Eye on nature

Two questions: if one sees a heron looking into a river, does this mean that there are trout or fish at that place? As an avid gardener I see snails as the enemy, but do they perform any useful function in the garden, and where do they hide during the day?

John Kennedy, Cabinteely, Co Dublin.

The heron is certainly hoping so. Eels, frogs, rodents, worms, insects, crustaceans, are also part of its diet. Snails do more damage in a tidy garden than in an untidy one as they prefer dead vegetation to growing plants. They also provide food for the thrushes and hedgehogs for whom your garden is also home.

In a bush in my garden there is a wasps' nest of light-grey papery substance. It is almost spherical in shape, about eight inches tall and six inches wide with a 3/4in exit low down. It seems too big for a tree wasps' nest.

Dick Page, Grange Con, Co Wicklow.

The nest does belong to one of the tree wasps, either the Norwegian wasp, Dolichovespula norwegica, or the tree wasp, Dolichovespula sylvestris. It can hold up to one hundred workers.

Walking in woods in Co Sligo, our son came across a badger at 11.30 in the morning. He also saw a mink. Do these animals come out in daylight? We have seen a kingfisher on a particular area of the River Suck on and off over 10 years; how long do they live?

Roisin Naughton, Malahide, Co Dublin.

Badgers and mink are not totally nocturnal. They come out in daylight in places where they are unlikely to be disturbed. Kingfishers can live up to 15 years but rarely survive so long. Later generations could also return to the same beat on the river.

In the book, The Perfect Storm, fishermen could gauge the speed of the wind by the sound it made in the rigging wires. Are birds attracted to perching on wires by a musical sound inaudible to humans?

Jeanette Huber, Kinsale, Co Cork

Most songbirds hear on much the same frequencies as human beings, as high as 20,000 cycles and down to 50 cycles. Humans can hear sounds as low as 16 cycles.

Edited by Michael Viney, who welcomes observations sent to him at Thallabawn, Carrowniskey PO, Westport, Co Mayo. e-mail: viney@anu.ie. Observations sent by e-mail should be accompanied by postal address.