24 ILLINOIS AUDUBON’ BULVo 
GULL AND JAEGER IDENTIFICATIONS 
by CLIVE E. GOODWIN 
(Reprinted from the ONTARIO ORNITHOLOGICAL RECORDS COMMITTEE 
REPORT OF 1974 published in the ‘‘Ontario Field Biologist”; these same 
species cause idetification difficulties in Illinois. Another species which 
should be included is the Glaucous Gull, Larus hyperboreus—Editor) 
CONTENTIOUS RECORDS 
The issue of jaeger and gull identification was reviewed in some detail 
over the year, to provide guidance in dealing with the reports of these 
species. 
Procedures used were identical to those used for contentious species 
in the 1973 report. A literature review gathered together as far as possible 
the significant published material on the species in question, and _ this 
material was then compared to actual specimens in the Royal Ontario 
Museum, The mode of comparison was to attempt to identify skins without 
reference to their labels, followed by a careful examination of the various 
corresponding plumages of the different species. 
The two comparison charts (TABLES 1 and 2) present the species 
reviewed in each group. The skua (Catharacta skua) has been added to the 
jaeger group for completeness, although it is not to be expected as the 
pelagics appearing regularly on the Great Lakes continue to be species 
breeding in Hudson Bay (which is not to say that is necessarily the source 
of these birds). 
On jaegers, it was agreed that experienced observers should be able to 
identify adult birds satisfactorily. Immatures presented much more diffi- 
culty, and concensus among the authors consulted and confirmed by the 
review of skins, was that immature Parasitic and Long-tailed Jaegers cannot 
be separated with certainty in the field. Pomarines in hand were distinc- 
tively different from immatures of the other two species, but the features 
are of questionable value in the field, although the bird’s heavy bill, robust 
size and extensive white in the wing should provide a basis for identifica- 
tion if well seen. 
