This is

in late April in the Arizona desert.

It's already over 90 degrees by 11 a.m.

and the mercury is still rising.

A cactus wren sings, perched atop a many-lobed cactus.

Then it hops down to its nest, tucked among the spiny lobes of the prickly pair.

In a desert realm where it's hot enough to fry an egg on a flat rock,

how can the delicate nestlings of a cactus wrens survive? Well, cactus wrens, which may nest several times between March and September, carefully orient their nests in tune with the season.

Their bulky twig structures shaped roughly like footballs have a side entrance.

That tubular entrance curves toward the inner chamber.

When building a nest for the hot months,

the Wren faces the opening to receive the afternoon breeze.

This circulates cooling air through the chamber and over the chicks.

By contrast, a cactus wren building a nest in early March orients the entrance away from the cold winds of that season, keeping the chicks

snug and warm. For Bird Note, I'm Mary McCann. Bird Note gives you the sounds of birds every day,

and you get the sights as well when you follow us on Instagram,

at Bird Note Radio.