(Press-News.org) CHAMPAIGN, Ill. -- Brown-headed cowbirds have a reputation for being deadbeat parents: They lay their eggs in other birds' nests and then disappear, the story goes, leaving the care and feeding of their offspring to an unwitting foster family. A new study suggests, however, that cowbird moms pay close attention to how well their offspring do, returning to lay their eggs in the most successful host nests, and avoiding those that have failed.
The new findings are reported in the Proceedings of the Royal Society B.
"Cowbirds may be paying attention not only to their own reproductive success, but to other cowbirds' as well," said University of Illinois Ph.D. student Matthew Louder, who led the study with Illinois Natural History Survey avian ecologist Jeff Hoover and INHS biological surveys coordinator Wendy Schelsky. "No one's ever suggested before that cowbirds or even other brood parasites pay attention to their own reproductive success." Louder is now a postdoctoral researcher with East Carolina University in North Carolina and Hunter College in New York.
Cowbirds are native to North America and are one of only a few bird species that engage in brood parasitism, the practice of tricking other species into raising one's young, the researchers said. Other brood parasites include the cuckoo, which targets nests with eggs that look very similar to its own. Some host species recognize foreign species' eggs and roll them out of the nest.
A previous study from Hoover and Scott Robinson, of the Florida Museum of Natural History, found that some female cowbirds notice when a host bird has ejected their eggs, and will ransack the "offender's" nest. Hoover calls this behavior "mafia-like retaliation." Some cuckoos also do this.
"There were a lot of implications of that earlier work, and one of them was that cowbird females aren't abandoning their eggs in another species' nest; they're paying attention, to a certain point," Hoover said. "And so we wondered how long they continued to pay attention."
In the new study, the cowbirds targeted prothonotary warblers nesting in experimental nest boxes that the researchers had modified to exclude predators. The researchers manipulated events in the nests to clarify whether the cowbirds randomly selected hosts or if the previous performance of a nest - in terms of cowbird survival - became a factor in their nest selection. The researchers removed cowbird eggs from some of the warbler nests and left them in others. They tracked whether the cowbird nestlings - and the warblers - survived to fledging age.
"We try to discriminate between host success and cowbird success," Schelsky said. "The cowbirds might be selecting nests where young cowbirds succeed, but they might also prefer nests where the warblers are doing well, and not pay attention to cowbird survival."
The team found that the nests that successfully hosted cowbirds were much more likely to be parasitized again, while those that failed to fledge cowbirds were significantly less likely to be targeted by cowbird females the next time around.
"They're learning both from success and from failure," Hoover said.
"And warbler success isn't really relevant to the cowbirds," Schelsky said.
While they are unable to say whether the same females are targeting the same nests again and again, the researchers said it is likely that that is the case.
"Our results mean that somebody's paying attention, and it makes the most sense that the female that's laying the eggs would be paying attention to her own reproductive success," Louder said. "We think that other females are also paying attention."
INFORMATION:
The Illinois Natural History Survey is a division of the Prairie Research Institute at the U. of I.
Editor's notes:
To reach Matthew Louder, call 660-441-7509; email mckimlouder@gmail.com.
To reach Jeff Hoover, call 217-244-2922; email j-hoover@illinois.edu.
To reach Wendy Schelsky, call 217-333-4712; email schelsky@illinois.edu.
The paper "A generalist brood parasite modifies use of a host in response to reproductive success" is available online or from the U. of I. News Bureau.
CORAL GABLES, Fla. (September 9, 2015) -- Have you ever wondered why we call a dog a dog and not a cat? Is this an arbitrary decision, or is it based on iconicity--the resemblance between word structure and meaning? New research shows that for Indo-European languages, like English and Spanish, iconicity is more common than previously believed.
The results are important for understanding the nature of human language, explains Lynn Perry, assistant professor of psychology in the University of Miami College of Arts & Sciences and co-lead author of the study.
"Many linguists ...
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A team of physicists has taken pictures of a theorized but previously undetected magnetic wave, the discovery of which offers the potential to be an energy-efficient means to transfer data in consumer electronics.
The research, which appears in the journal Physical Review Letters, was conducted by scientists at New York University, Stanford University, and the SLAC National Accelerator Laboratory.
"This is an exciting discovery because it shows that small magnetic waves--known as spin-waves--can add up to a large one in a magnet, a wave that can maintain its shape as ...
Patients with liver failure could benefit from a treatment that helps the immune system to combat infections linked to the condition, research suggests.
A study in mice has revealed that treatment with an immune-boosting molecule called CSF-1 helps to trigger the body's natural defence mechanisms in the liver.
Researchers say that if the therapy proves successful in patients, it could help those who are unsuitable for a liver transplant.
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Brain plasticity is the ability of the brain to change both anatomically and functionally in response to changes in the body or in the environment.
For many years, researchers believed that the brain did not suffer major changes after childhood. Although brain plasticity predominates in the first years of life, research done in the last 30 years has shown that it may also occur in adulthood, continuing to change through learning. Brain plasticity may also occur following injury, amputation or nerve damage.
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In a deception that likely has evolved over thousands of years, a caterpillar that feeds on corn leaves induces the plant to turn off its defenses against insect predators, allowing the caterpillar to eat more and grow faster, according to chemical ecologists in Penn State's College of Agricultural Sciences.
The finding is one more revelation about the myriad of chemical signals that pass between plants and insects that scientists at Penn State and around the world have been discovering in recent years. In this case, the agent of deceit is the caterpillar's feces, or ...
Organic electronics has many advantages: it is inexpensive, flexible and lightweight. In terms of applications, we are only limited by our imaginations. There has been a lot of development in polymers since the phenomenon of conducting and semi-conducting plastics was discovered and in 2000 awarded a Nobel Prize. Their weakness is still speed; plastics conduct a charge slowly, compared to silicon, for instance.
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An effective smart phone application should make data collection easy, but not so easy that the user forgets to access and reflect on that information, according to a team of researchers.
People who accessed a sleep monitoring app through a small display window -- often called a widget -- on an Android smart phone were more likely to manually enter their diary information, as well as interact with that data than users who monitored their sleep without the feature, according to Eun Kyoung Choe, assistant professor of information sciences and technology, Penn State.
"As ...
