Shoot them all year - very very difficult to get on top of foxes once the cover is up like it is now
Far less welfare issues if you shoot before they breed
Theres no need.
Depending, on why you’re doing it.
If you’re controlling foxes or corvids to protect sensitive ground nesting bird populations, let them establish their territories and then take them out of your core area and the surroundings. You don’t need to get them all, get one of a pair of crows and the nest will fail. One bird is also unlikely to be able to hold a territory .
Targeted control measures will significantly reduce predation in your core area. The numbers of vermin will bounce back as the young of the year become independent and start to establish their own territories, typically July or August, by then your ground nesting whatevers should have fledged and be pretty much immune to predation.
A large proportion of this years vermin crop will die off from natural causes over the winter all on their own whether you shoot them or not, why make work for yourself? Wait until spring and cull the survivors and the breeders.
You’ll save yourself time money and ammunition.
If you’re controlling foxes and crows because you want to release poults or run free range poultry, that’s a different matter.
You are creating the problem yourself by putting dumb, easily predated protein out in the countryside.
You can absolutely guarantee that you will attract every critter with pretensions to be a predator onto your patch, and you will attract them in high numbers because of the concentrated protein source that you provide.
You do indeed need to shoot on sight for most of the year, but you also need to accept that the problem wouldn’t exist if you weren’t artificially pumping all that extra protein into the environment.
Stop injecting the excess protein into the environment and your predator populations will drop back to whatever level local resources can support.
You may also wish to concede that in this instance the only thing that you are protecting is a financial investment.