The Zoologist — August, 1874. 4101 



date on which it appears is very uncertain ; another bird is stated 

 to appear with regularity. Again, we say, one bird comes eight 

 or ten days after another, and so on. Let us first consider the 

 regularity with which migrants make their first appearance, and 

 then the average date of the first appearance. 



Some migrants are first detected by the ear, as the cuckoo, corn 

 crake, chiffchafF, whitethroat, &c. ; others by the eye, as the Hirun- 

 dinidae, the flycatchers, &c. Those detected by the ear may be sub- 

 divided into those which make remarkable and loud sounds, as the 

 cuckoo and corn crake, and those whose note is less striking and less 

 intense, as the willow wren, chiffchafF, whitethroat, &c. Few will 

 controvert the statement that some migrants are large and others 

 are small. Birds, such as the cuckoo and corn crake, which 

 announce their arrival over a comparatively wide area, and 

 whose first appearance is readily detected, should afford tolerably 

 accurate results. Conclusions based on the appearances of such spe- 

 cies as the willow wren and chiffchaff will be less correct; and those 

 birds which are generally detected by the eye will furnish results 

 which contain a still larger amount of error. Any circumstance, 

 in fact, whether it be due to the size, the note, or the habits of the 

 species, or to the habits of the observer himself, which tends to 

 diminish the probability of detection and facilitate concealment, 

 lessens the value of the statistics we have been speaking of, and 

 frequently, in my opinion, leads us to imagine that a bird is 

 uncertain in its appearance when in reality it is not. The observer 

 himself is an important element: if he is not situated in a favour- 

 able position ; if he is here one week and there the next; if he is 

 irregular in his habits; and lastly, if he is not a careful ornitholo- 

 gist, his observations are worse than useless.* 



As to the average first appearances, a single example will show 

 how easily we may be misled. Let us compare the spotted fly- 

 catcher and the cuckoo : suppose a single specimen of each species 

 to arrive, if it were possible, on the same day during twenty years 

 in a wooded demesne one mile square, the chances I should say 

 are ten to one, perhaps more, — even in the case of a good ob- 

 server, — but that he detects the cuckoo some days before the 

 flycatcher; and perhaps, if we judge from his twenty years' 



* I am increasingly of opinion that these records of arrivals which occupy so 

 large a space in our journals are without any scientific value, and are of interest 

 only to the respective writers. — Edward Newman. 



SECOND SERIES — VOL. IX. 2 Q 



