Fossilised bird grave sites are common in New Zealand, but one particular cave in Martinborough has revealed thousands of bones of flightless birds who plunged to their deaths.
Curator of vertebrates Alan Tennyson describes how over thousands of years rare and extinct birds such kākāpō, kiwi, North Island takahē, and moa fell through the concealed entrance.
Alan says “It might not look like a spectacular cave but this site has become the richest site in the whole of New Zealand for some species including the nearly one metre tall extinct adzebill.”
For over 100 years, enthusiasts and scientists have collected perhaps 1,000 individual birds and reptiles from this cave, known scientifically as a pitfall trap, which are now in Te Papa’s collections.
There are so many specimens that only around half have been registered and thousands still lie untouched in the dark cave.
Martinborough 1,000 years ago
Thousands of years ago the Martinborough area wasn’t the heavily farmed vineyard landscape we know today. It was covered in thick forest perfect for ground dwelling flightless birds and reptiles to roam.
Much of the land near Martinborough is underlain by limestone and this rocky landscape creates many hidden holes. The thick vegetation at the time would have concealed these and our flightless birds had very little chance of making it out alive once they fell in.
Excavating the pit
The pitfall trap was first found by a deer hunter in 1914. Since then, Te Papa and its forerunner the Dominion Museum, have mounted several expeditions to the cave, excavating several tonnes of earth and bones.
The first expedition took place in 1920, and the most recent expedition in March 2017 included our vertebrate curator Alan Tennyson.
The bones Alan collected haven’t been cleaned yet but Alan could identify straight away the beak of kākāpō, Finsch’s ducks leg bones, and even a tuatara jaw:
Cataloguing tons of bones
Alan explains that scientists work out how many of a species there are based on the minimum number of a particular bone. “For example the strong limb bones preserve much better than a sternum or a skull. So to work out the minimum number of birds you count the minimum number of femora or tibiotarsi.”
Because of the huge amount of material collected only about half of the bones have been sorted into individual specimens. So far, among the larger birds, 80 kākāpō, 7 North Island takahē, 25 moa, 30 kiwi, 90 Finsch’s duck, 11 weka and 22 adzebills have been identified.
The sheer number of specimens identified from the cave give a good idea of how common birds such as the kākāpō and adzebills were in the Martinborough region.
Alan believes the best thing to do with the cave now is to leave it. “Time and energy needs to be spent cleaning, sorting, identifying, and registering the huge backlog of material that we already have, and leaving the material in the cave still protects it.”
“In the future better technology might come along that helps us do a more systematic excavation and allows us to know how deep the pit goes.”
With thanks to
We’d like to thank Luke and Clint Easton who’ve generously donated many fossils from the Martinborough cave over the recent years and organised Alan’s expedition to the cave in March 2017.