Uncertainty drives the evolution of 'cooperative breeding' in birds

August 17, 2007

Rather than striking out to start a family of their own, members of some bird species will stick around longer to help a relative raise their young. Now, researchers report evidence that in African starlings such altruistic tendencies are most common among species that live in savannas, where the rainfall in any given year is virtually impossible to predict. The findings appear online August 16 in the journal Current Biology, a publication of Cell Press.

"When the unpredictability of your environment is high, you don't know in advance what conditions you will be facing when the next breeding season rolls around," said Dustin Rubenstein of the University of California, Berkeley and the Cornell Laboratory of Ornithology. "Faced with this uncertainty, it pays, evolutionarily speaking, to live and breed in social groups that will help you weather the bad times and make the most of the good times. Living in cooperative family groups may be like a form of insurance against the unpredictable nature of the environment that allows individuals to maximize their reproductive success over the course of their lifetimes."

Over the past few decades, mounting evidence has shown that many species of cooperatively breeding birds live in semi-arid tropical and sub-tropical environments, particularly in sub-Saharan Africa and Australia. Although that pattern suggested that the environment might explain the behavior, few studies showed a strong relationship between the incidence of cooperative breeding among species and any particular environmental feature, the researchers noted.

In the new study, the researchers examined the pattern of breeding behavior exhibited by 45 species of African starlings in relation to the environments in which they live-including savannas, deserts and tropical forests-while controlling for the evolutionary relationships among them. They also examined the rainfall patterns typical of each of those environments in 47 African countries as far back as 147 years ago.

They found evidence that different starling species have independently evolved the cooperative breeding system upon moving to savannas, where they showed that the amount of year-to-year variation in rainfall is greatest. Rubenstein's group suggested that cooperative breeding is probably advantageous in environments that vary over time because it allows for reproduction in harsh years, as well as sustained breeding during benign years.

Such a strategy might become more widespread in an increasingly uncertain future, the researchers suggested.

"Some researchers have argued that climate change will lead to greater temporal environmental variability," Rubenstein said. "That is, we might expect more extreme weather like severe droughts and devastating floods, and ultimately more variable environments than we see now. If this increase in variability occurs, many species of animals-including humans-will have to adapt to the increasing unpredictability of their environments. By studying how animals have already adapted to temporally variable and unpredictable environments, we can gain insights into how social behavior may change in the wake of climate change."

Cell Press

Cooperative Breeding in Birds: Long Term Studies of Ecology and Behaviour
by Peter B. Stacey (Editor), Walter D. Koenig (Editor)

Stacey and Koenig discuss the phenomenon of cooperative breeding among birds, an unusual kind of social behavior common to only a few hundred species worldwide, in which individuals other than the male-female pairs help to raise the young of a single nest or den. Because certain individuals aid in raising offspring which are not their own, cooperative breeding gives rise to some of the clearest examples of altruism among animals. This unique breeding behavior is of interest to evolutionary biologists and behavioral ecologists since such species exhibit some of the most unusual and bizarre social behavior observed anywhere in the animal kingdom. The studies are all long term and consequently the book summarizes some of the most extensive studies of the behavior of marked individuals ever...

Habitat-use patterns in cooperative and non-cooperative breeding birds: testing predictions with western scrub-jays.: An article from: Wilson Bulletin
by D. Brent Burt (Author)

This digital document is an article from Wilson Bulletin, published by Wilson Ornithological Society on December 1, 1996. The length of the article is 5653 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web browser.

From the author: I propose a method to test extensions of models concerning the maintenance of cooperative breeding systems that examines patterns of habitat use relative to the distribution of habitat components among territories. I analyzed habitat use and behavioral time budget data for a Texas population of the Western Scrub-Jay (Aphelocoma californica). As a non-cooperative population, one of two...

Cooperative Breeding in Mammals
by Nancy G. Solomon (Editor), Jeffrey A. French (Editor)

Cooperative breeding refers to a social system in which individuals other than the parents provide care for the offspring. Since individuals delay breeding and invest in the offspring of others, cooperative breeding poses a challenge to a Darwinian explanation of the evolution of social behavior. The contributors to this book explore the evolutionary, ecological, behavioral, and physiological basis of cooperative breeding in mammals. The book contains a collection of chapters by the leading researchers in the field, and it is the first book dedicated exclusively to the study of mammalian cooperative breeding.

The Florida Scrub Jay: Demography of a Cooperative-Breeding Bird. (MPB-20) (Monographs in Population Biology)
by Glen Everett Woolfenden (Author), John W. Fitzpatrick (Author)

Florida Scrub Jays are an excellent example of a cooperative-breeding species, in which adult birds often help raise offspring not their own. For more than a decade Glen E. Woolfenden and John W. Fitzpatrick studied a marked population of these birds in an attempt to establish a demographic base for understanding the phenomenon of "helping at the nest." By studying both population biology and behavior, the authors found that habitat restraints, rather than kin selection, are the main source of the behavior of Florida Scrub Jays: the goal of increasing the number of close relatives other than descendants in future generations is of relatively minor importance in their cooperative-breeding behavior. The Florida Scrub Jay lives only in the Florida oak scrub. All acceptable habitat is...

Helpers at Birds' Nests: A Worldwide Survey of Cooperative Breeding and Related Behavior
by Alexander F. Skutch (Author), Dana Gardner (Illustrator)

In Helpers at Birds' Nests, renowned naturalist and ornithologist Alexander Skutch provides vivid, detailed accounts of a remarkable aspect of bird behavior--the aid that one bird gives another who is neither its mate nor its dependent young and who may even belong to a different species. In graceful, clear prose, Skutch makes accessible to amateur bird-watchers examples of cooperation in species as far-flung as the little rifleman of New Zealand, the Laysan albatross in the mid Pacific, and the neotropical birds of Skutch's own Valley of El General in Costa Rica. Skutch describes the cooperative behavior of more than fifty families of birds. Each family is introduced by a brief sketch of its distribution and outstanding features, followed by intimate, nontechnical accounts...

Ecology and Evolution of Cooperative Breeding in Birds
by Walter D. Koenig (Editor), Janis L. Dickinson (Editor)

Cooperative breeders are species in which more than two individuals participate in raising young at a single nest. Although relatively rare, this behavior entails dramatic forms of cooperation and competition, and provides important insights into many areas, including sexual selection, incest avoidance and other subjects. This book will be of interest to students and professionals interested in bird behavior and ecology.

The first ten years of the co-operative Breeding Bird Survey in Canada (Canadian Wildlife Service report series)
by Anthony J Erskine (Author)

An Observation of Cooperative Breeding in the Ovenbird.: An article from: Wilson Bulletin
by David I. King (Author), Tracey B. Champlin (Author), Paul J. Champlin (Author)

This digital document is an article from Wilson Bulletin, published by Wilson Ornithological Society on June 1, 2000. The length of the article is 1242 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web browser.

Citation Details
Title: An Observation of Cooperative Breeding in the Ovenbird.
Author: David I. King
Publication: Wilson Bulletin (Refereed)
Date: June 1, 2000
Publisher: Wilson Ornithological Society
Volume: 112 Issue: 2 Page: 287

Distributed by Thomson...

A case of cooperative breeding in the Hooded Warbler.: An article from: Wilson Bulletin
by Scott A. Tarof (Author), Bridget J. Stutchbury (Author)

This digital document is an article from Wilson Bulletin, published by Wilson Ornithological Society on June 1, 1996. The length of the article is 1198 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web browser.

From the supplier: Videotaped evidence reveals an instance of cooperative breeding in Hooded Warblers. A dominant banded male (B) permits an unbanded auxillary male (U) to mate with his banded partner. The feeding rate for B is higher compared to that of U but is in the same range as the female. Why B also allows U to raise his offspring has always perplexed ornithological researchers because Hooded Warblers...