PhD‐theses - Ethologische Gesellschaft

Research Update
WHO DETERMINES THE END OF BROOD CARE IN THE ZEBRA FINCH (TAENIOPYGIA GUTTATA)?
Inka Spiller
inka.spiller@uni‐oldenburg.de
Bachelor Thesis, Supervisor: Fritz Trillmich & Tobias Krause; Dept of Animal Behaviour, University of
Bielefeld
A long‐standing question concerns the ending of brood care in mammals and birds: This is
supposed to lead to parent‐offspring conflict, with parents selected to end care earlier than
offspring would like. Who decides in this: parent(s) or offspring? I studied this question in an
altricial birds, the Australian zebra finch (Taeniopygia guttata) by cross–fostering young of
different ages. In one treatment the parents received 3 ‐ 15 days younger chicks and in the
other chicks that were 3 ‐ 7 days older than their own. In addition, there were two control
groups: In the first, parents were permitted to rear their own chicks and in the second they
received cross‐fostered chicks of the same age (+/‐ 2 days).
Parents extended brood care when they received younger chicks and shortened it
when getting older ones. Young always fledged when about 18‐20 days old, independent of
treatment and at the same time as the two control groups. To determine whether parents
stop feeding when chicks present stimuli normally shown by 19 day old young, I kept young
of 5 broods artificially for up to 6 days longer in the nest. These young were equally fed by
the parents. The results demonstrate unequivocally that young determine the age of
fledging.
After fledging, parents fed chicks of all treatment groups for approximately the same
duration whether they had received older, younger, or equal‐aged chicks. Also the ones that
had been fed in the nest for longer than normal were fed outside the nest for about the
same period. My results demonstrate that in this altricial bird young determine the age at
fledging and increased time of brood care in the nest does not shorten parental care after
fledging. Thus there is little evidence for parent‐offspring conflict.
22