Bird Sudoku Level 137 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 137 Strategy
Hard Level 137 uses a 9x9 board with 29 perch cells, 9 blockers, and 8 habitats. Use the row and column counts first, then test each open diagonal flight line.
Bird Sudoku Level 137 Solution
Bird positions in the solution: R2C6, R2C7, R3C4, R4C7, R5C1, R5C5, R5C7, R8C1, R8C6, R8C9, R9C6.