The last big El Niño year was a disaster in the Tawaki colonies, with most chicks starving to death, hence we were all anxious going into this season knowing it was another El Niño year.  However it was an entirely different story this year.

At Gorge river, 9 out of the 10 monitored nests with camera deployments were successful, with at least 4, probably 6 or 7, raising a double clutch. (As chicks from different nests often sit together, it can be hard to tell when they are from the same nest, unless they are seen chasing the same parent for food.) The most important thing to mention, is that in the last 9 years, only one nest has definitely been seen raising a double clutch – two chicks. So this was a very different El Niño year!

 

Tawaki Ranger, Catherine Stewart, reports on the interesting 2023 tawaki season at Gorge River.

Gorge River Tawaki Monitoring 2023

 

Aim: Tawaki nests were monitored for survival/failure due to predation and to assess general chick growth and apparent health as an indication of food supply, etc.

Method: 27 nests were checked 5 times between 18/8/23 and 8/11/23 at intervals of 10 days to 3 or 4 weeks. 10 of these nests had Little Acorn trail cameras set.

An additional 16 nests known from previous years were checked on 18/8/23.

Two lured cameras were set early in the season and again at the end. The cameras were baited with sausage in a fine metal mesh ball inside a tin can wired to a tree approx. 1m above the ground.

 

Results/Conclusions for the season

Nest checks

Most birds were sitting on eggs by August 18th.

Of the additional 16 old nests, 13 showed no sign of having been used. At 2 nests, sitting birds jumped off, possibly suggesting new pairs, and subsequently these were found empty with no sign of egg-laying. The last nest is an old one which has been used continuously (mostly with success) for more than 10 years, but no egg has been seen since 2021. A bird was sitting but not seen on subsequent visits.

There was no sign of hatching at the end of August. All eggs were hatched by September 22nd. Chicks appeared well-fed throughout the season and grew quickly. As few chicks were seen during nest checks later in the season, it is assumed, from the earlier evidence, that they survived, though we could only confirm 2 successful nests that were additional to those monitored with cameras.

Nest cameras

Of the ten camera-monitored nests, one was found empty on September 22nd but, due to camera/operator failure, no reason could be determined. Although 2 adults remained for approx. one more week, the egg was no longer present.

When a nest was seen on September 22nd with 2 healthy chicks present, a nearby camera was shifted over to it. The following 2 weeks showed them persisting into the post-guard phase when chicks are left alone and both adults leave to forage.

Eight (probably nine) of the ten camera-monitored nests were successful. Photos were reviewed from September 22nd to November 8th. Double clutching where two chicks were raised was seen in 6 (possibly 7) of these nests near or after the end of the guard phase. The presence of 2 chicks was confirmed beyond the middle of October in 2 of these. The other 4 nests are considered likely to have raised both chicks; however no photo actually showed 2 chicks together with the parent that would have distinguished them from 2 chicks from separate nests crèching together.

During the nest check on November 8th, a pair of chicks was seen in a feeding chase after the same adult. These were likely from the other monitored nest.

Camera Traps:

Using the same protocol as last season, two camera traps were run for 21 days from August 31st. As one camera failed to record anything, they were both re-baited and set for another 21 days from September 22nd, and again from November 8th.

Result: Several rats and possums were seen near the bait and just one stoat, at the end of November.

Just one stoat was seen on a camera. Subsequently 2 chicks were still present and were raised successfully.

Tracking Tunnels: Not run this season.

 

Catherine Stewart, West Coast Penguin Trust, February, 2024