Warmer climate brings welcome invaders

Night herons have nested for the first time in Britain. A pair raised two chicks at Westhay Moor nature reserve in Somerset. 

Black crowned night heron (Nycticorax nycticorax).

This owl-like member of the heron family is a regular breeder on the other side of the English Channel and it is from there, presumably, that the entrepreneurial pair came. Non-breeding night herons have been visiting England in recent years. They are also rare vagrants to Ireland (one was seen in Bandon on July 26), so it’s worth keeping an eye out for this rather elusive marsh bird, as it may also begin nesting here.

Being tall and skinny is de rigeur in the heron world; necks legs and toes are always long. The night heron bucks the trend, however; medium-sized and grey plumaged, it is stocky and short-necked, with legs slightly shorter than those of the familiar grey heron. The crown is dark; hence the name ‘black-crowned night heron’. Large eyes enable the bird to operate in poor visibility. Oddly for creatures walking on stilts, night herons roost in leafy trees by day, venturing onto wetlands at dusk to catch frogs, fish and creepy crawlies under cover of darkness. They usually nest in trees with other herons and egrets.

The species’ arrival in Britain as a breeding bird is probably down to climate change. Has global warming a dubious silver lining? Milder conditions are encouraging creatures from southern climes to settle and breed in our part of the world. Land-mammals reptiles and amphibians from mainland Europe can’t reach our island but fish from sub-tropical waters are visiting our shores.

Most climate refugees are birds. The heron and egret family, in particular, have seized the day; several species have set up shop in Britain. Stephen Moss of the Somerset Wildlife Trust recalled that only two members of the family, the grey heron and the bittern, nested in Britain in the 1970s. Now, six species breed in Somerset alone. Little egrets, which had been extending their range northwards in France, nested in Britain in 1996. Cattle egrets bred in 2008 and little bitterns two years later.

Colonisation by the most glamorous member of the family, the great white egret, was eagerly awaited; individuals had been visiting Britain and Ireland increasingly. The species breeds in every continent except Antarctica, although numbers are low in Europe. The wetlands it frequented were drained and egrets were hunted to the brink of extinction to provide feathers for the millinery trade. Although the nearest substantial breeding colonies are in Austria and Hungary, this glamorous bird nested in Somerset in 2009.

According to the Meteorological Service, average temperatures in Ireland rose by three quarters of a degree in the last 20 years. Our part of the world is getting warmer and wetter, which should suit herons and egrets. Being the off-shore island of Europe’s off-shore island, it’s not so easy for mainland European birds to get here.

The little egret, the most conspicuous recent addition to our list of common birds, was seen for the first time in Ireland as recently as 1940. Ten years later, it had become a regular visitor. Then, in 1997, about a dozen pairs nested at a heronry near Youghal. The new arrivals prospered and colonised other locations along the south coast. Little egrets nest now not only in coastal counties but in inland ones as well.

The next member of the family to set up shop here is likely to be the cattle egret. It staged a mini-invasion in 2007. According to the Bird Atlas, there were at least 29 cattle egrets in Ireland by the end of that year, although none stayed on to breed.

Our other great hope is that the bittern, of Irish literary fame, will return, but that’s another story.


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