118 BULLETIN OF WISCONSIN NATURAL HISTORY SOCIETY. VOL. 4, NO. 4. 
The external diameters of nests measured gave from twelve 
to fourteen inches across these belts. In collecting for the purpose 
of making a group to represent the colony, in a few minutes' time 
we scooped up with our hands from about the nests several quarts 
of these shells, whereas a fish barrel filled with sand and gravel 
taken with a shovel from the general surface of the island yielded 
none at all when examined at the museum. It would therefore 
appear that these were brought from a distance by the terns and 
not collected from the surface of the island. Although to our 
eyes these rings possessed a decorative value, we hardly believe 
that they were placed there by the terns for that purpose. It is 
also difficult to believe that they were deposited by fecal ejecta, 
for there were no indications that these birds soil their own nests, 
as would be necessarily the case were this the source of the shells. 
If these were ejected from the mouth as are indigestible portions 
of the food of some birds, we would not expect them to so evenly 
encircle the nests, as most birds appear to have fixed habits of 
orientation when incubating or brooding. 
The gulls seemed to be rather unsettled in their nidification, 
tending to the construction of more flimsy nests ; but the materials 
that were used in these were essentially the same as employed in 
their more massive ones. If the terns have degenerated in nest 
building we would hardly expect that a remnant of this instinct 
would be exercised on such unnatural material as these small 
conical gastropods. Probably close observation of the nidification 
and incubation of this tern will yield a simple explanation of this 
phenomenon. 
The eroded character of the shells and the broken walls of one 
or two whirls of most of them seem much like the ordinary beach 
worn examples of these species as found upon the lake shore at 
Milwaukee ; but it is possible that a short time in the digestive 
tract of a bird might produce similar erosions. In this connection 
the following remarks of Sharpe would indicate that the place- 
ment of shells about the nests has been noted in England, though 
the habit could hardly have been noticed in as well marked ex- 
amples without eliciting more detailed mention: "The latter (its 
nest) is only a depression in the sand with a few shells or bents 
of grass for lining." 
Ridgeway says of its nesting : "Unlike most other terns, and 
