NWA 6/8 - 21/2012

A Northwoods Almanac for June 8 – 21, 2012 by John Bates

Two Weeks in the Scottish Highlands

            Mary and I just returned late last night (6/4) from two weeks of hiking in the highlands of northwestern Scotland, and though our legs be a wee bit tired, we had a glorious time. I apologize for not responding to those of you who e-mailed and called over this time with many interesting sightings, and for not reporting those sightings in this week’s column. I promise to write them all up in my next column.

            As for what natural history connections exist between northern Wisconsin and northern Scotland, so much overlaps that it’s hard to know where to begin! It’s always fascinating to see non-native, invasive species in Wisconsin that are no problem in their native land. Mute swans, starlings, and house sparrows come to mind right away, and it’s notable that several of them are in decline in Britain. Starlings have been declining sharply in Britain for many years, in part due to changes in agricultural practices and the loss of permanent pasture. Our “RSPB [Royal Society for the Protection of Birds] Handbook of Scottish Birds” actually suggests “these birds can be helped by the provision of nestboxes,” a suggestion that would horrify North American birders.

            House sparrows, too, have declined – a 62% loss in Britain between 1974 and 1999, a decline that continues to this day and is somewhat of a mystery.

            Mute swans, however, are doing fine. They number 1,000 pairs in Scotland alone, and have recently been expanding their range largely due to a ban on the sale of lead fishing weights and the prohibition of lead shot in cartridges used over wetlands. The swans were once prized for food at banquets, and I suspect their failure to appear today on local menus has also improved population growth.

Red Squirrels – An Endangered Species in Scotland

            Invasive species cross the ocean both directions, of course. Our North American grey squirrel was introduced into Britain in the late 19th century (1876 onwards), and has replaced Britain’s native red squirrel in most of its former range.

Three factors have led to the profound decline of red squirrels. Red and grey squirrels occupy a similar ecological niche. Both are small tree-dwelling mammals that rely on similar food sources (tree seeds, nuts, berries, etc), but because of differences in their ability to digest large seeds and acorns from broadleaved trees, grey squirrels have a competitive advantage over red squirrels that results in weight loss and reduced breeding success for reds.

Extensive tree cutting between 1914 and 1945 throughout Britain, and subsequent felling of Scots pine and Norway spruce plantations as they mature, have largely been replaced with new plantations of Sitka spruce that offer a limited food supply for red squirrels. Remaining woodlands have been further fragmented by the loss of an estimated 50% of the hedgerow habitat in Scotland between the 1940s and 1980s. Continuity of habitat is important, and the loss of hedgerow links between woodlands has resulted in the isolation of red squirrel populations, increasing the risk of losses from predation when red squirrels have to cross open areas.           

But the most devastating reason for the decline of red squirrels has been the incursion of the Squirrelpox virus, carried by gray squirrels. Harmless to them, it’s lethal to the native reds, with the reds dying a horrible death over two weeks. The Squirrelpox virus also has the devastating effect of speeding up the rate at which grey squirrels displace and replace reds (usually about 15 years) by a factor of twenty, denying researchers adequate time to develop an effective vaccine for reds.

Scotland is home to over 75% of Britain’s endangered red squirrels with the country representing one of the last strongholds for the species in the UK. We saw numerous red squirrel road-crossing signs throughout Scotland, and a very concerted effort has been undertaken to vastly reduce the grey squirrel population.

Scotland’s red squirrel is a bit different than Wisconsin’s, most notably in having pointed ear tufts, but otherwise looks and acts the same. How interesting that a species that is considered so common to us is of such great concern to people in Britain.

Other Invasive North American Species - Mink and Ruddy Duck

            Ruddy ducks became established in Britain and Europe after escaping from wildfowl collections. In Spain, ruddies hybridize with an endangered species of white-headed ducks, but because ruddies are a dominating species, the fear is that they will exterminate the white-headed duck from all of Western Europe. Thus, a major cull of ruddy ducks is currently being carried out by many countries across Europe.

            As for American minks, Scotland has been overrun by them. The animals were brought to Britain back in the 1950s to be farmed for fur coats, and now tens of thousands are running wild and wreaking havoc on other species.

The minks patrol river and loch banks looking for birds and frogs and small mammals — in particular voles. Voles are beloved in Scotland, famed by Scottish novelist Kenneth Grahame who used a water vole as a main character in his children's book The Wind in the Willows.           

Now, 95% of the voles are gone, thanks in large part to the minks. The Scots have a major campaign to clear their lands of the invaders, with the goal to kill them all! So far, nearly 4,000 square miles of Scotland have been declared mink-free.

           

Osprey Reestablishment

And then there are those species that are circumpolar in their distribution, some of which are doing very well here, but are struggling there. Ospreys are particularly notable. The osprey used to be distributed throughout Europe, but heavy persecution, mainly by Victorian egg and skin collectors during the 19th and early 20th century, brought about dramatic decreases and extinctions. 

The osprey became extinct as a breeding bird in England in 1840 and in Scotland in 1916. In 1954, it recolonized naturally and a pair has nested successfully almost every year since 1959 at Loch Garten, an RSPB reserve in Scotland’s Cairngorms National Park. The Osprey Centre at Loch Garten has become one of the most famous conservation sites in the world – over 2 million people have visited to see a particularly famous pair of nesting ospreys, the 27-year-old female of which has now returned for 22 consecutive years to breed, and has successfully reared 50 chicks. She winters roughly 6,000 miles south in West Africa.

The osprey’s overall reestablishment was very slow, probably because of organochlorine pesticides in the food chain and due to the continued activities of egg collectors, and had reached only 14 pairs by 1976. However, by 2001, 158 breeding pairs were located, mainly in Scotland. That same year saw the first successful nesting of ospreys in England.

Ospreys now number around 200 pairs in Scotland, and we saw one nest on top of an electric pole, just like around here, on a trail at the Pass of Killiecrankie not too far from Loch Garten.

Handa Island Seabirds

            Perhaps the birding highlight of our trip was a visit to Handa Island nature reserve near the tip of northwestern Scotland. Managed by the Scottish Wildlife Trust (SWT) Handa’s dramatic sea cliffs host one of the largest seabird breeding colonies in Europe with around 100,000 breeding birds, including internationally important numbers of guillemots and razorbills.

From the cliff path, we could observe the nesting bird's daily activities. Around 45,000 guillemots nest precariously on narrow cliff ledges, along with thousands of kittiwakes, fulmars, razorbills, and a small number of puffins that breed in burrows lining the cliff edges.

Great skuas and Arctic skuas nested on the ground across the moorland areas of the island, along with red grouse and common snipe on the island, all of which were remarkably approachable because of no hunting on the island. We were able to watch a red grouse displaying for a female who paid him little attention, instead continually bathing herself in dirt. Arctic tern colonies have also recently formed on the southern shores and we could see them feeding in the shallows of the landing beach.

Back in the U.S. – Great Backyard Bird Count

Participation in the 15th Great Backyard Bird Count, February 17-20, shattered all previous records. Bird watchers in the U.S. and Canada submitted more than 104,000 checklists, reported 623 species, and observed more than 17.4 million birds. New checklist records were set in 22 states and in 6 Canadian provinces.

Participants reported the northern cardinal on more checklists than any other species for the eighth year in a row, closely followed by the mourning dove. The most numerous bird species reported during this year’s count was the snow goose, followed by the tree swallow, with its first-ever top-10 appearance. A single massive flock of an estimated one million tree swallows was reported in Ruskin, Florida (Google this event to see videos)!

This year’s GBBC results are available on the website (http://www.birdsource.org/gbbc/). GBBC maps show reports for snowy owls that plainly demonstrate the massive influx compared to previous years. The maps also show that common redpolls moved farther south in western areas in search of food, while a lack of acorns may have reduced reported numbers of blue jays in the Northeast. Sandhill cranes and red-winged blackbirds were also found to be already migrating during the count.