Bonaparte's, June 19, 1955, I. 
Correction about the adult bird previously mentioned. Apparently 
a male. Attempted a forced copulation with one of the first-year birds. 
Just like Black-headed Gull. Copulation Call like that of the Black-headed 
Gull, except for the characteristic buz>z.y twang. 
This adult continued its usual pairing behavior. Tonight, however, 
it did several diagonal Swoops and Soars (at Black Tern) during its little 
circular flights. These Swoops and Soars were exactly like those of the 
Black-heade d Gull . in physical form. Couldn't hear accompanying call 
very well, but I think it was a "Plaintive Charge Call" (i.e. long-drawn 
screaming Long Call Notes) during the Swoop. 
Still haven't seen adult give aerial Long Call in Oblique. 
When I frighten a group of birds, they fly up, circle, silently. 
This can certainly be classed as a Silent Panic. 
- 
Watched an Erratic Flight performance this morning, involving two 
first— year Bonaparte's Gulls and one Common Tern, It was noticeable that 
these "Erratic Flights" of the gulls included definite Swoops and "Flying 
Soars , and that the Swoops were definitely directed, either toward the 
other gull or toward the tern. This was definitely a relatively aggressive 
performance. 
A few additional remarks about "Gakkering" . Often given by bird 
on post (first-year bird) when a flying bird tries to dislodge it. 
Characteristic sequence is "Gakkering" (in semi-U or semi— 0 posture, very 
well orientated, neck sometimes twisted, wings sometimes raised anchor 
spread) - Oblique - Forward. The "Gakkering Call" itself is harsh, 
rapid, and rhythmic. Very much like The Forward Call part of the Long 
Call. Possibly louder??? The rhythm of the whole usual performance can 
be indicated by the following diagram* 
There seems to be a Landing Call. Given by both the adult and the 
first-year birds. Relatively rare, (as one might expect in the circum- 
stances, as the birds either land far apart or fight over a small post). 
Can't say much about it. A series of Long Call Notes, getting successively 
shorter and deeper in pitch, I think. Probably has fewer notes than the 
Landing Calls of some other species. 
