Singing Sparrows

From The New York Times we learn that chipping sparrows love their neighbors, but only if they are weaklings. Male intruders can invade and take over another bird’s territory and strong invaders are usually the winners. Male chipping sparrows will form a neighborhood coalition to defend their territories, but apparently only if the intruder is weaker.  And how do they know this?  By the intruder’s song.  If the intruding sparrow’s trill is weaker, i.e. slower, then that bird is less aggressive.  A faster trill indicates a strong invader.

Stick to those music lessons, little chippers!

Click here to read the New York Times article.

In a Bird’s Nest, an Animal Behavior Puzzle

From The New York Times

Sometimes the scientists who study animal behavior solve puzzles and other times they uncover new ones. The war between mockingbirds and cowbirds is a case in point.

Cowbirds are brood parasites, meaning they lay their eggs in the nests of other bird species, thus unloading the messy and demanding business of chick-rearing. They also peck holes in the eggs of the host birds, destroying as many as they can.

Mockingbirds are a favorite target of this plan, and it seems to make perfect sense for them to viciously attack cowbirds when they catch them in the nest.

But when Ros Gloag, then a doctoral student at Oxford, and her colleagues in Argentina looked closely at the war between chalk-browed mockingbirds and shiny cowbirds, they found something unexpected, as they reported in the November issue of Animal Behaviour.

They stationed small video cameras near the nests of 40 pairs of chalk-browed mockingbirds. Over two breeding seasons they recorded more than 200 attacks on intruding cowbirds.

They were surprised to find that these attacks, which their videos show to be quite vicious, did not stop the cowbirds from laying eggs. The cowbirds would hunker down and let the much large mockingbirds deliver hammer blows to the head, but in matter of seconds they would lay an egg and flee.

How could such a failed strategy persist in evolution?

The answer, according to Dr. Gloag, now a postdoctoral researcher at Australian National University, was that the attacks did prevent the cowbirds from carrying out the second prong of their plan, destroying the mockingbird eggs already in the nest.

So the mockingbirds managed to save some of their offspring. They still end up raising unwanted baby cowbird guests. But, said Dr. Gloag, once the eggs hatch, the larger mockingbird chicks compete very well with the smaller cowbirds.

PERMALINK + VIDEO: The New York Times

An Earlier Exodus Amid Climate Change

From The New York Times

Birds are migrating earlier and earlier each year, and scientists have long suspected that climate change is responsible. A new study by researchers at the University of East Anglia in England shows that individual birds migrate like clockwork, but nesting and hatching are happening earlier as a result of warmer temperatures, and this appears to be linked to the advancing of overall migration patterns.

PERMALINK: The New York Times

Juncos — Not So Ordinary After All

Sharon McInnis, October 28 | Excerpted from BIRD CANADA | bird canada.com

Posted on Fat Finch, November 16, 2013

When we moved to Gabriola seven years ago, the first bird I saw in the overgrown, untended garden we inherited with our ‘new’ house was a junco. Although it seems amazing to me now, I’d never noticed this bird in the city. With its black hood and unusual metallic chipping ‘song’, I figured it must be very rare indeed. Then I discovered there are about 630 million Dark-eyed Juncos (Junco hyemalis) in North America. So not very rare after all.

In fact, the junco is one of the most abundant backyard birds on the continent. A ‘rock star study organism’, it’s also one of the most thoroughly studied bird species on the planet. For over forty years Ellen Ketterson, a pioneer in the field of animal behavior from the University of Indiana, has been studying juncos. She explains the fascination: the junco “really lets you study it. … They build their nests on the ground, so you can find them. They thrive in captivity, so you can provide them with seeds, or put them in different social configurations. And they’re content. They actually reveal their biology to you.” Ketterson is one of the scientists whose work is described in “The Ordinary Extraordinary Junco”, an 88-minute video series produced by biologists and filmmakers from Indiana University.

Dark-Eyed Junco by Garry Davey

This fascinating free program explores how juncos behave, especially in terms of evolution. Until seeing this series, the word ‘evolution’ conjured up images of dinosaurs to me. But apparently “Evolution doesn’t just happen over huge numbers of generations or millions of years. It can happen to you or me, or any animal, within our own lifetimes. Amazingly, epigenetic changes to our DNA mean that the genes we pass on to our children can differ from the ones we inherited.” (Zoobiquity, Posted on October 28, 2013 by Sharon McInnes, Natterson-Horowitz and Bowers)

One example of such rapid evolutionary change began in the early 1980s when a small flock of junco migrants remained on the campus of the University of California (UCal) instead of returning to the nearby mountains in winter. When scientists began to study the campus birds, they discovered that this urban population was a new isolated breeding population of Oregon Dark-eyed Juncos. The Ordinary Extraordinary Junco tells the fascinating tale. But let me give you a sneak preview.

Essentially, the UCal juncos demonstrated rapid evolution driven by urbanization. In this case, campus life, with its constant barrage of stimuli, changed the very nature of the juncos. They became, for example, more flexible when foraging and nesting, and bolder than their rural counterparts. They explored more food opportunities, allowed humans to get three times closer than rural juncos (in half the time), and sang at a higher frequency in order to be heard in a noisy urban environment. Ultimately, on the bustling campus, with cars and feral cats and construction noise and artificial lighting at all hours, natural selection favored assertive, flexible, bold juncos. Juncos with spunk.

It turned out these more enterprising juncos were also more attentive, involved parents. As the breeding season of the braver urban birds shifted, for example, the males became more interested in parenting (helping to find food for the nestlings) and less aggressive. (Scientists found they had less testosterone at this time.) These ‘brave’ juncos that were also ‘better’ parents were more likely to survive, breed, and pass on their genes. Soon (in evolutionary terms) these new traits became the norm for this newly-evolved isolated population.

I understand behaviour changing in a new environment; that happens all the time – with birds and people. What surprised me is that the birds’ appearance changed so quickly (they had less white in their tails and less black in their heads within thirty years) and that their genetic makeup, their actual DNA, changed. But apparently this kind of rapid evolution is happening with other populations of urban birds around the world now, just as it did with Darwin’s finches in the Galapagos Islands and cichlid fish in Africa.

If I haven’t whet your appetite quite enough to inspire you to drop everything and go watch the 8-video series, check out the trailer at http://www.youtube.com/watch?v=3kvJTMvaKUg. Then, for the whole amazing story, just google The Ordinary Extraordinary Junco. And enjoy!

This article was first published in The Flying Shingle on October 7 2013.
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