While sitting on a bench beside a local green, I noticed a gull performing an excellent version of Riverdance. Then it stopped and scrutinised the grass around its feet. This sequence was repeated for about 15 minutes. I assume the gull was trying to attract worms to the surface with its rhythmic dance. Was it? If so, how does the strategy work?
鈥� Yes, like many species of birds, some gulls have learned the earthworm-raising trick. Earthworms stay underground during the day unless flooded out by rainwater or alarmed by ground vibrations that suggest the approach of a mole. Just jab a garden fork into earth well populated with earthworms and some will pop out to avoid the little creature in black velvet.
鈥淛ust jab a garden fork into earth well populated with earthworms and some will pop out to avoid moles鈥�
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Different birds have different techniques. Blacksmith plovers, rather than hunting earthworms, flush out grasshoppers, caterpillars and moths by tickling short grass with a trembling foot held forward.
Gulls that have learned the trick stamp for earthworms. Similarly, I have seen thrushes stamp by hopping hard with stiff legs. Once I was startled to see a red-winged starling watching an olive thrush鈥檚 technique attentively, then having a go itself. It did get a worm or two, but its technique was faulty, with long, loping leaps instead of jerky thumps, so it did not scare enough worms and soon gave up. Or maybe it just didn鈥檛 like the flavour of those earthworms it had caught.
Jon Richfield, Somerset West, South Africa
鈥� The gull was indeed trying to get worms to surface. Underground, the rhythm of the gull鈥檚 feet sounds much like rain.
Earthworms like to surface during rain because it enables them to move around overground without drying out 鈥� this is impossible when it is dry. By tricking the earthworms, the gulls get an easy meal. The gulls may have learned this trick from watching other gulls, or they have inherited the behaviour.
Laura Still, Devon, UK
鈥� I was sitting on in South Australia recently, watching a gull 鈥減uddling鈥� the sand at the water鈥檚 edge before inspecting the water for any food items it might have disturbed. It seemed to be doing quite well for itself.
By an amazing coincidence, I had a copy of New 杏吧原创 in my hand at the time. I always read The Last Word first, so, moments later, when I opened the back cover and read the question about worm baiting I was, to say the least, rather surprised.
It appears that the gull seen by the questioner was applying successful food-gathering behaviour that evolved in one environment to another. This does make sense when one considers that gulls originate not in marine environments, as is frequently supposed, but in moorland ones. Presumably the behaviour evolved in environments that contained bogs, where the puddling behaviour would work successfully in damp ground some way from the water鈥檚 edge.
鈥淚t appears the gull was applying successful food-gathering behaviour that evolved in one environment to another鈥�
The vital question, though, is whether the gull was successful in drawing up worms, or anything else edible, to the surface.
Graham Houghton, Aldgate, South Australia