Michael Viney responds to queries and observations on nature.
Part of our patio is paved with a mixture of stones from a sand pit. Recently we have seen 10 or more rooks sifting through them, tossing some aside, but swallowing others. Martin Byrnes, Oranmore, Co Galway
The were most likely picking small stones for their gizzards.
On a recent walk with children in Tomnafuinnseog oakwood in Co Wicklow, the girls found oak leaves with brown discs attached to the underside. There were also very few acorns. J. Tyner, Shillelagh, Co Wicklow
The discs are galls - growths like spangles, caused by tiny gall wasps. Their grubs feed on leaf tissue and will emerge in early spring.
Recently, we saw a caterpillar about 6cms long, covered with tufts of pale yellow-green hair and a horn at its tail. On its back was a distinctive black mark like an eye. Aideen and Peter Roche, Howth, Co Dublin
It sounds like the caterpillar of the pale tussock moth, and it would have been preparing to pupate.
Michael Viney welcomes observations at Thallabawn, Carrowniskey PO, Westport, Co Mayo; e-mail: viney@anu.ie. Include a postal address.