How a lowered wing decides which way a bird sinks
Speed and spread of one wing steer the bird to one side or into a descending circle
Leonardo works out how the manner of lowering a single wing governs the way a flying bird tilts. If the wing is dropped quickly and drawn in, the bird sinks on that side; dropped quickly and spread, it sinks on the opposite side; dropped slowly and spread, it wheels down in a circle around that wing. A row of three small bird silhouettes is sketched over a wavy line at mid-page, and further mirror-script lines on the sheet are not included in the transcription.
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Speed versus spread of the lowered wing
A wing lowered quickly and slightly gathered in makes the bird sink on that same side, while a wing lowered quickly but spread out makes it sink on the opposite side. Lowered slowly and spread, the wing sends the bird wheeling down in a circle around it. The note breaks off as it begins a further case of a lowered wing.
Three small bird silhouettes over water
Three tiny birds are drawn in profile along a wavy line across the middle of the page, matching the caption's mention of bird silhouettes shown with a wing lowered and then extended. They serve as diagrammatic shorthand for the two wing positions discussed in the text.