Usual culprit scatters the seed

I HAVE TO protect the seed beds in my vegetable garden with hoops of plastic water pipe covered in netting. This is to try to keep blackbirds out.

The blackbirds are very persistent and will find the smallest hole in the netting and squeeze in through it.

When they get inside they scratch around in the finely raked soil looking for small worms and other tasty morsels. They’re not interested in the seeds because at this time of year they’re almost entirely carnivorous. But the vigorous scratching scatters the seeds out of the neat rows they’re sown in and leaves them to dry out in the sun.

The interesting thing about this is that the culprits are always blackbirds. I also have song thrushes in the garden. They are about the same size as a blackbird and very closely related but they never scratch up the seed beds.

I watch both species of bird closely in breaks from working in the garden and it’s obvious that they can exist together in a confined territory because they have quite different feeding strategies and there’s very little competition.

In scientific terms they’re both occupying different ecological niches in the garden. While the blackbirds are scratching at the soil the thrushes are in the hedge bottoms searching for slugs and snails. The only time I see them together is after rain when they both start feeding on the lawn for subterranean creatures that have been forced to the surface by the water.

I’ve noticed other examples of similar species that are able to co-exist because they have different habits. Rabbits and hares are similar and closely related, though hares are quite a bit bigger. They’re both grazing animals and have similar diets, but they have very different habits. Because of this their ranges overlap in the fields and bogs round my house.

There are two main differences. The first is that rabbits burrow and hares don’t. This means that the rabbits have their headquarters on the well-drained esker gravel while the hares can colonise the boggy bottoms where a burrow would be continually flooded. The hares even make forms on high tussocks right out on the raised bog.

But their feeding grounds do overlap and the reason that this works is that the two species adopt totally different tactics for escaping from predators. Hares like to have as much open spaces around them as possible so they can use their superb eyesight to spot a predator while it’s a good distance away and then use their great speed to escape. They like to graze right out in the middle of large, open fields.

RABBITS, on the other hand, are not happy unless they are a few leaps away from dense cover, preferably with a burrow in it. They graze a few metres from a thick hedge or a dense clump of furze. So while the two species are feeding on the same things they are doing it in different places and are not in competition with each other.

An even more striking example of this comes from watching the sparrow hawks that live on the lane and examining the remains of their kills. A female sparrow hawk is about twice the size of a male and looks like a completely different species. The two sexes also have quite different diets. The male concentrates on small song birds like finches, robins or sparrows. The female preys on much larger birds, up to the size of a wood pigeon or a jackdaw.

In this case two individuals of the same species are occupying different ecological niches. This is very useful to them, particularly when they’re rearing young. If one food source becomes scarce there is a fair chance that the brood will survive by being fed on the other.

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