Bonaparte* s, June 18, 1955, I. 
Had fewer opportunities to watch the birds today. 
Must add a few words about the single adult bird, in complete 
nuptial plumage, mentioned yesterday. 
Almost certain this was pairing behavior. Not only did the bird do 
”G-.C”s toward all nearby flying birds, but it also made little circular 
flights in the interim (usually not very aggressive, no more than Long 
Call Notes) , and occasionally attacked nearby birds on the ground, (I 
couldn’t watch this very well, but the whole procedure was very reminiscent 
of territorial defense). A post, I suppose, is exactly what one would 
expect as a station in a tree-nesting gull. The displaying bird, unfort- 
unately, got very little response from the flying birds. So, the adult 
would occasionally fly over to a nearby first-year bird on the ground, 
and would then apparently attempt an ”M. C. " • I definitely saw the adult 
do Oblique - Forward - Upright and Head-flagging - Head-tossing in these 
circumstances. Again, these didn’t seem to get much in the way of a 
response. 
Today, however, the adult may have succeeded partially. At least, 
one of the nearby first-year birds goes into a pronounced Upright, facing 
away from the adult, whenever the adult flies by. 
I S i I I . 
I am beginning to believe that this adult bird must be a female. 
It is not very large, and it is not nearly as aggressive as some of the 
first-year birds. In addition, the fact that the adult did Head-tossing 
during its ”M.C.” is perhaps suggestive. 
All the aerial hostile patterns I have observed in this adult seem 
to be essentially the same, perhaps identical, with those of the first-year 
birds. I have heard first-year birds give Alarm Calls exactly like those 
of the adult cited yesterday. I have heard the adult give a long series 
of Long Call Notes exactly like those of the first-year birds. I have 
also observed a Swoop-” Flying” Soar performance by the adult exactly like 
the corresponding performances by first-year birds. I can’t detect any 
difference between the voice of the adult and those of the first-year 
birds, (Unfortunately, however, I have not yet observed a complete aerial 
Long Call and aerial Oblique Posture by the adult.) 
More about glides, in both first-year birds and the adult. Both 
glide frequently in ordinary flight. Obviously quite unritualized. 
The first-year birds also glide very frequently during their Erratic 
Flights. (I have never, incidentally, seen a really good Erratic Flight 
by the adult) • These glides during Erratic Flights may be either upward 
or downward. Sometimes quite prolonged — relatively. They do not 
appear to be ritualized either; but they can be easily interpreted as 
ambivalent hostile activities. They are thus, in all probability, strictly 
comparable to those of the Ring-bill; but they seem to be confined to a 
rather different situation. 
