Gap fill
Two of the same animal with a single gap between them: the gap must be the other animal.
Pip: Owl, gap, owl. Whatever goes in the gap can't be an owl. Fill it, then balance the row.
Interactive example · 1 of 2 · tap the empty cells
Pip: Same with foxes. Notice how one gap fill often unlocks a bookend.
Interactive example · 2 of 2 · tap the empty cells
Why it works
Gap fill is bookends' sibling: both come from the same three-cell window. Scan each line for the pattern A _ A before you count anything.
Try it
Today's Daily is the same puzzle as the app. Unlimited practice is one click away.