Wednesday, October 6, 2010

The Crow in the Walnut Tree




In our nut tree orchard, I might as well put up a sign for the crows: "Will This Be For Dine-In or Take-Out?"

That seems to be the only question on the minds of the crows as they swooped in for all the ripening almonds last year. I knew a slim harvest awaited as I approached the tree, only to see about a dozen crows take flight, carrying those tasty morsels in their beaks.

Crows, although quite clever, will wait until nearly all of the hulls have split, exposing the shell to their Dremel-like beaks. Then, their drilling through the almond shells begins in earnest to harvest the nut meat.

This year, we got smarter. After checking "Harvesting and Storing Your Home Orchard's Nut Crop" from the University of California Division of Agriculture and Natural Resources, we found out that the best time to thwart the birds is to begin harvesting almonds when 75% of the hulls have begun to split open (usually in late August here). As a result the 2010 almond crop was saved by a timely harvest.

 There are several strategies to thwart marauding birds at harvest time: netting, red and silver mylar flash tape (which resembles flames to them) and noisemakers such as bird bombs, shell crackers, gas cannons and electronic distress calls. 

crow
Clever Crow
The effectiveness of alternating flash tape and noisemakers, though, is quite limited against clever crows (I'm pretty sure there are no stupid crows). 

 University studies have shown crows will return to the trees and tolerate those sound and vision deterrents within a few hours. Think of it as Dinner Show entertainment.

And this Remington euphemism from the University of California on crow control: "However, given their abundance and damaging nature, they can be removed by landowners, tenants, or persons authorized by landowners or tenants when damaging crops."

But that UC Integrated Pest Management information on bird control advises: "Where permissible, occasionally shooting at a few birds will increase effectiveness of your noisemaking techniques, because birds will begin associating loud noises with the real hazards of firearms. However, shooting is not permissible in most urban or residential areas."
Oh, yeah...there is that little problem.

Bird netting is the best preventative measure, but can be a chore on trees of any height above eight feet. And, if you don't secure the netting to the ground, well...I have seen scrub jays hop beneath loose netting to get to ripening cherries. 

Although the almond problem was solved, we forgot that crows have a varied diet. Yesterday, while moving mulch, I noticed a single crow flying away from the WALNUT tree. My dread turned to relief quickly. Good news, I thought: there was no nut in his beak! 

 

But I went up to the tree, and saw these, still dangling on the branches:
The dine-in crow was back!





A quick check of that UC harvest information on walnuts was in order: "Begin harvesting walnuts when most (85% or more) of the nuts can easily be removed from the tree, and when the hulls can readily be removed from all or nearly all (90%) of the harvested nuts."

 
Sure enough, the green hulls on many of the walnuts were beginning to crack, exposing the shells.

Guess what we did that evening?



Apparently, the problem of crows swooping in for nuts is a worldwide issue. Here, Danish instrumental folk band Basco spreads the warning.

2 comments:

  1. So, your nut harvesting schedule is now pretty much dictated by crows, eh?

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  2. Bird Gard makes an excellent bird repeller- the University of Arizona just finished a field trial

    ReplyDelete