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Re: Absent Jays

From:

Gail Mackiernan

Reply-To:

Maryland Birds & Birding

Date:

Tue, 15 Mar 2005 17:47:46 -0500

Quite a few years ago, I heard a paper at the annual AAAS meeting which
related the phenomenon of "mast years" (years in which oaks and other
nut-bearing trees produce exceptional quantities of seed) to the Passenger
Pigeon. The premise was that this phenomenon was, as John notes, an
adaptation to avoid complete consumption of the seed production by a
predator -- in this case, the Passenger Pigeon. Data from contemporary
sources indicated that mast years occurred in synchrony across all the
nut-bearing species and across large regions of the country (which at the
time, would have also included the American Chestnut, an important component
of eastern forests until its near-elimination in the 1920s and 30s.) Mast
years were also important to humans, as cattle and hogs were typically
fattened in the autumn on forest mast -- thus the availability of
contemporary accounts of "good" and "bad" years.

However, after the Passenger Pigeon became extinct, although "mast years"
continue to occur, they have ceased to be synchronous species-wise and over
vast regions. The author concluded that the pigeon was the major "forcing
factor" for the evolution of this phenomenon, and after its demise, the
timing of mast years has become irregular. There is no longer a
continent-ranging, superabundant seed predator in the picture.

I have never run into any other papers on this subject so not sure if this
hypothesis withstood the test of time, but it was certainly an interesting
presentation.

Gail Mackiernan
Colesville, MD

on 03/15/2005 4:56 PM, John McKitterick at  wrote:

> Oaks and some other trees are known to have considerable fluctations in the
> numbers of acorns that they produce. What's more, all of the trees in a given
> area will fluctuate together. Obviously, birds that rely on acorns will leave
> an area that is not producing acorns to go to one that is. The Passenger
> Pigeon was such a bird, and would flock in tremendous numbers to those areas
> that were producing lots of acorn mast.
> 
> I would guess that the Eastern Shore had a good acorn crop this year, while
> here in Howard County there was no acorn crop to speak of. I don't believe
> that these fluctuations are weather related, but I would guess that it is a
> form of adaptation to reduce the predation of the acorn crop.
> 
> Good observation by Phil....
> 
> --John McKitterick
> Columbia, MD
> jbmck-at-comcast.net
>