On the basis of the Arctic's calls I looked at the 
repertoire of the common, roseate, Sandwich, Caspian and black 
terns based on my own obs supplemented by the people who know 
about them. Also a complicated correspondence with Bergman 
about the Caspian where the two le t ters"r"and"a" just about 
exhaust this species' alphabet but not its Inflection. 
Reviewing these species one can make out the following 
list of characteristics of the various calls; 
Food begging. Regular repetition of a single ^syllable . frequency 
varies from sp. to sp. Pre-feeding and pre-cop. 
Weak alarm call. Single monosyllable, often hard 
Stronger alarm call. Relatively longer than last. Give* towards 
intruders near the ne at .. 
Chatter. Rapid repition of a single^ByTlable . Accompanies 
aerial swoops and ground hostility. 
Fish call. A single polysyllabic call often occurring singly, 
but several calls may be strung together though usually 
in a rather irregular way. A bird suddenly starts 
to utter this call when he catches a fish which he 
intends to take to his mate of chick, and keeps it 
up till the fish is delivered. «*• 
Soft Call. A soft growly call consisting of the rer^tlon of a 
fairly simple phrase. The growling may go on for 
many seconds. Especially at nest relied, also sometimes 
in 1, greeting or scraping. 
Clash call. A single loud call, not metallic. Accompanies fighting 
or the lowest point of a swoop. 
One of the most interesting points in this survey of these 
calls concerns the Fish call. In the Caspian this is different 
from the ag ; gressive call and B. denies any aggressive content. 
This fits very much with my impression of the fish call on the 
Saidwich and Roseate. In the common and Arctic the fish calL 
is indistinguishable from the jiflrmsl. flftgEg-S slve call. N.B. The 
fish call of the Arctic is kyp« . 1 » uflo oall they makewwith 
a 
fish. 
Thus Caspian, Sandwich and roseate nave a fisn call wnicci is 
not commonly used in fights and when threatening use the chatter 
( - gekkering) : 
; rctic and common rarely use the chatter 
in fights but i slims nly the fish call. The black tern ^ has 
a fish call and a chatter but which is used in fights I don t 
know. These facts suugest that there has certainly been a shift 
in motivation of the calls in the different species. i/hether 
there is no aggressiorfjffi the fish call of the Sandwich etc 
I don't know but if it were as conspicuous as in tne 
Arctic it couldn't be missed. 
