Hello Michael
The egg of a Black-eared Cuckoo and other Bronze-cuckoo species can be
somewhat similar in appearance to the eggs of a Gibberbird. Although
Black-eared Cuckoo are known to seek hosts with domed nests, they spend
much time on the ground and it may not be too surprising if Gibberbirds
are also parasitised.
When we resided in far north of South Australia, occasionally I would
see Gibberbirds and other chat species nesting particularly in wet years
and in the 1970's, had the opportunity to work with egg collections of
the South Australian Museum.
Although I can't recall observing a cuckoo egg within a Gibberbird
clutch, as you probably already know the cuckoo's egg is usually
different to it's host, not only in colour and marks, but also by
comparison of it's 4 SS's, size, shape, sheen and surface texture.
Most of the Chats show egg pattern variation within a clutch, more than
is normal for many other species, however eggs within a single clutch
should be uniform (4SS's) notwithstanding aberrations and variation that
occurs between clutches from different individuals.
You also probably know that Morcombe's Field Guide to Australian Birds
has a well illustrated nest and egg section at the back which is most
useful. If you want to send me a copy of your photo, I would be happy
to give my best guess.
Regards
Ian May
Price, South Australia
Michael Todd wrote:
Hello all,
I'm sorting through my photographs from the last 12 months and have been
baffled by some photos that I took of a gibberbird nest that had 2 eggs
back on the 5th August at Davenport Downs in south-west Qld.
The strange thing is that the 2 eggs in the nest were quite different in
colour and pattern to such an extent that I at first assumed that there
was a cuckoo egg in the nest. After closer re-evaluation I now think
that there wasn't a cuckoo egg in the nest. One egg was noticeably
pinker in colour, with denser markings than the other.
Normally I'd look up venerated egg references like North or Campbell
with a problem like this but the Gibberbird wasn't described until AFTER
these volumes were published (early 1900's).
Now, this egg variation within a clutch may be normal for Gibberbirds,
I'm no expert on them. I'd love to hear from anyone who knows about
Gibberbird eggs or for that matter whether it is normal to have a lot of
variation within a clutch of eggs.
Cheers
Mick
Mick Todd
Toronto, NSW, Australia
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