You asked if I would have done it differently and the answer is yes:

I would have set the exposure beforehand using a grey card or some grass etc.  and then used manual settings. 
The reason I would have done that is I wouldn't try getting a spot metering on a bird that small. I would want the shutter speed decided for the lens I was using, and the aperture for dof I wanted. By deciding beforehand and getting set up I would have time to choose the settings more carefully.  It also allows freedom of composition because the bird doesn't have to be where the spot is (I know you can move the camera and lock the exposure - but time again when bird might fly away) .  By having exposure set I would be ready for any bird, all black, all white or coloured, not just one that averages out to grey.  

But then again there's people more expert than me here so lets see what they say.

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html