I thought I would delve into an area of bird biology that has interested me for a long time - Parasitology.
Many years ago, I did my honours dissertation on the Cospeciation of rails (pūkeko, takahē, weka, banded rail) and their feather lice. For this, I had to wash many a pūkeko carcass in soapy water and filter this water to collect their feather lice. I then analysed the DNA of both the lice and the host birds and compared the two phylogenetic trees. Cospeciation occurs when two groups interact closely (e.g. parasite + host), and they speciate in tandem - for example, when pūkeko diverged into the new species takahē, the lice species also diverged into a new species.
So, to make it kiwi, let’s dive into 5 kiwi parasites:
Chewing (feather) lice.
As with rails, each species of kiwi has their own species of feather lice. Two different genera of lice can be found on kiwi, Apterygon and Rallicola. Apterygon is specific to kiwi, hence the aptery "without wings" in its name. Both genera are chewing lice - they eat the keratin of feathers rather than sucking blood. Typically they don't have a huge effect on the health or success of a bird, but they can be an indicator of poor health. Birds that aren't able to preen enough will often have an abundance of lice, and they can, in turn, be quite irritating, scurrying around. In terms of natural selection, scraggly birds with a lot of louse-damaged feathers aren't as attractive and often reproduce less.
Something that is often overlooked is the threat level of parasites. If their hosts are threatened, the parasites are also threatened. Apterygon mirum is endemic and considered vulnerable. It is found exclusively on North Island brown kiwi. Rallicola rodericki is at risk and has never been found on mainland NIBK - only on NIBK living on a few northern islands. The kiwi we have been seeing on Maungatautari have had a healthy population of lice - presumably A. mirum. All the chicks at Wairakei are free of lice but will likely soon catch them in the wild when they share roosts and interact with other kiwi.
Ticks.
New Zealand isn't home to many ticks, but there is a kiwi tick, Ixodes anatis (and a tuatara one, too!). I. anatis is endemic to New Zealand and can be found on NIBK and Tokoeka. The introduced cattle tick, Haemaphysallis longicornis, is also found on NIBK.
Again, as a host species becomes threatened, their parasites do too, and as such, I. anatids is vulnerable. Unlike feather lice, ticks have been shown to have a negative effect on kiwi - and their removal has been shown to increase condition score (here is an interesting read: https://mro.massey.ac.nz/items/384e4aab-f868-4f88-bace-91edf17645cd). There does not seem to be any kiwi tick-born protozoal infections - so there is no kiwi Lyme disease to worry about when we are crawling with ticks at SMM.
This year we saw a lot of ticks on the birds at Maungatautari. I don't know how to accurately tell the difference between all the life stages of both the kiwi tick and cattle tick - but we likely had both present. If anyone has a paper showing how to ID the different life stages of the kiwi tick, I'd love to have a copy.
This is a kiwi tick lifecycle of Ponui ticks from Natasha Bansal's PhD:
Mites.
Similar to lice, there are feather mites (which eat keratin) and blood-sucking mites.
These pesky little things are my least favourite of the ectoparasites we're seeing at SMM. They're teeny tiny and hard to spot, and we are seeing some very irritated skin on some birds, which seems to be due to a mite infestation (I call it mitey-bumps; the scientists use a different name...). Speaking to Megan Jolly, she wonders if it could be an autoimmune response - with some birds showing this overreaction. There's a bit of research that could be done with kiwi mites, and I'm hoping we can work with Wildbase to learn more about this mitey presentation.
Coccidia
Moving away from ectoparasites to endoparasites, coccidia is likely a familiar word to you all.
Coccidia are a type of protozoa. Generally, they are host-specific, except for the most widely known one - Toxoplasma gondii - which makes rats attracted to the scent of cats, is thought to cause 'crazy cat ladies', causes abortions in sheep, and basically is really bad for a lot of animals. There are currently six recognised species of coccidia in kiwi.
Coccidia tends to attack intestinal, kidney, and liver cells. If an animal has no immunity and is stressed or otherwise immunocompromised, the infection can cause a huge amount of damage to the intestinal system, leading to anaemia, exhaustion, and death. Infected animals shed spores or oocysts; these are very hardy and can last years in soil. In areas of high stocking density, coccidia can build up in the environment and cause a lot of disease in a population. Fortunately, the creche at Wairakei has very low levels of coccidia, and we are now working with Emma Scheltema from Massey to get a better idea of what species are present in the creche.
Ventricular worms
The digestive system in birds is a bit different to mammals:
The proventriculus is similar to our stomach in that it stores food and is glandular - it is the site of HCl excretion. One species of nematode (roundworm) has been found to live in the proventriculus. Prior to 2021, little was known about these worms in kiwi, and diagnosis often required scoping or necropsy. Fortunately, we now have a faecal test to detect the presence of these nematode eggs. As adults, they embed in the wall of the ventriculus, and it is probable that this is causing discomfort and likely pain to the bird. A bad infestation of these worms can lead to poor body condition, anaemia, and, if they're left unchecked, death.
It is believed that there is a secondary host fostering young ventricular worms between kiwi hosts, but the identity of this species has not been eluded yet. More research into these worms is needed!
Article written by Gaia O'Hare
Poutiaki Kiwi | Kiwi Ranger, Wairakei Golf & Sanctuary
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