Nav: Home

Brightly-colored fairy wrens not attacked by predators more than their dull counterparts

April 02, 2019

In "Conspicuous Plumage Does Not Increase Predation Risk: A Continent-Wide Test Using Model Songbirds," published in the American Naturalist, Kristal E. Cain examines the factors that drive the predation levels of Australia's fairy wrens. After measuring attack rates on both conspicuously and dull colored 3D fairy wren models in various habitats, Cain found that bright or "conspicuous" plumage is not associated with an increase in predation.

"These findings do not support the long-standing hypothesis that conspicuous plumage, in isolation, is costly due to increased attraction from predators," Cain writes. "Our results indicate that conspicuousness interacts with other factors in driving the evolution of plumage coloration."

The forces shaping plumage color of female birds -- who are sometimes brightly colored like their male counterparts and other times much more dull -- is a long-debated topic of evolutionary biology that remains unresolved. Fairy wrens, who vary greatly in both female coloration and the habitats in which they live, are an excellent group for investigating the evolutionary forces shaping female plumage, Cain writes.

Cain and her co-authors produced 60 3D fairy wren models at the University of Melbourne School of Engineering. The models had three types: conspicuously-colored male purple-backed fairy wren, dull-colored female purple-backed fairy wren, and conspicuously-colored female lovely fairy wren. Field experiments took place at eight different fairy wren habitats across Australia that ranged from open savannah to dense forest. Mimicking actual fairy wrens' foraging habits, models were placed approximately 5 meters apart on bare ground or in short vegetation, attached to metal stakes with magnets. Cameras were used at some locations to determine that the models were knocked off their perches by attack or by accident, and in the case of attacks, to identify the predator.

Cain found that, contrary to their predictions, there was not a significant difference between attack rates on the conspicuous models and the dull models. Attack rates did vary, however, depending on habitat and latitude: predator pressure was stronger at sites that were open savannahs, as well as at sites that were further from the equator. These increases in predation in open habitats occurred more dramatically for female models, both dull and conspicuous, than for the conspicuous male models. Females also saw a greater decrease in predation pressure in habitats that fell on the opposite end of the spectrum: dense forest habitats or habitats closer to the equator.

"Our data suggest that adult birds living in open Australian habitats experience higher predation pressure than those in closed habitats, though it is unclear whether this pattern is due to differences in detectability, predator density, or both," Cain writes.

The lack of differences between attack rates between conspicuous and dull models imply that coloration alone doesn't predict how often a bird will be attacked. This doesn't mean, however, that conspicuousness is not an important factor, Cain writes. For instance, it is possible that a combination of predator behavior, sex differences in behavior, and conspicuousness against particular backgrounds may all play a role in the evolution of plumage colors.

As for the female models experiencing a wider range of predation across sites, Cain writes that this finding joins a substantial body of empirical evidence suggesting that predators may avoid male birds, or that they preferentially attack females or cryptic bird species. There are many theories as for why this may be the case, including some studies that have found that birds that are conspicuously colored, male, or both, are more vigilant against predators.

Further research is needed to determine the mechanisms that are at play with fairy-wrens, Cain writes. "These conflicting patterns suggest that this relationship may be less straightforward than is often assumed and that explicit tests of the relationship between color and predation risk are required. "
-end-


University of Chicago Press Journals

Related Birds Articles:

Birds become immune to influenza
An influenza infection in birds gives a good protection against other subtypes of the virus, like a natural vaccination, according to a new study.
Even non-migratory birds use a magnetic compass
Not only migratory birds use a built-in magnetic compass to navigate correctly.
When birds of a feather poop together
Algal blooms deplete oxygen in lakes, produce toxins, and end up killing aquatic life in the lake.
Birds of a feather mob together
Dive bombing a much larger bird isn't just a courageous act by often smaller bird species to keep predators at bay.
Monitoring birds by drone
Forget delivering packages or taking aerial photographs -- drones can even count small birds!
The color of birds
New research provides insight into plumage evolution.
Migrating birds speed up in spring
It turns out being the early bird really does have its advantages.
Birds on top of the world, with nowhere to go
Climate change could make much of the Arctic unsuitable for millions of migratory birds that travel north to breed each year, according to a new international study published today in Global Change Biology.
City birds again prove to be angrier than rural birds
The researchers' observations shed light on the effects of human population expansion on wildlife.
Teaching drones about the birds and the bees
Unmanned Aerial Vehicles (UAVs) of the future will be able to visually coordinate their flight and navigation just like birds and flying insects do, without needing human input, radar or even GPS satellite navigation.

Related Birds Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Climate Crisis
There's no greater threat to humanity than climate change. What can we do to stop the worst consequences? This hour, TED speakers explore how we can save our planet and whether we can do it in time. Guests include climate activist Greta Thunberg, chemical engineer Jennifer Wilcox, research scientist Sean Davis, food innovator Bruce Friedrich, and psychologist Per Espen Stoknes.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...