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.
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[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.
Southwick Country Park Nature Reserve 