FreeLists / va-bird / [va-bird] Re: Raven and Burrowing Owl articles

["Paul Bedell" <pbedell@xxxxxxxxxxx>]

Denise,

Thanks for pointing out two very fascinating articles!  These are "must
read" on my list now.

Paul Bedell

----- Original Message -----
From: "Denise Ryan" <Denise_Ryan@xxxxxxx>
To: <va-bird@xxxxxxxxxxxxx>
Sent: Tuesday, September 07, 2004 2:17 PM
Subject: [va-bird] Raven and Burrowing Owl articles


>
> Ok, not necessarily a VA/DC Bird thing, but still interesting.  =
> Burrowing Owls using tools and  Ravens eating Eared Grebes in =
> Yellowstone.
>
> Denise Ryan
> Washington, DC
>
> ************************************************
>
> Scientific American.com
>
> September 02, 2004  =20
> =20
> Cunning Owls Bait Beetle Prey  =20
> =20
> The wise old owl is a staple of nursery rhymes. New findings provide =
> more evidence that the animals are, in fact, quite crafty. According to =
> a report published today in the journal Nature, owls use mammal dung to =
> lure prey.=20
> A few examples of avian tool use have been reported, but in many cases =
> the birds were captive animals and it was difficult to assess the =
> advantage their wild counterparts could glean from the behavior. In the =
> new work, Douglas J. Levey of the University of Florida and his =
> colleagues studied wild populations of burrowing owls (Athene =
> cunicularia). The researchers removed all traces of mammal dung from the =
> nests of two owl populations in Gilchrist County, Fla. Half of the nests =
> then received an amount of dry dung typically found surrounding a nest. =
> After four days, the researchers analyzed the birds' droppings and =
> collected discarded remains of eaten beetles to determine the owls' =
> diets. They discovered that owls with access to dung ate 10 times more =
> dung beetles than those with bare nests did.=20
>
> The scientists also tested whether the owls might be using the dung to =
> mask the scent of their nests, but found that it did not offer =
> sufficient protection from predators. Instead, the owls appear to "fish" =
> for dung beetles using excrement as bait. The results of this study, the =
> authors conclude, provide "an unambiguous estimate of the importance of =
> tool use in a wild animal." --Sarah Graham=20
>
> ***************************************************************
>
> Subject: Scientist writes about bird massacre ( Article in 8/30 Billings
> Gazette and Bozeman Chronicle)
>
>  Scientist writes about bird massacre Associated Press
>
>  BOZEMAN (AP) - A Yellowstone National Park ornithologist who saw four
>  ravens systematically kill 141 grebes describes the spectacle in the =
> new issue of Yellowstone Science, a quarterly magazine.
>  Terry McEneaney had known for a long time that ravens are efficient =
> predators. But he was astonished last May when he saw four of them =
> attack so many grebes on icy Yellowstone Lake.  Western-eared grebes =
> generally do not spend much time in Yellowstone, but on May 1 hundreds =
> passed overhead, en route north for the summer.  McEneaney was at the =
> lake, looking for bald eagle nesting sites, when he saw a grebe on the =
> frozen water. Shifting cloud shadows apparently had fooled the bird into =
> thinking it was landing on open water.  "Then I saw another grebe, and =
> another grebe, and another grebe,"McEneaney said. "They were all over =
> the place."  Grebes need open water for takeoff, so once they landed, =
> they were stuck there.  Enter the ravens.  At first, only one was on the =
> ice. It "flew out to one of the stranded grebes and pulverized it with =
> its long beak until it was dead," McEneaney wrote in the magazine.  The =
> raven left the grebe where it lay, then moved to another and pecked it =
> to death, as well. At about 11 ounces, grebes are much smaller than =
> ravens.  Twenty minutes later, three more ravens joined in and started =
> killing grebes.  Then two bald eagles showed up and began eating the =
> grebes the ravens had killed.  McEneaney watched for three hours and =
> kept track of the action.  After the ravens had killed 92 birds, they =
> began dismantling the carcasses and flying to the shore, where they =
> cached the grebe meat in the snow, said McEneaney, who has studied =
> ravens for nearly 20 years. "When there's an abundance of food, they =
> cache it," he said. "They went back and forth, back and forth."He had to =
> leave, but when he returned at day's end, all 141 grebes were dead.  =
> McEneaney said he has watched ravens carry off 13 baby magpies, pluck =
> trout from a stream and even try to peck a mired bison to death, =
> starting with its eyes. What he saw at Yellowstone Lake in May topped it =
> all.  "I've never seen anything of this magnitude," he said. "I didn't =
> believe they could do that much predation in one day."  McEneaney said =
> he never considered trying to intervene. The ice was not safe, and park =
> regulations require Mother Nature be allowed to take its course. "That's =
> what it's all about," McEneaney said. "As gruesome as it sounds, it was =
> really interesting to watch. It's etched in my mind."
>  Copyright =A9 2004 Associated Press
>
> >
> =20
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