Monday 2 April 2018

Forest flashback

After nearly twenty years of pest control in this piece of forest we see and hear a noticeable increase in bird life. Tui, bellbird, tomtit, silvereye, grey warbler, kingfisher, shining cuckoo, fantail and morepork numbers all seem to have benefitted. However, it is sobering to imagine what we might have experienced when the largest trees in this forest were mere saplings. Prior to the arrival of humans, and rats and mustelids in particular, the forest was an astonishing place.
Deep in the forest we might have come across the two metre high Giant Moa stretching even higher to graze the vegetation. We might have caught a glimpse of a Little Bush Moa as it scurried into the dense ferns and scrub to escape the eagle eye of a circling Forbes' Harrier.
Little Bush Moa
Another possible predator would have been the flightless Adzebill, a very large, grey Takahe-like bird with a huge bill. This may have been searching for young seabirds in their nesting burrows below the higher peaks and ridges.
 Another flightless and possibly nocturnal small rail-like bird, the Snipe rail could also have been feeding amongst the forest litter.
Snipe Rail
At night calling morepork would have shared the rocky crags and larger rotten trees with another owl, the much larger Laughing Owl or Whekau. The naturalist Thomas Potts commented that "If its cry resembles laughter at all, it is the uncontrollable outburst, the convulsive shout of insanity". The Whekau spent a lot of time on the ground hunting native bats that fed in the forest litter.
An unusual nocturnal resident may have been the New Zealand owlet-nightjar which was virtually flightless and also spent time hunting insects on the forest floor.

Owlet Nightjar 
In addition to all our native song birds today we would have seen and heard many of the rare endemics now restricted to predator free islands and fenced reserves. As well as all these, we could have seen two species of flightless wren searching the forest floor for insects - the Bush wren or Matuhi and the Stout-legged wren.
Bush Wren
Finally, Huia and North Island piopio would join the chorus of Kokako, Saddleback, Robin and Stitchbird.
Piopio
Much of this has gone forever. It is our responsibility to do everything we can to protect the remnant that is left - it is all we have got and it is doubly precious as a result.


Extinct species referred to:-
North Island giant moa  Dinornis novaezelandiae
Little bush moa  Anomalopteryx didiformis
Forbes' harrier  Circus teauteensis
North Island adzebill  Aptornis otidiformis

Snipe rail  Capellirallus karma
Laughing owl  Sceloglaux albifacies
New Zealand owlet-nightjar  Aegotheles novaezelandiae
Stout-legged wren  Pachyplichas yaldwyni
Bush wren  Xenicus longipes
Huia  Heteralocha acutirostris
North Island piopio  Turnagra tanager


Information on these species has been drawn from "Extinct Birds of New Zealand" by Alan Tennyson and Paul Martinson published by Te Papa Press.

Monday 26 March 2018

Harriers and Kereru

Ex cyclone Hola recently passed east of the Peninsula only dumping 50mm of rain and packing moderate winds. It has been a wet year so far with more than 650mm of rain recorded at the house. It will have been a lot more higher up the divide. 
With continuous rain and wind I spent some time yesterday watching the forest for activity from the comfort of the living room. Flocks of silvereye feeding in the lower vegetation were blown from one spot to another and every so often a kereru would fly up into the gale to ride the buffeting wind before hurtling back into the canopy of an emergent rata. It is difficult to imagine any purpose to these sallies other than sheer enjoyment in the power of the elements and their mastery of them. 
Watching the kereru got me to thinking about one characteristic behavior we have frequently observed. Whenever a Swamp Harrier (also known as the Australasian Harrier or Harrier Hawk) drifts up the valley quartering the forest, kereru will fly up from the forest canopy and fly around apparently in some panic until it moves on. The harrier is quite a small raptor and no threat to an adult kereru. It feeds mostly on carrion and small animal prey (although no doubt given the opportunity, a harrier would take a squab from a nest). The adult kereru's response to these harrier visits seems excessive. However, the swamp harrier is a relative newcomer to New Zealand - having arrived only a few hundred years ago.

Swamp Harrier

What is fascinating is that 500 years ago or so these hillsides would have been the domain of a far larger predator that would have targeted kereru as a main source of prey. The Forbes' Harrier (Circus teauteensis ) known from fossil remains, was four times the size of our swamp harriers today. Of NZ's aerial predators only the Haast's Eagle was larger. Forbes' Harriers were formidable killers taking large prey even including small moa. They became extinct in the prehistoric period presumably as a result of human hunting although the introduction of pacific rats could have resulted in egg and chick loss.

Is it possible that todays kereru, which evolved for millennia alongside the Forbes Harrier have transferred their flight response to the smaller, but similar shaped, swamp harrier? Perhaps, deep in the kereru's DNA, the survival of the species over thousands or millions of years still drives the behavior of our birds today. 
What else that we witness in our forest is a vestige of an extraordinary lost past?
Forbes Harrier
Image from a painting by Paul Martinson in Extinct Birds of New Zealand by Alan Tennyson and Paul Martinson.

Monday 26 February 2018

Summer 2018

This is my first blog since 2015. So much has happened up here in the forest in the past few years. Many of our discoveries and observations have been posted on the Mahakirau Facebook page, on the Mahakirau website or on Nature Watch. However, a number of people have asked that I continue to post on my blog as it does provide another (personal) record of what goes on in our fabulous piece of paradise. So where do I start?
Metrosideros fulgens
I am looking out from the house over the valley towards the east coast. The forest appears to be extremely healthy. Every shade of green, with subtle differences of colour, form and texture enabling the observant viewer to identify many of the more than fifty species of tree we have in our forest. This spring and summer have been excellent for all the flowering trees and climbers and the green on green has been punctuated by other splashes of colour. At the moment the scarlet of the climbing rata (Metrosideros fulgens) is spectacular and follows a fine and prolongued season for the magnificent emergent crimson northern rata (Metrosideros robusta).
From our bedroom we look into the canopy of one of the tall rata in the valley below. As it came into flower the resident tui became increasingly defensive and belligerent. Prolonged singing was punctuated by aerial chases after other tuis, bellbirds and silvereyes if they dared enter the canopy.
The tui's world has calmed down at the moment following a very good breeding season. We had a nest in the tawa (Beilschmiedia tawa) above the house but I never managed to work out how many young they successfully fledged although we regularly had young birds pestering their parents for food. Many species seem to have had a particularly good breeding season this year with bellbirds successfully raising numerous young and more than one brood. The young bellbird's incessant squeaking contact call takes on a 'dripping tap' dimension. Once you are aware of the call it drives you to distraction. Such constant calling might at first seem counter intuitive as it provides an obvious target for predators. However if you attempt to find the source of the call you soon realize what ventriloquists they are. Even when you can see the bird the call seems to come from everywhere.
Silvereye are another species that has had a good breeding season. Flocks of at least thirty birds have been feeding in the low canopy around the house often bringing fantail, grey warbler, tomtit and bellbird with them. Five finger berries, and the insects they attract, are a favourite target and at times the bushes have been alive with juvenile silvereye calling and vibrating their wings in anticipation of their parents providing food.
One of our resident moreporks
For the past few nights our family of morepork have been busy around the house. They have at least three young that have been flying in a somewhat ungainly fashion, landing on the ends of mamaku fronds which collapse under their weight so that they end up hanging upside down endeavoring to look nonchalant. The young morepork call is very un-owl-like. A sort of soft trill that is more insect like than bird (described in the literature as a gentle high-pitched cricket-like trill). They don't begin to sound like adult morepork until they are about five months old.
The forest this spring and summer has been a far cry from the silent bush of the past. I will cover our recent experiences of predator control and successes with our rare endemics in future blog posts.