They like ragwort, which one is meant to eradicate on sight. Bit of a conflict there...they are lovely moths
We spend quite a lot of time clearing ragwort from the grassland nature reserves.
Grazing animals have evolved to eat around the stuff; I have a vivid memory of a field close to the Little Hay TV mast with a lot of horses and more ragwort (flowering) than grass.
However if the grass is mown for hay or silage, the ragwort is much less likely to recognised. So, if there is even the remotest possibilty that the grassland might be mown for a hay crop, the ragwort has to be removed. Those are the rules. It's a bit like H & S.
We do find ragwort plants with colonies of cinnabar moth caterpillars. It is sad
that they are to be excluded from the nature reserve.
We have housemartins nesting in the eves
Lucky you. Saw my first martins yesterday in the Cotswolds.
Are the droppings as good a fertilser as guano?