Is this the one?
From here:
http://forum.poetryco.../viewtopic.php?t=6959
Sparrow by Norman MacCaig
He's no artist
His taste in clothes is more
dowdy than gaudy.
And his nest - that blackbird, writing
pretty scrolls on the air with the gold nib of his beak,
woudl call it a slum.
To stalk solitary on lawns,
to sing solitary in midnight trees,
to glide solitary over grey Atlantics -
not for him: he'd rather
a punch up in a gutter.
He carries what learning he has
lightly - it is, in fact, based only
on the usefulness whose result
is survival. A proletarian bird.
No scholar.
But when winter soft-shoes in
and these other birds -
ballet dancers, musicians, architects -
die in the snow
and freeze to branches
watch him happily flying
on the O-levels and A-levels
of the air.