Bonaparte* s, June 17, 1955, II. 
Circling . Essentially like Ring-bill in physical form. Perhaps 
somewhat more erratic. 
Erratic Flight . Reaction to human disturbance. Just like that 
of the Black-headed Gull, but even more extreme. May possibly occur 
in intra-specific encounters; but a little difficult to tell exactly 
what are the releasing and orientating stimuli in some of the doubtful 
cases. 
Pursuit Flight Pe rformance . I have only seen the Pursuer's 
patterns. “Mostly chasing Common Terns. Have had a glimpse or two 
of intra- specific chases. 
Swoop . With Pursuit Flights. Just like the diagonal Swoops of 
the Blaek-headed Gull and Franklin's Gull. 
" Flying" Soar . Follows Swoops. Like ordinary Soar; but accomplished 
by beating wings. 
Soar . Possibly occurs during some Pursuit or Erratic Flights; but 
must be rare (at best) and relatively inconspicuous. 
The following incident may be significants 
One bird, disturbed by me, flies up. Into loose flock of Black and 
Common Terns*. Flies round and about, up and down. Occasional Swoops 
and "Flying" Soars. Occasional sudden, extreme, downward plunges; with 
wings half- folded, motionless. Followed by flying up again. None of 
these Scoops or plunges were obviously directed at a particular object 
or animal; but they may actually have been so in reality. The whole 
performance was perhaps slightly reminiscent of some Erratic Flights 
or hawking for insects; but the bird apparently gave Long Call Notes 
in flight, and "looked” rather aggressive. 
mm mm mm «s «g» r.s» ’’.an gJ sa-sr? -.-2 • s* r-j * «** <d» ssm ss» 
Additions, as a result of further observations in the evening. 
A large flock was assembled, including perhaps 60 birds, and also includ- 
ing a few adults in complete nuptial plumage. 
There is definitely a complete Long Call in the air. Sounds Just 
like the complete Long Call on the ground or water. Given by rapidly 
flying birds, beating their wings very rapidly, (this flight, surprisingly 
enough, is not particularly buoyant or tern-like in fact, I haven t 
yet seen any tern- like flight under any circumstances in this species;. 
Accompanied by a very .marked Oblique Posture, much more marked than any- 
thing in Franklin's G, 11 or anything I remember in the Bxack-headed Gull. 
The posture is almost reminiscent of the Little Gull s aerial Vertical 
posture. No sign of any aerial Forward posture. (All the observed 
aerial L 0 ng Calls were given by immatures). 
An adult bird was heard to give definite Alarm Calls, obvio 118 -*-^ 
