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News for July 2001

Bird On! News
5th July 2001

David Tomlinson

Even more English ospreys

Last month I celebrated the fact that ospreys had, at long last, nested in England for the first time for at least two centuries. Even better news was to follow, for it has since been reported that a second pair of ospreys has nested in England. This time the site was announced at the same time: Rutland Water. Here there has been an exciting joint venture between Anglian Water and the Leicestershire and Rutland Wildlife Trust to try and establish breeding ospreys on the huge reservoir. For the last few years fledgling ospreys have been taken from Scottish nests and reared and released at Rutland.

A great deal of preparation took place before the Rutland project began in 1997, as well as lengthy talks with Scottish Natural Heritage which granted the licences for collecting the young ospreys. Masterminding the scheme was freelance conservationist Roy Dennis who has extensive experience of re-introducing raptors to Britain. (The successful return of both sea eagles and red kites to Scotland was largely thanks to his hard work.)

The Rutland project wasn't a first; the Americans have already shown how successfully ospreys can be translocated. In the USA more than 1,000 young ospreys have been translocated with one project alone taking 140 birds. The success rate has been remarkably high with most birds returning to nest at their introduction site four or five years after release. It is the male ospreys that are most important to the success of the reintroduction schemes as they return first from their winter quarters, establish their territory, and then attract a passing female. This is what has happened at Rutland this year for the male is a released bird with a ring while the female is unringed.

Dr Stephen Bolt, principle scientist with Anglian Water, has been heavily involved with the scheme since its start and was always optimistic about its chances of success. I spoke to him when the scheme was originally launched and he explained that one of the advantages of the project was that unlike imported red kites and sea eagles the Scottish-hatched birds did not have to spend any time in quarantine. Poisoning - a problem that has beset both kite and eagle re-introductions - wasn't a difficulty either.

The Rutland ospreys will not be cosseted and protected from disturbance. American ospreys live happily alongside man, even nesting on the top of telegraph poles by the sides of busy roads. If the birds are to thrive at Rutland, then they will have to be similarly tolerant of human activities for the lake boasts a successful trout fishery and a popular sailing club.

It had been hoped that Rutland's ospreys would mark the start of the new millennium by nesting in 2000. The fact that they waited until 2001 suggests that 2000 was really the last year of the old millennium and that the birds were waiting until 2001. Hopefully the Rutland ospreys will fledge their young successfully and that before too long we will have ospreys nesting at other suitable sites in southern England.


Late martins cause concern

As I write this, I am entertained by the happy murmuring of house martins in the nest box just a few feet from my desk. House martins have nested on my house for every one of the 18 years I have lived here and their presence was an encouragement for me to buy the property in the first place. Over the years numbers have varied from one to four pairs, all of which nest in artificial Schwegler nest boxes which are much better than the nests the martins build themselves as they don't fall down.

This year the martins caused a great deal of concern. Not only were they late back from migration, not appearing until early May, but it wasn't until May 18th that they were seen inspecting the nest boxes for the first time. They then disappeared again and didn't return until mid June when they were at last seemed to settle in and get down to the serious business of egg-laying.

Such a delay between arrival and breeding means that they are unlikely to raise more than one brood or, if they do attempt a second brood, the chicks will be fledged very late in the season and be less prepared to undertake their formidable migration to tropical Africa. For some years now there has been concern about falling numbers of house martins in Britain and reduced productivity seems to be one of the reasons. Why this should be happening is a mystery.


Turtle dove problems

Due to careful research by the Game Conservancy Trust we do know why turtle doves are less productive in the number of chicks they rear each summer. The dainty turtle dove is the only member of the pigeon family that is a summer visitor to northern Europe. Most of our turtle doves winter in West Africa, returning to Britain in late April. They have a hazardous journey as they are still shot on spring migration in southern France by chasseurs who ignore the protection the doves are now meant to enjoy under the European Bird Directive.

If it wasn't for the research that has been undertaken it would be easy to explain the turtle dove's decline in the British countryside on the illegal shooting. However, though it can hardly help, shooting doesn't seem to be the major factor in the dove's disappearance. According to French ornithologist Guy Jarry writing in the Atlas of European Breeding Birds:

"Changes on its wintering grounds form the major reason for its decline. The long drought periods in the Sahelian and Sudanese region since the early 1970s led not only to a reduction in food supply, but also to an overall scarcity of water, and the turtle dove must drink at least once a day."

So a decline in the quality of the dove's wintering ground seems to be a major factor but according to the Game Conservancy increasing agricultural intensification in the UK has played an equally major role in the crash of numbers. The turtle dove is one of several farmland birds whose numbers have dropped alarmingly in the last quarter century. Grey partridge, corn bunting , tree sparrow , skylark and linnet have all suffered similar declines.

In 1998 the Game Conservancy Trust launched a three-year project to investigate the turtle dove's decline. The study has shown that the most important reason is lack of food. Because of a shortage of weed seeds the birds are increasingly dependent on food resulting from man's activities and they make little use of natural sites. In spring the birds are most likely to be found feeding on spilt grain or at livestock feeding sites, while they favour harvested stubbles in late summer.

The knock-on affect of this is a reduction in the number of breeding attempts the doves make each summer. There's generally an interval of three or four weeks between the birds' return to their breeding grounds and the first egg being laid. So instead of attempting to rear three broods during the summer as they did in the 1960s, pairs are only managing to produce 1.25 broods per breeding season. This late nesting seems to be connected with a lack of food in May. Could it be that the house martins are suffering from a similar shortage?


What's phylogeny?

Few bird books have been as long awaited as Sylvia Warblers, a Helm Identification Guide that has just been published by Helm. The authors are Hadoram Shirihai, Gabriel Gargallo and Andreas Helbig, while the British input has been from David Cottridge, the photographic editor, and the llustrator, Alan Harris.

The sylvia warblers include some of our most musical summer visitors - including the blackcap, garden warbler and whitethroat - but it is around the Mediterranean that the greatest diversity of these attractive little birds can be found. Here you can look for such beautiful species as Sardinian, Cyprus and Marmora's warblers, all of which are depicted in this book by David Cottridge's superb photographs and the exquisite colour plates painted by Alan Harris.

However, for the great majority of birdwatchers much of the information included in this 570-page book will be totally beyond them - it was certainly beyond me. The clue to the complexity of the book lies in its subtitle: Identification, taxonomy and phylogeny of the genus Sylvia. If you don't know what phylogeny means, then you are unlikely to find this book the good read you were expecting as it's about as digestible as uncooked dough. It is aimed squarely at the academic ornithologist, of whom there are few in number, not the birdwatcher.

The book includes a considerable number of shots of warblers held in the hand. Such shots may be of interest to those who want to discover every last detail about a bird's plumage but they are of little use to the great majority of birdwatchers who never see a hand-held bird. In addition, shots of hand-held birds are both unpleasant and unattractive to the eye. I find that such a plethora of hand-held pictures is off-putting and they detract from the pleasure of looking at the superb wild portraits taken by David Cottridge.

With a price tag of £60, Sylvia Warblers is expensive too. I can see a very good case for a £25 simplified edition without all the in-hand shots and the highly detailed tables explaining such things as "monthly pre-nuptial moult state in Eastern Orphean Warblers" or "the summary of published biometric data for Ménétries's warbler" that few people are interested in. How about it, Helm?

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