[birding] Acorn frenzy

[Lisa Millbank]

Hi Joel & everyone,
I think those little grubs are acorn weevil larvae (Curculio sp.).  After shelling and quartering lots of acorns for food, we've found that the little bugs don't hollow out the entire acorn.  They eat a small path through the cotyledons of the acorn and usually don't damage the other parts of the embryo.  I have a feeling that a big, otherwise healthy acorn can sometimes still germinate despite the damage.
Someone did research on Blue Jays to see if they had a preference for infested acorns or not.  The idea was that the protein-binding properties of the tannins in acorns aren't very good for Blue Jays.  They do very poorly on a diet of pure acorns.  It was thought that eating weevil grubs gave them enough surplus protein to cope with the effects of tannins in their diet, so they should choose acorns with grubs over intact ones.  But the experiment showed that the Blue Jays preferred bugless acorns.
Scrub-jays seem pretty astute about which acorn they want to take.  We sometimes put out a pile of acorns for the jays who visit our apartment.  Small or damaged acorns are always the last to be taken, while all the nice fat ones will be taken nonstop until they are gone.  
I also wonder that if they detect the presence of a larva in an acorn they cache, then they might remember to eat that one soon, as it will be more susceptible to decay.  Someone else experimented with Western Scrub-jays and discovered that they not only have exceptional spatial memory, but that they remember the perishability and time of storage of each of the thousands of food items they bury, and selectively retrieve the caches that are the most likely to spoil.  It wouldn't surprise me at all if they remember to save particularly nice, intact acorns for later because they won't go bad so quickly.
Lisa
www.neighborhood-naturalist.com      
 
----- Original Message ----- 
From: "Joel Geier" <joel.geier at peak.org>
To: <lisaaves at peak.org>
Cc: <list at midvalleybirding.org>
Sent: Thursday, October 01, 2009 8:50 PM
Subject: Re: [birding] Acorn frenzy & more Lewis's Woodpeckers


> Hi Lisa & All,
> 
> There seems to be a good crop of acorns again this year! Not quite as
> big as the incredible mast crop a couple of years ago (or was it last
> year?), but Coffin Butte has quite a few.
> 
> I picked up a handful (14 acorns) thinking to augment our population of
> seedling oaks, since our sheep managed to get to some of the ones that
> we had going due to inadequate fencing. The acorns have been sitting on
> my desk for a few days, and so far I've found 3 acorn grubs that bored
> their way out and started crawling around my desk. So I guess that for
> every few acorns that those scrub-jays store, one will turn out hollow
> due to grubs. Or I wonder if they can detect the acorns with grubs?
> 
> Some other interesting news: A place in SW Marion County (not publicly
> accessible) had an amazing 15 LEWIS'S WOODPECKERS today. There seems to
> be a major invasion going on this fall.
> 
> Happy birding,
> Joel
> 
> 
> On Thu, 2009-10-01 at 11:22 -0700, lisaaves at peak.org wrote:
>> I have to smile whenever I see a Western Scrub-jay flying overhead these
>> days; most of the time it seems that they're carrying an acorn treasure to
>> bury somewhere, or they're purposefully heading off to find another one. 
>> Jays with oaks in their breeding territories are having to tolerate the
>> invasion of their neighbors on constant acorn-collection sorties.  It
>> seems like the jays who travel to adjoining territories to find acorns
>> usually carry them back to their home territories to bury.
>> Mr. Pill at work seemed to molt later than most jays, so he still has a
>> mangy-looking head.  His shabby plumage, odd sideways skipping gait, and
>> his mean temper make him quite a spectacle these days as he fruitlessly
>> tries to chase away the other jays in his territory, who are helping
>> themselves to his acorns.  He also must cram two peanuts into his bill
>> each time I feed him, no matter how long it takes to get both of them to
>> fit.  Today I had an all time high of 8 jays getting peanuts from me, soon
>> to return to gathering acorns from the nearby red oaks.  Only 1 crow
>> showed up.  Maybe that many screaming, swooping, rascally jays are just
>> too much, even for a crow!
>> Peanut Queen and her mate at Starker Park also seem a little stressed
>> about all the neighbor jays visiting their territory as they snap up
>> acorns from the red oaks planted around the duck pond.
>> At the herb garden at work, an Anna's Hummingbird was getting nectar from
>> red zinnias.  I enjoyed it when she hovered a couple of feet in front of
>> me and inspected me from various angles, giving her little "chip" calls,
>> before zooming away.
>> Lisa
>> www.neighborhood-naturalist.com
>> 
>> 
>> 
>> 
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