News for August 2001

Bird On! News
7th August 2001

David Tomlinson

• Helping the grey partridge
• Late-nesting house martins
• An invading army
• Herons also flying high

Good news for a change

We are so used to bad news when it comes to bird stories, so good news comes as quite a shock. However, there is no doubt that last summer's Common Bird Census figures (just released by the British Trust for Ornithology) are the best for a long time. They certainly make encouraging reading as a number of species in long-term decline showed appreciable increases in population.

Song thrushes , for example, have long been a cause for concern. Once one of the commonest birds in Britain, their population has been falling steadily for many years with the long-term trend (1974-1999) showing a decline of 55%. Last yea, numbers were up by 17%, an encouraging figure. Mistle thrushes have also been declining though not as badly as their smaller cousin, the song thrush, and last year numbers rose by an impressive 31%.

Others birds to enjoy a good season were chiffchaff (+25%), chaffinch (+7%), blackcap (+14%), whitethroat (+20%), robin (+13%) and red-legged partridge (+27%). In addition, great spotted woodpeckers continued their steady upward trend with +17% and tawny owls checked a recent decline with an impressive 33% rise.

The overall picture indicated a good season for most of our resident species and a number of summer migrants. However, there was less good news about the once-common seed-eating farmland birds such as the turtle dove, skylark , tree sparrow and corn bunting , with none recording any significant increases.

Quite how these birds have fared this season remains to be seen but early indications suggest that, if anything, it has been rather more successful season than last year, which is good news indeed. A number of reasons have been suggested ranging from lack of disturbance in the countryside due to foot and mouth restrictions on access to the wet winter producing an abundance of luxuriant growth and thus lots of nesting cover. In addition, it has been a generally fine summer so far with several spells of warm weather and this certainly helps nesting birds rear good broods.

Certainly I have never had so many young birds - tits, finches, nuthatches and great spotted woodpeckers - visiting my feeders as I have had this summer. I continue feeding throughout the year and as a result the garden is constantly busy with families of visitors.

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Helping the grey partridge

At the annual Game Fair held at Shuttleworth in Bedfordshire at the end of July the Game Conservancy Trust launched its latest guidelines on conserving the grey partridge, once one of the most popular and abundant farmland birds in Britain but now a species whose survival is severely threatened. Though grey partridges remain on the quarry list in Britain, the CGT urges that they should only be shot on ground where there is a population of more than 20 birds per 250 acres. The only places in Britain where they do occur at a shootable density are on estates where special efforts have been made to conserve them. Ironically, a ban on shooting partridges would do nothing to help the species as there would be less incentive for sporting estates to help this popular bird.

Steps that can be taken to help wild greys include the construction of beetle banks across large arable fields to increase the amount of nesting cover, managing the grass between grass between hedgerows so that there is always old dead grass from the previous year available for nesting, and to make judicious use of set-aside strips to create grassy nesting cover next to cereal crops. Partridge chicks depend on insects for their survival, so the use of unsprayed conservation headlands along the edges of cereal crops also helps chick survival.

Research by the GCT has shown that partridge numbers are suppressed by foxes and crows, and that effective predator control by a gamekeeper can easily treble a partridge population in a few years. However, the Trust also points out that "with adequate nesting and winter cover, as well as sympathetic farming systems which improve chick survival, a partridge stock should maintain itself, albeit at a low density, even in the presence of predators".

There is no doubt that on the farms and sporting estates which follow the GCT's guidelines on partridge conservation, other typical farmland birds such as turtle doves and skylarks do much better too. In East Anglia the rare and endangered stone curlew thrives on sporting estates where partridge conservation and ground predator control receive a high priority. The owner of one such estate once told me that he had been verbally attacked by animals rights activists for controlling the foxes on his estate. His retort was that you could see foxes anywhere in Britain but there were very few places where you could still see stone curlews. If controlling the foxes helped the stone curlews nesting on his farm, then he would continue to keep the fox population in check.

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Late-nesting house martins

Last month, I noted that house martins were nesting much later than usual this summer, and so reducing their productivity. Of the two pairs nesting on my house this year I'm still waiting for one to hatch its first clutch while the other pair at last hatched off at the end of the third week of July. This is the latest I have ever known house martins hatch their first brood and has to be a cause for concern as they typically raise two or even three broods each summer.

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An invading army

In recent weeks, birdwatchers in Eastern Britain have been reporting sightings of crossbills. It is now certain that hundreds of thousands of crossbills from the forests of northern Europe are irrupting, and many of them are heading across the North Sea to Britain. The first indications of the irruption were noted in Shetland in June when small parties of these striking finches were seen feeding on shoreline thrift. Since then increasing numbers have been recorded inland in Britain.

Crossbill irruptions are periodic and largely unpredictable with the biggest invasions rarely occurring more than once in a decade. The last major irruption into Britain was exactly 10 years ago. The irruptions are always triggered by an acute food shortage for crossbills are highly specialised feeders depending almost entirely on the seeds of larch, spruce and pine. When the cone crop fails the birds have to move to avoid starvation.

Crossbills are widely distributed throughout Europe, occurring wherever there are coniferous forests. However, they are at their most numerous in the forests of Scandinavia and Siberia and this area is the source of the current invaders. They are early breeders with their annual cycle starting as early in January, so a high proportion of the irrupting flocks are young birds that fledged back in March or April.

Irrupting flocks wander widely, and may turn up anywhere there are a few cone-bearing conifers, usually pausing for a few days to feed before moving on once again. However, if they find a forest that suits them, then there is every chance that they will not only stop for a few months, but may even stay to breed next year.

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Herons also flying high

One species that is flourishing in Britain is the grey heron. For some 70 years the BTO has organised a count of heronries. Over the years the sample coverage of colonies has fluctuated but 417 were counted in both 1999 and 2000 and the total pairs found breeding remained very high - 6,607 compared with 31 more the previous year, a drop in numbers that is insignificant. Heron numbers surged upwards between 1988 and 1998, and today their numbers remain at an unprecedented high level. They are invariably badly affected by long periods of freezing weather, but the recent run of mild winters has suited them perfectly. I can remember that as a child 40 years ago it was a noteworthy occasion to see a heron, but that is certainly not the case today. Herons are handsome birds, and unless you have a goldfish pond or a trout hatchery, they are good to see around.