Scottish Rock Garden Club Forum
General Subjects => General Forum => Topic started by: Anthony Darby on December 09, 2012, 08:56:24 AM
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European catfish in South Western France have learnt how to catch birds by temporarily beaching themselves, a behaviour not seen in their native habitat.
These catfish live in the River Tarn (in the city of Albi) which contains a small gravel island. Pigeons come here to clean themselves, but unfortunately for them the catfish population has adapted to this food source. They have developed a strategy of lunging out of the water, grabbing a pigeon and wiggling back into the river. This behaviour is reminiscent of the way bottle-nose dolphins and killer whales sometimes hunt, so much so that the researchers (University of Toulouse, France) refer to these catfish as "freshwater killer whales" in the title of their paper.
It's thought that these catfish only target moving pigeons, as no attack on stationary birds was ever witnessed. They also erect their barbels (the"whiskers" that give them their name) when approaching pigeons, suggesting they were using them to sense the vibrations caused by bathing birds. Analyses of carbon and nitrogen levels of sample catfish (crayfish, smaller fish and pigeons all have different levels, so the team could see which prey a fish had been eating) demonstrated that catfish which ate birds ate fewer fish.
What's especially interesting about this behaviour is that it's not been seen in the catfish's native habitat. The European catfish was introduced to Tarn in 1983, and seems to have successfully adapted their behaviour to fit their new environment. It's not known what triggered this new strategy - have the catfish eaten the majority of the local fish? If not, why go to this effort? Though it currently stands as an example of unusual behaviour, this result could provide new knowledge of how new behaviour arises in a foreign ecosystem.
Breaching Catfish (http://www.youtube.com/watch?v=g1y7ASI3ZkQ#)
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Anthony,
fascinating video! :o 8) It is a dream of any fishermen (including me ;D) to catch one of those powerful giants (>1,50 m). 8)
It is well known that Silurus glanis is not squeamish regarding the food. From worms over insects, living and dead fish, frogs and snakes, young waterbirds, mice and rats. In short all what fits into its mouth ;D.
The interesting thing is that obvious the catfish from river Tarn hunting during the day while usually it is a nocturnal species.
The fishs metabolism is strongly influenced by the water temperature. As warmer the water as shorter are the feeding pauses and as more hungry they become. As a newly introduced species to the river Tarn they have developed very well under those favourable conditions. And now, probably ordinary fish and other food getting short, they have developed new food sources - just because they are hungry!
Here are some more amazing records... http://www.fisch-hitparade.de/fischhitparade/ranglisten.php?jahr=all&fischart_id=67&pageID=1 (http://www.fisch-hitparade.de/fischhitparade/ranglisten.php?jahr=all&fischart_id=67&pageID=1)
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saw more Waxwings yesterday and loads today hawking for insects
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Ran the moth trap (with the 125W MV bulb) for the first time. Nothing but a dozen or so micros and half a dozen LBJs. These last went to the forest geckos. Will run it again tonight with a low wattage bulb and compare.
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Anthony thats a great video. Never thought catfish would be that big.
Angie :)
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Felt really bad yesterday. I was raking the dead foliage out of a large clump of Iris douglasii when I rolled our resident hedgehog out of his cosy lair. He/she didn't unroll and I tucked him/her back in as well as I could but didn't want to replace the tree leaves as they were now all mixed up and wet. Hope I haven't done any lasting harm as this is the first year I have actually seen one here instead of just their droppings.
Erle
Anglesey 1°C at 23:00
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An amazing slo mo video of feeding Waxwings
For some reason there is a problem but if you click on the title below the image it will take you to the web site
Waxwings feeding at 200fps on Vimeo (http://vimeo.com/55290315)
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Yes, I clicked on the name below the frame and really enjoyed seeing the waxwings - still none in the garden though they've been seen elsewhere in the area.
Just wonderful little birds!
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Ran the moth trap with the MV bulb last night. Again, lots of micros and LBJs, but also this Spangled Green Owlet. It's from Australia, where it is known as the Green Blotched moth. The book says: "Seen on both main islands, mostly in autumn on the coast. The caterpillars feed on native shore lobelia (punakuru, Lobelia anceps) and verbena." Okay, so it's not autumn, but we are not far from the coast and Verbena bonariensis is a common weed. The blur is the moth vibrating its wings to raise its muscle temperature before flying off.
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Very pretty moth Anthony but i seen a picture of a Mygalomorph in New Zealand Porrhothele antipodiana my friend is just about to mate his pair but what a spider.
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Its a nice start Anthony, ;D ;D
Cosmodes elegans .
Seems it is a true migrant species?
http://www.ento.org.nz/nzentomologist/free_issues/NZEnto05_3_1973/Volume%205-3-240-243.pdf (http://www.ento.org.nz/nzentomologist/free_issues/NZEnto05_3_1973/Volume%205-3-240-243.pdf)
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Yes Ron. Sorry, forgot to put in the Latin name. Nothing of note last night. I'm a bit far north for Porrhothele antipodiana Davey. :( I have come across trap door spiders but haven't tried to dig one out. The Avondale spider (Delena cancerides) still eludes me. I think a lot of the habitat in Avondale has been "tidied up". >:(
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This made the 10.30 One News tonight! A Canadian golden eagle snatches a baby and drops it because it was too heavy. https://www.youtube.com/watch?v=vMUTSB4tHRk (https://www.youtube.com/watch?v=vMUTSB4tHRk)
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Kerrumbs!
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Aha! ::) http://www.nydailynews.com/news/world/video-shows-eagle-snatching-baby-article-1.1223441 (http://www.nydailynews.com/news/world/video-shows-eagle-snatching-baby-article-1.1223441)
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They made an excellent job of it!
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This is not faked. http://link.brightcove.com/services/player/bcpid621950116001?bckey=AQ~~%2cAAAAAGfncP4~%2cGEGqcvZXqq-10O9kiblOp3u1Y4HDxYAG&bctid=1845844183001#.UJxwV3YFAlE.email (http://link.brightcove.com/services/player/bcpid621950116001?bckey=AQ~~%2cAAAAAGfncP4~%2cGEGqcvZXqq-10O9kiblOp3u1Y4HDxYAG&bctid=1845844183001#.UJxwV3YFAlE.email)
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This is a pic I took of a Fish pond in a garden in California.
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Here are some bird photos I took with my new Nikon 3200 and 300mm lens. In the new year I'll be getting a 150-500mm lens. Anyone got one, Nikon fit, you don't want?
Brent goose
Brent geese flying
Oystercatchers in flight
Pintail
Pintail in flight
Purple sandpiper
Ringed plover in flight
Rock pipit
Turnstone
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Excellent pictures Mark. I told you your camera equipment was fine and it just required practice. The sigma 150-500 is a good choice of lens if you realise it's limitations.
Shooting moving objects on a dull day at f6.3 requires an increase in the ISO setting reducing the quality somewhat but is still very acceptable.
However, being realistic, not many people can afford a Nikon 400 mm 2.8 tele lens which costs as much now as my house did in 1971 !!
ps where did you get the sunshine ?
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Here's a wee cicada on one of house outside Christmas lights. I just followed its call to locate it. It may be a North Island Clay Bank Cicada (Notopsalta sericea)? They are often found around houses.
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ps where did you get the sunshine ?
Good to know you like the photos. Last Sunday was a lovely day over here just like today. Two of us headed down to North Bull Island, Dublin. A very high tide was due to bring birds closer to a causeway. As its a bird reserve they didnt have much fear but still kept their distance.
One more from there. Part of a large flock of Knot.
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486 seal pups on the beach at Horsey in Norfolk yesterday, including several happily sleeping on the path. One of the wardens told us that two pups spent a fortnight in the car park last year after their mothers had returned to sea and eventually were carried back to the beach on stretchers! What a great shape this one is.
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Lovely picture, Margaret. Three from Lincolnshire in late November.
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Hello, please can anyone identify this bird of prey spotted in the San Francisco bay area about 3 weeks ago. Thank you.
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Rob it looks like a Broad-winged hawk. Its in the same family as our Buzzard - Buteo platypterus
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I always thought a loud, ringing, bell-like call was a bell-bird, until I managed to tie the call the the bird. An Eastern Rosella (Playcercus eximius). Managed a brief snap of one in the birch tree bordering our house this evening.