The cats were caught in the act, raiding a nest of robin chicks in Wellington's Waimapihi Reserve.
It's putting Wellington's goal of becoming the first predator-free capital in the world, at risk.
It took eight months to capture the stoat.
Known as climbing asparagus, the fast-growing weed is destroying some of Wellington's natural areas.
Myna birds have been known to remove native species from their nests for their own use.
"It sits in the stomach and they can't digest it".
Forest and Bird's concerned moves to fast-track major building projects could put birds like the pūteketeke in peril.
Without action, DoC warns there could be a 95 percent population decline in the next few decades.
Seagrass meadows absorb a huge amount of carbon dioxide but are declining at an alarming rate around the world.