The first problem faced by a robin watcher is recognising individual birds. Lack solved this by trapping all the robins around Dartington, and placing different coloured rings on their legs. He used a wire cage trap, which the bird entered by a small funnel at ground level. Once inside it rarely found its way out again - its instinct when alarmed was to fly upwards, so that it did not notice the entrance.

Lack discovered that robins, which are curious about any strange object in their territory, are very easy to trap. He wrote:

If a trap was left for some days in the same territory the owning robin was usually caught at least once each day, and there was one bird which kept coming in. It was let out seven times one day and eight times the next. Towards the end, as soon as let out, it would sit waiting for one to move off and then would promptly go in again.

Having identified individuals, Lack was able to map their breeding and winter territories, and record how these changed over time. Breeding territories, held by a male and female together, were larger than those held in winter by individual birds. He learned that the average size of a territory was 1.5 acres, with the largest size, held by a breeding pair, being three acres.

Battling birds

Lack found that robins frequently strayed into neighbouring territories, in search of food. If spotted by the owner, the trespassing bird would be swiftly attacked, and would almost always retreat. Lack concluded:

Inside their territories, the birds sing, fight, display, and make themselves conspicuous; outside them they do not sing or display, they retreat if attacked, keep as inconspicuous as possible, and, if disturbed, usually fly straight back to their own domains.

Serious fights only occurred when a robin without a territory of its own was the intruder. Lack described one fierce battle between a mated cock, which owned the territory, and an invading cock. This ended in defeat for the owner:

The mated cock was...getting the worst of matters and had lost a great many feathers from his chin and one side of his face. After two hours he ceased to resist, and fled from the attacks of the newcomer....The hen took no part in the encounter, and after a while began to follow the newcomer about as if he were her mate.

The defeated cock, "looking very battered", remained in the territory for two more days, keeping in the bushes and occasionally singing mildly, only to be chased by the invader. He then disappeared, never to be seen again. The hen and the victorious cock then raised a family together.

Adventures with a stuffed robin

The most entertaining chapter in Lack's book records birds' reactions when he placed a stuffed robin, wired to a tree, in their territories. The robin's usual response was to threaten the stuffed specimen with song and displays, before attacking it. Yet individual reactions varied greatly. One hen robin continued to attack the space where the stuffed robin had been even after it was removed!

By chance I looked back, to see the hen robin return, hover in the air, and deliver a series of violent pecks at the empty air.

Lack's stuffed robin finally came to a spectacular end:

An exceptionally violent hen robin attacked the specimen so strongly that she removed its head. For a moment the bird seemed rather startled, but then continued to attack the headless specimen as violently as before, and it seemed as though it might have demolished it completely if I had not interrupted proceedings.

This led Lack to wonder how much of a stuffed robin was needed for the bird to recognise it as an intruder. So he mounted various robin body parts on trees, recording reactions. He found that as long as red feathers were present, robins would usually attack.

We tend to assume that the world that a robin sees is much like the world that we see. Suitable experiments show how false this is. A headless, wingless, tailless, legless and bodiless bundle of red feathers appears as a rival to be attacked... Even the empty air can contain a rival to be destroyed. The world of the robin is so strange and remote from our experience that into it we can scarcely penetrate, except to see dimly how different it must be from our own.

Copies aplenty

Between 1943 and 1965, David Lack's The Life Of The Robin went through four popular editions, including a 1953 Penguin paperback. Although currently out of print, it was such a big seller that copies of it are still easy to find in second-hand bookshops, on the internet or in your local library.