Possible Clues:

• Crap working month is over
• Sea-bird excrement
• Antigua not the place to find fertiliser
• With a gun that's broken. nothing will drop from the birds
• MP's first address to House
• Bird sitting on egg in dried excrement
• Bird droppings
• A fertilizer source
• O, a gun will make it fertile from the birds
• The birds keep dropping it with a gun round here