Studbook nr. 5, December 2008

EUROPEAN STUDBOOK CROWNED PIGEONS
" an array of populations which are actually or potentially interbreeding, and which are
reproductively isolated from other such arrays under natural conditions (Mayr, 1942)."
In other words, a species is a group of organisms that interbreed and produce fertile offspring only
with one another. Mayr's definition has enjoyed the broadest popularity of any definition offered
for species, but there are both practical and conceptual difficulties with it's application during the
course of biological classification.
The three species of crowned pigeons are, in contradiction to the definition of a species,
hybridizing. Both in the wild and in captivity, hybrids can be found. McMorris (1976) expects that
the Goura scheepmakeri is a result of hybridization between Goura victoria and Goura cristata.
These species both occur at the Siriwo River in the northeast of New Guinea and they are
hybridizing there too. The northern border of the range of Goura scheepmakeri is not far from this
point, so it might be possible that the hybrids have moved and settled themselves in the southern
part of New Guinea. This seems very plausible, also because of the colours of the different species.
In addition, comparing studies of the behaviour of the three species did not show any differences in
the behaviour of the species (Lommers, 1982; Van Rijn 1995). For this reason, it is probably better
to call the three species geographical races. But, geographical races may in time come to differ so
much from their parent stock that they evolve into new species (Goodwin, 1983).
Probably in the past the three species of crowned pigeons were geographical races, derived
from one species. They could have disappeared from large areas of its range through alteration of
the habitat, leaving isolated populations separated by areas of country no longer suitable for it.
When they came together again they have differed so much from their parent own stock, that they
have been evolved into a new species (Beehler, 1981).
The island of New Guinea used to be part of Australia (Pratt,1981) and at the edge of two plates,
New Guinea is tectonically active, with a considerable history of mountain-uplift, volcanic activity
and earthquakes. Today this is a still continuing process (Beehler et al., 1986). In New Guinea
several different geographical sub regions can be distinguished, each with some characteristic flora
and fauna. Lowland rainforest occurs along the entire coast, being broken in a few places by
anthropogenic grassland or eucalypti savannah. However, at the moment large areas of tropical
rainforest occur only in three regions:
• The vast Fly Platform south of the Central Ranges, extending from about Etna Bay at the
neck of the Vogelkop to Hall Sound on the SE peninsula, home of the Scheepmaker’s
crowned pigeons
• In the west, the Vogelkop peninsula, where the common crowned pigeons occurs, and
• In the north, the watershed of the Mamberambo River and its tributaries and adjacent
coastal plains, and the Sepik and Ramu basins. In this area the Vicoria’s crowned pigeons
occur.
Most of the islands, where crowned pigeons occur, are co-called ‘land-bridge islands’. Land-bridge
islands were in the past connected to the mainland (New Guinea), but since the sea level has risen,
they became isolated (Diamond, 1973). This development has taken place only recently.
Conclusion
Sometimes it is easy to determine species and subspecies, but because of the continuous evolution
of the earth, there are always mixed forms. Without doubt, all forms of crowned pigeons derive
from one species and they might have become separated by environmental and climatic changes.
They differ already a lot in phenotype, and DNA-research proved that their genotype is also quite
different.
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