Transcript
Robyn Williams: Back to birds.
They are modern dinosaurs after all, aren't they. And to New Zealand and the
origins of birds on Earth.
Could it be that many birds came from the
antipodes and then spread to other parts of the world? Could we be bird central?
It often seems like that, doesn't it! Well, Joel Cracraft is curator of birds at
the American Museum of Natural History in New York, and his paper on avian
origins is fast becoming a classic.
Joel Cracraft: Well, the New
Zealand wrens, just a few species in New Zealand, are the closest relative for
these large group of 60% of the rest of living diversity of birds, which are the
songbirds. Songbirds are divided into two groups; the oscines which are the
really true songbirds heavily into song, and then the sub-oscine birds which are
mostly in South America, and also some like pittas and broadbills in Southeast
Asia and Africa.
Robyn Williams: Where do the
parrots fit into that scheme?
Joel Cracraft: Well, recent
molecular work suggests that parrots are the sister group. They and all of these
songbirds, passerine birds, diverged from a common ancestor, some time probably
in the late Cretaceous. So the evolutionary relationships of parrots to some
other groups of birds has been very, very controversial, but a lot of new
genetic data seems to suggest that they are a sister group, and they all have
the same pattern in the southern hemisphere.
Robyn Williams: Isn't that
strange. Where would that put birds like the kakapo, the largest of all parrots,
still surviving, just clinging onto existence. Where would you put that in the
history? Very ancient or what?
Joel Cracraft: It is indeed, it's
a first branch off the parrot tree and it parallels the smaller songbirds, these
tiny, tiny, little New Zealand wrens, and then you have this giant parrot. Each
of those two are the sister group of the respective major, major radiation. So
with these two big orders, the Passeriformes and the Psittaciformes, the
parrots, you represent there about 70% almost of the species of birds in the
world. Those are two very ancient Gondwanan lineages.
Robyn Williams: And of course
that would make Australia, say, the second step in the process?
Joel Cracraft: It would make
Australia the second step in the process. Australia, that part of eastern
Antarctica where it was connected, including the southern part of New Guinea,
this is parrot and songbird central, this is where it all began. All the early
lineages are in Australia and New Zealand, and then their close relatives are
all over in South America, and only later did they get up to Asia where they
diversified spectacularly in Asia, in Africa, and then they later got into North
America and radiated there.
Robyn Williams: Of course I've
actually seen green parrots flying around Los Angeles in recent times. I don't
know where they came from but it's something of a spectacular sight, it reminds
me of Sydney.
Joel Cracraft: These are all
captive released birds that people have. Even in Chicago there is the famous
monk parakeet colony. I've seen parrots outside this museum here in New York
City. People release them and if they're like monk parakeets they're kind of
colonial so they find places where they can live.
Robyn Williams: It's amazing that
they can survive the winter.
Joel Cracraft: It is. I haven't
seen them now for some years, but they're still around the area.
Robyn Williams: Tell me, how do
you trace this history? Obviously you are now looking at DNA and the timelines,
but how do you follow it up with fieldwork as well?
Joel Cracraft: Behaviour is also
a very good set of data for relationships, and I've had a former post doc work
on the relationships of birds of paradise using very detailed behavioural
observations, treating the similarities and differences in behaviours as
different kinds of characters. So you can compare those characters just like you
can compare the DNA sequences as characters.
Robyn Williams: And they're all
telling the same story in parallel? Because you said it's
controversial.
Joel Cracraft: There just has not
been that much comparative behaviour. It's rather surprising, most behaviourists
are not doing huge comparative studies. And at the level of these birds, like
all parrots and all songbirds, behaviour would not be sufficiently plastic to
get enough characters to understand relationships, but you can do that within
smaller groups.
Robyn Williams: It's interesting,
David Attenborough always liked to be rather rude about Australian birds, he
said they all squawk and they don't sing, but I can send him a correction from
you indicating that there are plenty of associations. But he was also extremely
passionately fond of birds of paradise, especially going to Papua New Guinea
where there are so many wonderful ones. Have you looked there at the birds of
paradise in PNG?
Joel Cracraft: Oh yes, we're
studying those pretty heavily, trying to understand their relationships, because
they are very different from one another, and we've been unable to link them up
with behaviour or with looking at study skins, and now we have to use DNA. So
it's a major challenge. They radiated very recently, only about eight or nine
million years, mostly due we think to the uplift of the mountains, which took
songbirds and lifted them right up to the top in the montane forest, left their
relatives in the lowlands, and then climate change came along over the last
million or two million years and the forest moved up and down as glaciations
came and went, and that isolated many of the species that we see in New Guinea
today.
Robyn Williams: Yes, one wonders
whether the local people will stop hunting them because many of them are
endangered, and of course the feathers are precious in ceremonial garb, aren't
they.
Joel Cracraft: Actually most of
the birds of paradise are probably okay. If they're going to be hurt they're not
going to be hurt by so much of the hunting as they're going to be hurt by the
forest being cut away for logging. Most of those species of birds of paradise
are pretty narrowly endemic. That is, they're found only in one area, especially
in the mountains where the ranges of these birds are separated by deep valleys,
and there, if logging goes on, then they are in trouble.
But plume hunting, which started way back in the
19th century, actually was a way in which we discovered many new species because
the hunters went out, collected these poor birds and took them back to England
or to Germany or to the Netherlands, and all of a sudden people discovered, hey,
these are new, these are different, we haven't seen these before. But usually
the population densities of people in New Guinea were low enough that they would
not hunt out too much. That's starting to change, but they don't do as much
hunting now as they used to, but it still goes on in the remote
areas.
Robyn Williams: Tell me, why is
it, apart from the fact that for people like us it's really fascinating looking
at the lineage of birds and the ancient history and how they developed...why do
you think it's important really to do this kind of study?
Joel Cracraft: Evolution is the
integrative science of biology, the idea that there's descent with modification,
that's one of Darwin's key ideas. Two key ideas was descent with modification
and natural selection leading to adaptation. And because evolutionary biology is
so important for people, it tells us why we can study a fruit fly and if we find
something that is important, let's say, for genetics or for developmental
biology, the only reason it has any relevance to human beings is because of the
similarities that are there by descent with modification. And so it's very
important for us to understand the tree of life organisms because, just from a
selfish point of view, humans need to know what things are similar in all these
different kinds of organisms because that has applicability then to human health
and wellbeing.
Robyn Williams: And next week,
birds on the Great Barrier Reef and how their numbers are being affected by
climate change. I was talking then to Joel Cracraft at the American Museum of
Natural History in New York.
http://www.abc.net.au/rn/scienceshow/stories/2009/2642649.htm
