Endangered parrots picky about hollows

Dejan Stojanovic and a baby Swift parrotEMILY BOURKE: The endangered swift parrot lives in south-east Australia, but the species only breeds in Tasmania. A scientist who's spending his summer climbing trees to study the parrots has found that the birds will only nest in particular hollows.

Felicity Ogilvie reports from Bruny Island.

FELICITY OGILVIE: The endangered Swift Parrots have made their nest in the hollow of a dead tree in a forest on Bruny Island. The nest is 18 metres off the ground and there's a chick inside.

(Sound of chick cry)

Dejan Stojanovic from the Australian National University is using a rope and harness to climb up the tree to the parrot's nest. He gently removes the chick from the nest and carries it down from the tree. He weighs and measures the bird.

DEJAN STOJANOVIC: See she's quite mature.

(Chick sqwaks)

She'll be leaving the nest within the next few days.

FELICITY OGILVIE: The chick is one of 30 babies around the state that Dejan Stojanovic has been studying this summer. The parrots nest in the hollows of trees and Mr Stojanovic has found that the birds are very picky about what kind of hollow they will nest in.

Dejan Stojanovic climing a Swift parrot nesting tree. DEJAN STOJANOVIC: The swift parrot really strongly prefer tree hollows with small entrances, deep chambers and wide floors. And usually those hollows are quite a bit higher up the tree than the average hollow.

The important thing though is that that type of hollow the swift parrot's like is very rare. And of our sample of randomly selected tree hollows, only less than 5 per cent were actually suitable for swift parrots.

FELICITY OGILVIE: Why are the swift parrots so picky about what kind of hollow they want to nest in?

DEJAN STOJANOVIC: So, swift parrots are quite a small and tasty little bird if you're a predator, so it's quite important for them to put their babies in a really safe and secure environment.

So in particular, choosing a hollow with a small entrance immediately excludes most predators, because if you're a predator you're likely to be a little bit bigger than your prey. And so if a swift parrot can fit into a hole, hopefully its predator can't.

So it's really important that the swift parrots have enough trees in the bush so that the chances of finding a suitable hollow are increased.

FELICITY OGILVIE: He's also discovered that often what looks like a perfect nesting hollow from the ground looks very different when you climb up the tree.

DEJAN STOJANOVIC: I was finding that increasingly on climbing these trees I would notice that, in fact, these trees only had one or two hollows and those hollows were usually already occupied or, and anything else that looked like it was a hollow from the ground would in fact be, you know, a bit of black soot from a previous fire or a broken-off branch stub and wouldn't actually be real hollows.

FELICITY OGILVIE: Mr Stojanovic says that without climbing up a tree it's difficult to predict if there's a suitable hollow in the tree where the endangered swift parrot can nest.

EMILY BOURKE: Felicity Ogilvie.

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