Thank you so much for your kind and very interesting reply, kuhankeittäjä!kuhankeittäjä wrote: ↑August 13th, 2018, 12:46 pmHi Anne7!
Thanks for welcoming me, and for your kind reply to my worry about the health of Karl, the principal assistant of nesting of the BS family.
It is relaxing to read, that this behaviour is rather a rule than an exception. As you say, there might be a more general reason to it and, hence, the bird species may have adapted.
I have now seen it three times altogether, simultaneously being capable to identify the fish species, or at least I think I could do so.
The fish is perch, which is quite a sticky animal in close surroundings like fishnet of a human or crop of a bird. When it dies it spreads its back and head spikes and can move only ahead. It cannot be drawn out or regurgitated the other way. Have you any observation of other fish species in connection of this prohibited regurgitation?
Why it happens close to the end of the nesting period? There might be several reasons. Of all these it is familiar to me that this is the time of the year when perches have recovered from their mating stress in spring and left deeper waters, pack hunting juvenile fish flocks in shallow waters, where BS may catch prey. I can imagine that a flock of scared youngster fishes escapes almost to dry land to avoid being caught by a perch pack and there a BC can rapidly fill its crop with small fish. Finally it may catch a perch, its tail almost out of the beak. And there it sits fast. The BS must consume it by itself in a normal way. Why they then take this fish? My guess is that because it is good food, containing much protein. It also tastes good, at least in the mouths of human family members, so why not by the taste sensors of a BS.
The previous is layman's fictive explanation. The scientific truth may be something else.
Thanks for all who have made it possible to watch BS family life abroad via internet.
Having watched it for the first time, I have learned a lot of these big birds during this summer. I wish success in continuing your efforts to study their life and hope that these bird individuals can survive their next year, returning back to the north when the winter has gone. They have become almost our family members after having been electronically displayed and heard in the corner of our living room all day and most of the night.
You could be right! Probably some fish species are much harder to regurgitate than others.
It is very well possible that a perch can only be regurgitated in the right direction: head first.
It is a very good idea (to try) to observe which fish seems to be stuck in the troat!
Till now, I did not do that.
So I am unable to tell if it was always a perch that caused this regurgitation-problem, or if it also occured with other fish species.
EDIT: Unfortunatly, I do not know much about fish. Please feel free to help recognising them, kuhankeittäjä!
Here is a picture of a (very big) perch. I can imagine that those dorsal spikes can become problematic during regurgitation!
© photo: Dennis Hunt, https://www.anglingtimes.co.uk/fishing- ... o-matchman
And a smaller one:
© http://huntergathercook.typepad.com/hun ... -uk-1.html
About the common perch (Perca fluviatilis):
List of Freshwater Fishes for Estonia: