Sunday, August 07, 2011

Alien invaders and birds of prey

click photo to enlarge
I didn't realise, until the other day, that of all the alien wildlife invaders in the UK the worst of the worst was the so-called "killer shrimp" (Dikerogammerus villosus), a native of the Ponto-Caspian region of Europe, that is killing off our native shrimps and small fish. The BBC website carried a report by the UK's Environment Agency that listed (in the way that people do today) the "top ten" alien invaders. The list reads (starting with the worst) "killler shrimp", water primrose, floating pennywort, American signal crayfish, topmouth gudgeon, giant hogweed, Japanese knotweed, Himalayan balsam, and parrot's feather. What this list said to me is what a good medium water is when it comes to the spread of exotic plants and animals. The murky depths make it so much more difficult to detect the arrival and initial spread of an introduced species, to the point that when it does become apparent to scientists and lay people who spend time in and on water, it has reached a situation where containment or eradication is difficult, if  not impossible.

But, native wildlife has a remarkable propensity for holding on even under the strongest pressure as our red squirrels have shown in their fight against the onslaught of the introducd grey variety. Our birds of prey have been among the most oppressed species. Here it has been man that has caused their decline as landowners tried to rear ever larger numbers of gamebirds and farmers tried to kill off insects and plants that harmed their crops. But, with wider public pressure and awareness, legislation and scientific management, what appeared to be a hopeless situation has been turned around. Not for all species, of course - hen harriers are still being persecuted and numbers have fallen again after something of an increase - but for many. I read a while ago that the common buzzard has usurped the kestrel as the most numerous British bird of prey. They're certainly fairly frequent sightings in most parts of the country where formerly they were unusual.

One evening when I was photographing the strongly silhouetted shapes of these electricity pylons near a Fenland substation I became aware of a softer, "natural" shape among the sharp angles of the metalwork. Binoculars reveealed it to be a Common Buzzard (Buteo buteo) surveying the island of waste land below the steel "trees". Even in this instensively cultivated part of England the buzzard flourishes. Can you spot this one?

photograph and text (c) T. Boughen

Camera: Canon
Mode: Aperture Priority
Focal Length: 300mm
F No: f5.6
Shutter Speed: 1/500
ISO: 100
Exposure Compensation:  -0.67 EV
Image Stabilisation: On