this bird is a little larger than a sparrow, and the greater part of its body is of an azure blue color, with a slight intermixture of white and purple in some of the larger feathers, while the neck is long and slender. there is one kind that is remarkable for its larger size and its note; the smaller ones are heard singing in the reed-beds. it is a thing of very rare occurrence to see a halcyon, and then it is only about the time of the setting of the vergili?, and the summer and winter solstices; when one is sometimes to be seen to hover about a ship, and then immediately disappear. they hatch their young at the time of the winter solstice, from which circumstance those days are known as the “halcyon days:” during this period the sea is calm and navigable, the sicilian sea in particular. they make their nest during the seven days before the winter solstice, and sit the same number of 209 days after. their nests are truly wonderful;[176] they are of the shape of a ball slightly elongated, have a very narrow mouth, and bear a strong resemblance to a large sponge. it is impossible to cut them asunder with iron, and they are only to be broken with a strong blow, upon which they separate, just like foam of the sea when dried up. it has never yet been discovered of what material they are made; some persons think that they are formed of sharp fish-bones, as it is on fish that these birds live. they enter rivers also; their eggs are five in number.

the sea-mew builds its nest in rocks, and the diver in trees as well.