34 BIRDS OF THE NEW YORK CITY REGION 



its average date of arrival for the twelve years under discus- 

 sion, the date of arrival each year will in the great majority 

 of cases not coincide with such an average date. If this be 

 true of May birds, it is much more true of the earlier spring 

 migrants, which sometimes arrive on dates two weeks or even 

 a month apart in two successive years. For this reason arrival 

 dates have been given in the annotated list in great detail, 

 and every precaution has been taken to convince the student 

 that there is nothing fixed in the migration of our local birds. 

 Not a season has passed without breaking the arrival or 

 departure record of some species, and it is scarcely conceivable 

 that such a season will occur. If the very earliest or the very 

 latest spring arrival dates be considered, not a single state- 

 ment for any species in the preceding discussion would be 

 strictly true. The most that can be done, therefore, is to say 

 of a species that it belongs in a group which usually arrives 

 between certain limits. Any more specific statement is not 

 warranted by the facts, and is more misleading than helpful. 

 After the height of the migration, birds fall off very rapidly 

 in numbers, but there is often a "wave" between the 22nd 

 and 26th. This is the "wave" of female Warblers. The 

 Blackpoll, Bay-breasted, Magnolia and Canadian Warblers 

 become common, as do the transient thrushes. The late 

 arriving summer residents, such as the Wood Pewee and 

 Red-eyed Vireo, now become common. A very few new 

 species also appear at this time. It is exceptional when they 

 arrive with Group 4. 



(May 15-May 26) 



Olive-sided Flycatcher Kentucky Warbler 



Yellow-bellied Flycatcher Mourning Warbler 



Alder Flycatcher ?Short-billed Marsh Wren 



Nothing has so far been said about the bird-life of May 

 at the seashore. During the month the last waterfowl dis- 

 appear, the Laughing Gull, Terns and Shore-birds arrive. 

 They are, however, exceedingly irregular, and their migra- 



