Posts tagged “biology

Raven yanks another raven’s tail

The average adult raven is about 2.5 pounds and it’s hard to tell adults from juveniles.  The below video shows a power struggle between ravens at a food source.  At the very beginning you can see a raven on the far left grab another raven’s tail feathers with his beak and pull him or her away from the food.  Another seems to join in.  (By the way, if the video is blurry find the settings in the bottom right hand corner of the player and change it to a higher resolution.  Youtube automatically chooses a low setting so it will download faster.)

After reading Ravens in Winter, a book by Bernd Heinrich, I’m inclined to believe that the commotion going on in the video has to do with a power struggle (to gain access to the food) between the juvenile birds and the adults.  According to Heinrich, adults are usually silent at carcasses (dead animals in the wild), and juveniles are very noisy.  The juveniles “yell” at kills and make a commotion, possibly to attract more juveniles to the kill, in order to compete with the adults and gain access to the food.

Heinrich “proves” through observation and careful note-taking that ravens actively recruit other ravens to food piles.  He speculates, after studying raven behavior for many years, that this recruitment is not necessarily altruistic, or done in order to get the favor back some day.  Instead, it is probably related more to “gaining or maintaining access to the food than to sharing the wealth.”

Juveniles actively recruit, in order to overwhelm by sheer numbers, the adults at the carcass, so that the adults will give up defending the carcass, which they do when they are just too outnumbered.

So if we can extend this power struggle at carcasses in the field to city food (trash) then it’s possible the squawking raven in the video, the one being pulled from the food by his or her tail feathers, is likely a juvenile, being bossed around by the adults, who are not as vocal.

I strongly encourage any bird lover to read Ravens in Winter.  This bird that I see nearly every day of my life is actually quite mysterious and Heinrich helps us understand their possible and likely motivations.

Thanks for reading!  Happy New Year!

 


Black-Capped Chickadee Beak Deformity

Chickadee with beak deformityI made this little animation to show how this poor chickadee was being bothered by its beak deformity.  Every so often it would rub its beak against the edge of the bird feeder like this.  It appeared relatively healthy so it must have been able to eat satisfactorily, but apparently this deformity causes it to be obsessive about trying to scrape off the excess beak.


Bird Congregation

I don’t think this is a very common sight on the coastal plains of northern Alaska (or anywhere?), but as my husband drove in to Prudhoe Bay last spring, he spied this unusually large gathering of various birds.

Raven, Rough-Legged HawkThe rough-legged hawk and raven seem to be acting as sentries over the vast flocks, but they are watching for sinister purposes.

Rough-legged HawkYes, watching carefully.

Rough-legged hawk eating a duckSure enough,  a hawk has gotten herself a meal.

Rough-legged hawk But really, how can you blame her?

Short-eared OwlA short-eared owl perches nearby.

Kind of hard to believe that little twig can hold him up.  He must be all fluff.

And life goes on….


Butterfly Exits Cocoon

I imagine that most people who like birds don’t mind butterflies, so here’s a slideshow I created from photos taken last summer of a butterfly leaving a cocoon.  For over a week I kept the camera and its time lapse device set up outside, through heat and rain, waiting until it broke out of its temporary home… then the actual event lasted only a few minutes!  And because of memory card limitations I could only set the camera to take a photo every 30 seconds – I wish it could’ve been a shorter interval – but I’m still pleased with the few shots I got.

I don’t know the specific name of this butterfly but I’ve definitely seen it before.

Butterfly Leaving Cocoon 1Butterfly Leaving Cocoon 2

Butterfly Leaving Cocooon 3

Butterfly Leaving Cocoon 4

After the butterfly left the cocoon it crawled into some potato plant leaves and you can see that it dripped a dark fluid that looks like blood (but of course isn’t).  Apparently it’s a waste product that doesn’t come from their wings as I had first assumed but from their abdomen, being released after chrysalis, the cocoon stage.

ButterflyThe butterfly never opened its wings for me so I didn’t get that photo.  And I wish I knew the name of this butterfly!  Please comment if you have any idea.  Thanks and I hope everyone is having a terrific summer!


Redpoll Baby (and it just stopped snowing!)

Redpoll Baby

I’m happy to say my husband caught the birding bug!  He took this photo of a juvenile redpoll.  I would even go as far as calling it a baby redpoll.  It’s hard to tell how tiny it is, but he said just a couple inches, really small.  The short tail feathers probably enhance the tiny effect.

We’re a bit surprised that there are fledged redpolls this early in the spring.  It stopped snowing less than 2 weeks ago!  And now it’s 70 degrees, go figure.  Either way, my husband said this little guy flew away,barely, so maybe he or she will have a fighting chance.


Redpoll: Adapted to Gorging

Common Redpoll - Fairbanks, Alaska

These redpolls, and many more, are coming to our feeder lately in droves.   I’ve started putting seed out one or two times a day instead of letting them gorge themselves at the feeder nonstop.  I don’t want to test it out but I would be willing to bet they could empty the  entire contents of the feeder in only one day. (It’s on the small side but can still fit at least a quart jar’s worth of sunflower hearts.)

It’s unbelievable how much they can eat.  My guess as to how many birds visit the feeder per day is perhaps 30 to 40, though it could be upwards of 100 or more stopping by once a day (or less often).

Actually, they aren’t eating most of the seed.  Apparently they store it in their “esophageal diverticulum” and regurgitate it later to eat in peace.

Redpoll - Fairbanks, Alaska

These two”on-alert” fine fellows might actually be females (lack of red on their chests).

Once late May and June arrive, the birds practically disappear, so even if they are acting like little piggies at the trough right now, we still enjoy them!


“Planned Pigeonhood” in Waikiki

Pigeons in WaikikiIf you’ve been fortunate enough to visit the beautiful island of Hawaii you’ve probably visited Honolulu.  And if you’ve visited Honolulu that means you’ve probably been to Waikiki.  And if you’ve been to Waikiki that means you’ve seen the pigeons (a.k.a. rock doves).

Lovely birds, as special as any living creature, but not very popular with the tourists.

Hawaii is a common destination for Alaskans in the winter.  With an almost total lack of sunshine from November to February we pledge to ourselves that this winter we are getting out!  Hopefully it happens.  And there is nary a more direct route to full-on sunshine then the quick five or so hours from Anchorage to Honolulu.

Pigeon missing footThe pigeon on the very left is looking pretty mangy (click on the photo to see it larger).  There are so many pigeons in Waikiki, with no natural predators anywhere in sight, that they over breed and become a danger to themselves and people.  The photo on the right shows another pigeon from Waikiki, this one missing a foot and walking around a restaurant hunting for food scraps and somehow managing to avoid being clobbered.

So when I saw this posting by the Human Society about OvoControl, a contraceptive-laced food that property owners can feed pigeons, I was thrilled.  It describes how the manager of The International Marketplace, one of the most popular tourist destinations in Waikiki, chose to take a chance on the product and saw a 60% reduction in pigeons after 12 months. (It costs $9 a day to treat feed/treat 100 pigeons.)

Talk about an ideal non-violent and humane solution!  Maybe this will catch on in communities that are fed up with the overpopulation of this city-loving bird.