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Audio: Predators & Isolation
I first read about the disappearing birds of Guam in 2010. I was at the time, retraining myself to trust my instincts. It was a particularly difficult period in my life, so I carved out time to laugh. Usually, a funny book before sleep to stave off nightmares.
If I was in the mood for dysfunctional families, David Sedaris did the trick. If I wanted an entertaining and stimulating science story, my go-to was David Quammen and his series of essays in Flight of the Iguana: A Sidelong View of Science and Nature.
I would crawl into bed, shake my arms and legs to heat up the cold sheets, then I would sink in, open my book of choice and read till my eyes closed. David Sedaris was a laugh out loud page turner. David Quammen was an intellectual balm.
Then I read his essay, Island Getaway.
I don’t know why, but I’m continually surprised by how our very human issues and dynamics are mirrored in nature.
Take for instance the birds of Guam. Or, the birds who used to live on Guam.
In the North Pacific Ocean, there’s a vast range of submerged volcanoes with only their mountaintops showing. These volcanoes create the crescent-shaped chain of islands known as the Marianas archipelago. To the east of these islands is the lowest point on earth’s crust, the Mariana Trench.
Of the sixteen islands in this chain, only five are inhabited by humans. The southernmost island, Guam, is the largest, measuring 212 square miles, thirty miles in length and four to twelve miles in width. Its human population, as of the 2022 census, is 775 people per square mile. Of course, this is a silly reference point because people aren’t evenly distributed by square mile. I added the statistic only because it's a comparative number when we look at how and why the birds of Guam disappeared.
For centuries, bird songs filled Guam’s tropical forest air waves. Warbles and tweets, caw caws and hoots. The colorful blue and gold kingfisher, the Guam rail, the rufous-fronted fantail, the Guam bridled white-eye. Limestone mountainous ravines were alive with music from both native and endemic birds.
Then, for some uncertain reason, the island of Guam went silent. The birds were gone, or at least most of them.
In 1978, when the plummeting bird population was finally noticed, it had a death grip on most of the bird species.
David Quammen writes, “Pesticides were suspected. Disease was suspected. Lab analyses were done on some bird specimens, though, no Guam avian epidemic could be found. Then in 1982 a graduate student from the University of Illinois named Julie Savidge went out there to study the die-off, and she came up one other possible answer: Boiga irregularis.” 1
Near as they can figure, during WWII, a US military ship on route from a South Pacific island, docked in Guam’s port and a stowaway; a sneaky, slithering, unassuming brown snake, known formally as Boiga irregularis, slipped off the ship and invaded the island.
By 1984, the Guam Flycatcher was extinct. The Guam bridled white-eye; extinct. The Micronesian honeyeater; extinct on Guam. The Mariana fruit dove, extinct on Guam. The Guam Rail was saved from permanent extinction through a breeding in captivity program in a safe off-island location. The list goes on.
How did an entrenched and thriving bird population go extinct so fast?
Well, Boiga irregularis happens to be a bird-eating tree snake. Before this reptilian invasion Guam was almost as snake-less as Ireland. This means two things: One, the brown tree snake had no natural predators. And two, the birds of Guam had no street smarts.
“They had never been forced to learn certain hard lessons. For instance, they did not place their nest on the far ends of tiny branches or suspend them as elaborate hanging baskets; they did not carefully limit their trips to and from the nest site, so as to avoid giving away its position; they did not gather in colonies with a system of mutual warning calls.” 1
They hadn’t evolved in the presence of a snake and therefore had no innate training for survival in their presence.
Snuggled up in bed, reading about the disappearing birds, I felt a profound kinship with them. I had escaped a predator, but my extinction was still in question. I was in hiding. I had learned how to keep my location safe. I had learned to how to use police support at court appearances. I learned the importance of group support and how to call for help. And now, I was retraining myself to trust my instincts. Something had gone very wrong. I didn’t understand how I could have missed things that were right in front of me. The truth, it turns out, was that I was more like the birds of Guam. I didn’t know what I needed to know.
The few species on Guam that are fighting for survival, still don’t know how to protect themselves. This type of learning is an evolutionary process. They don’t have the luxury of learning as fast as we do.
At the time I was also reading Gavin de Becker’s book Protecting the Gift. It details what to teach yourself and your children to keep all of your safe and sane. It’s important to be afraid of what is dangerous and to take action. But it’s equally important to not be afraid of everything else. Learning to discern the difference was what I was striving for.
In the meantime, Boiga irregularis’ uninterrupted menace on Guam has been terrifying. This predator didn’t stop with the birds. According to the US Geological Survey, Boiga irregularis has “caused the extirpation of most of the native forest vertebrate species.” (Extirpation: to root out and destroy completely.)
The small island of Guam now hosts two million snakes. That’s 13,000 Boiga every square mile, and they do make the rounds. They’re responsible for thousands of power outages, the death of small pets and its bite is dangerous to children.
So what happens to an ecosystem when a predator decimates an entire bird population? The ecosystem unravels. A handful of decades later, trees and plants are dying because they lack birds and small animals to disperse their seeds. 2
The birds left a vacuum; an empty space where they once sang. Space for other species to thrive. Species for whom the birds were natural predators. On Guam, that species is the gangly yellow banana spider. During the wet season, the spider population is a veritable explosion with 40x more spiders on Guam, then on neighboring islands.
Nature always moves toward equilibrium. So, yes, Guam’s ecosystem is unraveling, but it will eventually find a new balance. The snakes are killing off their food sources; at some point they will decline in numbers. The spiders will keep a foothold unless they to become a food source. For the snakes perhaps?
And what will this new world look like? The music is gone. The progression seems to be leading us into a desolate forest cemetery, silent except for the slithering snake and the hanging tapestry of ghostly webs and spiders in waiting.
Islands are interesting to scientists. Whether it’s an island surrounded by water, or a man made island surrounded by cement, buildings, roads and humans. An island is a place where nature is confined and isolated. When nature is isolated, species adapt, they specialize and they take the long, or short, walk to extinction.
In human relationships, isolation is the first red flag of danger. When you are no longer tethered to a community to give you direction, perspective and support, the road to extinction is either long or short, but its end is the same: it’s the end of your life, or the end of your life as you once knew it.
If you feel isolated, the best thing you can do is keep yourself tethered to a supportive community. Ask for help. If you don’t get the help you need, keep asking for help from other sources. If you need to escape, you can, like some of the birds of Guam, be saved from extinction by relocation to a safe place.
Connect to Resources:
** When searching for resources, be sure to delete your browsing history if you are in an abusive relationship and they have access to your electronics.
National Domestic Violence Hotline: 1-800-799-7233 | there is an option on the website to search for resources in your city and state.
RAINN: Rape, Abuse & Incest National Network | 1-800-656-HOPE (4673)
Digital Safety guidance from the United Nations
Call 988 for Suicide and Crisis lifeline
Call 211 for local community services
1 / Flight of the Iguana: A Sidelong View of Science and Nature (Island Getaway) By David Quammen. Quotes from pgs 108, 109, 110. https://www.amazon.com/Flight-Iguana-Sidelong-Science-Nature/dp/0684836262
2 / Guam’s Plague of Snakes Is Devastating The Whole Islands Ecosystem, Even The Trees https://www.sciencealert.com/guam-s-plague-of-snakes-is-having-a-devastating-impact-on-the-trees
On Guam there is no birdsong, you cannot imagine the trauma of a silent island https://www.theguardian.com/world/2022/nov/01/on-guam-there-is-no-birdsong-you-cannot-imagine-the-trauma-of-a-silent-island
USGS: The Brown Tree Snake on Guam: How the Arrival of One Invasive Species Damaged the Ecology, Commerce, Electrical Systems and Human Health on Guam: A Comprehensive Information Source https://pubs.usgs.gov/publication/53889
Spiders Infest Guam After Native Birds Disappear https://www.futurity.org/spiders-infest-guam-after-native-birds-disappear/
Guampedia: Native Forest Birds of Guam https://www.guampedia.com/a-native-forest-birds-of-guam/