Saturday 19 November 2005

Highlights of a quiet afternoon birding

Dropping down from the ridge running west from Burnham Market you get a wonderful view over Titchwell marsh. On a bright November Sunday, you can see dozens of birdwatchers making their way to the hides that overlook the scrapes on Titchwell Reserve. At this time of year there are many different birds to be seen from these hides and, with lots of eyes scanning the flocks of waders and wildfowl, there is always the chance of something rare or interesting. But today I want to avoid the bustle of the crowds and find some solitude worthy of such a clear day. For me, one place to do this is at Gypsy Lane. Situated to the east of Titchwell, a small lay-by marks the entrance to a narrow lane running north to the coast and passing through a sequence of habitats.

The first part of the track is bordered by a strip of linear woodland, with a range of bushes and shrubs, from which the soft call-notes of foraging birds can be heard. It is well worth pausing to watch and listen as mixed feeding flocks, often of tits and late warblers, work their way past in search of insects and seeds. On this occasion there is no hoped-for rarity, like a Pallas’s warbler, but there are goldcrests in with the tits. As the trees thin, there is a glimpse of two jays, another bird that, like the goldcrest, is much in evidence this autumn. There are also glimpses out across Titchwell Marsh, over which hunting harriers may sometimes be seen – though not today. Then it is out from the cover of the woodland and onto the bank that puts you above the reeds, pools and saltmarshes which flank either side.

Almost immediately I can hear the scolding call of a wren from low down in the vegetation just a few metres away. Further off, I can hear the ringing calls of a small party of bearded tits as they move excitedly through the tops of the reeds. These are one of the birds I have come to see. Standing by my scope, I wait and listen as they move closer, slight movements in the reeds giving away their location. Finally they show themselves, brightly coloured and almost comical in appearance, these delightful little birds are always a joy to watch. Although they are scarce (nationally there are about 500 pairs), the counties of Norfolk, Suffolk and Essex hold about 40% of the breeding population and provide some of the best opportunities to see these birds. Only part way through my walk, and with the prospect of more birds to see, the journey up to the coast has already proved worthwhile, something I can reflect on over tea.

Friday 18 November 2005

Be prepared for busy bird tables

There was ice on the car windscreen the other morning and a definite chill in the air. Another indication of the drop in temperature was an increase in the numbers of birds visiting my garden feeding station. In with the regular greenfinches, were chaffinches, blue tits and coal tits, attracted by the sunflower hearts that I provide throughout the year. Providing food in this way gives a good indication of the numbers of birds around and of the availability of ‘natural’ food in the wider countryside. Towards the end of summer there is a noticeable drop in the numbers of birds visiting the garden, as birds that may have been breeding locally move out into the surrounding farmland and woodland to exploit the autumn bounty of fruits and seeds. Evidence from the 16,000 gardens that participate in the British Trust for Ornithology’s Garden BirdWatch scheme shows that this autumn trough is a national feature, repeated in gardens up and down the country. It is only when the bounty begins to decline, that the birds turn to gardens and the food that we provide.

Just how early into the winter birds like siskins, chaffinches and bramblings move into gardens is, in part, dependent on the size of the seed crop produced by trees like beech and sitka spruce. In some years, when the seed crop is particularly large, there is little need for these birds to visit gardens but in those years when seed is scarce, they can arrive early and in large numbers. The size of the seed crops of these two tree species follows a roughly four-yearly cycle, a strategy that enables the trees to reduce the impacts of seed predators on their precious seeds, with years of peak seed production followed by a number of years of much smaller crops. It just so happens that this year the quantities of beech seed (known as beechmast) and spruce cones are both small, something that has seen siskins arriving in gardens across East Anglia earlier than they would normally appear. This hints at a busy winter ahead, with large numbers of finches usng garden feeding stations. Because there tends to be a degree of synchrony in the size of the seed crop across large areas, we are also likely to see increased numbers of birds arriving here from Scandinavian forests. If, as the weather forecasters are predicting, we end up with a severe winter then this too will increase the numbers of birds visiting gardens. Joining the finches will come farmland buntings and thrushes, seeking the food needed to get them through the worst of the winter weather. So now is the time to stock up on birdfood, prepare yourself for the winter ahead and the sight of busy bird tables.

Thursday 17 November 2005

A four-spotted two-spot

We had a visitor to our office this week, quite possibly attracted by the lights that illuminate our work on these increasingly dark afternoons. The visitor in question was a ladybird, a two-spotted ladybird to be precise. This species is one of our most familiar ladybirds, easily recognised and seemingly as at home in urban areas as it is in the wider countryside. Two-spotted ladybirds often bring themselves to our attention through their habit of hibernating around our homes, even appearing indoors during spring. They are good creatures to have around if, like me, you are a bit of a gardener. Two-spotted ladybirds have a real taste for aphids, feeding on a range of different species including the black ones that are associated with leaf curl on cherry trees.

I should not have been surprised, therefore, to encounter one inside at this time of year. What did cause me to raise an eyebrow though was the fact that this particular individual was of the melanic form. In melanic individuals, the red and black colouration is reversed. So, instead of black spots on a red background there were red spots on a black background. Not only this, but instead of the two spots that give this species its name there were four! (It is worth mentioning that some melanic forms of this species have six red spots.) One of the surprising features of ladybirds is just how much variation in colour and pattern there may be within a species. While some species are pretty uniform in their appearance, others are very variable and the two-spotted ladybird is one of the most variable of all. The most common form of two-spotted ladybird is the one with a large black spot, set against a red background, on each wingcase. The melanic form is far less common. One recent study suggested that within a population about 4% of individuals would be melanic. Because this variability in colour and pattern has a genetic basis, you sometimes find clusters of a particular colour form within a small area. However, this was the first such individual I had encountered locally. One of the problems, for a budding entomologist at least, with having such variability is that it can make it more difficult to identify a particular species. The individual I had found was superficially similar to a pine ladybird but lacked the characteristic turned up edges to its wingcases shown by the latter species. I did take the ladybird home though, to double-check my initial identification with a hand lens. Seemingly underwhelmed by the amount of attention it attracted, the ladybird was released by my shed in the hope that it would find a safe place to spend the winter.

Wednesday 16 November 2005

Master of the reedbeds

Sunday morning found me settled in Dawkes hide, looking north across the Norfolk Wildlife Trust’s Cley Marshes reserve. It was early enough for the hide to be relatively still and the only other birdwatchers present were a handful of regulars. Judging by the conversation, these ‘old boys’ had been coming here for many years, enjoying the wide range of birds attracted by the reserve’s position on the North Norfolk coast. As I scanned the reed-fringed pools and wet grassland, passing over teal, shoveler, gadwall and resting waders, my gaze settled on the familiar shape of a harrier working the edge of the reeds in search of prey. As the bird turned, the sun caught on the golden cap – a marsh harrier and a real master of East Anglia’s reedbeds.

With a little patience, good views of this wonderful raptor are virtually guaranteed at a number of sites across Norfolk and Suffolk. Yet, the fortunes of this species have undergone dramatic change over the last 200 years. In the early 1800s, the marsh harrier was common across much of Britain and Ireland but widespread persecution led to a rapid and well-documented decline. By the late 1870s the species was restricted to the Norfolk Broads. Over the next thirty years there were a number of failed nesting attempts, the birds falling foul of persecution and the unwelcome attentions of egg collectors, and the ‘last’ recorded nesting attempt was in 1899. It was not until 1921 that a successful attempt was again documented and a recovery of sorts began. With the exception of 1937 and 1940, nesting attempts have been recorded every year since 1928, although there was another decline in breeding numbers in the 1960s. This was attributed to the use of organochlorine pesticides, which hit predatory birds hard because of their position at the top of a contaminated food chain.

Most of the recovery has happened since the mid-1970s and there are now thought to be at least 200 breeding females nationally. Male marsh harriers can form bigamous relationships, so the number of breeding females is the most appropriate unit by which to measure the population. Two important changes in the behaviour of this species may have contributed to the population increase. First is the tendency for some individuals to overwinter here, rather than make a migratory journey south to wintering grounds in southern Europe and Africa. The second change has been for birds to nest away from reedbeds, moving into arable crops, a habit that was first documented in west Norfolk in 1982. The skill of these birds when hunting and the way in which they use the wind to work their way across the ground make them a delight to watch, especially from a comfortable hide in good company.

Tuesday 15 November 2005

What is in a name?

As I opened the door the night before last, I was delighted to see a small beetle scurry in across the threshold. Metallic blue in colour and roughly a centimetre in length, I recognised it as Leistus spinibarbis, a ground beetle that I had first learnt to identify several years ago thanks to the tutorage of Brian Eversham and Mark Telfer. There is nothing particularly special about Leistus spinibarbis; it is not rare but enjoys a distribution that takes it from Britain, across Europe and into Africa. What is interesting, though, is that this species lacks a common name. Like virtually all of the other 360 or so ground beetles found in Britain and Ireland (and the vast majority of invertebrates worldwide) it is known simply by its scientific name.

Scientific names form the basis by which species are classified. They are necessary because the names given to individual species must be understood across the World. As such, they represent a common language by which researchers in different countries can be sure that they are referring to the same species. The application of scientific names is governed by an international code to which the naming of newly discovered species must adhere. The name Leistus spinibarbis follows what is known as the binomial system, first applied by the naturalist Carl Linnaeus in 1758. Under this system, the scientific name consists of two components: the first (Leistus) referring to the genus (a taxonomic subdivision of a family) and the second to the species (spinibarbis). There are five other closely related species of Leistus in Britain, all belonging to the same genus but each with its own individual species name.

Many people find scientific names off-putting, not least because they can be cumbersome in their construction. Try getting your tongue around Scybalicus oblongiusculus (another ground beetle)! The use of ‘common’ or vernacular names, like ‘blackbird’ or ‘robin’, is a good compromise but these only tend to work within a single country since they are intrinsically linked to the local language and culture. Having two parallel systems usually works fine and, as research and writer, I use both, switching between the two depending on audience. However, the lack of a common name may deter people from becoming more acquainted with a species. Understandably, if you are uncomfortable with the name of a species, then you are less likely to take a more detailed interest in it. This is unfortunate, particularly in the case of Leistus spinibarbis, which is superbly adapted for feeding on springtails. It’s jaws have a wide flange running along the edge, something that Mark Telfer suggested would suit a common name like ‘Blue Flange-mouth’. Maybe having such a name would help raise the profile of this delightful little beetle.

Monday 14 November 2005

20 pence flight from Norway

There is something special about birdwatching on the east coast during autumn. You get a real sense that vast numbers of birds are on the move, streaming into the country from across the North Sea. This was something that was brought home to me the other day as I walked the lanes around Happisburgh, enjoying the bright, clear weather that carries just enough edge to let you know that summer is truly over. Small groups of blackbirds were passing overhead, together with smaller numbers of redwings and occasional fieldfares. From the hedgerows, more ragged here than elsewhere in the county, came the high-pitched contact calls of diminutive goldcrests, busy searching for insects. Even though goldcrests breed in Britain (there are some 600,000 pairs nationally), these particular individuals were more likely to be migrants, freshly arrived from Scandinavia or western Russia.

As well as being the smallest British bird, the goldcrest has the distinction of being one of the lightest birds anywhere in the world to make regular sea crossings as part of an annual migration. For a bird that weighs roughly the same as a twenty pence piece (about 5.3 grams) such movements are truly remarkable. In some years, bushes and hedgerows at east coast sites may be literally ‘dripping’ with exhausted goldcrests during autumn. These are birds that must operate very close to their physiological limits. Information generated from bird ringing schemes, operating across Europe, has revealed that goldcrests breeding in the northernmost boreal forests are almost completely migratory in their behaviour. Birds from breeding populations situated further south are more likely to remain where they are to overwinter. Some coastal populations on the edge of the Arctic Circle in Norway also remain close to their breeding grounds in winter. By doing so, they have to cope with severe cold and nights that are 18 hours long. It has been calculated that these birds may burn off a fifth of their body weight each night, just to maintain their body temperature at a safe operating level!

This autumn has seen very large numbers of these tiny birds arriving on our shores. Even though the main arrival took place in the second half of October, and was centred on the Yorkshire and Lincolnshire coast, there still appear to be good numbers within East Anglia. Most mornings, while exercising my overly energetic spaniels in Thetford Forest, I encounter goldcrests foraging among the conifers. As if to reinforce the origins of some of these birds, I received a report last week of one individual caught within a mile or so of Thetford which sported a Norwegian ring. One wonders where the individuals I had seen at Happisburgh were from.