164 DWIGHT 



that moult will explain everything, I have not the slightest 

 doubt. In birds that suffer so great wear, it is well nigh impos- 

 sible to estimate the age of a feather from the amount of abrasion, 

 especially when the color is black. 



4. FIRST NUPTIAL PLUMAGE acquired by a partial prenuptial 

 moult which apparently involves chiefly the throat and head and 

 perhaps the tail. The black throat is present in most spring 

 specimens, in some it is lacking or represented by a few black 

 feathers. Greenish tails are regularly found with such birds ; 

 those with chestnut feathers have tails mottled with black, these 

 signs of individual vigor or precocity going together and consid- 

 erable individual variation being apparent. The bill becomes 

 slate-gray. All of the plumage is so worn when the birds arrive 

 from the south that it is impossible to estimate how long the in- 

 dividual feathers have been subjected to wear, which seems to 

 be considerable. The primary coverts, a key to young birds, 

 are always brownish unless they have been partly renewed by 

 black, probably at the postjuvenal moult. 



5. ADULT WINTER PLUMAGE acquired by a complete post- 

 nuptial moult apparently after the birds have migrated south 

 judging by the freshness of extra-limital specimens and the total 

 absence of local specimens. Contrary to general belief it is 

 likely that the chestnut and black plumage is assumed at this 

 moult. Several specimens from Guatemala without other data 

 show the end of a postnuptial moult from the greenish into the 

 chestnut dress, some of the new feathers still with sheaths and 

 the old worn greenish nuptial ones still in place among the au- 

 riculars and elsewhere. Both the black and the chestnut feathers 

 are broadly edged with greenish buff or brown, which probably 

 diminishes in amount with age giving a less veiled appearance, 

 in older adults. 



6. ADULT NUPTIAL PLUMAGE acquired by wear through which 

 the edgings are largely lost. There is no prenuptial moult as 

 in the young bird. The frequency of a few greenish feathers on 

 breeding birds indicates their liability to be left over even at the 

 first postnuptial moult which is usually so complete although it 



