Wednesday, 31 March 2010

Signs of the times: Spring #6

More comparisons between the British countryside of today and that from 1959-1961 in the paintings of Charles Tunnicliffe in the Ladybird "What to look for..." series of books.

"No matter how long the winter, spring is sure to follow". Anonymous proverb

I write this post about Spring while sitting in Stirling waiting for the arrival of a massive dump of snow described the Met Office forecast as “extraordinary”. So, Spring on hold for a couple of days, just as the frogs finally got busy in my garden pond and laid some big clumps of spawn. But, however delayed the Spring is in the real world outside, the world of Ladybird book Spring rolls on and, if I want to keep to the contemporaneous schedule of comparing today’s seasons with the world of 1959-1961, I need to crack on! So...

Picture 7 in the Spring book is an active little river scene which illustrates several interesting issues. A couple of grey wagtails, the pretty, yellow-breasted, grey-backed birds with the long tail, are an obvious feature. But there is also flowering butterbur among the pebbles, with some early flying bees. In the river, we see a fish, the Miller’s Thumb, and a freshwater crayfish.

The grey wagtail (Latin name: Motacilla cinerea) is an insect-eating bird, which is most common alongside fast-flowing upland streams, is found in much of the UK all year round, and in northern Scotland as a summer breeding visitor. Although not a threatened species in Europe, the grey wagtail population underwent a substantial decline in Britain, of 41%, recorded between 1975 and 1999, as shown by the following graph from the British Trust for Ornithology (BTO).

As a result, the species was moved from the UK's green to the amber list in 2002, and is still in that category despite substantial population recovery. The BTO gives no indication of what may have led to this decline of the subsequent recovery. One small indication of a climate change effect for this species is that, since 1968, the average date of egg-laying by grey wagtails has moved to be a week earlier. Although the trend is upwards now and grey wagtails seem to be recovering, it would be good to understand the initial cause of their decline.

The picture shows a flowering plant which the text describes as both the winter heliotrope and the butterbur. I’m not sure whether, when the book was written, both of these names referred to the same plant species, but today, these would be different species. Checking my wild flower field guide (Francis Rose: The Wild Flower Key. British Isles – N.W. Europe), the picture is definitely of the flowers of butterbur (Latin name: Petasites hybridus). This is a native species that can flower as early as November in some parts of Britain and, according to the text, “is one of the few sweet-smelling flowers we can gather at Christmas.”

A key source of information on the status of butterbur is the “New Atlas of the British and Irish Flora”, written in 2002 by the Centre for Ecology and Hydrology and the Botanical Society of the British Isles. Conveniently for my purposes, the Atlas says that the distribution of butterbur: “is little changed since the 1962 Atlas”. It seems that most of the butterbur plants in Scotland are in male-only colonies and may even have resulted from deliberate plantings as a source of pollen and nectar for hive bees. More on bees later in the Spring as there is already a lot to cover in this picture. Incidentally, had the picture truly shown winter heliotrope (Latin name: Petasites fragrans) rather than butterbur, this would have been the first non-native, introduced species shown in the book, being first introduced to Britain in 1806 and thought still to be spreading in Britain.

While the butterbur seems to be coping with the modern world, from a conservation perspective, the remaining species paint a more mixed picture of change. The freshwater crayfish peeking from under a stone would, in 1959-1961, almost certainly be a specimen of the then-common and widespread native white-clawed crayfish (Latin name: Austropotamobius pallipes). The story of this species isn’t that relevant to Scotland as it is not native here (although a couple of populations were introduced to two limestone lochs in the far north of Scotland in the mid-late 20th Century). The Joint Nature Conservation Committee describes the story of the white clawed crayfish thus:

“The white-clawed crayfish Austropotamobius pallipes lives in a diverse variety of clean aquatic habitats but especially favours hard-water streams and rivers. A major threat to the native white-clawed crayfish is posed by the introduction of non-native species of crayfish, which have been farmed in Britain since the late 1970s.” More on this below...

As the UK is required, as a result of the European Habitats Directive, to identify and designate sites for the protection of the white-clawed crayfish, it is also required to report back to the European Commission every six years on how well this protection is progressing. Unfortunately, the JNCC has to report that not only are populations continuing to decline, but that the rate of this change is accelerating. This can be illustrated by comparing a 2002 report figure of 260 occupied 10 km squares with a 2005 report figure of 241 occupied 10 km squares; a decline of approxiately 7%, equivalent to more than a 25% decline over 25 years.

The main cause of this decline? As well as pollution and habitat loss, non-native crayfish species were introduced into Britain for aquaculture in the late 1970s. Shortly afterwards, crayfish plague (a virulent disease caused by a fungus species, Aphanomyces astaci) broke out and spread rapidly. Native crayfish in rivers across declined rapidly thereafter across England. It is only in areas free of disease that the native white-clawed crayfish is likely to survive in the future. North American Signal crayfish, which are larger and more aggressive than the white-clawed crayfish, can also outcompete them for food and habitat. In Britain, signal crayfish are now well-established in the wild. In Scotland, Scottish Natural Heritage has a specific project under its Species Action Framework to seek to tackle the problems arising from this non-native crayfish

The final issue raised by this picture is the fish, the Miller’s Thumb, also known as the bullhead (Latin name: Cottus gobio). This is a small fish well-adapted to its life on the bottom of stream, rivers and stony lakes. Its distribution in Britain is described by the JNCC as:  “Good populations are widely distributed in freshwaters across almost the whole of England and much of Wales, but in Scotland the bullhead Cottus gobio is restricted to the Clyde and Forth catchments, where it is thought to result from an introduction.”

As it has been widely used by anglers as live bait for catching, e.g. pike, it is quite possible that this is how it was introduced into the Scottish rivers although, in their book, "Freshwater fishes of the British Isles", the fish biologists Peter Maitland and Niall Campbell highlight that it was once valued for its “sweet tasty” flesh (by the famous angler Isaac Walton and other historic authorities), it might also have been introduced to locations for gastronomic reasons. In Scotland, according to Peter Maitland in his book: “Scotland’s freshwater fish. Ecology, Conservation and Folklore”, its range in Scotland is probably slowly expanding in Scotland. For example, being recorded in the Union Canal, it is presumably capable of spreading across Central Scotland. The JNCC looked at the status of the bullhead using data on its distribution before 1972, from 1972-1992, and then after 1992 and, essentially, no evidence was found of a decline in range in Britain. So it is probably doing fine compared to its status in 1959-1961.

A European-funded conservation project I was involved with a few years ago produced guidance on the ecology of this species, which summarised its interest quite nicely as:

The bullhead has several fascinating behavioural traits that make it a unique and distinctive little fish. These include nest production and parental care by the male, defence of territory, visual threat displays and the production of sounds. It is a relatively adaptable species with a wide distribution throughout Europe, but its distinct habitat requirements mean that it is vulnerable where river channels have been modified or where there is a changed flow regime or increased siltation.”

[By the way, the snow never arrived here last night after all, other than a fine dusting that was gone by morning, even although perhaps only 5 miles away to the north and east, there was a big dump of snow. This is a disappointingly normal outcome for snowfall in Stirling.]


  1. Tonnes of butterbur at Muckersie...

  2. It's lovely with its great big floppy leaves. It used to be used to wrap butter in shops, you know!

  3. I love these articles! According to the weather man yesterday, there's a statistically higher chance of snow at Easter than at Christmas... just thought you'd like to add that to your statistics! Lots of snow, and frog spawn, in East lothian this week.

  4. big bro your a hive of information!, do you have the observor handbooks too?,

  5. @coastkid - ta! It is a good excuse to read up on things I ought to know but often don't! Yes, I collected my Observer books from mum's recently. Still thinking about their blogging potential! ;¬)

  6. @Christine - many thanks - you can probably tell that I am enjoying the experience. Nice to have complementary information like yours, along with complimentary comments!


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