452 REPORT—1896. 
DIGEST. 
INTRODUCTION. 
In presenting this Digest of the Results obtained concerning the Migra- 
tion of Birds, as observed at Lighthouses and Lightships around the 
coasts of the British Islands, to the Committee appointed by the British 
Association for the investigation of that subject, during the years 
1880-1887 inclusive, I beg to offer an explanation regarding the lapse of 
time that has taken place between my appointment and the completion of 
the work. 
In a word, this has been entirely due to the magnitude of the under- 
taking. 
I was instructed to base the Digest upon an examination de novo 
of the whole of the information furnished to the Committee during the 
eight years of its active existence. Thus the whole of the data required 
to be reduced to order before it was available for the purposes of the 
Digest. Moreover, at the outset there presented itself for consideration 
an extremely perplexing problem, namely—How to treat or arrange such 
a vast array of facts on a systematic plan which would render them com- 
prehensive, and at the same time suited to the enquiry in all its varied 
aspects. It was not until a number of abortive attempts had been 
embarked upon that a plan was devised which met the very special 
requirements of the case. The scheme finally adopted took the form of a 
Schedule. This was designed to show graphically for each species during 
each month (1) on what Day ; (2) Coast ; (3) Station ; (4) in what Num- 
bers ; and (5) whether during the Day or Night the particular species 
was observed during the particular month and year. It is needless to 
remark that such asystematic tabulation of at least one hundred thousand 
records, culled from several thousands of forms filled in by the Light 
Keepers, in each of which species were numerous and the dates wide- 
ranging, proved to be both a long and laborious task. 
The results now presented are, for the first time, based upon the ex- 
amination of the whole of the information communicated to the Committee 
Jor all the coasts : a most necessary condition, for from such a complete 
and comprehensive examination alone could it be at all possible to obtain 
results worthy of the enquiry, and an accurate knowledge of the nature of 
the various phenomena associated with the migration of British and Irish 
birds. Indeed, it is now in our power to declare that it is quite impos- 
sible, at certain seasons, to distinguish between the widely different 
Immigratory and Emigratory movements, without due examination and 
consideration of the whole of the observations, a fact the non-realisation 
of which has been fruitful of much misconception and of many misleading 
statements in the past. 
It is manifestly impossible to conduct an enquiry into the migration 
of birds over the entire British area, or even of the smallest section of 
it, under other than imperfect conditions. A hundred circumstances are 
against such a desirable consummation—even if a party of trained orni- 
thologists were placed at each station, it would fail to secure anything like 
perfect results. 
Remembering, then, the peculiar difficulties and the drawbacks that 
beset such an investigation, and the further fact that the entire staff of 
