Bob Brockie’s been counting animals for half a century… and now cabbage trees as well

By W.E.Wilson

Otaki ecologist (and cartoonist) Bob Brockie feels compelled to count living things.

He has been counting dead hedgehogs on New Zealand roads since the 1950s and says  the Kapiti Coast was once the hedgehog capital of the world….but no longer

In the 1980s he sometimes counted 30 road killed corpses between Waikanae and Levin – more  than any  other stretch of road anywhere.

Fewer hedgehogs around

But these days their numbers are well down with only one or two corpses and often none at all seen between the towns.

On the other hand he never saw a pukeko run over between Waikanae and Levin before 1989.

But Since 2000  he has counted over 30 dead on State Highway 1 mainly near Pekapeka. He says it’s like a shooting gallery for pukekos there as they stray on to the road in search of gravel.

Years ago Bob counted the number of snails and slugs at Queen Elizabeth Park – 20 000 snails per hectare and almost twice as many slugs.  They hide in the lupin bushes.

Duck count at Otaki ponds

These days he counts birds at the Otaki water treatment ponds. He has sometimes counted nearly 900 ducks there but they are not always the same ducks.

Up to 800 paradise ducks crowd into the place in  summer then disappear altogether. Shoveller ducks,  grey teal and mallards peak  in May. About 80 swans feed in the ponds for most of the year but nearly all disappear to lay eggs in spring.

White butterflies also interest Bob. He has counted them at Otaki for the last five years and finds their numbers usually peak in January – February.

He says there are few white butterflies on the wing this season and they’re late – indeed there are more monarchs than whites around at the moment.

The cabbage tree study

But Bob doesn’t just keep track of animal numbers.

He also counts cabbage trees. While driving about the country he notes the ratio of healthy trees to those still-standing ghostly virus-killed trees.

The Kapiti Coast is lucky, he says, as nearly all our trees are healthy.  Things are much worse in Northland where it’s hard to find a big living cabbage tree.

In 1990, Bob counted 139 healthy cabbage trees between Levin and Palmerston North. Since then the virus has killed 80 of them.

Bob also counts the bunches of flowers on those cabbage trees by the railway track just south of Paekakariki.

He finds that, since 1990, the Paekak trees have good and bad seasons in step with all the other cabbage  trees in the Wellington district  and they usually all flower heavily or poorly in alternate years.

‘Kokari’ on flax bushes

He also counts the number of flower spikes (‘kokari’) on flax bushes in the Plimmerton mire. In a good year the Plimmerton swamp is black with flower spikes.

In a poor year hardly a spike shows up. Most flax plants also  flower heavily or poorly in step with each other and in alternate years. The remarkable thing is that they do this in sync with the cabbage trees.

Bob would like to know what keeps all the cabbage trees and flax plants in step with each other over the region.

Still counting pigeons, swallows, pohutukawa  . . .  Bob says ecology is just Nature Study plus numbers.