Archive for the 'Crows, Ravens' Category

Feb 11 2015

Crows Exonorated!

In some cultures and for some people, crows have a bad reputation. Their black feathers and eerily intelligent behavior have linked them with bad luck and death.   Even those of us who like crows are upset when we see them take birds’ eggs and nestlings.  Our distaste for this extends to other members of the corvid family as well.

Some game and conservation organizations kill corvids believing this will help the small birds that corvids prey upon.  Does it?  A recent study published in Ibis says “No.”

The Institute of Research in Game Resources (IREC) studied 326 interactions between corvids and their prey in Europe and North America.  They monitored 67 prey bird species including passerines and game birds.

When researchers removed all predators from the study areas the prey-bird populations increased but when they removed only the corvids there wasn’t much change.  In fact, some prey populations suffered in the absence of crows!

Crows had an impact on reproductive success but this didn’t make much difference to the species’ populations.  Study author Beatriz Arroyo said: “In 81% of cases studied, corvids did not present a discernible impact on their potential prey. Furthermore, in 6% of cases, some apparently beneficial relationships were even observed.”

So is it good conservation practice to kill corvids?  “This method of managing populations is frequently ineffective and unnecessary,” says Arroyo.

Crows are exonerated!

Read more about the study here in Science Daily.

 

p.s. As you can see in the video, crows just want to have fun.  ;)

(video of a hooded crow on YouTube.  Hooded crows are native to Europe.)

 

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Feb 03 2015

In The Corvid Niche

Pearly-eyed thrasher (photo from Wikimedia Commons)
As I mentioned yesterday, there are no corvids in the Virgin Islands.  In fact there are no crows, jays or ravens in Puerto Rico and the Lesser Antilles but there is a bird who fills their niche.

The pearly-eyed thrasher is the size and shape of a normal thrasher but he’s not a skulker like the brown and Crissal thrashers of North America.  Instead he acts like a blue jay: bold, brash, adaptable and inquisitive.  Conspicuous in flight, he lands with a thud and hop-turns on his perch.  He calls in public and his youngsters beg loudly.

Like corvids, the pearly-eyed thrasher is omnivorous and opportunistic.  He eats fruit, insects and vertebrates including eggs, nestlings, lizards, land crabs and tree frogs.  He’s even earned a reputation for “stealing” because he’s willing to wait and swoop in when humans turn their backs at meal times.  The thrasher below was photographed at a restaurant in the British Virgin Islands “just waiting for the waitress to leave the area so he could enjoy the remains of breakfast left on the tables.”

Pearly-eyed thrasher (from Wikimedia Commons)

And like any corvid, he’s willing to peck an animal he thinks he can kill.

Last Friday during the Francis Bay bird walk our National Park Service guide, Laurel, looked around a corner and suddenly called, “Thrashie! Thrashie! He’s pecking a baby iguana!”  She rushed to the iguana’s rescue and the thrasher flew up to watch his prey.

Laurel showed us the green iguana which was about the same size as the thrasher.

Baby iguana just rescued from a pearly-eyed thrasher attack (photo by Kate St. John)

Here the iguana is a blur as it tries to get out of her hand.

Baby iguana, moving in hand (photo by Kate St. John)

Laurel hid the iguana among green leaves and we moved on to watch the black-necked stilts, leaving the pearly-eyed thrasher behind.

Who knows what happened next.

 

(Pearly-eyed thraser photos from Wikimedia Commons. Click on the images to see the originals.
Iguana photos by Kate St. John
)

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Jan 23 2015

TBT: Crows…

Published by under Crows, Ravens

American crows gather in a tree in Pittsburgh (photo by Sharon Leadbitter)

Throw Back Thursday (TBT) is on Friday today because of the short work week.

In the seven years since I started writing about Pittsburgh’s winter crows I can see that they’ve changed their ways.  No, they’re not less boisterous and gregarious.  No, they have not stopped gathering in huge roosts.  But they’ve made adjustments in where they roost and the flight paths they use to get there.  The huge flocks don’t fly over my house anymore.

Back in January 2008 the crows roosted at WQED and caused quite a stir which I addressed with my favorite poem called Crows by Doug Anderson.
(Click here to read…)

 

p.s. I carry the Crows poem with me wherever I go.  I’m probably the only person you know who carries a poem about crows in her purse.  :)

(photo by Sharon Leadbitter)

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Jan 11 2015

I’m Gonna Get You!

Raven chases bald eagle chasing osprey (photo from Wikimedia Commons)

This photo is tiny but it shows the pecking order in the sky.

The bird on the left is an osprey, the middle one’s a bald eagle, the right one is a raven.  Click here or on the photo to see a full size image with a better view of the birds.

The bald eagle wants the osprey’s fish. The raven’s harassing the bald eagle. It’s unusual that all three lined up in one big chase.

“I’m gonna get you!”

 

(photo by Ciar via Wikimedia Commons.  Click here to see the original photo with documentation.)

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Dec 04 2014

TBT: The Crows Know

Published by under Crows, Ravens

American Crow (photo by Brian Herman)

Throw Back Thursday (TBT):

As birds fly overhead they notice things we humans cannot see because we’re stuck on the ground with a narrow perspective.

Most birds ignore our activity but crows pay attention to humans and watch for things of interest.  How else could they find out it’s Garbage Day and show up just in time to poke holes on in our garbage bags?

In February 2011 there was an early morning mystery on my street.  At dawn, the crows leaving the winter roost flew over my neighborhood and saw it below.  Each flock paused, circled above, and cawed loudly. Click here to read what happened that morning.  The crows were the first to know.

This fall Pittsburgh’s winter crow roost has settled in the Hill District above Bigelow Boulevard near Cliff Street. Because of its location very few crows fly over my neighborhood at dawn.

If there’s a mystery this winter it will have to wait for us humans to discover it.

 

(photo by Brian Herman)

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Nov 14 2014

Crows Recognize Their Friends

Published by under Crows, Ravens

On Halloween I posted a video showing how crows recognize their enemies.  Libby Strizzi wondered, do they recognize their friends?  You bet!

In Gifts of the Crow John Marzluff, who conducted the face-recognition experiments at University of Washington, tells how the same American crows that harass the mask-face fly to perch near Lijana Holmes when she arrives on campus.  She feeds them a breakfast of eggs and meat every day.  It’s not just the food.  Crows know who their friends are.

In this video from Germany “Rabenvater” offers treats to hooded and carrion crows and records their antics.  He feeds them often (see his many crow videos) and they trust him.  Their relationship is so amazing that spectators pause to watch.

Not only do the crows trust him, they’re willing to raid his pocket that holds the treats.  Watch at 2:30 as a hooded crows thinks about the pocket and at 3:40 when a carrion crow spends time pulling out the treats and throwing away the peanuts.

Crows recognize their friends.

 

(YouTube video by Rabenvater)

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Oct 31 2014

Wear A Mask

Published by under Crows, Ravens

Here’s a scary thought.  If you’re an enemy to crows, they remember your face and harass you.

John Marzluff from the University of Washington shows how they remember their enemies in this clip from A Murder of Crows.

He investigated the phenomenon because he, like other crow researchers, was routinely harassed by crows after he captured and banded their young.  Were they remembering his clothing?  No, they remembered his face.

Perhaps you or a friend have experienced this too.  For instance…

Mike Olaugh of Minneapolis left a comment on my blog about blue jays and added this note about crows.  “The Crows … are ubiquitous no matter the conditions. We are near a cemetery and they have lived there for a century. I learned when I first moved here 20 years ago to leave them alone. They ganged up on my car and dropped on it en masse for a whole season. (I was trying to get them to stop roosting across the alley.)”

The crows recognized Mike and did something to drive him nuts until he left them alone.

Moral of the story:  If you harass crows, you may have to wear a mask.

Happy Halloween.  ;)

 

(YouTube video excerpt from PBS NATURE posted by Simon and Schuster as a promo for Marzluff and Angell’s 2012 book Gifts of the Crow)

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Oct 24 2014

Move Along, Move Along!

Published by under Crows, Ravens

Not everyone is as enthusiastic about winter crows as I am.  If you walk or park your car beneath the roosts you’re surely disgusted by the mess they make.  What to do? Move the crows.

Central New York state has lots of experience with crow wrangling.  At times Auburn has had 70,000 winter crows, more than two and a half times their human population of 28,000.  Years of trial and error have shown that killing crows doesn’t work but moving them does.

So now, Central New York gets ready every autumn to move the crows to locations that aren’t so bothersome.  This August 2012 video shows a seminar in Baldwinsville, 20 miles northeast of Auburn … as the crow flies.

Move along, crows. Move along!

 

(YouTube from Central New York, WSTM)

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Oct 20 2014

Planning Their Next Move

Published by under Crows, Ravens

A small assembly of crows (photo by Tom Harpel via Wikimiedia Commons)

Last month the crows had a meeting up north.

What are we going to do when it gets cold?  We can’t stay here.

Yup. These fields have grasshoppers now but they’ll be bare as soon as the frost hits.

Vince told me there are some nice places south of here in the Ohio Valley.  He recommended Wheeling Island and Pittsburgh.

I hear Pittsburgh’s great, especially the East End. Everyone had a great time last year.  Stay away from the Cathedral of Learning, though.  Peregrines live there.

OK, so we’ll go to Pittsburgh.

When do we leave?

In October.

In the past few days Anne-Marie, Julie and Anne have seen flocks of crows at dusk in Shadyside and Oakland.

The crows are back in town. Woo hoo!

 

(photo by Tom Harpel via Wikimedia Commons. Click on the image to see the original)

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Sep 12 2014

How Quickly Can You Pass These Tests?

This is a test.  For the next 3+ minutes wild New Caledonian crows will solve six physics problems in water displacement.

What will raise the floating treat?  If there are two treats which method is fastest?  The challenges are:

  1. Sand versus Water:  Will the crow know that there’s no point in dropping stones onto sand?
  2. Light versus Heavy objects:  Do heavy objects work better than light ones?
  3. Solid versus Hollow objects: Do solid objects work better than hollow ones even though the hollow objects weigh the same?
  4. Narrow water column versus Wide:  Which column takes longer to elevate?
  5. High versus Low water:  Is it faster to get the treat when the water is already close to the top?
  6. U-tube with a hidden connection:  Very hard! Will the crow figure out that one of the wide tubes governs the water level in the narrow one?

In the video the crows solve every problem but behind the scenes they faltered on the U-tube test so the scientists say they flunked it.

How quickly can you solve these physics problems?  Be quick on the U-tube test or else …

This experiment was tried with New Caledonian crows, Eurasian jays, and human children.  Read all about it here in PLOS One.

My favorite quote from the Discussion is: “The results from the current U-tube experiment suggest that New Caledonian crows are comparable to Eurasian jays, but differ from human children.”   ;)

 

(video from PLOS Media on YouTube)

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