As they say - "Sh!t happens", and despite all our best efforts, there will be casualties!
I recall one occasion where a group were advised to postpone plans to conservation graze a coppiced mossland with cattle due to their plans coinciding with the well known and established birthing period of the resident roe deer, not to mention the ground nesting birds in situ.
The advice was ignored and sure enough at least two new born kids were trampled, and god only knows how many nests were lost.
Sometimes the efforts of so called conservation bodies cause a lot more damage and disruption than the occasional, but unfortunate, chopping of a sitting hen!
Please also remember, your efforts in managing the land are contributing more to benefiting wildlife than if you left the land unmanaged.