September 2025
The Northland Rainforest in Spring: Returning Cuckoos, Unfurling Ferns, and a Forest Coming Back to Life
September in a Northland podocarp forest is a shift you can feel before you can explain it. The days are stretching, the light is coming in at a different angle, and something in the forest has changed tempo. Spring in this part of New Zealand is not a slow awakening — it is a fairly abrupt switching on, and once it starts, everything happens at once.
What the Birds Are Doing
The arrival of the shining cuckoo from the Solomon Islands is one of the clearest signals that spring has arrived. Its call — a rising, insistent whistle that carries further than you expect through dense forest — starts appearing in September and marks the season as reliably as a calendar. It is a migratory bird that has made this crossing every year for longer than anyone has been around to record it, and hearing it for the first time in a season still stops people in their tracks.
Tūī are loud and aggressive in spring, fighting hard over nectar sources and filling the canopy with a mix of song and mechanical clicking that sounds unlike any other bird. Kererū are beginning to pair up and move through the forest with slightly more purpose than their usual unhurried drift. Fantails are building nests and starting early broods, and the grey warbler — riroriro — is singing almost constantly, one of the most persistent and welcome sounds of a Northland spring morning.
Brown kiwi are actively incubating eggs through this period, the males taking on most of the sitting in their underground burrows while the forest carries on above them. Ruru call at night from the same perches they have used all winter, but their calls are more frequent now, and if you are outside after dark in September you are rarely without the sound of them.
How the Forest Itself Is Changing
The most visible sign of spring in the podocarp forest is the koru — new fern fronds unfurling from the crown of the ponga tree ferns in tight, perfect spirals. They push up through the older growth in a fresh lime green that stands out sharply against the deeper tones of the established canopy, and watching one uncurl over the course of a week is the kind of thing that sounds small until you actually see it.
The rimu, kahikatea, and tōtara are putting out new growth at their tips, adding bright colour to the upper canopy. Supplejack is shooting, threading new tendrils through whatever gaps it can find. The understorey is thickening quickly, and the forest floor — already dense with crown ferns and moss — is accumulating another layer of life on top of itself. The smell of the forest changes in spring too: less the deep, composting richness of winter and more something fresher and sharper, the smell of things actively growing rather than quietly breaking down.
Spring in a Northland rainforest is not a gentle or tentative thing. It is confident and fast and full of sound. You do not need to know the names of everything to feel that the forest around you is doing something — and that being inside it at this time of year is, by any measure, a good place to be.