birding-aus
Is it not true that the African Harrier Hawk (Gymnogenys typicus) is a
specialist hunter of things in cavities? I'm sure you have thought of that
one yet you say "there appear to be few natural enemies while the chicks are
still in the cavity". What about snakes but that defence would not work as
(as far as I know) snakes are deaf.
-----Original Message-----
From: Peter Thompson <>
To: <>
Date: Tuesday, 16 February 1999 23:56
Subject: birding-aus (Fwd) Defence calls in cavity nesting birds
birding-aus
------- Forwarded Message Follows -------
Date sent: Tue, 16 Feb 1999 13:52:02 +0200
From: "Craig Symes" <>
To:
Subject: Defence calls in cavity nesting birds
Information Wanted: Cavity Nesting Birds and Defense Vocalisation
Calls.
While attending the I.O.C. in July 1998 I in Durban, I had the chance
to discuss and share various ideas concerning my own and other
researchers studies worldwide
The Cape Parrot is a secondary cavity nester in the Afromontane
forests of south-eastern South Africa. Juveniles and adults make a
characteristic growling sound if threatened in their nest cavity, yet
there appear to be few natural enemies while the chicks are still in
the cavity. The cavity is usually quite deep and inaccessible from the
ground in an upright forest canopy or canopy emergent tree.
This form of vocalisation made by any bird species in the nest would
nonethelesss serve as an effective defensive mechanism for a cavity
nesting species. A mammal like growling sound emanating from a dark
cavity would surely raise suspicions to the actual occupant of the
hole to any intruder/predator. My question is, does it occur in other
cavity nesters or species constructing an enclosed nest? The
threatening defensive vocalisations of this species has driven my
interest in investigating the phenomenon in birds worldwide and
investigating and reviewing where such defensive mechanisms may be
utilised. I did post a similar request a while back on SABirdnet and
had a few responses. Thank you to those who did respond.
I am unaware of any publications directly confronting this issue and
would appreciate views and input on various species that different
subscribers may have studied or encountered.
Please bear in mind the following points when replying:
1. Species (Specific as possible)
2. Distribution of species (e.g. Cape Parrot Poicephalus robustus
robustus - Afromontane forests of south-eastern South Africa)
3. Type of defensive call of adult and/or nestling and form of threat
(e.g. mammal like growl when cavity hole approached, snake like hiss,
bee like buzz/hum etc.)
4. Potential/known nestling predators
5. Co-operative breeder/Polygynous/Polyandrous/Monogamous/Other
6. Type of nester: Primary cavity nester (constructs own cavity),
Secondary cavity nester (uses natural cavity or old cavity of primary
cavity nester, or, Constructs enclosed nest (e.g. Ploceus spp.)
7. Does the species in question supply nest material to the cavity and
what type of material.
8. Obligate/facultative cavity nester?
9. Further remarks.
I hope to accumulate data from various sources in investigating this
issue. Any input will be duly acknowledged should any publications
result.
If there is anyone on SABirdnet who is connected to any other
"chatgroups", or has any contacts who may be able to help, please
forward this message to them.
I look forward to a flood of responses.
Yours sincerely
Craig Symes
*************************************************
Craig Symes
Research Centre for African Parrot Conservation
Dept. of Zoology and Entomology
University of Natal
P/Bag X01
Scottsville 3209
South Africa
Phone: (0331) 260-5104/03/27
Fax: (0331) 260-5105
e-mail:
*************************************************
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