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Today I saw a Herring Gull and a Common Gull (UK common names) "worm-dancing" on an area of wet grass. Worm-dancing is when the bird taps its feet on the ground rapidly in order to drum worms to the surface (that its a worm hunting behaviour might be conjecture, I'm not sure it's been proven).

Shortly after, a pair of Jackdaws landed and also began hunting, but without dancing. They walked over the area poking about in the grass, whereas the gulls stayed in the same place.

So my question is firstly, which species/families has worm-dancing been observed in, and secondly is this thought to be learned behaviour (this might be determined by it being a local phenomenon in certain populations)?

EDIT: Originally misidentified a common gull as a black headed gull (corrected above). Today I saw a black headed gull alongside the two larger gulls, and it was hunting like the jackdaws, not worm-dancing. There might possibly be a size/weight requirement to be able to worm-dance effectively, if we accept the hypothesis that it's a method of bringing worms to the surface.

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  • $\begingroup$ Thrushes (Turdidae), like the Blackbird, don't actually dance, but they hop around when hunting worms. This might have the same effect as dancing. $\endgroup$ – RHA Apr 11 '18 at 20:46
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Short answer
Sea gulls indeed tap the ground to surface earth worms, which is known as worm charming. Traditional human societies have practiced a similar technique known as worm grunting, involving vibrating the ground. Worm grunting is obviously a learned behavior passed down for generations in Florida. In other animals, such as gulls, I wasn't able to find evidence whether it is learned or innate behavior.

Background
From wikipedia:

Worm charming is especially [observed] among birds. The methods used vary; however, tapping earth with feet to generate vibrations is widespread. One common example is the "Seagull dance". The wood turtle also seems to be adapted for worm charming, as it is known to stamp its feet – a behavior that attracts worms to the surface and allows the turtle to prey on them.

It is popular belief says that the charming mimics the drumming vibrations made by rain and that worms are attracted by it. However, studies have indicated that the charm vibrations sound similar to those made by burrowing moles, a voracious worm predator and that the charming behavior of worms surfacing reflects an escape behavior of worms, namely the abandoning of their safe burrows to expose themselves to the real danger once surfaced (Catania, 2008).

The authors investigated the charming reaction of the worms by studying human-indiced charming, a technique used by fishermen. For generations, many families in and around Florida's Apalachicola National Forest have supported themselves by collecting the large endemic earthworms (Diplocardia mississippiensis). This is accomplished by vibrating a wooden stake driven into the soil, a practice called “worm grunting”. This worm grunting is obviously learned behavior.

However, I couldn't find evidence whether the worm charming in birds and turtles is learned yes or no.

Reference
- Catania, PLoS ONE 3(10): e3472

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  • $\begingroup$ Do you have any information on which species/families practice worm-dancing, which was the main part of the question? $\endgroup$ – James Walford Jan 16 '18 at 11:58

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