I sit in the top of the wood, my eyes closed.
Inaction, no falsifying dream
Between my hooked head and hooked feet:
Or in sleep rehearse perfect kills and eat.
The convenience of the high trees!
The air's buoyancy and the sun's ray
Are of advantage to me;
And the earth's face upward for my inspection.
My feet are locked upon the rough bark.
It took the whole of Creation
To produce my foot, my each feather:
Now I hold Creation in my foot
The hawk is an immovable force of nature, its feet ‘locked’. It is unrivalled in power and cunning. 
 The words are clipped and  monosyllabic , with hard consonants. Also, ‘locked’ and ‘bark’ are  half-rhyming  to give the line unity. The effect is rather of an old-fashioned school-master barking out a lesson. 

Hawk Roosting