TCD MS 10515 folio 50r
[April 28th 1916]
low, a dungo or a tern, that is continually checking and altering its rapid flight, must be a distinct improvement. So I have been led to imagine that, in those birds that perform swift evolutions in the air, a forked tail has been evolved to provide them with a more powerful brake, not to give them a greater turning power, for this depends on very different agencies, but to allow them to check their rapid movement at any moment and in any degree during the changing directions of their flight. I observed that a tern, after capturing a fish in a position, such that the fish’s length was at right angles to its beak, was unable to swallow it. It overcame its difficulties by casting the fish high into the air and cleverly seizing it again more suitably as it fell down towards the water.