Researchers show increased risk of predators can evoke adaptive response in birds

March 28, 2011 by Bob Yirka report
A juvenile Eurasian Sparrowhawk in Betuwe, Netherlands. Image credit: Wikipedia.

( -- Evolutionary ecologists Michael Coslovsky and Heinz Richner of the University of Bern in Switzerland, have published a study in Functional Ecology where they show that when a female bird is exposed to more stress from predators, such as hawks, when ovulating, they tend to produce offspring that are smaller, which isn't a surprise as stressed offspring in many species wind up smaller than average; the surprise is that the smaller offspring also grew their wings both faster and longer than what would be considered normal for their species.

To get these results, Coslovsy and Richner went out into Bremgartenwald forest, near Bern and chose a group of great tits to use as a study group. They then exposed part of the group of mothers (during ) to stuffed sparrow hawks and audio recordings of their calls; the control group was exposed to song thrushes. Two days after the nestlings hatched, they (both groups) were captured, tagged and carted off to another part of the forest to be raised by adoptive parents. As they grew, they were all monitored and it was then the researchers discovered that the offspring of stressed mothers were in fact smaller, as expected, but they also grew their wings at an unusually brisk pace, and grew them longer (1.8 millimeters on average) than other from the control group.

Prior to this research, it’s been assumed that smaller growth in bird offspring is generally a negative effect brought about by a buildup of the hormone corticosterone. Now, with the news that smaller also produce wings at an earlier age, and grow them longer, it might be argued that all three changes are nature’s way of helping the survive in a more hostile than normal environment; less weight, combined with longer wings at an earlier age, would seem to increase the nestling’s ability to fly away at a younger age, and to do so more speedily to ward off attacks.

Of course, the results shown by Coslovsy and Richner are just one study, and have only been done on one species of bird; many more field trials will have to be made before any definitive conclusions can be drawn.

Explore further: Scientists shake Darwin's foundation -- chickens inherited parents' stress symptoms

More information: Predation risk affects offspring growth via maternal effects, Michael Coslovsky, Heinz Richner, Functional Ecology, Article first published online: 1 March 2011. DOI: 10.1111/j.1365-2435.2011.01834.x
via Nature.

Related Stories

Mother birds 'engineer' their offspring

May 23, 2007

Bird species that have relatively long incubation periods and short nestling periods for their body size have higher concentration of androstenedione than those species whose developmental time is shifted towards relatively ...

Mother's little helpers

August 16, 2007

An Australian bird has been found to produce smaller, less nourishing eggs when it breeds in the presence of other ‘helper’ birds that provide child-care assistance. This unique adaptation enables the birds to live longer ...

Mothers pass on disease clues to offspring

December 24, 2008

( -- When there is a threat of disease during pregnancy, mothers produce less aggressive sons with more efficient immune systems, researchers at The University of Nottingham have discovered.

Cuckoos evolve to fool angry birds

January 12, 2011

( -- Australian cuckoo birds have taken a new evolutionary step – mimicking the color of their host young to avoid certain death, according to a study by researchers from The Australian National University.

Recommended for you

Study suggests fish can experience 'emotional fever'

November 25, 2015

(—A small team of researchers from the U.K. and Spain has found via lab study that at least one type of fish is capable of experiencing 'emotional fever,' which suggests it may qualify as a sentient being. In their ...

New gene map reveals cancer's Achilles heel

November 25, 2015

Scientists have mapped out the genes that keep our cells alive, creating a long-awaited foothold for understanding how our genome works and which genes are crucial in disease like cancer.

How cells in the developing ear 'practice' hearing

November 25, 2015

Before the fluid of the middle ear drains and sound waves penetrate for the first time, the inner ear cells of newborn rodents practice for their big debut. Researchers at Johns Hopkins report they have figured out the molecular ...

How cells 'climb' to build fruit fly tracheas

November 25, 2015

Fruit fly windpipes are much more like human blood vessels than the entryway to human lungs. To create that intricate network, fly embryonic cells must sprout "fingers" and crawl into place. Now researchers at The Johns Hopkins ...


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.