Careless rapture of the song thrush

I SPEND a lot of my time sitting in front of a computer beside a window that has a splendid view.

In the foreground are fields and hedgerows, beyond that bog and woodland.

It was a mistake to put the computer there, because I’m continually being distracted by things happening outside.

The other day, I was doing some internet research on thrushes, when I glimpsed a movement out of the corner of my eye. There, only a few metres away, was the real thing — a song thrush and two blackbirds feeding on the edge of the field outside the window. The computer timed out while I watched them.

The song thrush and the blackbird are closely related. The thrush is a bit smaller and nothing like as common as the blackbird. My guess would be that around here blackbirds outnumber thrushes by five or six to one.

This would tally with the official figures, which say there are 1.8 million pairs of blackbirds in the country and about 390,000 pairs of song thrushes.

But these census figures are now rather out of date, and when the results of the new census become available, they will probably show a decline in the numbers of song thrushes and an increase in the numbers of blackbirds.

I wondered, as I watched the birds through the window, if there might be a connection between the two population trends. The blackbirds and the thrush were foraging the same bit of grass and I presume they were after the same food items — small slugs, earthworms, insects and spiders.

Was the song thrush losing out to competition from its larger relative? Both species seemed happy sharing the same feeding ground. Blackbirds are much more aggressive and territorial, but there are plenty of good hedgerows around here, so I doubt if competition for nesting sites is a factor. Direct observation wasn’t helping to solve my problem, so I went back to the internet.

There’s not much recent data from Ireland, though there are observations that blackbirds are spreading out of lowland habitats and colonising uplands, barren parts of the west and offshore islands. But in Britain, they’re so worried about song thrushes, they are on the Red List of endangered species.

The British data notes a rapid decline set in the mid 1970s, and today, it’s reckoned numbers have decreased by 73% in farmland and 49% in woodland.

The difference between the farmland figures and the woodland figures undermines my theory that song thrush numbers might be declining, because of competition from the larger and more successful blackbirds.

It makes it much more likely that changing agricultural practices in Britain in the 1970s triggered the decline. It could be pesticides, it could be hedgerow removal, it could be a change from spring to winter cereals, or it could be a switch from hay to silage — or a combination of all these factors.

Our countryside will suffer a great loss if this thrush declines in Ireland. The song which gives it its name was described by Robert Browning: “That’s the wise thrush; he sings each song twice over, Lest you should think he never could recapture, The first fine careless rapture!”

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