“It sat down, it sat down!”
This is the exclamation of an excited birder looking for banded dotterel/pohowera nests. It’s breeding season and its time figure out if our new predator cages will work to help boost nesting success.
Ever tried looking for a nest?
If you have no patience, forget it. Ultimately, you are watching individual dotterel run around in parabolic arcs, in the desperate hope you are observing a nesting female. Otherwise you’ll just be viewing the habits of a speed-walking bird. Say you hit the jackpot and you’re watching a nesting female, she’ll run around for what seems like an eternity before suddenly disappearing out of sight. She has then essentially sat down on her nest and is now completely camouflaged.
This magic act would be understandable if she were nesting in long grass or in dense understory. But she is completely camouflaged in a sparse paddock in Kaitorete, Canterbury and hiding in plain sight. If you look away from the spot she disappeared from, you’ll lose track of the nest entirely. You take mental notes of the odd-looking grass tuffs nearby that you think might help you confirm the nest location as you walk towards it.
This impressive ability to blend into a dry, almost bare paddock is astonishing and it is extremely effective at tricking avian predators who rely on their impressive vision. However, the camouflage has no effect on predators who use their nose to great advantage. They are most vulnerable when nesting, where both the incubating adults, the eggs and juveniles are easy prey. While more numerous than the more publicised New Zealand dotterel, pohowera are nationally vulnerable with their numbers declining, mainly due to introduced mammalian predators.
How can we reverse the decline?
Well good local predator control can really help give these populations a fighting chance until chicks fledge at 5-6 weeks. But often the predator control programmes already in place are only targeting some of the predators. In this study site, there was plenty of evidence that avian predators and stock were also causing chaos, but the local traps were designed for mustelids and rats. That is where the cages come in. DOC Mahaanui biodiversity ranger Allanah Purdie, is trialling the use of purposed built cages that are designed to protect bird nests from stock (because this is a paddock after all), avian predators and disrupt the ambush behaviour like that of cats, while having bars just wide enough to allow easy access for the pohowera to enter the nest. These are installed at every second nest discovered to compare their effectiveness. And just because she can, she is laying out traps for larger predators.
Do the cages work?
The preliminary results show a 100% exclusion of hawk predation and stock trample while a tweak of the cage design is now successfully excluding cats. The team found that 70% of nests produced chicks with the cage verses only 30% without. That is a dramatic difference in anyone’s book.
The cages are but one more tool in the toolbox for pohowera management. We need to keep up sustained predator control to reduce mustelid and rat numbers where the cages are not as effective, including the stages between chick to fledging. However, with each new insight comes a promise of better things for this species and it’s not hard to want to save something as interesting and fascinating as the banded dotterel. While nest finding is not a job for the faint hearted, it still beats a day in the office.
Ingenious approach to more than double nest success. Well done!