News for September/October 2001
Bird On! News
9th October 2001
Few birds are as cosmopolitan as the barn owl. It occurs widely in both North and South America, Europe, Africa, the Middle East, India and parts of south-east Asia and Australia. It's a bird that dislikes extreme cold so is generally absent from the chillier parts of the world such as much of northern Asia.
Though barn owls are widespread in Britain, they are seldom common. Our estimated population of 4,000 breeding pairs puts us in 5th place in Europe, behind Spain (66,000 pairs), France (30,000), Germany (10,000) and Italy (10,000). However, after years of decline there has been recent optimism that our barn owl population has stabilised and it may even be increasing slowly. Alas, last winter's floods have almost taken their toll of this attractive bird whose favoured habitat in the UK is lowland valleys. These valleys seldom suffer from prolonged snow cover which can make winter hunting difficult, while they usually have plenty of rough, uncultivated grassland that is the prime habitat of barn owl's prey: voles, mice and shrews.
A breeding survey undertaken earlier this year by The Hawk and Owl Trust has shown that in areas most heavily affected by last autumn and winter's flooding there were 70% fewer breeding adults in nest boxes than in previous years. In areas where nest-box occupancy was closer to normal many adult birds failed to lay eggs, while those that did have reared very few young.
According to the Trust's director, Colin Shawyer:
"This has been the worst year for barn owls since I began working on them in 1982. Everything points to a serious shortage of food. Detailed examination of over 600 sites revealed that small birds formed a large proportion of prey, rather than the small mammals that normally dominate the diet. Birds are rarely taken, except in extreme winters, and even then only occasionally. Farmers reported that they failed to see field mice scurrying from their burrows during spring ploughing, which was unusual. They presumed that the mice had all been drowned beneath the waterlogged fields."
However, a few areas have reported reasonable breeding success. On parts of the Wash in East Anglia the elevated sea walls have provided good hunting, and there barn owls have nested successfully in more nest boxes than in previous years, though the number of owlets reared was low.
This low productivity was a feature throughout much of England, though one notable exception was on the artillery ranges of Salisbury Plain where brood sizes averaged four owlets per box. Further cause for optimism is the fact that last winter's exceptional rainfall is unlikely to be repeated and that rodent populations are usually quick to recover.
According to Colin Shawyer:
"The Trust and others are continuing to create new habitats and put up nest boxes to achieve a robust population, able to overcome what we hope are only temporary setbacks, like the ones we have just experience. Those areas where the barn owl population has held up this year will be vital for recolonisation in the future."
With the world's barn owl population running into millions of pairs, it can be argued that organisations like the Hawk and Owl Trust are wasting time and money trying to maintain our tiny barn owl population. True, but the barn owl is an inspirational bird and one whose loss from the British countryside would be sorely missed. To watch a barn owl hunting a water meadow on an autumn evening, with wraiths of mist rising from the ground, is to witness one of the most delightful natural scenes. To lose our barn owls would be a tragedy indeed.
Britain's rare breeding birdsFor anyone with an interest in Britain's breeding birds the annual report of the Rare Breeding Birds Panel makes fascinating reading. Frustratingly, publication of the report takes time, so that when it appears in print it already seems somewhat dated. Thus the Panel's latest report, published in the August issue of the monthly magazine British Birds, concerns 1999. It's often difficult to cast one's mind back that far but according to the Report, "this was the fourth year in a row in which reports from all parts of the country spoke of bad weather disrupting the breeding season, with heavy rain and floods in some areas and unseasonable snow and storms in others, while high water levels and high tides were responsible for destroying nests, eggs and chicks".
Two breeding seasons have now passed since 1999, and the early indications are that this past spring was reasonably good for many species. In 1999, the Report notes that little egrets bred in nine localities with 30-36 pairs breeding. There can be little doubt that the number of nesting localities and breeding pairs has at least doubled, if not tripled, since 1999, for this delightful little heron is rapidly expanding as a breeding bird in this country. It first bred here as recently as 1996.
Nobody knows why little egrets suddenly and unexpectedly extended their range into northern Europe. Better protection may be one reason for the little egret (and the closely related American snowy egret) were once slaughtered for their so-called osprey feathers, the popular adornments of ladies' hats a century ago. Climate change is another possibility and there seems little doubt that little egrets favour hot summers.
But the little egret is far from being the only European heron extending its range. Following in its wake is the great white egret which looks like a bigger version of the little egret. The great white is the world's most cosmopolitan heron with an extensive range that takes in six continents.
Despite its abundance in the Americas, much of Africa and south-east Asia, the great white has always been a rare bird in Europe. Fifty years ago, it held just a tentative toe-hold in Austria (Neusiedlersee) and the Balkans. However, there has been a notable increase in numbers in the last 20 years and records have become far more frequent in western Europe. A summering bird appeared in Holland in 1976 and two years later the first pair bred. They now nest annually in Holland,
Steadily increasing numbers have been appearing in northern France in the recent years. Ringing has shown that the majority of these birds have wandered north from the Po Delta in Italy, which has a thriving egret population including many breeding pairs of great whites.
Though the great white remains a rare bird in the UK, it is now a regular summer visitor in increasing numbers while autumn and winter birds are also appearing more often. This species may still be some way from establishing itself as a British breeding bird but it looks set to do so soon.
Whether the great white nests here before the cattle egret in a moot point, for the latter is also spreading north and is now breeding in northern France at Marquenterre, on the estuary of the Somme. Cattle egrets - also known as buff-backed herons - are one of the world's most successful birds. They are widely distributed in Africa and south-east Asia, but were absent from the Americas until 70 years ago. Migrants managed to cross the Atlantic unassisted by man and they first started breeding in the New World in the early 1930s. Today they breed commonly from Canada to Argentina.
In Europe, Southern Spain was once the cattle egret's stronghold. The first signs of a northward expansion were noted in 1961, and they soon started breeding in the Ebro delta. In 1968, two pairs nested in the Camargue, and by 1975 that colony had grown to 125 pairs. Slowly but surely the pioneers moved north, reaching the Brenne (in central France) and the Dombes (to the north of Lyon) in 1992, and the Somme in 1996. England has to be the next step.
Cattle egrets can often be seen feeding in close proximity to cattle, but they are also great scavengers, and particularly fond of rubbish tips. This adaptability explains their success. Though originally birds of the tropics, they have the ability to cope with cool, temperate weather, as their success in New Zealand (colonised in 1963) and Canada has shown.
Potential colonistsIt is reading through the Rare breeding birds report that you often get the first hint of new potential colonists. There is no mention of either great white or cattle egrets being seen in suitable breeding habitat in 1999, but it is interesting to see that as many as seven pairs of spoonbills may have bred, at five different localities. The first breeding record was in 1998, though according to the Report it now seems that this might not have resulted in fledged young. Young were definitely fledged in 1999, the first proven nesting since 1688.
One bird that was thought to be a potential colonist 10 years ago was the common (or scarlet) rosefinch, and there were several breeding records in the 90s. The peak year was 1992, with as many as 20 pairs. Sadly, this potential colonisation seems to have lost its momentum, as in 1999 only five singing males were recorded, and none were known to have bred.
There were a couple of interesting breeding records of "lost" English breeding birds nesting successfully in Scotland in 1999. Red-backed shrikes, for example, were found at three Scottish localities, and at least on pair bred successfully. Similarly, a pair of wrynecks bred in Scotland, fledging five young. Fifty years ago, both wrynecks and red-backed shrikes were widespread (but declining) breeding birds in south-east England, but neither had ever been found breeding in Scotland.
The BTO's Swallow AppealBoth red-backed shrikes and wrynecks are summer migrants, returning back to the Tropics for the winter. Next year, the British Trust for Ornithology publishes its new Migration Atlas, which is the culmination of four years' work by 150 BTO authors, and the Atlas team at the BTO 's HQ at Thetford. It promises to be a fascinating publication.
The BTO has also launched its Swallow Appeal, which aims to raise funds to provide adequate conservation measures for migrant birds. In support of the Swallow Appeal is a delightful new book, called Rusty Flies South, aimed at three to six-year-olds. It tells the story in pictures and words of the swallows' migration. The pictures are charming, the story it tells is a poignant one. Copies of Rusty Flies South are available at £5 (including p&p) from BTO Swallows, The Nunnery, Thetford, Norfolk IP24 2PU.