I like Allan's hypothesis of CBCs calling or creating a commotion while in a
forest or woodland as a diversionary tactic to allow a female to sneak in
and parasitise a nest. This certainly makes sense to me.
Stephen Ambrose
Ryde NSW
-----Original Message-----
From:
On Behalf Of Allan
Richardson
Sent: Tuesday, 6 December 2011 7:59 PM
To: Laurie Knight
Cc: Birding Aus
Subject: What is the function of Channel-billed Cuckoo's
calling flights?
I've not noted large aggregations of C-bCu's in the day but we did flush
around 12 roosting together, while conducting nocturnal surveys out near
Gunnedah NSW. It was late in the evening, the tree was an isolated
individual surrounded by grassland and there were no fruiting trees nearby
to my knowledge. The birds were clearly roosting together not in response to
a food source, which made the observation very interesting to me. The time
of year was late January (2011), which suggested a post-breeding group
likely made up of many young birds and perhaps a few adults, unfortunately
there was no way to tell, they disappeared into the dark very quickly. I
guess we have no way of knowing how many C-bCu eegs are deposited in the
nests of other birds throughout the breeding season, could it be possible
that the the 12 were a pair and their reunited progeny for that year and/or
previous years?? There have been rumours, but have we established whether
post-breeding groups are related i
n any way? if so, is it intentional or just likely due to the birds living
and then departing from the same general area???
I have watched C-bCu's luring Currawongs out of the nest, presumably to
allow the female an opportunity to parasitise the brood. The birds fly high
around a stand of trees where the Currawongs are nesting, calling loudly,
and the Currawongs just cannot resist to try and chase them off. Perhaps the
indiscriminate calling we hear by individuals or pairs is an endeavour to
draw other birds out to alert the C-bCu's of occupied breeding
territories???
Other than that I think we might be able to assume that C-bCu's call for
some of the same reasons other birds call. We assume they don't establish
territories, but most birds defend breeding territories or food sources
within defined territorial bounds and it's likely that C-bCu's are carrying
out similar breeding season behaviour, albeit not tied to a personal nest
site (unless they view the nests of their surrogates as a resource worth
defending). Territory posturing may then explain the calling aggregations.
Other cuckoos appear to call as territorial proclamations: Koels are very
competitive, Fantailed, Horsefield's Bronze, Shining Bronze, Brush and
Pallid are very vocal and I recently noticed many a brawl amongst competing
Pallids in the Goulburn area (NSW sthn tablelands) this spring, induced and
fueled by calling individuals.
Certainly cuckoos are one of the easiest groups to attract by call, a
suitable whistle to Shining Bronze is the easiest way to get a closer view.
Allan Richardson
Morisset NSW
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