Too many robins?

This year, there seems to be a robin singing from every tree in the reserve.

We know that the population of robins in Britain has grown by almost 50% since the 1970s but rising numbers of a single species is not necessarily good news for the reserve or the countryside that surrounds it.

Robins are generalists that eat all sorts of things: seeds, fruit, toast crumbs, as well as insects. Generalists move into an ecosystem when it can no longer support the specialist feeders. If the park were no longer able to support seed-eaters like bullfinches, or insect specialists like tree creepers, the generalist robins will move into the gap. There might not be enough spiders to support a tree creeper but there are enough for a robin which can make up the shortfall with seeds and bacon rind.

[1] tree creeper and [2] bullfinch

Robins are a prey species. They are ground feeders, easy prey for our sparrowhawks and foxes; they are much inclined to building nests low down in loose undergrowth where their eggs and nestlings are vulnerable to weasels, stoats and jays. A robin singing from every tree can be a reflection of falling populations of these predators.

An ecosystem is a complex web of interrelationships. While we congratulate ourselves on the predators that we add to our species lists because we think of them as an indication of a healthy biodiversity, we need to understand that rising populations of generalist species, of opportunists like robins, blackbirds and magpies, can also indicate falling numbers of specialist species.


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