~' 
 
 
                                               Delta Duck Station 
                                               Delta, Manitoba         I

                                                 August 17,1943 
 
Dear A.L., 
 
 
       Thanks for the reprints and the references. I have not read Kalmbach's

paper but have sent for it. he used a good many Delta birds in his experimenl

 
       Thanks also for the food chains. As yet I have nothing but a box a

waste paper. You put it mildly when you said it took some figuring out. 
There are two kinds of services which I wonder If you believe about&

might be valid on a marsh arrangement. One is the type of service I am 
convinced the Kingbird gives. We cut out the willows in front of the house

for a view of the marsh and have seen a good deql of interest from the front

porch. I noticed that the pair of Marsh Hawks which nestL by the R.R.traoks

have a regular path of search which they have followed day in and day out
all 
season. It is in fact severpl paths by which they cover most of the marsh

in the region of the hatchery. The only umomammed area not covered by these

paths is a rather wide area about a kingbird's territory which is conspicuous

ly avoided. I have never seen a, Marsh Hawk in the heqrt of the Kingbird

territory and on its   lanhmamtu boundaries the hawk is always high-tailing

it away with the Kingbird after it. It is obvious that,avoiding the heart

of the Kingbird territory and harassed on its boundaries, this is the one

parcel of marsh not hunted by the Marsh Hawk, hpnce this must be . service

by the Kingbird to the species living within the boundaries of its 
territory. 
 
        The same thing works to a lesser degree with Crows. However, nesting

pairs of Crows ignore the Kingbirds, huntiro within their territorles~and

it is only transients or strangers which are sucessfully evicted. 
 
        Another type of service is a signal. When a Mlarsh Hawk comes near

the colony of Yellow-headed Blackbirds, the malles all rise in the air and

give a special note which is given only in the presence of a Hawk. This 
hawk cry is clearly recognized by Cootsam Virginia and Sors Rails ,and 
within a wide area about the blackbird colonyall Coots and Rails give their

alarm notes the moment the blackbirds cry "hawk". I do not know
whether 
they take cover, but certainly they are on the alert. Ducks, however, do
i 
not show any recognition of the blackbird's signal. The hawk cry of the 
blackbirds, incidentally, is paseed from one colony to another. When a 
hawk comes over the colony behind the stable, all the blackbirds in the 
pothole colony are antamot up in the air ready for the hawk as soon as the

stable birds give alarm, although they cannot yet see the hawk. 
 
         I think there probably are many more examples of such signal 
 service although as yet this is the most clearly defined example I have

 seen.  Ducks, of course, recognize signal movements of geese,and geese 
 recognize those of ducks; and one species of duck regognL..es many signals

 of other species. 
 
         As I told you in an earlipr letter, I was writing a manag'crrnt

 chapter for the bulletin. It has by now gotten completely out of hand, 
 that isjas far as a chapter goes. I have already more on paper than is 
 in the original Canvasback manuscript. It is pretty rough, but fits so 
 neatly together that I am very much pleased with it. Until the first of