BIRDS OF THE TRES MARIAS ISLANDS. 33 



tops of the scrubby trees growing on the rocky inner slopes of the island. 

 They were found about all of the Tres Marias, but usually occurred singly 

 and were nowhere common. Two or three were seen fishing in the 

 breakers alongshore at the north end of Maria Madre. 



Fregata aquila (Linn.)- Man-o'-war Bird. 



Hundreds of inan-o'-war birds were breeding on Isabel in April, and 

 on approaching the island many were seen soaring over the rocky sum- 

 mit. The first shot caused hundreds of others to take wing, and in a 

 few moments the air was swarming with them. They soared in con- 

 stantly intersecting circles, until the sky seemed covered with their 

 silhouetted outlines. So few had been seen alongshore near San Bias 

 that it was an interesting and unexpected sight. Upon landing, numer- 

 ous large, oval, and brilliantly red objects were seen in the tops of the 

 dark-green bushes along the slopes. These proved to be the gular 

 pouches of old male man-o'-war birds inflated to the size of a man's head, 

 the brilliant red color of the distended membrane making them very 

 conspicuous objects. It appeared to be a common custom of the birds to 

 sit quietly on the top of a tree for a long time with the pouches thus 

 distended and evidently serving as sexual ornaments. A few birds 

 were seen circling high overhead with their pouches fully inflated, but 

 as a general rule, when soaring, the pouches were closed. 



The nests were built of sticks and placed in the tops of low trees 

 and stout bushes from near sea level to the summit of the island. 

 Three or four of these platform-like structures were found together in 

 some of the larger bushes. Many of the young were hatched and, when 

 able to stand alone, would do their best with voice and beak to resent 

 our approach. The young are covered with white down until nearly 

 half grown. 



A few of these birds were also seen about the Tres Marias, and are 

 said to breed on San Juanito, but were not common. 

 Ardea herodias Linn. Great Blue Heron. 



A few solitary individuals were seen at various times during May 

 along the beaches, and it is probable that a few pairs may breed on the 

 islands. They were also noted by Colonel Grayson. 

 Ardea egretta Gmel. American Egret. 



The American egret is another species noted by Colonel Graysou, 

 which we did not see. It must occur merely as a straggler from the 

 mainland. 

 Ardea candidissima Gmel. Snowy Heron. 



Kecorded by Colonel Grayson as a straggler, but not seen by us. 



Nycticorax violaceus (Linn). Yellow-crowned Night Heron. 



A dozen or more night herons were noted and a young bird was shot 

 on a rock close to Isabel Island, where it must have strayed from the 

 mainland. As Colonel Graysou found them on the islands and took 

 13950 No. 14 3 



