Bird Sudoku Level 21 Hint
Pick a row, column, or habitat with a low remaining count, then check which of its perch cells are blocked by open diagonal flight lines.
Bird Sudoku Level 21 Strategy
Easy Level 21 uses a 6x6 board with 11 perch cells, 4 blockers, and 4 habitats. Use the row and column counts first, then test each open diagonal flight line.
Bird Sudoku Level 21 Solution
Bird positions in the solution: R1C5, R2C1, R2C5, R3C5, R6C4.