150 BULLETIN 107, UNITED STATES NAnONAL MUSEUM. 



of caves are also used, and I have even found them In slight hollows made by 

 the birds themselves beneath dense bushes on the hillsides, but I have never 

 known a bird of this species to occupy a burrow in soft ground. One egg is 

 nearly as often found as two, but this is frequently addled, and I believe that 

 the larger number constitutes the normal set. Nests are located from a couple 

 of feet above high-water mark to the very tops of the islands. No material is 

 used in construction, and a surprising number of eggs are cracked by the sharp 

 rocks with which they come in contact. 



Mr. Henry B. Kaeding (1905) reports this species as — 

 fairly common on and about Todos Santos, San Martin, San Geronimo, and San 

 Benitos Islands, breeding most accessibly on San Benitos, where, in addition to 

 nesting in the crannies in the cliffs, the nest is often placed under the foliage 

 of the maguey (Agave sJiawi), on the sandy slopes facing the sea. The eggs, 

 taken March 27, were slightly incubated. 



Xantus's murrelet is credited with raising two broods in a season. 

 Mr. Howell (1910) says: 



From my observations, it seems to be beyond doubt that these birds nest 

 twice during the year, once toward the last of March, as has been proved time 

 and again, and once more during the middle of June ; for I found fully as 

 many of their eggs at this latter datie as did Mr. P. I. Osburn earlier In the 

 season. Mr. Osburn has done considerable collecting here within the last few 

 years, and spent four days with me during June. I have even taken half- 

 incubated eggs from under the sitting bird as late as July 11, and it seems 

 hardly likely that one nesting could straggle along continuously from March 

 until July. And besides, no ornithologist has ever taken eggs of this species 

 in May, as far as I can find out, and there are plenty of them who have 

 visited the islands in that month In order to collect eggs of tbe other kinds of 

 birds that are found nesting here. 



Eggs. — Either one or two eggs constitutes a full set. In sets of 

 two the eggs are often very different in color, suggesting the possi- 

 bility that they may have been laid by two birds. Often one of the 

 two eggs is infertile. Mr. Howell says that 48 hours elapse between 

 the laying of the two eggs. The eggs are subject to great variations 

 in color and markings. Mr. Howell has handled a large series of 

 these eggs and writes to me that — 



None of our sea birds except the murre exhibits as much variation in their 

 eggs as does hypoleuous. Those even of the same set run from an almost 

 golid dark chocolate to a plain sky blue with a very few spots, but the majority 

 liave a sea green or drab ground color with a great variety of brown and 

 lavender cloudings, spots, and blotches. It is but rarely that both eggs of a 

 «et are of the chocolate type. 



Three eggs in the Thayer colection are elliptical ovate in shape, 

 smooth and somewhat glossy. One is "pale pinkish buff," finely 

 spotted over the entire surface and heavily blotched about the larger 

 end with various shades of " sepia " and other dark browns, with 

 numerous underlying spots of lilac and light drab. Another is light 

 "buffy brown," very finely sprinkled and conspicuously scrawled 

 with the above colors. StiU another is "wood brown," finely 



