2007 Research Reports.pdf - Fowlers Gap Arid Zone Research Station

1.4 Maternal effects in cooperatively breeding chestnut crowned babbler.
Investigators: Andrew F Russell 1,2 , Simon C Griffith 2 , Lucy E Browning 3
1
Department of Animal & Plant Sciences, University of Sheffield, Sheffield S10
2TN, UK,
2
CISAB, Macquarie University, Sydney, NSW 2109,
3
Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK.
Mothers are known to exert a strong influence on the growth, survival and reproductive capacity
of offspring in adulthood. Similarly, sibling competition can also exert substantial effects, in
extreme cases resulting in siblicide. Whether and, if so, how mothers reduce sibling competition
and maximise their own fitness is largely unknown. We began an examination of maternal
investment strategies in our population of chestnut-crowned babblers at the UNSW Arid Zone
Research Station at Fowlers Gap. Mothers can do a number of things to reduce competition.
They can change clutch size, egg size, hatching asynchrony and sex ratio. We collected data on
these four parameters by removing clutches of eggs from 50 groups and hatching the eggs out in
an incubator. This allowed us to collected detailed data on all parameters. In order to test
experimentally the effect of each of these parameters on maternal fitness, we then cross-fostered
out eggs into different nests from which they came, and in doing we manipulated all four
parameters. This experiment is the first of its kind and will reveal unexplored ways in which
mothers reduce sibling competition and maximise personal fitness.
1.5 Behaviour and ecology of the cooperatively breeding Apostlebird
Investigators: Jonathan Wright 1 , Anahita Kazem 1 , Andrew F Russell 2,3 , Simon C Griffith 3
1
Institute of Biology, NTNU, Trondheim, 7491 Norway,
2
Department of Animal and Plant Sciences, University of Sheffield, S10 2TN,
U.K,
CSIAB, Macquarie University, Sydney, NSW 2109
This long-term study of the apostlebird (Struthidea cinerea) population at Fowlers Gap has
continued to progress. Over 275 birds have now been caught, individually colour-banded and
bled (for genetic analyses of relatedness), representing approximately 75% of the birds in the
core study area within ~5km of the station. We have succeeded in habituating 71% of these
banded birds to the close presence of human observers, and the last remaining birds will be
habituated in 2008. The ultimate aim here is to get all individuals in the core study area to stand
on electronic balances on demand, so that we can measure short-term changes in body mass and
hence assess state-dependence within- and between-individuals in their behavioural strategies.
We now have 3 years data on the social structure, breeding group size and breeding success,
including detailed GIS mapping of the creek habitat used for nesting. Detailed behavioural
observations and experiments have begun on various topics, such as foraging, vigilance,
mobbing, vocalizations and helping at the nest. Specific data on ‘false-feeding’ behaviour and
individual provisioning strategies during nestling feeding have been collected during 2007 to
compare with earlier data collected by Iain Woxwold (Univ. Melbourne) from another less arid
site far to the southeast. Compared with populations further east, the social structure of the
Fowlers Gap population of apostlebirds seems to be surprisingly fluid and rather flexible in terms
of breeding group formation and reproductive effort, which both depend heavily on annual
variation in environmental conditions. The large wide-ranging flocks seen during the winter at
Fowlers Gap appear to constitute ‘clans’ of familiar and possibly related individuals. These nonbreeding
winter flocks fragment in the early spring and form smaller breeding groups of 3 to 15