Tuesday 20 March 2012

Peter Roberts reports on the Scottish Birdwatchers' Conference in Oban

A one-day conference in Oban on 17th March jointly arranged between the Scottish Ornithologist's Club and the British Trust for Ornithology included a number of short lectures relevant to wildlife conservation issues on Islay.

An opening talk entitled “White-tailed Eagles in Scotland: back for good”?  given by Richard Evans illustrated the former extensive range over much of Britain of this largest of British raptors, its gradual man-made decline to extinction in 1916 and its subsequent reintroduction starting on the Isle of Rhum in 1975. By 1985 the first young were fledging in the wild of what some would consider an iconic species. The release of additional young birds (taken as “surplus” from nests in Norway) ended in 1998 and in 2012 there are 58 breeding pairs along an extensive area of the rugged west coast and islands of Scotland. But, with a population growth of 10% a year and no signs of a slow-down, the main question posed by the lecture was “will this increase affect numbers of another iconic species – Golden Eagle?” Happily, so far, studies indicate the simple answer seems to be “No”! There is no shortage of habitat for either species and plenty of scope for expansion (illegal persecution of both eagles will probably be the limiting factor at least in the short term). Do the two eagles compete for food? Studies on Mull where both are nesting in good numbers suggest there is much less overlap in prey than first feared. White-tailed Eagles predominantly take fish and waterbirds, while Golden Eagles take a much higher proportion of hares, rabbits and game birds. However there is certainly more dietary overlap in Scotland than in other areas where they breed close together and both are recorded feeding together on carrion, where neither appears obviously dominant over the other. Do they compete for suitable nest sites? Again the answer was generally “no, not much”. White-tailed Eagles tend to nest at lower altitudes and in areas with greater tree cover than Golden Eagles. There has been no noted decline in Golden Eagle nesting distribution as White-tailed Eagles have increased over the past 20 years and each is far more likely to tolerate a close nest of the other species than another of its own. Historical records suggest that in the Western Isles White-tailed Eagles rubbed along with Golden Eagles where both nested in open coastal sites. So there is hope for a happy and non-confrontational outcome with our healthy population of nesting Goldies as, when and if the White-tailed Eagle arrives to breed again on Islay.

Islay's own resident Chough expert, Eric Bignal (ably assisted by his daughter Caitlin) gave a fascinating account of “Supplementary feeding of sub-adult Choughs on Islay”. Eric and many others have studied Islay's Choughs over decades to understand their ecology and keep this very special bird in good heart (Islay and neighbouring Colonsay are virtually the only places left in Scotland where Choughs occur). Eric has colour-ringed 1,552 chicks since 1981 and he probably knows most of the island's Choughs individually. He started by educating us about a few important points on Chough ecology. 1. Chough young stay with parents for a month or two after fledging then parents “abandon” them, the young joining non-breeding flocks that include surviving young from the previous 2-3 years which have not yet started breeding. 2. Two very important habitats for these family groups and non-breeders are silage fields after cutting and the island's sand dune systems. 3. There needs to be about a 30% survival rate of first year birds for the population to sustain itself. It is the survival of younger birds more than adult survival or fledging success that is more vital for overall species success. But then came the bad news. After many years when Islay Choughs flourished, the first year survival rate has dropped to 10% since 2007 and the population is in decline. Nobody is sure why this is happening. Could it be subtle habitat and land management changes or could it be a “temporary blip” caused by the recent severely cold and unusually wet winters, which are all known to cause higher mortality through a scarcity of invertebrate foods.

Whatever the reason it was decided by Eric and others supporting his work that it was too risky to just let the population decline further, so in December 2009 he began putting out daily supplementary food (aka mealworms) for Choughs. After a slow start they eventually cottoned-on to a free hand-out and there are now upwards of 50 birds at one site and 25 or more at another. The birds taking food include those important 1, 2, and 3 year olds that are our future breeders. By 2011 the survival rate of the first year birds was back up to the all-important 30%.

Clearly this isn’t a long-term sustainable solution, but until the problems of poor survival are addressed and the weather improves, at least it may keep this important population of a very special bird alive and well on Islay.

There were two very topical talks on “Marine Renewable Development” (offshore wind-farms and underwater turbines to you and me). One by Nienke van Geel addressed potential threats to the conservation of marine mammals, the other by Chris Thaxter looked at threats to seabirds. Renewable Energy development is still in its infancy, but Government and European targets for renewable energy in the future mean that there is a huge interest in developing this energy source. Yet we barely know how many of what species of seabirds, whales and dolphins are out there in our offshore waters, let alone how such developments may or may not affect their well-being. This is a very complex subject with no easy answers. The thrust of both talks was that researchers are still developing methods by which to assess what species are present, their numbers and how they use this offshore marine environment for feeding, breeding, resting, communicating and migrating. At the same time others are trying to work on plausible ways of assessing what effect the many and varied types of offshore energy sources may have on wildlife. Needless to say “computer modeling” was referred to on many occasions. I think one illustration of computer-generated results studying whether a dolphin was likely to hear an underwater turbine and thus avoid it, says it all. Depending on the many variables and parameters fed into the computer analysis it was shown that a dolphin might hear the turbine anything from 2 miles (about an hour) away or just 2 seconds before it presumably collided!

A more down-to-earth talk was given by Clive Craik who has been tirelessly studying – and doing something about – the scourge of feral Mink on seabird populations on the inshore islands of the west coast of Scotland for 25 years. Clive annually checks 155 small islands with about 8,000 pairs of seabirds on them. He showed us the horrific consequences of mink reaching these colonies – gruesome photos of hundreds of chicks slaughtered in a single night by one mink; dozens of adult gulls killed on nests, the mink killing far more than is required for food. Many colonies are now gone due to mink, but he tirelessly battles to eradicate mink with instant success when he does - birds recolonise and many young reared, but it is hard and costly work. He finished with examples of great lateral thinking: “if you can’t keep mink off close inshore islands, then build huge rafts that are mink-proof and let the birds breed there instead”. These now support some of the largest tern colonies in Scotland.

One of the final talks, given by Christine Urquhart, was relevant to many of us on Islay - goose conservation and management in Scotland. She highlighted the huge increases in most geese in Scotland over the past 40 years and gave a brief history of the 7 or so goose management agreements currently in place. She contrasted two species in particular – the rapidly expanding breeding populations of Greylag Geese and the decreasing winter numbers of Greenland White-fronted Goose. Greenland Whitefronts are in decline after past years of increase and are recognized as a high priority and “Red-listed”. Many former wintering areas are now no longer used and numbers continue to drop, due to a fall in nesting productivity. Reasons for this are unclear, though discussion centred on whether this was due to rapidly increasing and encroaching wild Canada Geese (a population of 40,000 pairs in a few short years) into areas of Greenland where the Whitefronts nest, or possible climate and habitat changes – there has for example been a marked increased in spring snowfall on breeding grounds. It is hoped that this is just cyclical and sooner or later weather patterns may change in the species favour again. Meanwhile, they are now no longer being shot in Greenland or as they migrate through Iceland and farmers on Islay, one of their wintering strongholds, are being given increased payment incentives for hosting Greenland Whitefronts on their land.

Greylags are a very different story. In the 1930s there were perhaps 500 breeding pairs in the NW of Scotland. Nowadays there are 47,000! No compensation payments are made to farmers on the Uists and Tiree, but lethal scaring is allowed with shooting of up to 33% of the population in recent years which is considered unsustainable. Culling at 15% of population was suggested as appropriate. The Orkney population is now rising rapidly and not only farmers are concerned for their land, but SEPA also concerned about contamination of some freshwater lochs.

The Conference was fascinating and informative, but the overriding impression one came away with is that there are always “more questions than answers” and that wildlife management is a constantly changing set of facts, ideas and aims that require never-ending reassessment and a pragmatic and fluid approach in the way we deal with them. On a more local note it highlighted how important Islay is for its fine an array of year-round wildlife.

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