PASSERINE BIRDS OF NEW YORK 127 



which, from the freshness of their feathers we know they must 

 have passed. The postjuvenal and the postnuptial moults are 

 virtually completed so far as the flight-feathers are concerned 

 before the species moves south. Most of the Flycatchers and 

 Swallows, however, disappear before these moults begin, but 

 they and a few others are exceptions. The progressive shrink- 

 age or involution of the sexual organs of adults is, as a rule, 

 quite marked before the postnuptial moult sets in, and it is 

 highly improbable any further attempt to rear young is ever 

 made once this retrograde process has begun. When the last 

 brood is on the wing and well able to care for themselves, the 

 moult of the parents begins, that of the male starting a little 

 before that of the female as becomes evident when a pair can be 

 secured. As the female attends to the wants of her family 

 longer than does the male, it is not surprising that her moult 

 should be the later. We can readily believe that when a 

 brood is raised to take the place of accidentally destroyed eggs 

 or young, the involution and the moult are both delayed. As 

 almost all of our migratory species move south on the comple- 

 tion of a moult which is accomplished somewhat earlier in 

 adults than in their progeny, it is natural to expect the former 

 to go first. My actual experience is that the last loiterers of 

 many of our summer breeding species are young birds. Some 

 species disappear almost entirely, as for instance the Golden - 

 crowned Thrush (^Seiunis anrocapillus) and later reappear when 

 migrants from the north arrive to replace them. The first 

 comers are not always adults but they are very apt to be. 



Species near the northern limit of their breeding range, such 

 for instance as the Hooded Warbler {^Sylvauia viitrata) or Blue- 

 winged Yellow Warbler {HclminthopJiila pinns), rapidl}^ disap- 

 pear on completing their moult. The specimens obtained late 

 in the season all prove to be young birds, and this is the case 

 with many species that I have pursued with the object of secur- 

 ing adults. The evidence of moult is that old birds migrate 

 south first because they are ready first. 



It is an undoubted fact that when a species has an extensive 

 breeding range, the birds towards its southern limits begin to 



