On Thu, 19 Apr 2001, Vella wrote:
> Around Sydney, I still see quite a few adult Superb Blue Wrens in full
> breeding plumage and less so with Variegated Wrens.
Ian Rowley's 1975 book "Bird Life" has a a chapter describing his
studies in the 1960s of Superb Blue Wrens in Canberra including
their moult timing.
I've appended an excerpt from a recent paper on the control of moult
timing in male Superb Blue Wrens. It was based on field work done on
the coloured-banded wrens you see in the Botanic Gardens in Canberra
by people from the ANU and Wollongong uni. The paper is:
A. Peters, L. B. Astheimer, C. R. J. Boland, A. Cockburn: Testosterone
is involved in acquisition and maintenance of sexually selected male
plumage in superb fairy-wrens, Malurus cyaneus Behav Ecol Sociobiol 47
(2000) 6, 438-445
"Superb fairy-wrens, Malurus cyaneus, are territorial, small (9-10
g),long-lived (up to 11 years), cooperatively breeding passerines
(Dunn and Cockburn 1996). Male plumage alternates between a dull brown
eclipse plumage in winter to an azure-blue and black nuptial plumage in
summer. Hence, males undergo two moults per year, a full post-breeding
moult into the brown plumage and a pre-nuptial moult into the colourful
plumage, replacing the head and body feathers. The duration for both
types of moult is similar(2-3 weeks). Whereas the post-breeding moult
occurs synchronously, timing of the pre-nuptial moult is extremely
variable. Moult canbe initiated at any time from March until November,
and in some years, a small percentage of males moult dire ctly from one
nuptial plumage into the next (Dunn and Cockburn 1999). By the end of
spring, all males have developed a complete nuptial plumage, andthere
is little variability in the extent or intensity of the plumage attained.
...
Early initiation of the pre-nuptial moult is the best predictor of male
reproductive success, which is heavily skewed in this species. Males
that complete the nuptial plumage at least 1 month prior to the start
of the breeding season are strongly preferred in female choice (Dunn and
Cockburn 1999). Timing of moult into nuptial plumage is an indicator of
male quality (Mulder and Magrath 1994). Timing is age dependent (males
moult progressively earlier until they are 5 years old) and condition
dependent (males moult later in harsh winters). Individual males show
high consistency in relative moult date between years (Mulder and Magrath
1994). The moult appears to be very precisely regulated:males that
moult into bright plumage very early in the season, in autumn or early
winter, can sometimes `turn around' and briefly moult into another brown
eclipse plumage before again moulting into a bright plumage (A. Cockburn,
unpublished data). As soonas males have developed their nuptial plumage,
they start to advertise their status by visiting neighbouring females
to perform court-ship displays (Mulder 1997)."
Andrew Taylor
Birding-Aus is on the Web at
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