60 GEOGRAPHICAL DISTRIBUTION 



The greatest difficulty which presents itself, in attempting to 

 estimate the number of visitors to our Islands, is to be found in 

 the vagueness of the records of their supposed visits. These 

 records display, for the most part, a lamentable want of know- 

 ledge of the nature and value of evidence. The mere statement 

 that a certain bird was shot at a certain place on a certain day is 

 not enough. The characters relied upon for the determination of 

 the species should in all cases be stated. The condition of the 

 plumage and the appearance of the feet should be noted, and any 

 peculiarity of habit which might possibly throw any light upon 

 the chances of the bird having escaped from confinement ought to 

 be recorded. Every scrap of evidence to prove that the example 

 was actually procured in this country in an apparently wild state, 

 and was examined in the flesh by absolutely trustworthy witnesses, 

 is of the greatest interest and scientific value. 



In consequence of the absence in so many cases of this all- 

 important evidence, too many records have to be accepted or 

 rejected on the most unsatisfactory ground the supposed proba- 

 bility or improbability of the occurrence of the species recorded. 



It seems to be generally admitted that birds which are only 

 seen and not procured, however competent the observer, must 

 be entirely excluded. The maxim of the " Old Bushman "that 

 what is hit is history, but what is missed is mystery, must be rigidly 

 enforced. Of birds that have only once been recorded as British 

 the balance of probabilities must be weighed as best it may. The 

 fact that the Siberian Thrush (Geocichla sibirica) has occurred at 

 ten or more places in Europe increases the probability that the 

 English record is a correct one. The circumstance that several 

 species of Gallinules (Porphyrio) are kept in aviaries and on orna- 

 mental waters very much weakens the evidence in favour of any 

 of them having visited the country in a wild state. Many examples 

 of the Virginian Colin (Ortyx virginianus) and of the Andalusian 

 Hemipode (Tumix sylratica) have been turned out in the attempt 

 to naturalise them in this country, and it is only reasonable to 

 suppose that records of the capture of either of these species pro- 

 bably refer to imported birds or their descendants. 



Some species are rejected on the ground of the inherent impro- 

 bability of their ever having voluntarily paid a visit to our Islands, 

 such as the Gold-vented Bulbul (Pycnonotus capensis), a species 

 supposed to be absolutely confined to the extreme south of Africa. 

 There can be no doubt that migratory birds are much more likely 



