Possible Clues:

• Small, long-winged songbirds
• The pigs fly around the wall
• Birds one eats?
• Small swift birds
• How pigs might fly around the brickwork
• 24 acrosses the migrants
• The way the pigs fly round the wall (8)
• One gets down to the ones like the end of 2 down (8)
• The birds of this puzzle
• Birds splash around in water on board ship