Mariana Crow :: Corvus kubaryi

Bad at Goodbyes :: Episode 011

The Mariana Crow is a critically endangered avian in the corvus family native to the western Pacific Ocean, to the island of Rota in the United States Commonwealth of the Northern Mariana Islands.

• (00:05) Intro
• (02:05) Species Information
• (27:58) Citations
• (29:55) Music
• (42:20) Pledge

Research for today’s show was compiled from

• Dr. Sarah K. Faegre’s doctoral dissertation from the University of Washington’s entitled “Behavioral Ecology of the Mariana Crow” – https://digital.lib.washington.edu/researchworks/items/1ba5ba23-dfe4-4fb1-ab54-d02428388d61
• U.S. Fish & Wildlife Service – https://www.fws.gov/species/mariana-crow-corvus-kubaryi
• Birds of the World; Cornell Lab of Ornithology – https://doi.org/10.2173/bow.marcro1.01
• Dr. John Morton’s “Ode to crows ravens jays and magpies” – https://www.peninsulaclarion.com/life/refuge-notebook-ode-to-crows-ravens-jays-and-magpies/   
• Journal of Fish and Wildlife Management Vol 6 issue 2 – https://doi.org/10.3996/112014-JFWM-085 
• “Observations On The Behavior And Ecology Of The Mariana Crow” – The Condor, the Journal of The Cooper Ornithological Society issue 88 – http://dx.doi.org/10.2307/1368898 
• “Population status and nest success of the Critically Endangered Mariana Crow” from Bird Conservation International vol.25 issue 2 – http://doi.org/10.1017/S0959270914000045 
• Saipan Tribune July 15, 2024 – https://www.saipantribune.com/news/local/ga-population-increasing-through-rear-and-release-program/article_71a30c4e-41ae-11ef-b3c3-a3b3d9a99163.html 
• IUCN – ​​https://www.iucnredlist.org/species/22705959/129626293 
• Wikipedia – https://en.wikipedia.org/wiki/Mariana_crow

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A note on accuracy: I strive for it! These episodes are well-researched and built from scholarly sources, hoping to provide an informed and accurate portrait of these species. That said, I’m an ambient musician! I am not an academic and have limited scientific background. I may get things wrong! If you are using this podcast for scholarship of any kind, please see the cited sources and double-check all information.

Welcome to Bad at Goodbyes.

On today’s show we consider the Beard's Mallee.

The Mariana Crow is a critically endangered avian in the Corvus family native to the western Pacific Ocean, to the island of Rota, in the United States Commonwealth of the Northern Mariana Islands.

The Mariana Crow is considered a small crow, measuring approximately 15 inches in length, and weighing roughly half a pound, with a wingspan up to 40 inches. Its anatomy is typical of the Corvus (crow) family, warm blooded with a sturdy build, strong legs, and a large brain size in relation to its body mass.

The Mariana Crow's plumage is predominantly black, with suggestions of different colored sheen across its body: a slight greenish gloss on the head; a deep blue gloss on its back, wings, and tail and dull green-ish sheen on its lower belly. The base of the feathers are a light grayish color, sometimes appearing almost white on the neck.

Their wings are broad and powerful, allowing for agile flight and maneuverability.

The Mariana Crow's black legs are strong and adapted for perching and walking. Each foot has four toes – three facing forward and one backward – equipped with sharp claws for gripping branches and prey.

Their beak is black and proportionally large, with a slightly hooked tip designed for foraging and manipulating food.

Their eyes are large and dark, and are set on the sides of the head, providing a wide field of vision for spotting food and potential threats. Their vision is particularly keen, allowing them to detect subtle movements and discern fine details in their environment aiding in hunting and foraging for food, spotting predators, and navigating their habitat.

They possess excellent hearing, enabling them to locate prey, such as insects hidden beneath leaves or in crevices.

While their sense of smell is not as well-developed as their sight and hearing, Mariana Crows may use olfactory cues to detect the scent of carrion or rotting fruit, for finding potential food sources.

They are opportunistic omnivores, consuming a range of foods, based on seasonality and availability.

Their diet includes a variety of invertebrates, like insects, spiders, and larvae, which they extract from crevices and foliage. Reflecting their island home, hermit crabs make up a substantial portion of their diet and they also hunt small vertebrates like gecko.

Mariana Crow also occasionally consume plants, feeding on fruits and seeds, again based on seasonality and lack of abundance of other foodstuffs.

Mariana Crow, like other corvus species, are highly social, highly intelligent beings.

They are very vocal communicators. They employ locational calls which are a high-pitched caw used while perching, foraging, or flying to announce and triangulate location with other crows.

Mated crows use a more nasally locational call only with one another, for example when a mate is arriving at the nest or when the two are collaborating during nest building. Breeding pairs caw in a unique way specific only to their partner.

Both adult and young will “monologue” which is a series of quiet guttural and squalling sounds usually made at the nest, often accompanied by playful behaviors like ripping leaves or hammering branches.

Mariana Crow have also been recorded making alarm calls, a series of sharp, rapid caws used to signal danger.

Mariana Crow form small family groups, generally consisting of a breeding pair and their most recent offspring, who all stay together until the young mature and disperse, these juveniles leave to seek their own mate and begin their own new family group.

The breeding season usually begins in August, but can occur throughout the year. Both parents play an active role in building the nest which is a sturdy structure made of various natural materials, including twigs, rootlets, vines, and fibers. Mariana Crow are territorial and will defend their nesting area vocally, physically, and with trickery.

In her field notes, Dr. Sarah Faegre, who has studied the Mariana Crow for over ten years, describes being cawed at, divebombed, and pecked by parents protecting their nest. She also recounts observing a fledgling fall, nearly right at her feet, and hop off awkwardly into the forest. Worried for the fledglings safely, she quickly followed, led on a winding path deeper into the woods, as the bird scrambled along the forest floor. As she got close the crow suddenly spread to full wingspan and took flight. It was in fact an adult male crow that had convincingly mimicked the physical behavior of a fledgling, to lead Dr. Faegre away from the actual nest.

So though the Mariana Crow have a range of strategies to protect their young, on average one clutch per year fails. Usually due to weather damaging the nest and eggs, or a successful predator, like the monitor lizard eating the eggs or small chicks. When a nesting attempt fails, the breeding pair will quickly rebuild and mate again. Pairs may nest multiple times each year based on initial nest failures.

The female typically incubates the eggs, usually between one and four per clutch, while the male provides protection and forges for food. Mariana Crow chicks are altricial, meaning they hatch helpless, born with closed eyes, very few feathers, and are unable to feed themselves. Both parents then share the responsibility of feeding and protecting and nurturing the young chicks. This biparental care is exhibited by the Mariana Crow throughout all stages of offspring rearing.

The chicks start to develop feathers within a few days of hatching, but it takes several weeks for their full plumage to come in, and a bit more than a month before they leave the nest at all. They are still not strong flyers at this point and continue to rely on their parents for food. They gradually learn social behaviors, speech, and how to forage for themselves under the guidance of their parents. This rearing period, during which the initial breeding pair does not breed again and the family flocks together while the young mature and learn, can last multiple years.

Young crows have been observed interacting with objects in a playful and exploratory manner like manipulating twigs and seeds, tearing leaves, hammering on branches, and repeatedly placing and removing objects from hollows. These behaviors do not seem to be related to feeding, but rather appear to be a form of exploration and play.

Relatedly, Mariana Crow demonstrate cultural transmission of generational knowledge. Adult crow have been observed teaching their young how to extract hermit crab from their shells. Adult crow do this in a consistent sequence: placing the shell, pecking at specific structural weaknesses in the shell, and skillful crab extraction, that includes snipping a weak bit of the crab abdomen and shaking from its shell. Young crow learn this by observing and then mimicking their parents, initially displaying errors in sequence and targeting. Adults will repeat their demonstration, over many months, until the young have mastered the process. Observations of captive crow have shown that this is not innate behavior, it is learned and transmitted, from parent to young, across generations.

Mariana Crow also have an unusually altruistic relationship with young who have disabilities. For example, breeding pairs have been observed extending their care for fledglings with birth abnormalities – like crossed bills or missing toes – who otherwise would struggle to feed or walk. The breeding pair were observed forgoing mating cycles for multiple years in order to nurture these young to independence.

Mariana Crow can live up to 25 years in the wild.

The earliest fossils we’ve found for the Corvid family date to the middle Miocene period, roughly 17 million years ago.

————

In the dream, I walk the streets at night, in the dream I am unworried by the late hour, by the darkness. I am, as ever, thinking about doors closing, and things I wish I’d said. A streetlamp flickers like the end of a flimstrip. And then, in the dream, a caw from the charcoal shadows. I do not look, I know not to catch the crow gaze with my own. But I slow my steps and deliver my whisper. I say “Please tell your mistress I seek her.”

A low rustle and then the game, to follow the crow caw in the blackness, 20 feet ahead to right, I follow, its voicing then around the next corner, I follow. And the city is getting less concrete now and I feel the brush of leaves in a deepening dark. And perhaps I’m learning crow song, at least getting better at guessing crow intention, I draw closer through full woods now and then into a place with little light, warm and black and undefined but for a bridge of dim constellations. I have imagined this path, this journey, my whole life.

I hear a far off fluttering of wing and offer my own foolish caw, a kind of thanks. And then step to the starlit bridge, to finally plead my case. In the dream.

————

The island's bioregion is classified as tropical rainforest, characterized by lush vegetation, high biodiversity, and a warm, humid climate. Rota's landscape is diverse, featuring rugged limestone cliffs along the coast, rolling hills in the interior, and dense forests covering much of the island. These limestone forests are their nesting site and provide foraging opportunities for the Mariana Crow.

Rota's climate is tropical, with high temperatures reaching into the 90s °F in the summer. Winter lows rarely dip below 75 degrees. The island receives an average annual rainfall of roughly 90 inches, mainly during the wet season from July to November.

The Mariana Crow, shares its island with Rufous Fantail, Beach Morning Glory, Island Blind Snake, Swordgrass, White-throated Ground Dove, Sword Fern, Yoga Tree, Monarch Fern, Paipai, Micronesian Starling, Perfume Tree, Monitor Lizard, False Elder, Micronesian Gecko, Fruit Bat, Fig Trees and many many others.

Historically, the Mariana Crow population on nearby Guam was decimated by the human introduction of the Brown Tree Snake, an invasive predator. These snakes are not currently present on Rota, and rigorous efforts are in place to insure the snake does not migrate to the island (they have been known to hide in airplane wheelwell, accidentally hitching a ride throughout the Micronesian islands).

Local human activities continue to negatively impact the Mariana Crow population. Agricultural and urban development contribute to habitat loss and degradation, and there is past evidence of crow persecution. Biologists use this term persecution to describe deliberate and targeted acts by humans to harm native species. With the Mariana Crow, for example, scientists found a breeding pair dead beneath their nest. Killed by gunshot.

And lastly typhoons, with destructive winds and torrential rain, cause nest failures, increase adult bird mortality, and can shorten breeding seasons. Human induced climate change is expected to further exacerbate the frequency and impact of these extreme weather events.

I love when I can close these episodes with a bit of good news.

Based on that information Faegre and her team devised a totally wild conservation plan. They started stealing eggs!

You’ll recall that when a breeding pair of Mariana Crow loses a nest, like to predation or weather damage, they quickly breed again, renest, lay another round of eggs and try for a second brood. That behavior proved true in the case of egg removal. So the biologists carefully monitor wild nests and early in the breeding season collect a limited number of eggs (I believe it is up to 15 per year). The collected eggs are incubated and hatched and the chicks are hand-reared in captivity. Once past that critical 1-2 year mark, they are released back into their natural habitat. Meanwhile, our original breeding pair will have hatched another clutch of eggs, some of which will likely survive into adulthood too.

To date, 85 Mariana Crow from this captive-rear-and-release program have been reintroduced to the wild, with 61 individuals surviving. And thriving: the released crow have begun breeding themselves, producing four fledglings so far.

Our most recent counts estimate that less than 250 Mariana Crow remain in the wild.

Dr. Sarah K. Faegre’s doctoral dissertation from the University of Washington’s entitled “Behavioral Ecology of the Mariana Crow” – https://digital.lib.washington.edu/researchworks/items/1ba5ba23-dfe4-4fb1-ab54-d02428388d61

U.S. Fish & Wildlife Service – https://www.fws.gov/species/mariana-crow-corvus-kubaryi

Dr. John Morton’s “Ode to crows ravens jays and magpies” – https://www.peninsulaclarion.com/life/refuge-notebook-ode-to-crows-ravens-jays-and-magpies/

“Observations On The Behavior And Ecology Of The Mariana Crow” – The Condor, the Journal of The Cooper Ornithological Society issue 88 – http://dx.doi.org/10.2307/1368898

Saipan Tribune July 15, 2024 – https://www.saipantribune.com/news/local/ga-population-increasing-through-rear-and-release-program/article_71a30c4e-41ae-11ef-b3c3-a3b3d9a99163.html

Wikipedia – https://en.wikipedia.org/wiki/Mariana_crow

I honor the lifeforce of the Mariana Crow. I will endeavor to learn its name, in its language, and until then I will carry its human name in my record. I am grateful to have shared time on our planet with this being. I lament the ways in which I and my species have harmed and diminished this species.

And so, in the name of the Mariana Crow I pledge to reduce my consumption. And my carbon footprint. And curb my wastefulness. I pledge to acknowledge and attempt to address the costs of my actions and inactions. And I pledge to resist the harm of plant or animal kin or their habitat, by individuals, corporations, and governments.

I pledge my song to the witness and memory of all life, to a broad celebration of biodiversity, and to the total liberation of all beings.