Birds co-operate within a communal nest to achieve a common good

July 7, 2014

A new insight into one of the biggest questions in science – why some animals, including humans, work together to maintain a common good – has been achieved by scientists at the University of Sheffield.

Sociable weavers, a highly social and co-operative breeding bird from the savannahs of southern Africa, build the largest nests of any bird, housing colonies of up to several hundred birds that can often weigh tonnes and last for decades. The massive nests consist of individual nest chambers which are used throughout the year for breeding and roosting and are embedded within a communal thatch.

The thatch covering the nest doesn't originate from individual chamber building but requires separate investment from colony members to build and maintain it. As such it provides a from which all colony members benefit in terms of buffering extremes of temperature, supporting individual nest chambers and protecting from predators.

The question that researchers from the University of Sheffield's Department of Animal and Plant Sciences addressed is how sociable weavers work together to successfully build and maintain this public good, while keeping freeloaders at bay. This is a general problem in such situations because some individuals may cheat the system by benefitting from the public good, without contributing to it. There are several potential solutions to this problem, one of which is that co-operative behaviour is directed towards relatives.

Dr Rene van Dijk, from the Sheffield research team led by Professor Ben Hatchwell, said: "Our study shows that relatedness between colony members is low, on average, but co-operation over thatch-building is kin-directed due to the positioning of relatives within nests. Sociable weavers do not contribute to thatch building equally, but those that do contribute to it are more closely related to their neighbours within the colony than are non-builders.

"Crucially, related birds are positioned close to one another within nests, so that thatch building investment also benefits their relatives. Additionally, relatives visit each other's nest chambers suggesting again that the communal benefits are shared among kin.

The study not only demonstrates that the influence of kin selection may stretch beyond that of nuclear and extended family groups thus promoting co-operation in large social groups, but it is also the first study to show that kin selection may promote the communal construction and maintenance of an animal-built physical structure. Such structures include nests, mounds and burrows.

"This co-operation is similar to how human families may decide to accept a lodger into their home. If the lodger isn't related to the family, he or she may pay rent but otherwise they will not care too much about the upkeep of the house. However, if the lodger is a known family member, then you would expect them to maintain the house which he or she may stay in for a longer period and possibly inherit. It may seem like a small difference, but it tips the balance towards a more co-operative society."

Understanding how individuals resolve conflicts over contributions to, or exploitation of, common resources remains a major challenge in ecological research as well as in social sciences. The dilemma of payoffs from social benefits being generally higher when individuals co-operate, while selfish individuals do better than co-operators within groups, presents a temptation to defect and hence an evolutionary paradox.

"On a broader scale, our research reveals one mechanism through which co-operation between individuals for communal tasks is achieved, but there may be other solutions to the same problem that we see in other animals, including humans, Dr van Dijk added.

"For example, cooperative behaviour may be enforced by social conventions or laws and failure to comply with these may result in collapse of the public good. In terms of humans, global fish stocks are an example of a communal resource and if fishermen and their governments don't work together to agree on policies that are enforced, then global fish stocks will be exhausted and the industry will collapse resulting in the loss of a common good."

The mechanism for the maintenance of cooperative behaviour in sociable weavers revealed by this study is unlikely to operate at such a global scale, but within smaller communities the idea of kin-directed is likely to be widespread and relevant across many other species.

The research is published in the journal Ecology Letters.

Explore further: Feathered friends are far from bird-brained when building nests

Related Stories

Helping family is key for social birds

July 11, 2012

(Phys.org) -- Social birds that forgo breeding to help to raise the offspring of other group members are far more likely care for their own close relatives than for more distant kin, a new study has found.

Long-tailed tits help each other out

March 21, 2013

Long-tailed tits which lose their eggs or young may help to feed neighbours' chicks, researchers have found. But the degree to which they'll co-operate varies from year to year.

Chickless birds guard nests of relatives

December 20, 2013

(Phys.org) —New research has solved a mystery as to why some birds choose not to reproduce, and instead help to guard the nests of their close relatives. This occurs in about nine percent of all bird species.

Recommended for you

Researchers design first artificial ribosome

July 29, 2015

Researchers at the University of Illinois at Chicago and Northwestern University have engineered a tethered ribosome that works nearly as well as the authentic cellular component, or organelle, that produces all the proteins ...

Studies reveal details of error correction in cell division

July 29, 2015

Cell biologists led by Thomas Maresca at the University of Massachusetts Amherst, with collaborators elsewhere, report an advance in understanding the workings of an error correction mechanism that helps cells detect and ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.