Black-fronted tern nesting Ashley Rakahuri River, 2021 -2022
Fifteen of the 17 images are from the Ashley Rakahuri Rivercare Group’s webcam. They, and two photos at the end, were compiled by Grant Davey: “The nest was found on 11 November but working back from the hatching date, the egg that hatched must have been laid about a week before this.”
The full story Grant Davey
This is a quite typical black-fronted tern (BFT) nest – two eggs among quite large stones. Sometimes these birds have just one egg, more rarely three – there was a three-egg nest less than 10m away. The nesting construction is rudimentary to say the least. I found the nest on 11 November after one of our trappers said that there were terns in the area. BFT nests are quite easy to find – you disturb a bird of its nest, back off maybe 50m and wait for it to return, which it will normally do within a few minutes.
The nest was only about 10m away from a strongly flowing braid, but about a metre above it. BFT usually nest further from the water. The photo shows a trail/motion detection camera which was placed there on the 11th. It was set up to take a photo with every movement, meaning it took 5,318 photos in just under a month – even though it sometimes failed to detect movement – especially at night. This camera cost about $300 – making it lower to middle-end technology. For reasons that can be seen in the next few slides – more expensive cameras are not advisable.
- November 11: A BFT shown on the nest on the 11th, about 30 minutes after I left the site. They readily return to their nests during the day.
- November 12: One bird replacing the other on the nest. Males and females look identical, any individual characteristics must be very subtle.
- November 12 (night): In the background of this night photo (invisible infra-red flash) you can see a pied oystercatcher near the nest, with the BFT crouching down. BFT often leave their nests when disturbed in this way (hares, paradise ducks, deer and predators such as cats and rats can also disturb them) and sometimes do not return. From trail camera images taken in the last two years, they do usually return, but it can be up to 6 hours later. The eggs seem to remain viable when left for this amount of time.
- November 14: Nicely lit early morning photo of a bird leaving the nest.
- November 16: Northwesterly winds cause nasty sandstorms on braided rivers. One of the reasons for nesting among large stones is probably that they give some protection from the wind.
- November 27 (night): A miserable wet night on the nest.
- November 28 AM: The river has come up and flooded the nest – the eggs can be seen in the water in the foreground close to the bird. It would be more accurate to call this event a small fresh rather than a flood.
- November 28 AM: The river continued to rise and at least one of the birds continued to keep a close eye on the nest. By this time the camera must have nearly been flooded. The river was by now moving the eggs, only one is visible. And one of the large stones appears to have been rotated. This may be another reason why nests are made among large stones – smaller stones or sand would have allowed the water to wash away the eggs.
- November 28 (night): By 9pm, floodwaters had receded somewhat and a branch on the left side of the image has been washed in. Possibly the nest might have been occupied soon after this – but there is a gap in the photographic record. The nest had been flooded for at least six hours.
- November 29: By 9.48 the next morning a bird was definitely back on the nest.
- December 01: A very young chick on the nest at midday. Incubation time for this species is approximately 25 days, so the egg would have been laid about a week before I found it. The birds continued to sit on the nest for several days after hatching, but the second egg didn’t hatch, and I didn’t see it once the nest had been abandoned.
- December 05: Four days after hatching the chick was wandering around the nest. Unfortunately, the camera didn’t capture any photos of it being fed – which is usually with small fish, less commonly worms and insects.
- December 06: The chick calling for food. Until they fledge, they are very vulnerable as they are slow and clumsy runners (and bad at taking selfies).
December 08: I found that the nest empty, so moved the camera to the other nest a few metres away. Unfortunately, the three eggs in that nest were eaten by a rat early in the morning of 11th December.
14. January 08: A group of 22 BFT were on the ground about 300m upstream from the nests. Among them was one fledgling. It seems probable that it is the one that survived the flooding and rat predation – eggs from the only other nest I found in the area were also eaten by a rat (Image 17).
15. January 08: Already a skilled flyer.
16. December 11 (night): Rats.