DTI001 19_07_17

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Avian predators vs songbirds

The abundance of bird predators – corvids, hawks and others – in our gardens and countryside is a pressing issue. One birdkeeper with strong credentials on this subject is GRAHAM WELLSTEAD, a professional falconer and song canary expert who has also observed the changing role of bird predators at first hand. Here’s what he has to say…

There is no doubt that sparrowhawks do kill small birds, but are they the main predator?There is no doubt that sparrowhawks do kill small birds, but are they the main predator?

First of all I should declare an interest. I am a practising falconer – have been since 1949, flying many species, but with a particular interest in sparrowhawks. So I was interested to read articles in the national press on the subject of culling magpies and crows initially, followed possibly by a wider cull, including buzzards and sparrowhawks. However, I should say at the outset that the population increases of songbird predators do not tell the story properly.

Figures quoted in national newspapers include:
■ Sparrowhawk numbers up by 152 per cent since 1975
■ Carrion crows up by 119 per cent
■ Jackdaws up by 103 per cent
■ Magpies up by 98 per cent
■ Buzzards up by 60 per cent since 1967

Leading results
These may well be accurate, but percentages can, like all statistics, be made to produce any result. As a falconer and enthusiastic amateur naturalist, I have walked almost daily on a 750-acre estate in Surrey. The estate contains a variety of habitats: old pasture, mature oak woodland, stands of birch and pine. A stream flows through it and areas of wetland and rough patches are left for wildlife. Miles of new hedgerows have been planted over the past 15 years and some are now mature enough to be laid. The land is not farmed for crops, so no pesticides are used. The livestock is sheep, a few cattle and pigs, and about 30 horses, stabled during the week and turned out at weekends and holidays.

First hand observation
Over the past 21 years I have carefully monitored several species, including sparrowhawks, two species of owl, and harvest mice. (At one time I was lecturing on, among other things, wildlife habitat, and together with my students carried out live mammal-trapping to see if the land would support barn owls.) Over the years I have observed substantial population changes, especially corvids. When I was a youngster, one crow was a crow and three crows were rooks. Crows did not travel in groups. Today the estate holds at least 35 pairs of crows. Sparrowhawks are usually restricted to one breeding pair on the estate, occasionally two, plus one or two non-breeding females.

The jackdaw population has exploded in the past 10 years and almost every mature tree in 300 acres of woodland has one or more pairs. They are difficult to count since they are never still for long, but when they do take to the air there are more than 300. Jackdaws will take young birds, but spend most of the time feeding in pasture.

Magpies are everywhere and their domed nest can be seen in every hedgerow, sometimes two or three active nests in 300 yards of the more mature hedgerows. The magpies feed both on and off the estate and pairs can be seen feeding on the roads in the early morning every 100 yards.

We had no resident buzzards until four years ago and they have bred once, but are now absent, probably driven away by the large gangs of corvids.

 

He may seem cuddly, but foxes are more than capable of robbing nests near the groundHe may seem cuddly, but foxes are more than capable of robbing nests near the ground

Are they a threat?
Returning to those percentages: 152 per cent increase in sparrowhawks over 36 years is a small number when the starting point is one breeding pair in a 750-acre estate. A 119 per cent increase in carrion crows when the starting point is 30-plus pairs is a dramatic increase, and they certainly do take young songbirds.

There is a communal winter roost of magpies not far from the estate with more than 200 birds. The species actively searches and strips hedgerows of young songbirds and, being omnivorous, will supplement its diet with road kills, human rubbish – anything.

It is too soon to draw any conclusions on the rising buzzard population in my area, but they are largely carrion feeders, will take young rabbits and do eat a lot of worms. I cannot see the buzzard being a threat to songbirds.

Sparrowhawks as predators
There is no doubt that sparrowhawks kill small birds. A female is capable of catching and holding anything up to the size of a woodpigeon, and in the estate woodland there are thousands of woodpigeons, especially in winter when they feed on acorns.

When disturbed, the noise of their take-off is like an express train. Female sparrowhawks often major on woodpigeons, killing one virtually every day, whereas the smaller male can only handle birds up to the size of a blackbird.

Male sparrowhawks weigh less than 140g (5oz) and are vulnerable to starvation in their first winter. Because of this vulnerability, especially in hard weather, although the population is growing, it is unlikely to achieve the same proportional increase as the ubiquitous corvids. I would be concerned if, like crows, sparrowhawks reached a density of three pairs per 10 acres.

Other predators that do take small songbirds are the owls and the common kestrel. The estate used to have anything up to 10 pairs of tawny owls. The loss of many major oak trees may have produced a dearth of sites for these hole-nesting birds. We only had two males calling over the past winter. There are no barn owls, but we do have several pairs of little owls. They, too, will take songbirds, but feed mainly on worms and large insects, so their impact is minimal.

The kestrel is not common, which is something of a surprise since the habitat is good. However, the large numbers of magpies, crows and jackdaws may be a reason why this species is reluctant to settle. One pair is resident, but I have not seen offspring for three years.

Jays are one of the songbirds under threatJays are one of the songbirds under threat

Don’t blame the farmers
As pesticides are not used nor cereal crops grown on the estate, the decline in songbird numbers cannot be accounted for by farming practices. In spite of the estate having a benign attitude to wildlife of all kinds, it does not hold songbirds in great numbers. I see parties of a dozen or more long-tailed tits through the winter.

The areas of thistle and teasel attract hordes of wonderful goldfinches. Winter migrants such as fieldfare and redwings are resident in variable numbers.

However, there are no tree sparrows and few, if any, house sparrows. No buntings or yellowhammers, and bullfinches – once common – are down to two or three pairs. Almost certainly the songbird species are hammered badly by the corvids, including the jay, which by virtue of the oak woodland is present in very strong numbers. I would support a cull of corvids, since they have so few natural enemies and may soon be the only birds that one sees. However, unless such a cull is kept up, the infill from surrounding areas would make the whole exercise a waste of time.

 

Not just bird predators
Small songbirds do well on the estate, but would doubtless do better if the land were managed by a gamekeeper and the corvids were culled. There is a strong population of long-tailed tits, for example, but last summer I found five of their feather-and-moss nests destroyed by magpies and grey squirrels. It’s not just predatory birds, of course – last May I watched a fox clamber into a bush and take something away. On inspection I found an empty blackbird nest pulled down. Judging from the nest condition it had contained young chicks – all gone.

 


Graham Wellstead has kept birds of prey since 1949 and contest song canaries since 1980. A member of the British Roller Canary Club, Graham has returned to contesting. He answers queries on birds of prey and roller and waterslager canaries on our Ask the Experts page.


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