Thursday, 31 January 2013

The curse of Big Garden Birdwatch

What is it about the RSPB’s annual Big Garden Birdwatch weekend? Why do all the birds mysteriously disappear from my own garden? 

Normally on a fine January day I can look out of my suburban window and expect to see up to four species of tit (Great Tit, Blue Tit, Coal Tit and Long-tailed Tit) visiting my bird feeders, a Robin below them on the bird table and a Dunnock delicately pecking up food spilled onto the lawn beneath. 

Blackbirds are likely to be working their way clumsily through my berry-bearing bushes, perhaps joined by a few Redwing. One or two Woodpigeons will almost certainly be strutting across the grass. And Magpies and Jays may be driving the smaller birds away from the bird table.

If I am lucky, a Great Spotted Woodpecker may visit the bird feeders or a Green Woodpecker may fly down to peck at ants on the lawn. And this year an overwintering male Blackcap has been creeping about in my hedges.

The only RSPB-specified garden bird I do not expect to see is the House Sparrow, which disappeared from my area years ago.

But come Big Garden Birdwatch weekend, everything vanishes. Last year I sat at the window and watched a variety of birds flying over my garden or visiting neighbouring gardens. But they completely ignored my own blessed plot. After 20 minutes with not a single bird to record, I gave up. 

This year I again set aside an hour to watch the garden. It was a beautiful sunny morning after a long cold spell, and the birds should have been out and about feeding. But once again, the garden was empty. I had topped up the bird table and feeders and put out new fatballs, but the delicacies that had been so popular on the Friday were now no longer an attraction. In the first 10 minutes I counted 10 species — but all were either in neighbouring gardens or merely passing overhead. Even the Woodpigeons that normally spend all day on my lawn were laughing at me from a neighbour’s ash tree. So once again I lost interest and gave up. 

Guess what? On the Monday my garden was again alive with birds.

Friday, 4 January 2013

Pigeons versus peregrines

From time to time, racing pigeon owners call for a cull of birds of prey to "protect" their own birds. Some have even taken matters into their own hands and illegally killed Peregrine Falcons.

Although it may be easy to blame a bird of prey when one of your pigeons fails to return to its loft, it seems that raptors actually account for only a small proportion of lost pigeons. Research cited in a 2000 report by the government-backed UK Raptor Working Group (on which pigeon racing interests were well represented) suggests two main reasons for racing pigeons failing to return to their lofts. It seems that at least 40 per cent of lost birds die through exhaustion or collision (with overhead wires, buildings, road vehicles, etc) and a similar proportion remain alive but either get hopelessly lost or choose to join a feral population. There is even some evidence that increasing numbers of pigeons are going astray because mobile phone towers interfere with their navigation, which depends of the earth’s magnetic field.

Evidence also suggests that most racing pigeons that succumb to raptors are already lost to their owners before they meet their end. One study of pigeon leg-rings retrieved from Peregrine nests concluded that more than 70 per cent of the victims had either gone feral well before being killed or were so far from their race flightpaths that they would never have returned to their owners anyway. 

Pigeon fanciers also tend to blame raptors for the disappearance of birds exercising near their lofts. But the evidence for this is slim. It appears that many pigeons, particularly young ones, simply decide to move on elsewhere. And those that are killed locally are more likely to be victims of the UK’s biggest slayer of birds — the domestic cat. 

Just look at the figures: we have about 7.5 million pet moggies and a further million feral cats. The Royal Society for the Protection of Birds estimates that cats annually kill around 55 million birds. In contrast, the UK’s latest estimated breeding population of Peregrines is just 1,402 pairs. So, if pigeon fanciers wish to protect their investments, shouldn’t they be calling for a cull of cats rather than of birds of prey?

Gulled by an aberrant gull

Leucistic Herring Gull
One technique used in the study of wild birds is ringing. Usually a small, numbered metal ring is placed round the bird’s leg, so that if it is later recaptured, or found dead, the ring may help provide information about migration, longevity and other aspects of its life. 

Some birds may also be fitted with brightly coloured plastic leg rings that allow them to be identified without recapture and therefore with minimum disturbance. Each bird is given a unique combination of small rings of different colours, which are read in a specific order. 

Larger birds may instead be fitted with rings bearing conspicuous letters or numbers that can be read in the wild with the aid of a telescope. I recently had an encounter with one such bird that has become something of a celebrity among London birders. 

I was sitting in a hide at a reservoir in north-west London when another birder thought he had spotted a rare Iceland Gull. But the bird soon turned out to be an aberrant example of a Herring Gull — a common species. The bird had extremely pale (leucistic) plumage, with all-white wings (like an Iceland Gull’s) rather than the Herring Gull’s usual grey wings with black and white tips. 

The four-character alpha-numeric code on its leg rings confirmed its celebrity status. The bird had been ringed a few years earlier by members of the the North Thames Gull Group, who use a cannon net to snare birds feeding on waste at landfill sites on the Essex side of the Thames estuary. Once caught, the gulls are extracted from the net and marked with numbered leg rings. Some, like the bird in question, are also given orange rings bearing large letters or numbers that can be read with a telescope. 

So is this gull’s celebrity due to its leucistic plumage? Not entirely. Its birding fame derives mainly from the characters on its four leg rings — S, H, 1 and T. These more or less spell out an expletive that birders may use when they realise that the pallid gull is not after all a rare species.