Hey Birds! A cautionary tale of tiny kiwis

Wikimedia/G. D. Rowley, PD-1923
Wikimedia/G. D. Rowley, PD-1923
A sketch of the little spotted kiwi from Rowley, G.D., Ornithological Miscellany, 1875–78. The bird once roamed New Zealand’s isles, but saw population losses in the 1800s due to hunting and the introduction of new predators. Source: Wikimedia Commons/G. D. Rowley, PD-1923.

Most people who visit New Zealand never see a kiwi in the wild. You might catch a glimpse of one in a dimly lit indoor cage, but in the wild the country’s national bird is a rare sight. Just to clarify, I’m talking about the awkward looking bird, not the odd looking fruit. New Zealand has five species of kiwi birds, native inhabitants of the “land of the long white cloud”. Thanks to introduced predators and hunting, four are on the REDD list. On the other hand, the little spotted kiwi (Apteryx owenii) has been a conservation success story. That is, until now.

Even though the little spotted kiwi is extremely rare very rare, it’s the only kiwi bird without “endangered” status. Its success story is an interesting one. Around a century ago, things were looking decidedly not good for the little spotted kiwi. It had disappeared from New Zealand’s north island altogether, and in 1912, conservationists took five remaining birds from the Jackson Bay on the South Island and moved them to a small island 5 kilometers off the North Island’s coast called Kapiti. Whether or not a native population already inhabited the island is still up for debate today, but the birds were spotted there in 1929, well after relocation.

By the 1980s, the original south island population was gone, but the birds on Kapiti were actually doing pretty well. Meanwhile, another population on D’Urville island wasn’t doing so great. Conservationists did the same thing again: moving the last remaining male and female birds on D’Urville to nearby Long Island, along with three birds from Kapiti. Around the same time, individuals from Kapiti and founded populations on some of New Zealand’s other coastal isles.

Island chart of LSK population movements through conservation efforts. Source: HMT/Ramstad et al.
Island chart of LSK population movements through conservation efforts. Source: HMT/Ramstad et al.

Taking the last individuals from a species in danger of becoming extinct  and focusing all of the energy on protecting them — either in a small area of their native range in the wild or in captivity — is a go-to worst-case scenario tactic in conservation. It worked for cheetahs, the mexican wolf, and another of New Zealand’s avian residents, the Takahe. So, the Kapiti island population flourished, exceeding 1600 individuals today. Based on numbers alone, spotted kiwis are doing great.

But, recent study published in Proceedings of the Royal Society B gives conservationists pause. Results suggests that these populations have inbred themselves into a genetic bottleneck — when a population drops, its genetic variation gets slashed. Basically, they lack genetic variety. A new disease could swoop in and easily wipe them out; the same goes for other challenges like sudden changes in climate (something that’s not out of the realm of possibility in the next million years).

“Yes, we have eight populations, and yes, they are all growing in size in terms of number of birds,” Kristina Ramstad, a co-author and a biologist at Victoria University in Wellington, NZ, told Science. “But they are all incredibly low in genetic diversity. … If the right disease comes along, it could wipe all of them out.” Science‘s Traci Watson outlines another species — the bengali tiger — that suffers a similar problem: a companion study in Proceedings of the Royal Society B found that the tigers retain only 7% of their ancestors’ genetic variation.

A map of the four populations of little spotted kiwis sampled in this study. There are four others, making eight existing populations in total. Source: HMT.
A map of the four populations of little spotted kiwis sampled in this study. There are four others, making eight existing populations in total. Source: HMT.

As for the kiwi study, Ramstad and her colleagues compared genetic data at 15 spots in the species’s genome from populations on Kapiti to those on Red Mercury, Tiritiri Matangi, and Long Island. All four populations were almost genetically identical and had telltale signs of genetic bottlenecks in recent years. Mysteriously, Kapiti birds are losing some measure of genetic diversity each year. The other groups are too. In fact, little spotted kiwis have the lowest diversity of all kiwi species. On Long Island, a single mating pair from Kapiti founded the population that persists today, and that the birds from D’Urville haven’t contributed at all to the overall genetic diversity of the species. For whatever reason, they never mated and disappeared.

“We don’t know why [the D’Urville birds didn’t breed],” Ramstad told Scientific American. “We don’t know how long little spotted kiwi live and we don’t know what’s their oldest age of reproduction. It’s still a bit of a guess, they keep outliving the scientists following them. So the birds [from D’Urville Island], could have been too old, or one of them could have been infertile. It could simply be a case that they didn’t fancy each other.”

So, what’s the takeaway message here: should conservations be doing something differently? or is the game just stacked against them? Keeping up connections between surviving populations — so that they mate and pop out genetically diverse kids — seems to be as important as making sure populations in protected areas have the best shot at survival. The sentiment seems to be that things are just a heck of a lot more complicated than originally thought. And, that’s no reason to throw in the towel. New Zealand’s Department of Conservation plans to relocate Kapiti birds (which have the most genetic diversity of the bunch) to smaller islands to boost their DNA. “Don’t keep all of your kiwis on one island” remains the best tactic at the moment.

For more info, check out Science and Scientific American‘s excellent pieces on the study: here and here.

Advertisements

Chestnuts galore: Happy 30th, TACF!

This year marks the 30th anniversary of the American Chestnut Foundation — a group of chestnut enthusiasts and academics who’ve been stalwartly trying to revive the species since it’s decline in early 20th century. It might surprise young’uns like me to hear that chestnuts once comprised a quarter of eastern forests, which if you think about it is a whole lotta trees. That all changed when a fungus commonly called chestnut blight hopped aboard nursery exports from Asia, and spread across the entire chestnut range within 40 years.

At the end of last summer, I visited TACF’s research farm in Meadowview, a wide part of the road in southwestern Virginia. It was part of a feature article that I wrote for Nature on how TACF and other chestnut restoration efforts are starting to see results. The main goal at Meadowview is to breed an American tree with the right selection of genes from Chinese chestnut to provide resistance to the blight. (Unlike their American counterparts, Chinese chestnuts can survive the blight.) It took them a little under 25 years to do this, but they’ve started to export their chestnut breeding pipeline to local TACF chapters across the US.  I took some pictures while I was there:

This slideshow requires JavaScript.

The other side of the Chestnut revival story begins with researchers at SUNY in upstate New York, who have developed genetically modified American chestnuts — American chestnut trees with candidate resistance genes from other chestnut species or other plants. Last March, a test plot of gm chestnuts was planted at the New York Botanical Garden — right across the street from where the blight was first discovered at the Bronx Zoo. In August, I went up to NYC to visit a friend, and of course, I dragged her on a side trip to NYBG to see their baby chestnuts.

This slideshow requires JavaScript.

It might seem bleak from an outsider’s perspective, but perhaps one day chestnuts — maybe even genetically modified chestnuts — will comprise eastern forests once again. For more background, here’s my piece. And, if you’re super curious people have written books about this saga (American Chestnut: The Life, Death, and Rebirth of a Perfect Tree does a great job portraying the colorful cast of characters involved, and then apparently Barbara Kingsolver based a character on TACF’s chief scientist in her novel Prodigal Summer.)

Image Credits: HMT.