Kiwis

[00:00:00] Alex Re: Hello. Welcome to On Wildlife. I'm your host, Alex Re. On this podcast, we bring the wild to you. We take you on a journey into the life of a different animal every week. And I guarantee you, you're going to come out of here knowing more about your favorite animal than you did before. The animal that we're talking about today is an extraordinary bird with a lot of non bird like features.

[00:00:24] This animal is associated with the great ostrich and emu, but on a much smaller scale. And it also shares its name and a striking resemblance with a fruit. So come with me as we start to peel away at the intriguing life of the Kiwi.

[00:00:59] Kiwis are endemic to New Zealand. This means that they're found nowhere else in the world naturally. And they're actually New Zealand's national bird. They belong to the genus Apteryx. And in ancient Greek, this means without wings. Now, even though they do have wings, they aren't able to fly. They just don't have the structures that other birds have that help them fly.

[00:01:25] For example, they don't have an elongated breastbone, also known as a keel. In birds that can fly, The keel anchors wing muscles and helps keep them oxygenated for long flights. Their wings are also incredibly small in proportion to the rest of their bodies. Think about an airplane with really small wings.

[00:01:46] It's not going to be able to get off the ground. And most birds have hollow bones, but kiwis actually have bone marrow just like us and other mammals. Another feature that helps birds fly is their feathers, but kiwi feathers are long and skinny. They look more like strands of hair, which is definitely not going to help them with flight.

[00:02:09] They belong to the ratite group, along with ostriches, emus, rhias, and cassowaries. And what do all of these birds have in common? They're all flightless. The kiwi is different from the others in this group, though, because all of these other flightless birds are large and long necked. Kiwis can only get up to 2 feet tall and weigh about 7 pounds, so they're roughly the size of a chicken.

[00:02:36] There are five species of kiwi. The brown kiwi, great spotted kiwi, little spotted kiwi, roe and tokoika. And most of them have unique characteristics that can help us determine which species is which. The brown kiwi is probably the one you're picturing in your head. They're the most common species and they live the closest to where humans are.

[00:03:01] The Great Spotted Kiwi is the largest species, and their habitats are usually high up in the mountains. This is a really harsh environment that not a lot of other animals like to live in, which means less animals trying to eat them. The Little Spotted Kiwi is the smallest species. They're the most vulnerable to predation, and they're the only species that's extinct on the main islands of New Zealand.

[00:03:28] The ROI is the rarest kiwi species, and they only have one population left in the wild. One of the main reasons for this is that they only lay one egg per year. And finally, the tocoa, they're very similar to the brown kiwi, and a lot of people say they're just a subspecies of brown kiwis because of their similarities.

[00:03:50] All the species of Kiwi look pretty similar. They all have brown feathers that look more like hair that cover their whole body. They're kind of pear shaped. And because their wings are so small, they kind of just blend into the rest of their body. And they have pretty long legs and beaks compared to the rest of their body.

[00:04:10] What do you think is a benefit to having a long beak? While you think about it, let's take a quick break.

[00:04:28] The science word that I want to tell you about today is Arboreal. This is usually describing an animal that likes to live in trees. Can you think of any arboreal species? Okay, so we were just talking about how kiwis have really long beaks. The beaks are pretty flexible, too. And if you guessed that they help kiwis eat, then you'd be right.

[00:04:56] Kiwis have a varied diet. You can find them eating small invertebrates like insects, fruit, seeds, amphibians, and even some small fish. Because their beak is so long and thin, it helps them get into those tiny nooks and crannies where their prey might be hiding out. Not only that, but on the tip of their beaks, they have specialized sensory pads that can feel vibrations.

[00:05:22] So without even needing to see where their prey is, they can find it using their beaks. Because of this unique feature, kiwis are classified as probe foraging birds. If you look closely, you'll see that kiwi beaks are unique to other birds in another way too. Every other bird in the world has nostrils at the base of their beak, close to their face.

[00:05:47] Kiwis are the only bird that has nostrils on the tip of their beak. And this allows for an extra great sense of smell when looking for food. and when watching out for predators. If you listen to past episodes that we've done about birds, you may remember that most birds don't have much better of a sense of smell than us, aside from a few exceptions.

[00:06:10] Kiwis are one of those exceptions. It's also helpful to be able to feel and smell around your environment if you can't see. Well, kiwis have some of the worst eyesight in the bird world, but they don't really need it because most kiwis are nocturnal. This isn't very common when it comes to birds, but all of these adaptations in their beak make them the perfect nighttime forager.

[00:06:37] Kiwis also have large ear openings to help give them excellent hearing. Some scientists believe that kiwis are nocturnal because they used to have to compete with another bird called the giant moa, which is now extinct, for food. Others think that it's because insects are usually more active at night, meaning more food for the kiwis.

[00:07:00] There are a couple of subspecies that are active during the day, but most kiwis are only active at night. Kiwis also have powerful legs with sharp claws on each of their four toes. These are helpful when searching for food, but they're also great tools for digging. Instead of building nests in trees like a lot of bird species, kiwis dig burrows.

[00:07:24] These burrows can be small, but they can also be over 6 feet in length, which is a lot for a small animal. Each individual can have around 50 burrows in their territory. And they're a great way to hide from predators. They can't fly away, so they run into a burrow if they feel threatened. Kiwis usually line their burrows with moss and leaves, and they'll cover the entrance with debris so that they're completely hidden.

[00:07:51] Females also use burrows to lay their eggs. The burrows are usually made months in advance, so that they're grown over with brush to be used as camouflage for the nest. The breeding season starts in late winter and ends in early summer. Males and females mate for life. However, it has been noted that females sometimes leave their current mates for more favorable mates.

[00:08:16] Males attract females by following them around and making grunting noises. So they don't really have any elegant mating displays. Kiwi eggs weigh roughly 20 25 percent of the female's body weight, which is insane. For scale, a chicken's egg is only around 3 percent of its body weight. Kiwis have the highest egg weight to body weight ratio in the animal kingdom.

[00:08:43] Their eggs contain twice as much yolk as other birds their size, which helps protect the egg from bacteria and fungus common in their moist environment. Females eat a huge amount of food to be able to grow these eggs, and then they fast for the few days before laying. But how did they evolve to have eggs this big?

[00:09:04] Kiwi ancestors used to be much larger than modern day Kiwis. And as their ancestors began decreasing in size, the egg stayed the same, resulting in a well developed chick at the time of hatching. It's thought that an abundant food source historically allowed tons of nutrients for kiwis to develop these large eggs.

[00:09:27] Also, being flightless removes the issue of the egg weighing too much. Some species can lay six eggs a year. After the egg is laid, the male takes over the nesting duties. Incubation is between 75 and 85 days. And unlike other birds, they don't turn their eggs. In most other bird species, the chicks have something called an egg tooth, which helps them break out of the egg when they're first ready to hatch.

[00:09:56] Kiwis don't have this, so they have to use their strong legs to kick themselves out. Kiwis are also precocial. This means that the chicks are relatively independent from birth and can feed themselves right after they hatch. And the large yolk acts as an initial food source after hatching. Eventually, the young kiwi leaves the burrow with the father and begins hunting for food.

[00:10:22] And they can stay with dad for up to 20 days before going off on their own. Unfortunately, only 5 percent of chicks reach adulthood. This is another reason why kiwi populations are in trouble. We'll talk more about this and some other interesting facts. Right after the break.

[00:10:52] Time for today's trivia question. What is the largest ocean in the world?

[00:11:05] The answer is the Pacific Ocean. It holds 187 quintillion gallons of water. That's 187 with 18 zeros at the end of it.

[00:11:27] Okay, we're back. The availability of resources and the amount of Kiwis living in an area can affect how they interact with each other. In areas with a lot of Kiwis, some groups exhibit cooperative polyandry. This means that all parental duties are shared evenly among the males. Kiwis are also very territorial.

[00:11:51] They want to protect the burros that they've spent time making, as well as other resources in their territory. In order to do this, They patrol their area every night. And they mark the boundaries of their territory by leaving their droppings around the environment. This is very un bird like behavior, and that's been a theme of this episode.

[00:12:13] A lot of their physical and behavioral characteristics remind me more of a mammal than a bird. I think that's one of the reasons kiwis are so interesting. They're living evidence of convergent evolution, meaning that they evolved to have similar characteristics as mammals because of their environment.

[00:12:33] Not because they have a recent common ancestor. Kiwis benefit their environment around them, and they're also a great indicator species. Their varied diet helps us get a look at the health of a plethora of other organisms in their ecosystems. Also, because they eat fruits and seeds, they help disperse plants throughout the forest.

[00:12:55] But according to the IUCN Red List, Four out of five species are listed as vulnerable, and one is labeled as near threatened. This is due to their slow rate of reproduction, invasive species, and habitat loss. For instance, in the late 1800s, stoats, which are kind of like ferrets, were introduced in New Zealand to control rabbit populations.

[00:13:21] But instead of curing one problem, They cause another, because they also like to prey on kiwis. Kiwis never evolved to protect themselves against stoats, because they aren't a natural predator. So they're basically like sitting ducks. New Zealand is also losing more and more of its forested areas, leaving less room for kiwis to live.

[00:13:45] This causes more inbreeding between kiwis, because there's not enough space. And this, in turn, affects the survival of the chicks. Luckily, there are a lot of great organizations that are working to help Kiwis right now. Like Save the Kiwi Trust, Forest and Bird of New Zealand, and the Department of Conservation in New Zealand. Check these out if you want to learn more about Kiwi conservation.

[00:14:12] Thank you so much for coming on this adventure with me as we explored the world of Kiwis. You can find the sources that we use for this podcast and links to organizations that we reference at onwildlife. org. You can also email us with any questions at onwildlife. podcast at gmail. com. And you can follow us on Instagram at on underscore wildlife or on TikTok at onwildlife. And don't forget to tune in next month for another awesome episode. And that's On Wildlife.

[00:14:50] Jess Avellino: You've been listening to On Wildlife with Alex Re. On Wildlife provides general educational information on various topics as a public service, which should not be construed as professional, financial, real estate, tax, or legal advice. These are our personal opinions only. Please refer to our full disclaimer policy on our website for full details.