“I watched a Blackbird”

I watched a blackbird on a budding sycamore
One Easter Day, when sap was stirring twigs to the core;
I saw his tongue, and crocus-coloured bill
Parting and closing as he turned his trill;
Then he flew down, seized on a stem of hay,
And upped to where his building scheme was under way,
As if so sure a nest were never shaped on spray.