Wow, a 15 kg bird with a 3 meter wingspan would be quite scary.

Apparently the availability of animals like moa, extinct flightess birds weighing hundreds of kilos with few or no other predators, put a lot of evolutionary pressure to grow big to fill the niche.

Apparently these birds evolved from relatively small eagles who accidentally ended up in New Zealand less than 2 million years ago, then evolved to a larger size faster than almost any known vertebrate, growing to be like 10x the size of their ancestors.

It seems once humans arrived in New Zealand around 700 years ago, the eagles relatively quickly disappeared.