Michael Viney responds to queries and observations on nature.
At 1 a.m. on May 16th we clearly heard a cuckoo call. Is this considered normal behaviour?
Patricia Delahunt, Newry, Co Down
Cuckoos occasionally call at night and have always done so. It is thought that it may be because of competition, but that is hardly likely since they have become so scarce.
After deserting the river for a couple of years, at last a pair of swans have nested below the town, and six eggs were laid. How long will it take for them to hatch out?
Michael O'Regan, Bandon, Co Cork
Swan's eggs take from 34 to 38 days to hatch.
Twice recently in south Co Dublin I have observed a heron involved in an aerial dog-fight with a flock of crows, during which the heron displayed remarkable agility for a bird of its size. Is there any reason, apart from territorial disputes, that crows would attack a heron?
Ruairi Ferrie, Drumcondra, Dublin 9
It may well have been territorial near a nesting area, but the crows could have been chasing a competitor for food.
• Send observations to Michael Viney, Thallabawn, Carrowniskey PO, Westport, Co Mayo; email: viney@anu.ie (include a postal address)