[00:00.00]The cats were removed from Stephens Island,
[00:03.22]but it was too late for the wren.
[00:05.13]Now only known from a few cat-chewed museum specimens,
[00:08.75]evolving to be flightless had proven fatal.
[00:12.26]So it seems there is a trade-off.
[00:14.29]The freedom of island life allows a species to relax its guard,
[00:18.61]but that can leave it defenceless.
[00:21.56]on the main islands of New Zealand,
[00:23.85]similar dramas have played out time and time again.
[00:27.56]Forests dominated by giant kauri trees once covered the North Island.
[00:32.97]The fragments that remain look much like they have for millennia,
[00:36.49]but looks can be deceiving.
[00:38.52]A few centuries ago,
[00:39.82]this forest echoed with the calls of strange and wonderful birds.
[00:44.76]Most famous was the giant moa,
[00:47.33]which looked a bit like an ostrich,
[00:49.24]but taller than an elephant.
[00:51.04]And there are many more birds
[00:52.83]whose haunting songs now exist here only in memory.