Magpies and other bird predators

First issue May 1997

For a printable (PDF) version click here

See also: magpie, sparrowhawk

'What can I do about the magpies that I have just seen eating a young song thrush in my garden?' asked a distressed gentleman over the telephone. Essex Wildlife Trust receives many questions about magpie control and they give rise to some heated and emotional debates. 'What is the Wildlife Trust doing to control magpie numbers? Why are they increasing so fast and killing so many of our songbirds?' asks another caller.

Many people have noticed more magpies about than there used to be, and some have been upset by seeing them taking songbirds' eggs or their young. Birds of prey like the sparrowhawk and hobby that have been absent for many years are also returning to some parts of Essex. Both have small birds in their diet and sparrowhawks eat little else. If you put up a birdtable to feed songbirds, it is natural to be annoyed or upset to see a sparrowhawk picking them off or a magpie eating their young.

In some places songbirds are declining, and it is logical to link this to an increase in magpies or the return of the sparrowhawk, but the reality is more complex. Before we take drastic control measures like trapping or shooting, we must be sure we are doing the right thing. This leaflet summarises the evidence available to us at present and suggests some positive steps anyone can take to help.

Why are magpie numbers increasing?

Magpie numbers have been increasing steadily for the past 30 years or so, although the rate of increase is now slowing. Numbers have been going up faster in the town than in the country - at 8% a year as against 5% - and there are now estimated to be over two million magpies in Britain and Ireland. With their striking black and white plumage and their raucous calls they certainly make their presence known! They are probably doing better in towns because there is more food - some of it put out on birdtables for songbirds - and fewer predators. We don't know for certain why numbers are rising, but the most likely reason is that they are suffering less from persecution from gamekeepers. At one time the magpie was thought to be lucky, but it was branded a pest because it threatened gamebirds reared for shooting. So perhaps in the past magpie numbers have been kept at an artificially low level. The same can certainly be said for many of our birds of prey, whose numbers have been devastated by persecution and pesticide poisoning in recent decades but are now starting to recover.

Are bird predators a threat to songbirds?

When they take small birds, predators like the sparrowhawk or magpie are not being cruel, but are doing what is natural to stay alive and feed their families. The sparrowhawk relies almost entirely on small birds, but magpies have a very varied diet and will eat almost anything, animal or vegetable, including animals squashed on the roads. Small animals like birds and mice appear to form only a small proportion of their diet - studies show this to be only 1 or 2 per cent.

Generally, predator numbers are set by the availability of their prey. The fact that sparrowhawks are doing well now shows that there is a healthy enough population of songbirds to sustain them. As the available prey increases, we should expect the numbers of predators to increase, and vice versa. Predators have evolved mechanisms to limit their numbers so that they do not outstrip their prey, for example varying the number of eggs they lay. After all, if predators destroyed all their prey species this would be a certain route to their own extinction.

To sum up, if the habitat is right the songbirds will be there, no matter how many natural predators are around. At a national level they pose no threat to songbird populations, although there may be local effects in particular areas.

Should I try to get rid of magpies?

Sparrowhawks are fully protected by law and it is an offence to kill or capture them, even on your own land. Magpies have no such legal protection, so is it right to try to control them? The Trust believes not, because there are no valid conservation reasons for doing so. Further, no entirely satisfactory methods are available.

Gamekeepers have traditionally used poison, but this is strictly illegal and is also unselective, so is as likely to harm your cat or other wildlife as a magpie. It may be legal to shoot them if you have a licensed gun, but this will depend on the circumstances, and once again will endanger people, pets and other wildlife. Traps can be obtained to catch magpies alive, but are difficult to use effectively and humanely.

Even where they are practical, all these destructive methods have one weakness -- as soon as you remove a resident pair the territory is likely to be taken over quickly by other, non-breeding magpies.

What is happening to our songbirds?

Some garden songbirds are declining, notably song thrushes and (many people will be surprised to learn) house sparrows and starlings, but other evidence points the other way. Some small birds, like blue tits and great tits, are increasing nationally at present. And while there is some evidence of decline in gardens, there is none in the wider countryside nor on nature reserves where there is good habitat.

We do not yet know exactly why these changes are taking place, but they are more likely to be linked with changes in our use of the countryside, such as modern farming practices, than with predation. In the countryside also a number of common species are declining, for example the skylark. Songbirds have lived with predation for thousands of years, and the fact that they are still with us shows that they know how to cope. Some, for example, can make four or five breeding attempts a year, and if one brood is destroyed they just get on with the job of raising another.

Because adult songbirds can live for several years and young birds can breed in their second year, only a small proportion of birds need to breed successfully to maintain the population. Some birds are lost to predation, of course, but many succumb to starvation and cold in winter, and it is a sad fact that most young birds die this way. Bear in mind too that songbirds are threatened by four-legged predators such as stoats and, particularly in towns, domestic cats, as well as by winged predators like magpies and sparrowhawks.

How can I help songbirds in the garden?

The Trust believes that a constructive approach is more helpful than controlling natural predators. In other words we should try to help songbirds to nest where they are safer from magpie predation. Another way of helping is to participate in research into the causes of songbird declines. Contact the Trust for more details.

Five ways to help songbirds in your garden

1. Put up some nestboxes. Site them on walls and trees ideally where cats can't get at them easily. Good value boxes are available from all Trust centres.
2. Leave a window or door to your shed or garage open during the nesting season (March to August) so that swallows, robins or blackbirds can get in to nest on a shelf - magpies are unlikely to be bold enough to follow them.
3. Provide good thick hedges for birds to nest in. An impenetrable blackthorn thicket or a big patch of brambles is ideal, but a broad, twiggy hawthorn hedge is the next best thing, perhaps with an occasional guelder rose or dog rose to add a bit of variety. Take care not to clip it until well after nesting birds have fledged their young, as some birds come back and reuse the nest for a further brood. Dense, prickly shrubs like Berberis darwinii or Berberis julianae are almost as good for wildlife, and with the advantages of highly scented early blossom and attractive glossy green foliage all year. Other good choices: Pyracantha (autumn berries too); Cotoneaster simonsii (good pollen source).
4. Grow ivy over your walls or up your trees. Contrary to popular belief ivy does no harm to healthy trees and soundly built walls, and wrens and blackbirds will take to it as soon as it is thick enough.
5. Provide some dense, low cover near the bird table. Small birds will perch here in safety between forays to the bird table.