Tuesday 13 August 2013

Several Great Crested Grebes were fishing right at the edge of the Serpentine, a sign that the new season's fish have finally grown to a reasonable size and are quite numerous. This is also good news for grebe chicks. There are are only two of these at the moment, at the island (I think the half-grown one which was fishing on its own has not survived, though it would be good to be proved wrong). But there are now four nests on the go, and the grebes have been sitting on all of these for several straight days, so it looks as if they all have eggs. Better late than never.

The technique that grebes use for catching small fish in shallow water is quite different from their normal technique. They cruise around constantly looking under the surface to spot a little school of fish.

Having seen one, they make a quick horizontal lunge rather than a proper dive.

You can see from this picture that the grebe's legs are sticking out at right angles, a position that no web-footed bird would ever adopt. But for a grebe, with its unique turbine-blade toes, this is the beginning of the powerful thrust that propels it forward faster than any other foot-propelled bird.

The complete cycle is shown in this sequence photographed against a measuring grid.

It is from Christoffer Johansson and Ulla M. Lindhe Norberg, Lift-based paddling in diving grebe, a paper published by the Department of Zoology of Göteborg University in 2001, which you can see here.

The grebe in these pictures was reared from an egg by the researchers and filmed in a pool in a laboratory; they threw a live fish into the water to get it to swim past the camera. However, it is not going nearly as fast as it would when hunting in the wild; the paper quotes 1 metre per second, which is about 2¼ mph. A Great Crested Grebe can easily manage three times that speed, maybe more, and it is lilkely that its swimming stroke looks different at maximum speed.

After all that academic stuff you deserve a picture of a fluffy Mallard duckling.

This is from a brand-new brood on one of the ponds in the Italian Garden. The babies are still small enough to fit back into the egg. They were on the same pond as the other Mallard brood, and the two mothers were eyeing each other with a certain hostility. The ponds are heavily overgrown with weed, which is at the moment supporting two broods of Mallards, two of Moorhens and one of Coots, plus the solitary young Mute Swan that seems to have made the place its home.


  1. The academic stuff is a bit beyond my , well attention span certainly (if not comprehension). But I always like it that there are people who study such things in such depth. Whoever heard of a a 'tame' Grebe?
    Me, I'm happy with the fluffy duckling.

    1. Yes, that paper is pretty tough going. Also, I felt unhappy about the grebe that had never seen a real lake, and I hope they treated it kindly. But it is fascinating to see how this very different swimming stroke looks. There is hardly any video footage of a free grebe swimming, but try this brief clip of a Western Grebe (Aechmophorus occidentalis), the big American species:
      (Sorry, I can't do live links in the comments, you'll have to copy and paste it.)

  2. great video! and yes, much better a wild bird. Don't like the idea of captivity/ laboratory existence either.
    What divers they are!