From: gibsondesign at msn.com
To: ednewbold1 at yahoo.com; tweeters at u.washington.edu
Subject: RE: [Tweeters] Crow Farming: I'm a believer
Date: Thu, 10 May 2012 22:44:26 -0700





I don't know that Common Crows "farm" bird nests, but Clarks Crows do. AKA Clarks Nutcrackers - another smart corvid.

In the summer of 1981 I worked on a breeding bird survey (for Dave DeSante of the Point Reyes Bird Observatory) at 10'000 ft in the High Sierra just East of Tioga Pass. It was the fifth and last (as far as I know) year of a five year study mapping and taking data on all the breeding birds in one area of the Slate Creek Valley, where the Carnegie Institute did its famed high altitude plant studies. I spent 3 months keeping track of all the breeding birds on my 40 acre plot. There were 4 such plots if I remember right. The vegetation at 10'000 ft at that latitude was basically timberline- somewhat like Sunrise on Mt. Rainier, the plant details being a bit different of course.

Clarks Nutcrackers were well documented as "farming" as was put, or scoping out nests through the season to achieve a maximum bite-full of young birds. In my own observations on that fifth year , I found it to be true.

By the time I arrived in mid- June the Nutcrackers had all fledged - the youngsters with shorter beaks which grew to full length (or close) by mid-July. Just in time for all the other breeding birds to be eaten. Very often the scenario was that some songbird would build a nest, eggs were laid, the young hatched, and just before fledging the Nutcrackers would swoop in and eat em all! If they found them early the Nutcrackers would surveill these nests quietly all along. Waiting.

In the early part of the season hearing a bunch of raucous Nutcrackers in the valley usually meant that a predator was about or a nest was being "hit". Witnessing these "hits" was really something. First the scout Nutcracker would appear at the nest, of let's say a Yellow-rumped Warbler, and start screaming, the parent Warblers nervously flitting about. Then one after another more Nutcrackers would pile on, all screaming loudly. For the little guys I imagine it was something like being invaded by a gang of Hell's Angels - the little Warblers totally delaminating at that point as the Nutcrackers swooped in and ate all their kids. If it was early enough in the season some birds would try again with another nest. It's tough out there in birdland!

As to Holly being especially good for prickly nest protection, I have my doubts. We have a Holly here at home. I know it's invasive, but my wife's name is Holly and so it stays because she can also be extremely prickly and if I removed it.... well I would really have problems. I'm thinking that the density of the plant would be more important than prickles for Crow control, like trimming any native conifer or trim- able plant to a dense branching pattern on the outside (sort of hedging it) and leaving the base open for smaller birds to come up from underneath to nest up "inside" the shrub. Or whatever. Many plants, including natives should work as well as a dense Holly. Just sayin.

Jeff Gibson
Everett Wa

Date: Thu, 10 May 2012 12:39:06 -0700
From: ednewbold1 at yahoo.com
To: tweeters at u.washington.edu
Subject: [Tweeters] Crow Farming: I'm a believer




Hi all,



It's been a dismal year so far at Butyl Creek (the recirculating creek in our backyard here on residential Beacon Hill, Seattle) but we did have a Nashville Warbler in yesterday evening and 2 Orange-crowns just bathed with a Wilson's Warbler a minute ago.


This morning I saw an incident that further convinces me that Crows "farm" bird nests. I heard the local Robin family getting excited and calling urgently for backup, but I was still slow to look up from the computer. When I did I was surprised to see a Crow in a horizontal dive in my direction, evoking the image of a Cooper's Hawk, and headed straight for the Holly tree where the Robins have a nest. Without ever slowing down, the Crow pulled a full-sized baby out of the nest and was gone.


What's interesting about this is that about three weeks or a month ago the Robins got terribly upset and called me out. At that time I was armed with a Super-soaker and I chased a Crow away. That Crow's behavior was not really attacking, it was perched in the Holly tree peering around, and it's behavior was totally consistent with a reconnaissance mission. It left the area.


Obviously nothing here proves anything, but I see these events as consistent with the notion that Crows are locating nests, waiting for the nestlings to reach max. weight while still immobile, and then making their move. It would also explain generally that when I've witnessed Crow predation, it always seems to be of a full-size nestling.


Well, I don't expect a single person in tweeter-land to agree with me, but maybe at least I can get some sympathy for two suddenly unemployed Robins.


And two more thoughts: The Holly-tree the Robins nested in is dense, but getting less so as it ages. Are young non-native Holly trees the best (only?) hope for tree-nesting species in the urban zone? Birds clearly need armored vegetation for any hope of safety from Crows, and native vegetation doesn't seem to offer much. I would think twice before removing Holly from yards in the urban zone for environmental reasons.


The other is, I've long believed that Crows are the main reason for the loss of our formerly abundant Nighthawks. If Crows can find nests in Holly trees, how could they ever miss one on an open rooftop?




Just wondering,


Ed Newbold ednewbold1 at yahoo.com




























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