Re: Herbivore protection

[John Bois <jbois@umd5.umd.edu>]

On Tue, 10 Jun 1997, Stanley Friesen wrote:
> For mass nesting there must be sufficient suitable nesting spots in the
> colony area.  And there must be sufficient forage available in the vicinity
> of the nesting colony to feed both the adults *and* the rapidly growing
> chicks.

Having now read something I can answer some of these questions.  Yes,
their favorite food was beech nut, and acorns (in breeding season, at
least).  The Norteastern forests were ideal in this respect.  Plenty of
good nesting spots, too. 

> It is quite conceivable that the above factors far outweighed predator
> density as choice factors.

This may be true.  A.W. Schorger, in _The Passenger Pigeon: Natural
History something-or-other, says they had very little predation.  They
were attacked on the way to the nesting sites by hawks (including
accipiters as you said), falcons, eagles.  Mustelids (ferrets) took some
at the sites.  When they settled on a farm fied to eat the grain the birds
left a sentry and if a predator bird approached they panicked.  In the
colony, though, it was difficult to panick them.  They sought company.
Their colonies were usually rectangular in shape and had very sharp
boundaries.  Birds at the boundary would ignore a fully fruited tree even
if it were right next to the colony's boundary.  A falcon chasing a
passenger pigeon was seen herding it away from the trees into the open
where it was then successful in killing the pigeon.  So the birds
definitely felt secure in the trees and with good reason.  However, they
totally swamped the local predators and suffered only negligible
predation.  And, I am sure, the few predators that struck this pigeon
ElDorado were utterly satiated.

> It is also possible that the historically
> observed nesting sites were maintained due to what amounts to tradition.
> That is they were chosen *long* ago for reasons now lost in history, and
> the condition during historical times was irrelevant to the choice.

Interestingly, and probably unlike duck-bills, they did not have site
fidelity.  A scout searches the location and the next day or so the flock
alights.  The authors confesses he is mystified at the parameters of this
decision because often the colony is _not_ in the prime parts of the
forest (forage wise).