are frequently entirely obscured by a coating of mud. The eggs look as if they had been purposely 

 rolled about on the muddy ground so as to cover up their light colors and make them appear like 

 chunks of earth or stones, a procedure which must be very effectually protective. 



In long-diameter the eggs measure from 1.25 to 1.35, and in short-diameter from .85 to .98; a com- 

 mon size is about .92 x 1.30 inches. 



DIFFERENTIAL POINTS: 



The size, shape, and colors of the eggs will easily distinguish them, excepting in extreme cases, from 

 any other species. See "Upland Plover." 



REMARKS : 



The three eggs illustrated, Plate XL VII, Fig. 1, were selected from a number of sets in the pos- 

 session of Mr. J. B. Porter, of Glcndalc, 0. They represent the different sizes, shapes, ground-colors, 

 and markings commonly observed. Mr. Porter, to whom I am under obligations for the examination and 

 use of his specimens, has several years found the Black Tern building in large numbers in the marshes 

 in Ottawa county, and has collected a o- od many e^o-s and noted their breeding; habits. Dr. F. W. 

 Langdon, who has also observed the Black Tern in its summer home, wrote of it, in Volume III, No. 3, 

 of "The Journal of the Cincinnati Society of Natural History," as follows: "A very common summer 

 resident in the marsh; nesting, or rather laying its eggs on the little islands of decaying vegetation and 

 mud formed by sunken muskrat houses. . . . The sun appears to be their chief incubator, although 

 the decaying vegetation of which the abandoned 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 discovery. 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 e<xas 

 taken by us early in July, more than half were fresh or nearly so." 



In the spring and fall I have frequently seen Black Tern singly or in small flocks fishing along the 

 Scioto river. It seemed at these times to be fearless, often coming within a few feet of me, and then 

 gracefully sailing off as if its curiosity had been satisfied.. It often remains several days or even weeks 

 in the same locality. Having selected a stretch of river, it flies up and down, back and forth, constantly 

 watching for some small fry in the water beneath or catching small insects in the air. When a minnow- 

 is espied a rapid dive is made for it, the bird often going entirely below the surface and out of sight. 

 Suddenly it reappears and, stretching its long wings with a laborious and uncertain movement, rises in 

 the air again, to repeat, at the first opportunity, its difficult work for food. Its flight is graceful and 

 even careless. It sails through the air with the ease consequent upon a, large expanse of wing and a 

 small light body. Now circling up, now dropping like a feather upon some log lodged in the current. 

 Here it sits for a few moments, apparently contemplating suicide, then suddenly, as though some circum- 

 stance over which it has no control had decided the matter, it starts off to repeat its search for food. 



160 



