Do goosanders continue to "hunt in packs" while on the wintering waters ?
Hi Juha
Well like many other birds that feed underwater I've certainly seen goosanders dive in close proximity - and at the same time - with one another. Presumably underwater they are all watching each other in the hope the other birds will panic a fish towards themselves. It's an interesting question whether this behaviour is true cooperation or just opportunism - a sort of by-product of flocking behaviour.
For my money, cormorants definetely do cooperate to surround and pin down a fish shoal, sometimes with almost military precision. I'll never forget watching an extended line of about 20 cormorants on a lake in Northamptonshire cruising along and then all slipping under within a few seconds of each other to herd a shoal against the shoreline. I've also seen pairs of birds of prey - merlins, marsh harriers and the like - hunting cooperatively.
A good answer to a stupid question. Thank you, Colin.
I was puzzled by the behaviour of sibling groups. I'm guessing they were sibling groups, as there never was any adult males and the number was about right, a dozen or so. The group would paddle along the edge of reedbed, and split up when encountering an opening in the reeds. Some stayed and loitered at the mouth of the opening and others swept along the shoreline in a rectange-like fashion. Spotted this "manoeuvre" many times during the early autumn.
But I do tend to imagine things :}