Tuesday, 20 July 2010

Signs of the times: Summer #8

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 bees, no honey; no work, no money”
Anon. proverb

(Copyright: Ladybird Books)

Summer Picture 8
It really is all about the birds and bees this time – literally – as Summer picture 8 shows a scene where three house martin nests under the eaves of a building, busily attended to by several house martins, are also being eyed up by a male house sparrow, potentially with a view to taking possession of one, while the nearby sweet smelling flowers of a lime tree are alive with visiting bees. In the background, in a logical progression from the previous picture, the next stage in the hay-making process of 1960 is being shown, with a farm-hand standing a-top a hay stack, arranging bundles of hay delivered up an elevator.

The house martin (Latin name: Delichon urbicum) originally nested on cliffs but seems to have adapted extremely well to nesting now under the eaves of buildings. The picture shows three nests – each has been made by a pair of house martins from up to a thousand beakfuls of mud from a nearby pond or other source of mud and, typically, house martins do prefer to nest in loose colonies. Like their close relatives, the sand martin and the swallow, house martins are aerial hunters, feeding, on the wing, on flies and aphids. The British Trust for Ornithology identifies that their loosely colonial habit and association with human settlements actually makes them extremely difficult to monitor, as the loss of a colony is no guide to decline overall as those birds may simply have joined up with another colony. The BTO reports that the available long-term data for this species suggest a rapid decline, although their Breeding Bird Survey results show an overall increase since 1994. Here is the graph for the population in England:

The species “was moved from the green to the amber list in 2002, because of moderate decline in the CBC [Common Bird Census] trend for 1974–99, and is newly listed as of European concern following declines elsewhere in Europe”. Yet, in Scotland, between 1995 and 2007, Scotland’s house martin population increased by over 100%.

Similar to what I discussed previously for the swallow and the sand martin, the success of house martins in Europe seems to be linked with the record of rainfall in West Africa, where they over-winter. I find it a pretty joyful Summer experience to watch groups of house martins, often mixed with sand-martins and swallows, busy feeding on the wing, chirruping away noisily.

The house sparrow (Passer domesticus) has to be one of the most popular species of bird in this country, probably not least down to its personification in popular culture as a “cheeky chappy” bird, the “cock sparrer”. Probably not for nothing was the happy-go-lucky pirate hero of the “Pirates of the Caribbean” films was Cap’n Jack Sparrow. Unflashy brown and grey plumage, perhaps the simplest of all songs – the house sparrow call literally is just “chirp” – and a habitat selection for many sparrows in the vicinity of houses and gardens in our settlements, where they nest in noisy colonies in hedges, under eaves, etc, all contribute to our familiarity with this little bird. So, a major decline of the house sparrow in Britain in recent decades has been something of a cause celebre for the conservation movement. The British Trust for Ornithology points out that there are inadequate data for monitoring trends in house sparrows before 1976 but, as the following graph from the BTO shows, since that date there has been a significant and dramatic decline in the population of this species.

The BTO summarises the suggested possible causes of the decline of the house sparrow as including: a general reduction in food supply - less grain being spilt during agricultural operations and tighter hygiene regulations - increases in predation, and toxic additives to unleaded petrol.

There is, however, a more complicated picture – the above very strong decline at the UK level masks different trends at regional level. In Scotland, for example, as the graph below shows, in Scotland, there has been a strong recovery of the house sparrow population here since 1995 (84%).

I think I have noticed the effect of this increase here in Stirling. When we moved to our present house in the late 1990’s, I did not see a single house sparrow in this area, until about 4 years ago, when they appeared in considerable numbers, perhaps a consequence of rising populations out in the surrounding farmland.

A potential effect of a warming climate, the average date of egg-laying by house sparrows in the UK is now eight days earlier than in 1967. My favourite house sparrow moment was while growing up on a farm in East Lothian when, one day, I found two male house sparrows on our gravel path, beaks locked together in some battle for what-I-don’t-know. And they stayed like that for about another minute, unmoving, as I stood next to them until I touched one gently on the back and said “Hello”, at which point they let go, shook themselves and fled in a panic!

The lime tree in flower in the top let of the picture is the most common lime tree species in Britain, “the Lime Tree” (Latin name: Tilia cordata x platyphyllos). I learned something new in looking up information for this post. I hadn’t known that the common lime tree we see planted in parks, streets and avenues everywhere is actually a fertile cross between two other native lime tree species, the small-leaved lime (Tilia cordata) and the large-leaved lime (Tilia platyphyllos). As native trees, these latter two species have a largely southern distribution, although there are pockets of native populations of small-leaved limes in southern and western Scotland. As a native species, the fertile cross which is so widely distributed as a planted tree actually does occur in a few woods in England where both parent tree species are found. The relative size of the leaves and flowers on the lime in this picture suggests that it is the common lime hybrid. Lime flowers are wonderfully sweet-smelling and are the basis of the lindenblumen (lime-flower) tea beloved on continental Europe. We collected and dried some lime flowers last summer and kept them in an airtight jar. The addition of boiling water to a few flowers makes a subtle honey-ish tea (which apparently was used as a mild sedative during the last war). We’ve been too busy at just the wrong time this year and missed the chance to collect some fresh flowers but, a year on, the lime flowers we dried in summer of 2009 still smell sweet and are still perfectly useable.

The New Atlas of the British and Irish Flora reports the distribution of this hybrid lime species as stable since 1962. In Flora Britannica, Richard Mabey writes: “All groups of lime trees, of whatever species, are wonderfully fragrant when in full blossom in July. They are also the noisiest of trees at this time, and the roar of bees in them can often be heard 50 yards away.” I can confirm this – our neighbours have two mature common lime trees over the wall from us and on dry days this Summer, particularly when sunny, they have been alive with bumblebees and honey bees. The loud hum reminds me of a high power electric cable and is the collective sum sound of thousands of insects harvesting nectar and pollen. And, by the way, honey produced from lime flowers is delicious.

And so, neatly, on to the bees in the picture, which look to me like honey bees (Apis mellifera). Since the Ladybird Summer book was published, coverage of honey bees has moved from specialist bee-keeping literature to the front pages of national newspapers, on account of the global decline in honey bees. This is an issue of major global concern as bees, including domestic and wild honey bees, as well as other bees such as bumblebees are responsible for pollinating the agricultural and horticultural crop responsible for one in three mouthfuls of our food. Similar to the problems in the USA, Europe and elsewhere, some 15-30% of Britain’s honey bees may have died in recent years. Proposed causes so far range from the likely to the plain wacky-sounding, from parasites like the verroa mite, diseases like the bacterial foul brood (of which there has just been an outbreak in Scotland), pesticides and other artificial chemicals, to GM crops and mobile phone signals, all hypothesised to have led to collapses of bee colonies. In practice, perhaps there are several causes all leading to colony or hive collapses alone or in combination. Such concern is there over this issue in Britain that, in a new initiative, up to £8m will be made available for research into bees by the Biotechnology and Biological Sciences Research Council (BBSRC), the Natural Environment Research Council (NERC), the Wellcome Trust and the Scottish Government. The new funding is in addition to the £2m announced previously by the Department for Environment, Food and Rural Affairs (Defra) to help bee research. The funding increase will be a big rise in government spending on bee research, which previously amounted to £1.2m annually in the UK, much of which was spent on bee inspectors.

Finally, just a quick word about the next stage in the annual hay-making process in 1960, shown in the picture’s background, where the farm-worker (Flatcap? Of course!) is loading hay bundles from an elevator on to a hay stack. Hay hasn’t been made this way done for decades, since the advent of, first, “square” (cuboid, actually) and then round hay bales, and the rise of silaging instead of hay-making.

1 comment:

  1. Good post, I expect like with most things there are many causes for species decline and increase. In the world of trees it is never one causal agent.

    I recently spoke to a chap who told me of the dramatic increase in crop density oner the last 100 years so that yield per acre has increased by 150%. He blamed that for the decline of song birds.

    Thanks for sending me a link to this post.


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