592 BRITISH GENERAL MIGRATORY MOVEMENTS 



IX. IRREGULAR VISITORS 



Irregular visitors do not occur on our shores at any particular season, for their movements 

 are influenced by various factors. Some of these movements are recurrent at long intervals, 

 and partake of the nature of irruptions or invasions. The sporadic invasion of our islands, and 

 indeed of the whole of Western Europe, by hordes of Pallas's sandgrouse is probably the most 

 extraordinary of these irruptions; excessive fecundity of the species in its eastern breeding 

 area appears to occasion this attempt to colonise a wider field an attempt which invariably 

 ends in failure. The extraordinary visitation in certain years of crossbills, waxwings, even 

 bramblings and siskins, as well as marked occurrence in numbers of the rudcly-shelduck, are 

 also suggestive of sporadic invasion. 



Amongst these irregular visitors must be classed a large number of birds which have 

 occurred on one or more occasions, but which do not arrive with sufficient regularity to be 

 included in the list of birds of passage. Mr. Eagle Clarke lists 53 from Continental Europe, 

 17 from Asia, 2 from Africa, 29 from North America, 9 from the Arctic regions, and 

 10 from Southern Oceans. 



These numbers may be increased or decreased according to the judgment of any 

 ornithologist, for there are many birds which were treated as casuals a few years ago, but are 

 now known to be regular visitors. The barred-warbler is a good example. Prior to 1879 it 

 was unknown in Britain. Twenty years later Saunders enumerated twelve occurrences, and by 

 the beginning of 1912 the number had risen to thirty-two. Since the publication of the Hand- 

 List, the preface of which is dated April 1912, no fewer than twenty have been observed. Is it 

 to be considered as a lost or accidental wanderer any longer? Has it not been overlooked 

 in the past ? 



The remarkable work accomplished by Mr. Eagle Clarke and his assistants at Fair Island, 

 the Flannans, St. Kilda, and elsewhere, and by the Misses Rintoul and Baxter at the Isle of 

 May, has added many unexpected recurrences of these " vagrants," and it is no idle guess to 

 state that far more must have passed unnoticed. In 1899 Saunders said that the blueheaded- 

 wagtail " can hardly be considered as more than an irregular visitor on migration " ; now it is 

 classed with regular summer visitors and birds of passage. Blyth's reed-warbler and the 

 Scandinavian chiffchaff were included in the Hand-List (April 1912) on the strength of single 

 occurrences at Fair Island and the Isle of Wight. Fair Island has since produced four or five 

 of the former, one has occurred at Holy Island and one in Holderness, while Mr. Eagle Clarke 

 says of the chiffchaff that " it appears to be a regular migrant " at Fair Island, and several have 

 occurred on the Isle of May. 



The more systematically that ornithologists work, the more of these so-called " vagrants " 

 or " gypsy-migrants " will have to be included as regular birds of passage. This remark applies 

 most to those which reach us from Continental Europe and North Asia, for it is reasonable to 

 recognise the birds whose normal range extends no farther than South or even Central Europe 

 and Africa as lost wanderers when they appear in Britain. The subalpine warblers which 

 travelled from Southern Europe to St. Kilda and Fair Island are instances of birds wandering, 

 hopelessly lost, farther and farther from their base, and an even more striking instance is that 

 of the masked-shrike, which, on leaving winter quarters in Africa for its Asiatic summer home, 

 found its way to the Kentish shore. 



Mr. Eagle Clarke says of the American visitors, that those " which find their way to our 

 shores unaided are birds which have a high northern summer range, and they doubtless reach 

 us after having travelled by way of Greenland, Iceland, and the Faeroes, not by an impossible 

 passage across the open Atlantic. In this way their voyages are not more wonderful than those 

 annually performed by the wheatear, redwing, whimbrel, and others along similar lines of 



