, does not.[17]
Colonial behaviour has its costs as well. It has been noted that parasitism by haematozoa is higher in colonial birds and it has been suggested that blood parasites might have shaped adaptations such as larger organs in the immune system and life-history traits.[18] Other costs include brood parasitism and competition for food and territory.[3][4] Colony size is a factor in the ecological function of colony nesting. In a larger colony, increased competition for food can make it harder for parents to feed their chicks.[19]
The benefits and drawbacks for birds of nesting in groups seem to be highly situational. Although scientists have hypothesized about the advantages of group nesting in terms of enabling group defensive behavior, escape from predation by being surrounded by neighbors (called the selfish herd hypothesis), as well as escaping predators through sheer numbers, in reality, each of these functions evidently depends on a number of factors.[17] Clearly, there can be safety in numbers, but there is some doubt about whether it balances out against the tendency for conspicuous breeding colonies to attract predators, and some suggest that colonial breeding can actually make birds more vulnerable.[3] At a common tern colony in Minnesota, a study of spotted sandpipers observed to nest near the tern colony showed that the sandpipers that nested nearest the colony seemed to gain some protection from mammalian predators, but avian predators were apparently attracted to the colony and the sandpipers nesting there were actually more vulnerable.[20] In a study of a least tern colony in Connecticut, nocturnal avian predators in the form of black-crowned night herons and great horned owls were observed to repeatedly invade a colony, flying into the middle of the colony and meeting no resistance.[21]
For seabirds, the location of colonies on islands, which are inaccessible to terrestrial predators, is an obvious advantage. Islands where terrestrial predators have arrived in the form of rats, cats, foxes, etc., have devastated island seabird colonies. One well-studied case of this phenomenon has been the effect on common murre colonies on islands in Alaska, where foxes were introduced for fur farming.[22]
Human use
Colony-nesting birds have been used by humans as a source of food in the form of eggs and meat,
The use of seabird droppings as fertilizer, or guano, began with the
See also
Image gallery
Seabird colonies can be predominately a single species or a mix of species:
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Nesting Australasian gannets at the Muriwai colony in New Zealand
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A dense colony of Sandwich terns (Sterna sandvicensis)
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A colony of 200,000 king penguins on South Georgia island
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Seabird colony with great frigatebird, red-tailed tropicbird, red-footed booby, sooty tern and black noddy. Tern Island, French Frigate Shoals, Northwestern Hawaiian Islands
Colonial nesting can be so close that multiple nests are interwoven:
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Sociable weaver nests in Namibia
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Monk parakeet nest colony
Another variation is to have closely grouped separate nests:
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Red-rumped cacique nest colony by a river.
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Nest holes of sand martins
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Cliff swallow nests in Utah, US
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Artificial gourds provided for purple martins, US
Heronries and rookeries are often in the top of a stand of trees:
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Painted stork heronry in Gujarat, India
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Yellow-billed stork heronry in Tanzania
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Corvid rookery in Cambridgeshire, Great Britain
References
- S2CID 1396792.
- ^ a b c
ISBN 978-0-7167-4983-7.
- ^ PMID 21238100. Archived from the original(PDF) on 3 October 2011. Retrieved 25 January 2009.
- ^ a b
Rolland, Cecile; Danchin, Etienne; de Fraipont, Michelle (1998). "The Evolution of Coloniality in Birds in Relation to Food, Habitat, Predation, and Life-History Traits: A Comparative Analysis" (PDF). The American Naturalist. 151 (6): 514–529. S2CID 29490540. Archived from the original(PDF) on 20 June 2010.
- ^
Picman, J.; Pribil, S.; Isabelle, A. (2002). "Antipredation value of colonial nesting in Yellow-headed Blackbirds". Auk. 119 (2): 461–472. S2CID 85785635.
- ^ "Bird Web, Seattle Audubon Society: Tufted Puffin". Retrieved 27 February 2010.
- ^ a b "Triangle Island Seabird Research Station". Retrieved 27 February 2010.
- ^
Wehle, D. H. S. (1983). "The Food, Feeding, and Development of Young Tufted and Horned Puffins in Alaska" (PDF). Condor. 85 (4): 427–442. JSTOR 1367981.
- ^ Garrison, Barrett A. (1999). A. Poole (ed.). "Bank Swallow (Riparia riparia), The Birds of North America Online". Ithaca: Cornell Lab of Ornithology. Retrieved 27 February 2010.
- ^ "San Diego Zoo: Birds: Sociable Weavers". Archived from the original on 23 December 2010. Retrieved 27 February 2010.
- S2CID 86417025.
- ^ Schwertner, T. W.; Mathewson, H. A.; Roberson, J. A.; Small, M.; Waggerman, G. L. (1999). A. Poole (ed.). "White-winged Dove (Zenaida asiatica), The Birds of North America Online". Ithaca: Cornell Lab of Ornithology. Retrieved 27 February 2010.
- ^ Jackson, Jerome A. (1994). A. Poole (ed.). "Red-cockaded Woodpecker (Picoides borealis), The Birds of North America Online". Ithaca: Cornell Lab of Ornithology. Retrieved 6 March 2010.
- S2CID 85693361.
- . Retrieved 6 March 2010.
- ^ Ward, P.; Zahavi, A. (1973). "The importance of certain assemblages of birds as "information centers" for food finding". Ibis. 115 (4): 517–534. .
- ^ a b Ehrlich, Paul R.; Dobkin, David S.; Wheye, Darryl. "Coloniality". Retrieved 27 February 2010.
- ^
Tella, J.L. (2002). "The evolutionary transition to coloniality promotes higher blood parasitism in birds" (PDF). Journal of Evolutionary Biology. 15: 32–41. hdl:10261/58350.
- . Retrieved 27 February 2010.
- ^ Alberico, Julie A.; Reed, J. Michael; Oring, Lewis W. (October–December 1991). "Nesting Near a Common Tern Colony Increases and Decreases Spotted Sandpiper Nest Predation" (PDF). Auk. 108 (4). Retrieved 27 February 2010.
- ^
Brunton, Diane H. (1997). "Impacts of Predators: Center Nests are Less Successful than Edge Nests in a Large Nesting Colony of Least Terns" (PDF). Condor. 99 (2): 372–380. JSTOR 1369943.
- ^ Ainley, David G.; Nettleship, David N.; Carter, Harry R.; Storey, Anne E. (2002). A. Poole (ed.). "Common Murre (Uria aalge), The Birds of North America Online". Ithaca: Cornell Lab of Ornithology. Retrieved 27 February 2010.
- ISBN 978-0-06-055804-8.
- ^ "Guano". Microsoft Encarta Reference Library 2003. Microsoft Corporation. 1993–2002. 60210-442-1635445-74407.