All unnecessary weight is eliminated. . . . Even the brain cells needed for song are lost and replaced seasonally in some birds.
All the Birds of North America, p. 63

At midnight, in the sunroom of the ward,
when you’re locked in your pajamas, stupid
with heartbreak, and your throat a frozen stream,
you’ll read how birds in winter lose their minds,
or lose that part that urges them to sing—
each glad cell dying in the blood, until
they know no love but the sparse, sterile seed,
the bitter pills that fatten and preserve
their hearts against this thoughtless cold, this dark.
And yet they seem at peace with this: they love,
they turn away from love, they wait for love
to come for them again, and trusting, sing
the song they knew was gone for good—I knew
you’d come back, I knew it, I knew you’d come.