Environment – Count uncovers ups and downs

‘Tick-tick, tick-tick, tick-tick’. Did you hear that? What was it? Well, it was one of two possibilities. If it sounded like two stones being tapped together it was a mātātā/fernbird, if it was more like separate ‘tick, tick, tick’ calls it was a pūweto/spotless crake. 

Even though both are quite common on Tiritiri Matangi, they prefer to stay hidden among the vegetation and are difficult to see. Pūweto sometimes feed at the muddy edges of freshwater pools so that’s the place to watch for them. Thankfully, most of the birds on the island have much more recognisable voices and are easier to spot and now is a great time for a visit. The nesting season is finished, lots of youngsters are around and so bird numbers are at their peak and the birds will have completed their annual feather replacement and be looking at their best.

We have just completed our annual survey of Tiritiri’s forest birds. The total counts have been gently declining for the last six years and this year was our lowest in the nine years we have been counting. Changes in the totals are dominated by our ‘big three’ species – pōpokatea/whitehead, korimako/bellbird and tīeke/saddleback with population estimates of 1350, 1010 and 690 respectively. All three are at their lowest, or equal lowest, estimated populations. There are still large populations for an island with about 170 hectares of bush. We remain unsure about why numbers are falling. It’s been observed elsewhere that newly introduced species sometimes increase to a population larger than a site can support over the long term, followed by a decrease to a lower level.

There are some interesting changes in other species. Tūī numbers are down 85 percent from the average over all years. But they are strong fliers and, if there is insufficient food for them at any time, they can easily fly to the mainland and feed there. We often see them begin their daily commute by circling ever higher above the Island, then setting off towards Whangaparāoa. It is likely that, at the time of the survey counts, they were feeding elsewhere. Despite cyclone Gabrielle and the heavy rainfall this time a year ago, our tiniest bird, the tītipounamu/rifleman, has had an amazing season and numbers have almost doubled. There are now many hundreds.

If you are considering a visit, the ferry company Explore is offering a discount for SuperGold card holders for weekday trips. And if you join the Supporters of Tiritiri Matangi you become eligible to join working weekends (the next one is on King’s Birthday weekend) or supporters’ weekends (reduced bunkhouse costs, next one on May 11). Both of these provide opportunities to get to know the island and to enjoy both night-time and early morning walks.