Crows nest...seagull's more like)

I've often wondered why the crow's nest of a ship is called a crow's nest and not a seagull's nest. My great uncle Roderick was a sailor and he told me that birds would frequently build their nests in the masts of ships, causing all manner of problems.
Nowadays, of course, seagulls spend more time inland. Here's an excellent nest that I spotted on a recent trip to Cwmgrwfi.