Xil INTRODUCTION. 
allowed, accidentally or designedly (vide p. 107), to escape ; 
and there are many birds, for example the Picide, whose 
importation in cages rarely, if ever, occurs. - 
Those who find it difficult to believe in the appearance of 
Picus martius 11 England after so short a journey as the 
passage of the German Ocean, must feel still greater difficulty 
in admitting the claims of any American species of Picus to 
a place in the British list. And yet there are records, ap- 
parently trustworthy, of the capture of no less than three 
different species of this genus in England (vide pp. 122, 123), 
all of which are inhabitants of the New World. 
In attempting to ascertain the claims of such species as 
these to be admitted in a list of British birds, there are two 
difficulties which constantly beset the conscientious historian 
who meets with records of their capture here. These are :— 
first, the published communications of over-zealous collectors, 
who, anxious to record their possession of a species which 
they deem rare, hasten to give it a name before they have 
satisfactorily identified it; and, secondly, the results of 
the many attempts which unscrupulous dealers make (un- 
fortunately too often with success) to palm off foreign species 
upon unwary collectors, with the assurance that they have 
been killed in some part or other of the British Islands. 
There can be little doubt that many of such records, to which 
of necessity reference has been made in the second part of 
this work, are, for the reasons above mentioned, worthless, 
although perhaps originally published in perfect good faith by 
the owners of the specimens. It has been practically im- 
possible, through lapse of time, death of parties, or ignorance 
of their addresses, to test the value of every reported oc- 
currence of rare visitants; but yet, whenever this was 
possible, it has been done, and oftentimes with the best 
results. In many cases where it could not be effected, the 
