NORTHERN MacGILLIVRAY's WARBLER 539 



little change being detected in successive songs. In the first three "words" the 

 "z" sounds were strong, whereas the last two were more liquid. In singing, the 

 bird would throw its head back, and put much bodily effort into the process of 

 utterance. Soon the bird dropped close to the ground and sang from within the 

 shrubbery, changing his position frequently. The sharp tsip of the female was 

 heard at this time. After a few songs the male flew up to a perch 30 feet above 

 the ground, sang twice, and then went below again. * * * Other individuals 

 studied and timed while they sang gave their songs at intervals of 10 to 14 seconds. 

 Song production is not continuous, however. * * * 



The "z" sounds heard from the bird at Hazel Green are entirely lacking in 

 other songs studied. Two of these clearer utterances we wrote as follows : 

 syr-pit, syr-pit, syr-pit, syr-sip-sip-sip-sip (J.G.), and another cheek-a, cheek-a, 

 cheek-a, cheek-a, chee-e-e-e (T.I.S.). The first syllables are loud, clear, and 

 set of£ from one another, while the shorter ones (sip) are given rapidly, faster 

 than a person can pronounce them, and sometimes are run almost into a trill. 



Field ma7'ks. — ^MacGillivray's warbler is quite unlike any other 

 Avestern warbler. Its dark gray head, neck, and upper breast, the 

 latter almost black, its olive-green back and its bright yellow under 

 parts are distinctive in the adult male. The female and young are 

 similarly marked, but the gray is much paler, sometimes grayish 

 white. Where its range approaches that of the mourning warbler, 

 the two white spots above and below the eye of the adult male will 

 distinguish it. The young bird is less easily recognized, but in all 

 plumages the tail of the western species is the longer. 



Enemies. — This warbler is seldom bothered by the cowbird ; I can 

 find only four published records of such parasitism. 



Winter. — Dr. Alexander F. Skutch contributes the following: 

 "MacGillivray's warbler is an abundant winter resident over the 

 whole highland area of Guatemala, from 10,000 feet down to at least 

 2,000 feet on the Pacific slope. Avoiding the forest, it lurks near or 

 on the ground on bushy movmtainsides and in low, dense thickets — 

 just such habitats as, at lower altitudes in Costa Rica, are chosen by 

 the closely similar mourning warbler. So well do these birds remain 

 concealed, as they forage screened by the foliage, that the bird- 

 watcher must learn to recognize their distinctive, sharp tuc^ tuc in 

 order to gain a just motion of their abundance ; were he to rely upon 

 sight alone, he would call them everywhere rare. Like nearly all 

 birds of similar habits, they live in solitude rather than in flocks. 



"MacGillivray's warbler arrives in Guatemala during the second 

 half of September, and departs early in May. On the Sierra de 

 Tecpan, they were much more in evidence at the end of April than 

 they had been earlier in the year, suggesting that the population of 

 wintering birds had been augmented by transients from farther south, 

 for the species winters southward to Colombia. In Costa Rica they 

 appear to be very rare, in sharp contrast to their abundance farther 

 northward. 



