It's always been my understanding that finches do this to aquire grit for their digestive systems.? Yes?? No?

Rolan Nelson
Fircrest, WA
rnbuffle at yahoo.com

--- On Wed, 7/21/10, Scott Carpenter <slcarpenter at gmail.com> wrote:


From: Scott Carpenter <slcarpenter at gmail.com>
Subject: [Tweeters] Finches Eating from Road Surfaces
To: "Tweeters" <Tweeters at u.washington.edu>
Date: Wednesday, July 21, 2010, 2:38 PM


Although not in Washington, I recently came across a mixed flock of Pine Grosbeaks, Pine Siskins, and Cassin's Finches eating something from the surface of a dirt/gravel road in a national forest.? The location was in Routt County, Colorado, along CR 38 between the town of Steamboat Springs and Buffalo Pass in the Zirkel Wilderness.? The location was much closer to Buffalo Pass than Steamboat Springs.

My guess, though I don't know for sure, is that this road is not salted during winter, leading me to believe these birds were eating either dirt or rocks.? They were definitely ingesting dirt and rocks, though perhaps their goal was to ingest something attached to the dirt and rocks.? My guess that the road is not salted is based on the fact that the road is in a national forest, it has gates (and signs) for closing it during the winter, it is in a high elevation area that receives a large amount of snowfall, and the generally poor condition of the road (one of the worst I've been on, with big rocks, craters, etc.).? Of course, I could be wrong.? Along the lines of salt consumption, perhaps the birds are after minerals delivered by the snow melt?? Or perhaps they are simply after grit to aid in digestion of seeds?

Photos of this, including the road surface, can be seen at:? http://www.westerngrebe.com/PineGrosbeak/

Scott Carpenter
Portland, Oregon


On Mon, Jul 19, 2010 at 9:39 AM, Kelly McAllister <mcallisters4 at comcast.net> wrote:




I've seen flocks of Pine Siskins and Red Crossbills on US 2 near Steven's Pass, during winter. I've also seen what I thought was unusual bevavior of "winter finches" under bridges. A pair of Evening Grosbeaks were totally absorbed in eating the dirt under the Indian Creek bridge, US 12, near Rimrock, a couple of summers ago. I approached very close and they paid no mind to me at all. Also on US 12, this past spring, a flock of Red Crossbills gathered under the Cora bridge on the Cowlitz River and pecked around among the rocks under the bridge. I think that Richard Carlson is probably correct that these attractions to particular patches of what appears to be gravel or bare dirt is salt-seeking behavior. I wonder if the roadside patches that Christy saw the birds frequenting might have been some kind of stockpile locations for gravel mixed with salt or maybe they were places where run-off water, laden with salt, pooled up and evaporated. There are some
interesting dynamics here that I'd like to better understand.
?
Kelly McAllister
Olympia, Washington
?






-----Inline Attachment Follows-----


_______________________________________________
Tweeters mailing list
Tweeters at u.washington.edu
http://mailman2.u.washington.edu/mailman/listinfo/tweeters