of the nest which it constructs for brooding, and
which has the appearance of an oven. It is very skilful and knows how
to build a dome of clay without scaffolding, which is not altogether
easy. Having chosen for the site of its labours a large horizontal
branch, it brings to it a number of little clay balls more or less
combined with vegetable _debris_, works them altogether, and makes a
very uniform floor, which is to serve as a platform for the rest of
the work. When this is done, and while the foundation is drying, the
bird arranges on it a circular border of mortar slightly inclined
outwards. This becomes hard; it raises it by a new application, this
time inclined inwards. All the other layers which will be placed above
this will also be inclined towards the interior of the chamber. As the
structure rises, the circle which terminates it above becomes more and
more narrow. Soon it is quite small, and the animal, closing it with a
little ball of clay, finds itself in possession of a well-made dome.
Naturally it prepares an entrance; the form of this is semicircular.
But this is not all. In the interior it arranges two partitions: one
vertical, the other horizontal, separating off a small chamber. The
vertical partition begins at one of the edges of the door, so that the
air from without cannot penetrate directly into the dwelling, which is
thus protected against extreme variations of temperature. It is in the
compartment thus formed that the female lays her eggs and broods,
after having taken care to carpet it with a thick layer of small
herbs.

"In favourable seasons, the Oven-birds begin building in the autumn,"
Hudson tells us, "and the work is resumed during the winter whenever
there is a spell of mild, wet weather. Some of their structures are
finished early in winter, others not until spring, everything
depending on the weather and the condition of the birds. In cold, dry
weather, and when food is scarce, they do not work at all. The site
chosen is a stout horizontal branch, or the top of a post, and they
also frequently build on a cornice or the roof of a house; and
sometimes, but rarely, on the ground. The material used is mud, with
the addition of horse hair or slender fibrous rootlets, which make the
structure harder and prevent it from cracking. I have frequently seen
a bird engaged in building first pick up a thread or hair, then repair
to a puddle, where it was worked into a pellet of mud about the size