Biology Reference
In-Depth Information
(a)
(b)
3
3
Nest predator
Adult predator
2
2
1
1
0
0
-1
-1
North America
South America
Pre-
presentation
Pre-
presentation
Model
presentation
Model
presentation
Fig. 8.3
Responses of North American and South American songbird parents to
presentations of: (a) a nest predator (experimental playback of calls of a jay) and (b) a
predator of adults (presentation of taxidermic mount of a hawk). Responses measured as
reduction in feeding visits to a brood of nestlings. South American parents value their
own lives (future broods) more (stronger response to adult predator) while North
American parents value their current brood more (stronger response to nest predator).
From Ghalambor and Martin (2001). Reprinted with permission from AAAS.
Notiomystis cincta
. On territories where broods were fed experimentally with extra
carotenoids in a sugar solution, their mouths became redder and this enhanced begging
display led to increased provisioning by the parents, probably because redder mouths
signalled healthier offspring, worth more investment. However, on other territories,
where the adults were also provided with carotenoid-rich sugar feeders, this increased
the chance that they had a second brood that season. The pairs that had second broods
did not respond to the enhanced begging signals of their current brood. Therefore,
parents strategically varied their sensitivity to their current brood's demands in relation
to their future prospects of breeding that season.
Response to
current brood
demands varies
with parents'
future breeding
prospects
Flexible care in St Peter's fish
Galilee St Peter's fish,
Sarotherodon galilaeus
, is a mouth brooding cichlid found in rivers
and lakes throughout Africa and Asia minor. Parental care may be provided by either
sex alone or by both parents. This flexibility within a species provides an ideal opportunity
to test whether males and females vary their care in relation to the costs and benefits.
Mating is monogamous; pairs dig a shallow depression in the substrate together, then
the female lays batches of 20-40 eggs into the depression and the male glides over
them, fertilizing each batch in turn until the clutch is complete. Then either the female,
or the male, or both parents pick up the eggs in their mouths, where they protect the
eggs and young fry for about two weeks. The pair bond dissolves after mouth brooding
begins, even in cases where both sexes provide care.
