[Marches Farmer]

Just done my monthly check through all the poultry for nasties.  Found a few lice on the cockerels and hens of two small breeding groups (home reared, not bought in), for the first time in years.  Treated, of course, and trying to work out why those and none of the other breeding groups, when it occurred to me that most of the breeding groups are presently in big runs with game panels and netting across the top to keep out wild birds but those two runs are nearest the boar pen and crows often perch on the top edge of the game panels waiting for the boar to finish feeding so they can fly down and search for leftover pellets and grain (they must be optimists - he's a hungry lad!)   Maybe the source?

[HappyHippy]

I'm no expert, but I'd say almost definately the crows 
We've got a similar situation here  Time for a few warning shots to try and scare them off (I stand zero chance of hitting them, so don't even try  )
Hope you get it cleared up soon  We've been recommended 'Smite' seems to be quite good 

[chrismahon]

I think every pest falls from the sky and lands on chickens. Without doubt wild birds will drop lice and in our case Northern Fowl Mite. Just need to check your birds every week MF because in the warm months pests multiply rapidly.