314 BULLETIN 113, UNITED STATES NATIONAL MUSEUM. 



eggs with little mincing footsteps and indicate by example how she should 

 come and sit on them. In this performance the male bird did not wholly cover 

 the eggs with his breast feathers, as the incubating birds usually do, but rather 

 squatted over them and followed the aerial revolutions of his m^te with a 

 constantly moving head. The wife made several stops as though intending to 

 alight on her eggs, and finally did so, coming lightly to the ground and running 

 up to the eggs and covering them properly with her breast feathers. There 

 would be peace and quiet until some (to me) undiscovered alarm would send the 

 whole colony into the air " baying like a pack of hounds." After several sweep- 

 ing flights through the air the whole skimmer colony would settle back on the 

 eggs and remain quiet, except for the thin yelps that went on all the time, 

 whether there was anything untoward to excite them or not. 



Although the breeding season is often much prolonged by various 

 disasters only one brood is raised in a season. The normal set con- 

 sists of four or five eggs, though three often constitute a complete 

 set, and sometimes as many as six or seven are laid. In the Breton 

 Island reservation egg laying begins the very last of May or first 

 of June; on the Virginia coast the laying season begins fully three 

 weeks later ; the black skimmer is therefore one of the last of the sea 

 birds to lay. The period of incubation seems to be unknown ; so far 

 as I have been able to observe only the female incubates.^ 



Eggs. — A series of black skimmer's eggs makes a striking feature 

 in a collection, showing many interesting variations of bold and 

 picturesque color patterns. The ground color is rarely pure white, 

 but usually pale bluish white or creamy white, varying on the one 

 hand to pale .greenish blue, almost a heron's Q,gg color, and on the other 

 hand to deep " cream buff " or " pinkish buff." They are usually 

 heavily marked with various shades of brown, from " tawny olive " 

 and " burnt umber " to " seal brown " or " clove brown " ; some- 

 times fairly evenly distributed as small spots, but more often in large 

 irregular blotches or splashes in an endless variety of patterns. 

 Nearly all of the eggs are more or less heavily spotted or blotched, 

 and some are very prettily marked, with various shades of "lilac 

 gray," " lavender gray," or " olive gray." In shape they vary from 

 rounded ovate to elongate ovate, with a prevailing tendency toward 

 the former shape. The measurements of 58 eggs in the United States 

 National Museum average 45 by 33.5 millimeters; the eggs showing 

 the four extremes measure 51 by 32, 45 by 36, 41.5 by 31, and 43 by 

 30.5 millimeters. 



Young. — Mr. Arthur has sent me the following notes on the be- 

 havior of young skimmers : 



While the colony under observation were still incubating their eggs I had 

 an excellent opportunity to note the young in all stages, from those almost 

 ready to fly to the young just out of the shell, and I also had an opportunity 

 of noting the way the young skimmers are fed. This is done in two ways: 

 The downy young are fed by regurgitation, the food being dropped by the parent 

 bird on the ground ; but so avid are the little ones for food that they pick at 



