LIFE HISTORIES OF NORTH AMERICAN PETRELS AND PELICANS. 263 



age 53.7 by 33.8; the eggs showing the four extremes measure 58 by 

 35, 57.5 by 37, 47.5 by 33.5, and 50 by 29 millimeters. 



Plumages. — I have never seen the naked or the downy young of 

 this species, nor can I find any description of either in print. The 

 nesting season is so prolonged and variable that it is usually impossi- 

 ble to even approximately guess at the ages of immature birds in 

 collections, but apparently the sequence of plumages to maturity 

 is similar to that of other cormorants. In the fresh juvenal plumage, 

 in which I have seen birds in November, January, and April, the 

 head, neck, and under parts are deep, rich, dark brown, " Vandyke 

 brown," or " warm sepia," paler on the throat and darker on the 

 crown, flanks, and lower belly. This plumage is probably worn for 

 about a year, but it wears and fades out to much paler colors, nearly 

 to white on the throat and belly. The upper parts are much as in 

 the adult, but duller and browner, with less conspicuous black edgings 

 on the back and scapulars. The fully adult nuptial plumage is not 

 acquired until the second breeding season. Adults in winter plumage 

 are similar to those in breeding plumage, except that they lack the 

 white plumes about the head and neck, where there is also more 

 brownish mottling. I have seen adults in full nuptial plumage in 

 July, August, September, November, and December. There is 

 probably one complete molt each year and one partial molt ; the tail 

 is apparently molted twice. 



Behavior. — Doctor Nelson (1903) writes of the behavior of Mexi- 

 can cormorants as follows : 



Last March we campetl on a small river at the bottom of a deep canyon in 

 central Michoacan ; this stream runs a tortuous course between high rocliy walls 

 and at short intervals breaks into foaming rapids. Our camp was on a narrow 

 sandy flat at the water's edge, under the overhanging branches of some small 

 mahogany and other trees that had secured a foothold in the talus at the foot 

 of a cliff. As we lived here unsheltered except by the foliage, the happenings 

 among the wild life of this solitary place were under constant observation. 

 Among the interesting daily events was the passage up the river each morning 

 of several Mexican cormorants, always flying singly, their glossy black plumage 

 gleaming in the intense sunlight as they turned. They were evidently on their 

 way to some fishing ground higher up, and several hours later — usually about 

 midday — came back following, as in the morning, all the wanderings of the 

 river, and giving a touch of completeness to the wild character of the sur- 

 roundings. 



In the summer of 1897 we found them in abundance about the lagoons and 

 rapids of the coast country in southern Sinaloa, and especially at some shallow 

 rapids in the Rosario River a few miles above the town of Rosario. During the 

 early part of the rainy season the river was low and at the place mentioned a 

 short descent in the boulder-strewn bed of the stream made a stretch, forty or 

 fifty yards long, of brawling rapids. Every morning dozens of cormorants flew 

 up stream to the rapids from the mangrove-bordered lagoons near the coast. 

 They flew low along the water, sometimes singly and sometimes in small 

 parties, usually keeping side by side in a well-formed line when two or more 



