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 recog-nized as such without the eggs, consist- 
ing as they did of merely a few fragments of grass or bulrushes so dis- 
posed as to prevent the eggs from rolling ; in most 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. B. Bobertson, 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 RYNCHOPID.^. 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 suYface. 
