Made by Jari Keinänen

”Hey, have you ever seen a seagull dancing? Funny looking thing, I say.”  

-> Just take a look<- 

” What makes a bird paddle grass like that?”

Sometimes seagulls do paddle the ground with both of their feet at a rapid pace that might look like a dancing in our eyes, but its not a mating ritual or dance. Instead this foot padding is a technique called worm grunting and seagulls use it to find food. Birds stomp the ground in order to attract worms to surface.

If you can see the whole method done successfully, you’ll notice that the seagull finds a damp area of land (usually a field of grass), starts stomping the ground with a rhythmic pace, stops to inspect surroundings and snatches a spotted worm with its beak. Worm grunting is common with European and American gulls, but also used by American wood turtles and humans.

Averege herring gull walking in Hillhead student residents area. Photographed by Juho Niva •Obsevation of worm grunting via Google Map

“They luring worms by stopping the ground? Why does it work on worms?”

Seagulls stomping causes vibrations that penetrates the ground layers. Earthworms surface, when they detect those shockwaves. Long time zoologists’ thought that because vibrations resemble the sound of heavy rain worms surface in order to avoid drowning.

However the newest explanation is that sound is similar to the noise moles make when they dig tunnels underground.

Whatever the reason is the seagull exploits the worms escape reaction so they crawl directly into their beaks.

Two herring gulls performed worm grunting in the eastern border of Nibb Bay golf course, south side of River Dee, Aberdeen. Taken on Tuesday 15th of February 2011 at 3.45 pm

“Well, that seems a very complicated trick for a simple bird. Are you sure they invented it by themselves?”

It is possible that seagulls learned it from other bird species and they are just copying what they have seen. We have to keep in mind that birds can be very clever in general. For example, crows are known to make tools. Seagulls have improved to be an inventive and opportunistic predator…

herring gull. Photo was taken in River Don right next to brige on Tuesday 22nd of February 3.00 pm

There have been reports (example Helsinki, Finland 2010) that gulls snatch tourist’s food in big cities by first hitting people on the head while they are eating outdoors and after that they come to steal what ever they manage to make people drop from their hands. When it comes to food, seagulls really put their minds into it.

Photograph from Finnish newspaper article make by MTV3-newschannel in 30th of June 2010

“So, how did seagulls figure this thing out in the first place?” A bit like the invention of the first wheel, we can’t really know how worm grunting came to be. We do know that seagull learned it at some point. After one seagull learned an effective way to find food, this knowledge spreads to other member of this species through social learning.

Like human children, young seagulls get to know new things by watching and learning. Seagull by Juho Niva

They have to dance to earn it!

Reference:

Foot-padding in four American Gulls with comments on its possible function and stimulation – D.A. Buchley, 1965 

Worm grunting fidding and charming – Humans unknowing mimic a predator to harvest bait –K.Catania, 2008  

Diversification and cumulative evolution in New Caledonian crow tool manufacture -G. Hunt, R. Gray 2002 

Newspaper article: Lintupoliisit ratkaisu häiriköiviin lokkeihin? – MTV3-newschannel 2010

Thanks to Juho Niva for the photos and also you for watch!