Hi Russell,
Unfortunately, I don't know the answers to your questions and perhaps
someone else has answers. Or perhaps it would make a good topic for an
honours research project.
Kristin et al. (2004) indicate that impaling /wedging of prey has developed
independently in three groups: the Butcherbirds (Cractacidae) in Australia,
the Bush Shrikes (Malaconotidae) in Africa and the True Shrikes (Laniidae)
in Europe, Asia, Africa and North America. The authors state:
"The evolutionary pathway of impaling appears to result from trial-and-error
activity, like most other behavioural processes. A simplistic explanation of
impaling is that it was probably learned by the ancestral shrike dragging a
heavy prey item, which wedged into a fork or other projection, allowing the
individual to learn the use of a tool for dismemberment. Territorial
behaviour and use of regular impaling sites allow individuals to store food
and communicate with conspecifics, in some species resulting in the caches
becoming parameters for sexual selection. Impaling inedible objects (e.g.
insects containing inedible toxins) to improve the visual impact may have
evolved into the discovery that after some time they become edible (as the
toxins are broken down), which open a new feeding niche. The overall
impression is of a behavioural adaptation that evolves quickly in response
to local ecological pressures and that allows the True Shrikes to adapt to a
wide range of habitats, ranging from the freezing snowfields of Alaska to
the burning sands of the Sahara Desert."
With respect to the Grey Butcherbird, HANZAB Vol 7 states that prey that are
too large to be swallowed whole, such as lizards and small birds or
nestlings, are usually wedged into a crack or a fork on a branch or impaled
on a thorn, where it is torn to pieces before being eaten. Surplus food is
stored in the same way (caching) and portions taken as needed.
Hope this information is of some use to you.
Reference:
Kristin, A., Yosef, R. And Tryjanowski, P. (2004). Advances in Shrikeology:
the 4th International Shrike Symposium, Chemnitz, Germany. Biological Lett.
41(2): 59-63.
Stephen Ambrose
Ryde NSW
-----Original Message-----
From:
On Behalf Of Russell Woodford
Sent: Monday, 17 May 2010 6:42 PM
To: Stephen Ambrose
Cc: birding aus
Subject: RE: Grey Butcherbird Larder: comment on impaling
again...........
Hi Stephen
This is an interesting observation - do you know if there is anything
in the literature about it? Sorry, I am being lazy! I should look for
myself but you would know better than me. Also, do you think there is
any way of distinguishing "impaling" behaviour from "wedging"? That
is, do you that it is possible to tell if sometimes butcherbirds
"choose" to wedge, and at other times impale their prey? Again, I
wonder if there is anything in the literature on birds choosing one
strategy over another - in any species. I know some species have
developed amazing repertoire of behaviours, but I am interested in
whether or not they can select between them.
Regards
Russell
Russell Woodford
On 17/05/2010, at 5:15 PM, Stephen Ambrose wrote:
> Not long at all. It tried securing the food in one part of the tree
> initially. In that first instance, it did look as if it was trying
> to wedge it into a fork, but not very successfully. After about 2
> minutes it gave up trying this first location and moved to another
> part of the tree where the prey item was definitely impaled. That
> took at least another 2 minutes at a guess (wasn't timing, just too
> interested in observing what was happening). It probably took that
> long because the carcass looked a bit cumbersome to handle, rather
> than it being difficult to impale. For the next 10 minutes the bird
> tugged at the flesh, flying off at least twice before returning to
> the carcass to feed again.
>
> Stephen Ambrose
> Ryde NSW
>
> -----Original Message-----
> From: Peter Shute
> Sent: Monday, 17 May 2010 5:00 PM
> To: ;
> Cc:
> Subject: Re: [Birding-Aus] RE: Grey Butcherbird Larder: comment on
> impaling again...........
>
> It must surely take some effort and skill to get the bird onto the
> twig. Did it take it very long?
>
> Peter Shute
>
>
> --------------------------
> Sent using BlackBerry
>
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