Day 405#: Ōkārito Kiwi
Today's animal of the day is the Ōkārito Kiwi (Apteryx rowi)!
Photo credit: Patrick Crowe
Also known as the rowi, this rare species of flightless bird is native to the forests of Ōkārito, which is located along the western coast of New Zealand's South Island. They look very similar to the North Island brown kiwi and the South Island brown kiwi, and because of this, for a long time scientists thought that these three were all subspecies within the same species, called the brown kiwi. However, genetic testing in 1995 showed that these "subspecies" had enough genetic distinction to be classified as their own separate species. Despite this, the species wasn't formally described until 2003.
Photo credit: Mark Anderson
They might not look like it, but kiwis belong to the group of birds known as Ratites, which includes many of the other large flightless birds alive today, such as ostriches, emus, and cassowaries. However, kiwis are more closely related to the extinct elephant birds (which were also native to New Zealand) than they are to any of the other living Ratites. They are also strictly nocturnal and will spend the day sleeping in an underground burrow or hollow log before coming out at night to forage for food. Their diet consists mostly of worms and insects that they find by probing the soil with their sensitive beaks, along with their strong sense of smell and the whisker-like bristles near the base of their beaks.
Photo credit: Gemma Thomas
While their coloration is mostly the same regardless of sex, they are sexually dimorphic, with females being quite a bit larger than the males and having longer beaks. The larger size of the females makes sense when you see how large their eggs are. Their eggs weigh 20% of the female's body weight, and because of this, they are only able to lay one egg per clutch. However, they can sometimes have two or even three clutches per breeding season, though usually only if something bad happened to the first egg. Unlike most other kiwis, where the males will do all of the incubation by themselves, rowi form lifelong pair bonds and both parents will take turns sitting on their giant egg. However, the male still does most of it. This species is also a lot more involved in raising their chick compared to other kiwi species. Chicks stay with their parents for four or five years, and while they need to find food on their own from the moment they hatch, the parents will lead them to good foraging patches and shelter them in their burrows during the day. Older chicks will even help raise their younger siblings as practice for when they have their own offspring.
Photo credit: Stewart Nimmo
Sadly, because the Ōkārito kiwi lived on a land mammal-free island for millions of years, they were not well adapted when European colonists brought rats, cats, dogs, and stoats to New Zealand, which hunted both the birds and their eggs. Between this and habitat loss, the species fell to just 165 individuals! Thankfully, conservationists were able to create several predator-free sanctuaries for this species, some on the mainland and a few on nearby small islands. Conservationists have also begun Operation Nest Egg, which involves observing wild nests and rescuing any eggs that are at risk of being eaten by predators. The eggs are then hatched by humans and the chicks raised in captivity until they are old enough to be released back into the wild. Luckily, this doesn't seem to affect the kiwis much, and there haven't been any observed differences in the behavior between these captive-raised kiwis and the ones born in the wild. These efforts have done wonders for the species, and as of the last survey done in 2019, their population is up to a little over 600 individuals!
