On Sunday police were called to two separate incidents involving people shooting birds in Barnet.
At 11.39am they were called to fields behind Marsh Lane, Mill Hill, where shots were heard fired.
It is believed that trespassers were using shotguns to shoot pigeons on the private land.
Police searched the area but no arrests were made.
They are warning people that it is an offence to trespass on private land with a gun, and that committing this crime can result in a prison sentence.
Later at 2.46pm police were called to Edgwarebury Park, in Edgware Way.
Callers reported seeing two white men in wax jackets, with a brown Labrador dog, shooting birds out of a tree.
It is thought they were using an air rifle.
Police used a helicopter to search the area but no arrests were made.