Resident exotic herons here on the rise

I HAVE been spending quite a lot of time around the canal recently, getting my boat organised for the new season.

Herons have been my constant companions, lumbering into the air as I drive up to the boat and then floating back to earth a hundred metres away to resume the motionless vigil of the dedicated fisherman.

They’re extraordinary birds. I always think there’s something exotic, or even prehistoric, about them — the great, grey pterodactyls of our waterways. They’re certainly large — a mature male can stand a metre tall, have a wingspan of nearly two metres and weigh up to two kilos.

There are close to 4,000 breeding pairs in Ireland and this number is augmented by winter visitors from Britain and the continent. And the number of resident herons appears to be increasing, probably due to improving water quality and a growth in popularity of garden fish ponds.

My small pond has so far escaped their attention but I know of other gardeners who have not been so lucky. A heron needs about 400 grams of fish a day, more if it’s feeding young. That’s a lot of goldfish or koi carp. There are various tactics employed to protect pond fish from them. The most effective and unobtrusive is probably a trip wire.

Herons almost always land on solid ground and then wade slowly and carefully into the water before they start fishing. If you surround your pond with a fine wire, or better still, transparent fishing line, staked about 20 centimetres high, the heron will hit it with its shins as it’s walking into position. This will freak it out and it will fly off to look for an easier pond.

In Dublin Zoo the herons have become even cheekier. They have learnt the feeding times for the penguins and swoop in to steal their fish. Similar behaviour has been reported from the Netherlands where some herons have lost their natural fear of humans and scavenge for rubbish in parks and streets.

Apart from fish, herons eat quite a lot of frogs. I have seen one hunting out in the middle of a raised bog. They’ll also take lizards, small birds and some mammals. I’ve seen a video of a heron killing and eating a young rabbit. Because they sometimes kill birds, particularly young birds, they are often mobbed by them in flight in the same way that true birds of prey are mobbed.

The collective noun for a group of herons is a ‘siege’. But they are never found in groups outside the nesting season.

They nest in colonies and the colonies of up to 50 pairs are usually in the tops of tall trees. But in parts of the country where suitable trees are rare they will nest in reed beds or, in Connemara, on the ground on islands in lakes.

They are preparing their nest around now and heronries are spectacular places in the breeding season. The sight of these ungainly, long-legged birds landing in the tree tops is worth seeking out. There are colonies all over the country. One quite close to me is on the Carton Estate outside Maynooth in Co Kildare; there’s another well-known one in St Anne’s Park in Dublin and one on Inchydoney Island in west Cork.

The one on Inchydoney Island is particularly interesting because the grey heron nests are interspersed with an increasing number of nests of little egrets. I have also heard rumours the little egrets have been joined by a small number of the considerably larger cattle egret. That would make three species of heron in one colony.

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