Ireland’s looming bird crisis

Back in 2002, the parties to the UN Convention on Biological Diversity set a target of halting biodiversity loss by 2010.

It is now 2010, the declared UN Year of Biodiversity, and although some endangered species have been saved, notably within the EU, in general species of flora and fauna are being pushed into extinction at a faster rate.

There was really little hope of halting species loss in such a short time, even though the idea had its genesis as far back as 1992, at the Earth Summit in Rio, though it didn’t get legs until the turn of the millennium.

But whatever hope there was then is now fast receding as climate change becomes the newest and most formidable driver of declines and extinctions.

One study has calculated that one quarter of Europe’s bird species will face extinction within the continent over the coming century based on the “intermediate” predictions for rises in global temperature set by the Intergovernmental Panel on Climate Change (A Climatic Atlas of European Breeding Birds, by Huntley, Green, Collingham & Willis, 2007). However, the world is presently on course for the worst-case scenario because of higher emissions of greenhouse gases.

In general, birds in the northern hemisphere will have to move north, while those in the southern hemisphere will need to move south, to keep up with climate change. The expected increase in temperatures in most areas will rise at a faster rate than the ability of wildlife to adapt, leading to mass extinction of species, according to the science journal Nature (Scott et al., 24 December 2009, Nature 462).

The authors of Climatic Atlas warn that we can expect to see the first avian casualties of climate change in Europe by 2020. They calculate that bird populations will move approximately 500 kilometres, and in some cases up to 1,000 kilometres, mostly north or north-east, to keep within their temperature “comfort zone.”

The problem will be most acute for “specialists” with patchy or restricted ranges  – think Alpine species, for example – for they will have nowhere to go: their future comfort zones lack the specialised habitats they need. Birds such as Alpine chough, wallcreeper and snow finch could easily be wiped out, as could black lark and pin-tailed sandgrouse, birds confined largely to Spain.

The “generalists,” or birds that thrive across a wide range of habitats and temperature zones, will be able to make the transition with greater ease. Many will be forced to move by the desertification of southern Europe, but more frequent droughts will prompt them to move out of the killing zone before then.

The migration has already begun, and I don’t mean the regular seasonal journeys undertaken by many bird species, or even the extreme hard-weather movements in which birds temporarily flee a frozen northern Europe. I mean the wholesale and permanent redistribution of bird populations within Europe.

But let’s focus on Ireland. Throughout most of the 20th century there was a stability and constancy to bird distribution here, as elsewhere, and the main changes that took place were declines linked to intensive farming and drainage; for example, the corncrake population collapsed.

Climate-driven immigration into Ireland appears to have started in the 1970s with the increasing occurrence of little egret and Mediterranean gull, birds that hitherto were virtually unknown here.

The little egret, a small white heron historically distributed in Europe around the Mediterranean and Black Sea, established its first nesting colony in Ireland in 1997, and today there are hundreds here all year round, nesting in south and east coast counties. England has been similarly colonised by the species.

That’s the most well-known example, but a wide range of bird species, as well as butterflies, are settling here, while others are moving out and heading north.

Another example is the reed warbler, a tiny skulking migratory songbird that, as its name implies, nests in reedbeds. It is so difficult to see that it took some time for the penny to drop: its numbers have rocketed. First confirmed breeding in 1981, it now nests throughout the south and east and probably remains undetected in many counties.

The great spotted woodpecker, thought to have inhabited Irish woodlands up to the 16th century, was extinct in Ireland before bird recording began, and for centuries it was assumed it had never made it to Ireland in the post-glacial colonisations. No one believed it would ever return, but in 2006 a pair nested in Northern Ireland, which seemed like a freak event until many were noticed in Dublin and Wicklow in the following two years. A dedicated search of Wicklow woodlands last summer located eight nesting pairs. This was bird history in the making; the unthinkable had happened. Colonisation of the entire country is now on the cards.

The invasion was attributed to a three-fold increase in great spotted woodpeckers in England and Wales over the past forty years, which is presumed to have forced this highly sedentary bird to seek out pastures new. But that increase in itself has not been explained. I believe global warming is behind it, and that birds in France and Spain moved northwards, spilling birds into Britain and then Ireland. Feathers have been collected from the nests to try to trace the birds’ origins using DNA profiling.

The Climatic Atlas, which uses climate, bird and habitat data to simulate potential future distributions, shows great spotted woodpeckers moving hundreds of kilometres north, abandoning the Iberian peninsula, colonising all of Ireland and even occupying Iceland within the century. This time-frame starts looking a little conservative now that we already have woodpeckers here.

The atlas provides a window into what we might expect to see turning up in the coming decades. A long list of potential settlers includes honey buzzard, short-toed eagle, kentish plover, little owl, tawny owl, hoopoe, green woodpecker, middle spotted woodpecker, lesser spotted woodpecker, woodlark, tree pipit, bluethroat, black redstart, cetti’s warbler, fan-tailed warbler, savi’s warbler, melodious warbler, dartford warbler, firecrest, marsh tit, willow tit, crested tit, nuthatch, short-toed treecreeper, serin, cirl bunting. Ireland currently supports around 153 breeding species, though some of these are rare or irregular breeders.

Some potential newcomers have already begun nesting here sporadically, including little ringed plover, lesser whitethroat and (reportedly) hobby, while some of Ireland’s extinct birds have made a return (e.g. marsh harrier and the above woodpecker) and still more are on course for a comeback, e.g. corn bunting, montagu’s harrier, turtle dove, bearded tit.

Others are projected to multiply and spread from a low existing base – including gadwall, pochard, goshawk, grey partridge, quail, nightjar, yellow wagtail, redstart, garden warbler and pied flycatcher – although their resurgence could be hampered by ongoing losses from habitat loss, hunting and other pressures on the continent and further afield. Some are already so depleted that there is a question mark over their very survival, never mind their making it to Ireland.

We can also expect to see an upsurge in visits by migrants relocating to other parts of Europe, for example spoonbill and glossy ibis, a number of which are in Ireland at the moment. These species are unlikely to nest here but may well become regular visitors (as their potential future ranges will be nearer to Ireland).

Turning to potential losses, Ireland’s more northern or boreal species, breeding here at the edge of their range, will be lost as breeding species as they retreat further north. The extent of the projected losses is alarming and includes species as common as long-eared owl and black guillemot – which are very hard to imagine being lost to Ireland – as well as northern eider, common scoter, red-breasted merganser, goosander, golden plover, dunlin, common gull, arctic tern and twite. However, some of these will continue to visit coastal wetlands as winter visitors.

Other northern species may be driven to the edge of survival as breeding species in Ireland, including merlin, red grouse, woodcock, redshank, common sandpiper, black-headed gull, little tern, whinchat, ring ouzel, siskin, redpoll and crossbill.

The loss or depletion of many of these species has already been signalled by some range contractions towards the northwest of Ireland between the early 1970s and early 1990s, when the last two atlas surveys were carried out. (Another atlas is scheduled to be completed next year.)

All this doom and gloom is based on modelling studies and it must be said that some factors that could not be computed may result in different outcomes (as indeed could an immediate end to further carbon emissions). For example, a species such as tawny owl, which is widespread in Britain, does not migrate and would be reluctant to cross sea water; so we could be in for a long wait for that one, though it is projected to occupy most of Ireland. There will also be a time-lag in habitat change, perhaps of a hundred years, as trees (for example) are long-lived, and this could tide birds over, temperatures notwithstanding, until the climate change problem is sorted out, though that is unlikely to happen quickly enough.

I should mention that two new species became established in Ireland prior to the 1970s. The collared dove arrived in 1959 and is now ubiquitous on lowlying land. It was not driven here by climate change but was still filling its natural range and had not yet reached its climatic limit. The same may be true for fulmar, here since 1911.

The situation is fluid, dynamic and unlike anything we have experienced before. How will birds cope with their rapid relocation or, in the case of the residents, the competition from outsiders? These questions are exercising the minds of conservationists, who may fear that their life’s work up until now has been in vain (more on that in a future piece).

One more imponderable prompted by a reading of the Climatic Atlas: how will Iceland cope with the expected influx of so many northward-driven birds? The country lost its entire forest cover within centuries of the Vikings settling there in the ninth century. Are its habitats suddenly going to become hospitable to a large proportion of birds abandoning the south? Let’s hope it doesn’t come to that.