For those interested in raptors, Paul McDonald's thesis on the Brown
Falcon is now available online at:
http://dspace.anu.edu.au/handle/1885/47695
McDonald, Paul (2003)
Reproductive
success, dimorphism and sex allocation in the brown falcon Falco
berigora PhD thesis, School of Botany
and Zoology, ANU
Abstract:
This project describes various aspects of
the breeding ecology and behaviour of the brown falcon Falco berigora,
a common
but poorly studied Australian raptor. In particular it examines (a) the
main
influences on reproductive success; (b) tests predictions of theories
proposed
to explain the evolution and maintenance of sexual size dimorphism
(RSD;
females the larger sex) in raptors; and (c) investigates sex allocation
patterns in the light of current sex ratio and parental investment
theory. The
study was conducted between July 1999 and June 2002 approximately 35 km
southwest of Melbourne, at the Western Treatment Plant (WTP), Werribee
(38°0’S
144°34’E) and surrounds, a total area of approximately 150 km2.
• In all plumage and bare
part colouration
of 160 free-flying falcons was described. The majority of variation in
these
characters could be attributed to distinct age and/or sex differences
as
opposed to previously described colour ‘morphs’.
• Nestling
chronology and development is
described and formulae based on wing length derived for determining
nestling
age. An accurate field-based test for determining nestling sex at
banding age
is also presented.
• Strong sex role
differentiation was
apparent during breeding; typical of falcons females performed most
parental
duties whilst males predominantly hunted for their brood and partner.
Based on
observations of marked individuals, both sexes of brown falcons
aggressively
defended mutual territories throughout the year, with just 10% of each
sex
changing territories during the entire study period. Males performed
territorial displays more frequently than females, the latter rarely
displaying
alone.
• The diet of the
population as a whole was
very broad, but within pairs both sexes predominantly specialised on
either
lagomorphs, small ground prey (e.g. house mice Mus musculus), small
birds,
large birds or reptiles, according to availability.
Robin Hide
