Jamvry 8, 194 
Professor Paul L. bringtOz 
Department of Zoolog  and htomology 
Iom State college 
Amsesl Iowa 
Dear Faul t 
I think you had better take over the paper as sole author. You can say, if
You wish, 
that I ssisted by oritieising the WS, and that Zabat and I will report later
on 
whatever comes to light through the present beatings. 
Please understand that I am not *ore or resentful over this unavoidable outcome.
If 
we could have worked together day by day, we might have gotten toether. but
the 
subject matter is just too difficult for us to do it i absenti. 
One special reason why I do not feel badly about it Is th-t I can now see
that even 
in ry last draft I did not fully grasp your present notion of the threshold
mechanism. 
One trouble is on p. 21 of your MS. It ws never clear to me that you are
here 
relegating "tradition" to a minor role, and are postuliting some
as yet undefined 
psychological state as constituting the *intolerance" mechanism. I get
mW present 
notion not from your US, but from your letter. 
The main reason why I an Fis ing off* Is that I have now become nok-deep
in courses 
and coulda't do the MS until June, and then I would ike to plunge into my
book rather 
than this MS. 
Even if I could revise your US editorially at this time, we might find ourselves

uable to agree on the "appearance of precision" to be incorporated
in the text. 
I think $our theory of threshold is plausible, Ingenious, and the best that
can be 
advanced at this time, but I do not consider it proven by the data, aad I
doubt whether 
it ever will be proven. although the banding ought to shed a little light
on a fraction 
of it: at least the tradition component. My advice (if I my offer any after
failing 
so lone to gsp the thing myself) is to assert that your theoey Is not fully

susceptible of profl that you are making certain plausible assumptions, and
are 
analyzing the area data to see if they contradict these assumptions (pp.
13-15 your MS). 
This Is a different-thing than analysing the data and deducing an inevitable
conclusion. 
I think the theory contains three assumptions 
1. Threshold is partly "food and cover" and partly an unknown psychological

state. You no longer limit your concept of this fste to "tradition"
or the 
dominance of old birds. 
2.  'Food and cover" changes only slowly for large areas, but the psychological

state my chnge quickly (year-to-year). Hence threshold may change quickly.

3. Food and cover sets the upper limit of possible thresholds, but the 
psychological state (intolerance) my depress the actual nn-emergeany 
survival below what the terrain could carry if the birds were In optium 
psychological state.