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Studies on intraspecific brood parasitism of the Mandarin Duck Aix galericulata

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This is typical nesting habitat for the Mandarin Duck: mature woodland next to standing water (right) where there are a lot of trees with holes for nesting. This cavity-nesting duck normally breeds in natural holes usually formed by the breaking off of branches from a trunk. Sometimes, with decay of the core of the tree the cavity may be many metres deep - but the hatchlings still manage to escape to the outside and then to water. The Mandarin Duck is a native of north-east Asia and Japan but was introduced as an ornamental waterfowl at the beginning of the 20th century.

Mandarin Duck habitat

 The Mandarin Duck is a native of north-east Asia and Japan but was introduced as an ornamental waterfowl at the beginning of the 20th century. The bulk of the population is found in southern England with some remote populations in Scotland. The British population was estimated at 7000 birds in 1988, probably about a third of the world population (Davies, 1988). The population is resident, although one bird ringed in Berkshire by our group has been recovered in Russia. The feral population ap pears to be highly successful in its typical habitat, and there is probably little genetic interchange with captive stock because of the pinioning of captives and the breeding biology of the species.
The Mandarin Duck has a highly variable clutch size which reflects the substantial amount of intraspecific brood parasitism in this species. It is, therefore, an ideal model species to investigate both the physiology of incubation and explore the nature of intraspecific brood parasitism.


A female Mandarin Duck in the hand

Our studies are on Mandarin Ducks laying in nest boxes. The provision of these artificial nesting sites did not alter the size of the clutches, which vary from 6 to around 40 (Davies & Baggott, 1989a). One peculiarity of the reproductive biology is that sometimes as many as a quarter of the clutches are never incubated, although they were of a range similar to incubated clutches. Deserted clutches, i.e. incubated and then abandoned, are fairly rare in this species.
Incubated clutches are larger earlier in the breeding season. However, the laying pattern is also extremely variable. When nests are monitored every day, there were days on which no eggs were added to a clutch, days on which one egg was added, and a smaller, though significant number of dyas when up to 4 eggs were added. Larger clutches had proportionately more days on which two or more eggs were added, although this was unrelated to clutch size..


A clutch of eggs

Larger clutches had a shorter laying period than expected, but a longer incubation period. The mean laying period for incubated clutches was 15.3 days; the mean incubation period was 33.5 days (range 30-39 days) for a mean clutch size of 12 eggs. Unhatched eggs resulted mainly from embryonic mortality; some of this was due to eggs being laid into a clutch after the start of incubation. Larger clutches did not have proportionately more eggs; overall 70% of eggs incubated hatched (Davies & Baggott, 1989b).
If clutches are identified as parasitized on the basis of more than one egg laid in a nest on any one day then the proportion parasitized in this species is 56%. However, the breaks in lay prevalent in this species indicate that the proportion of nests parasitized is much higher, although indeterminate. It is unwise in this species to identify a nest as non-parasitized solely from the absence of multiple laying of eggs. At present we have no way of accounting for the numbers of females laying into a single clutch, although we do know that only a single female incubates.

References

  • Davies, A.K. (1988) The distribution and status of the Mandarin Duck, Aix galericulata, in Britain. Bird Study, 35:203-208.
  • Davies, A.K. & Baggott, G.K. (1989a) Clutch size and nesting sites of the Mandarin Duck, Aix galericulata. Bird Study, 36:32-36.
  • Davies, A.K. & Baggott, G.K. (1989b) Egg-laying, incubation and intraspecific nest parasitism by the Mandarin Duck Aix galericulata. Bird Study, 36:115-122.


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  Last modified on: 20 September 2006