1921.] Bird-Migration by the Marking Method. 
499 
Y.—THE BLACK-HEADED GULL {Larus ridibundus Linn.); 
ANALYSIS OF RECORDS. 
The Black-headed Gull is found all the year round in the 
British Isles, and, as in the case of other sea-birds, its 
migratory movements are difficult to distinguish. During 
the course of the inquiry, 1,150 were marked, 316 of them 
as chicks in the northeast of Scotland and 294 as chicks 
in the north of England. The reappearances number 27 
in all, or 2*3 per cent. 
Of those marked as chicks in the northeast of Scotland, 
12 were recovered as follows 8 from the same or a neigh¬ 
bouring district, 2 from more southerly parts of Scotland, 
1 (Case 390) from Co. Down, Ireland, and 1 (Case 116) 
from near Bayonne, Basses-Pyrenees, Prance. 
Of birds marked as chicks in central Scotland, 4 were 
recovered as follows :—-3 from the same district or slightly 
to the south, and 1 from the extreme southwest of 
Scotland. 
Of those marked as chicks in the north of England, 
10 were recovered, all from the area of marking. 
TABLE XV. 
Seasonal Analysis of Reappearances of Black-headed Gulls 
MARKED AS CHICKS IN SCOTLAND AND THE NORTH OF ENGLAND. 
Month of 
Reappear- , 
ances *. 
1 ' 
Great Britain. 
Ireland. 
s.w. 
France. 
1 
Total. 
In or near 
area of 
marking. 
Over 100 miles 
south of place of 
marking'. 
June . 
1 
■9 _ 
1 
1 July . 
3 
jKjjjSB 
: — 
— 
3 
August . 
6 
■ 1 — 
6 
; September... 
6 
H — 1 
E91 
6 
i October. 
3 
1 
4 
November ... 
1 
— 
—■ . 
1 
December ... 
— 
1 
1 
January. 
— 
-.ESI 
1 
1 
J February ... 
1 
2 
— 
3 
Total. 
21 
3 
1 
1 
26 
G No records for March, April, or May.) 
