Lacking a pedigree in this discipline I'm not in a position to offer what the forum rules require in terms of informed critique but the anarchist in me has control of the keyboard, so may I say I like the composition that suits the diving attitude and gives room for the bird to move in to (yes, I know it's a 'still' and the gull won't actually move, no matter how long I wait...).
I feel an affinity with your shot on a 'before' and 'after' basis when I toggle between your Herring Gull and mine further down the forum.
Dorsal view and the tilted cross shape of the bird in this looks excellent, Will. And from your balcony, lucky chap. Composition works well for me, great IQ and nicely handled tonal range all against a simple but effective background. No nits from me on this one. Thanks for sharing.