Birds and eggs are part of the pine marten’s diet, and martens can be attracted to bird boxes in their search for food.
A number of mitigation techniques exist to prevent mammalian predators from gaining access to nest boxes for small birds and larger cavity-nesting species such as owls and some duck species. The most successful techniques are cone type baffles, stovepipe baffles, and entrance hole extenders (see figure). The cone type baffles are most effective when used on stand-alone trees or poles, whilst the entrance hole extenders have been used effectively in Scotland to prevent pine martens predating clutches of crested tits. The image below is an example of a cone baffle installed by VWT and Natural Resources Wales to protect an osprey nest in mid-Wales.