24 BIRDS OF PENNSYLVANIA. 



to hide the marking's and thereby make them less conspicuous. In two 

 or three instances only did we observe any attempt at a nest, and 

 these would not have been recognized as such without the egg's, consist- 

 ing as they did of merely a few fragments of grass or bulrushes so dis- 

 posed as to prevent the eggs from rolling ; inmost cases the eggs rested 

 in a slight depression on the bare mud. The sun appears to be their 

 chief incubator, although the decaying vegetation of which the aband- 

 oned muskrat houses consist, doubtless plays some part in the process. 

 In no instance did we succeed in flushing a bird from the eggs, although 

 they would appear in pairs to the number of twenty or thirty and hover 

 about within a few feet of our heads making a great outcry when we 

 approached their property, which was soon to be ours by right of dis- 

 covery. 



" At other times the birds were not at all gregarious, being usually 

 observed foraging singly or in pairs. Several young of the year were 

 taken, thus confirming the statement of the resident who informed us 

 that he had taken numbers of the eggs of the first brood in May. Of 

 the dozen or more sets of eggs taken by us early in July, more than half 

 were fresh or nearly so." At Erie Bay, near the city of Erie, single in- 

 dividuals or small flocks of these Terns are seen nearly every spring and 

 fall. Mr. George B. Sennett, of Erie, a gentleman to whom I am greatly 

 indebted for much valuable information concerning the bird-life of the 

 Erie-Crawford district, has observed the Black Tern in the vicinity of 

 Erie city only during the spring and fall. I have in my collection four 

 Black Terns, three of which were captured in Chester county (two in fall, 

 one in spring), the other was shot in Delaware county (September, 1880). 

 The following-named gentlemen report the occurrence of this species in 

 their respective localities : Lycoming county an irregular spring and 

 fall visitor August Koch, Williamsport, Pa. Lancaster county a strag- 

 gler Dr. A. C. Treichler, Elizabethtown, Pa. Venango county a rare 

 straggler Prof. J. R. Eobertson, Franklin, Pa. Mercer county" one 

 specimen shot in the spring, 1887" S. S. Overmoyer, New Lebanon, 

 Pa. Cumberland county one seen in the autumn Messrs. Win. M. and 

 S. F. Baird (List of Birds of Cumberland County, Pa., published in 1844). 



FAMILY RYNCHOPHXffi. SKIMMERS. 



THE SKIMMERS. 



Only one species of this family is found in the United States. These birds have 

 extremely long wings and webbed feet, but like the Terns, they rarely, if ever, it is 

 said, swim or rest upon the water. They have exceedingly odd-looking bills ; both 

 mandibles are quite flat, with blunt ends ; the upper mandible is much shorter than 

 the lower. They subsist almost exclusively on fish which they catch when skim- 

 ming close to the water's surface. 



