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Backyard Files: the global backyard

The exotic-looking scarlet tanager is thought to be rarer, globally, than the wild turkeys we see running around our communities.

By Stephen Press
Hometown Weekly Editor

As a small boy growing up in New England, one of my prized possessions was an old illustrated field guide depicting the birds of North America. It was missing its cover, and by the time I’d purloined it from my father in the middle of the 1980s, it was likely already out of date. Neither of those things were of any consequence to me.

More than anything, I enjoyed flipping through its pages with abandon, comparing the illustrations and range maps, and matching what I saw in the book with what I could see out my back window. The backyard, in turn, became the standard of normalcy for my young self. I started blindly assuming that “common” meant “what I can see outside” and “exotic” meant “what I can’t.”

On some level, I wasn’t alone. For years, humanity’s feathered fascination has been hampered by a key factor: so numerous and diverse are the world’s avian species that establishing a raw count of every individual bird - and with it, the ability to distinguish the truly rare from the abundant - had been near impossible.

In the August 2021 issue of Scientific American, a short piece called “Counting the Birds” addresses just such an issue. A new set of data - one that estimates the global abundance of 9,700 avian species, constituting 92 percent of all birds worldwide, has been released. The data is unique, as it represents the first time a reliable estimate has been attempted - a feat enabled, in part, by data submitted by thousands of individual birders on the eBird phone app.

“The results, published recently in the Proceedings of the National Academy of Sciences [PNAS] USA,” reads the article, “confirm a common pattern among animals: across the globe there are many species with small populations isolated in niche habitats and relatively few species that have managed to expand over a wide territory and grow their population into the hundreds of millions or billions. Eventually the findings could help with conservation efforts.”

Callaghan, C. T., Nakagawa, S., & Cornwell, W. K. (2021). Global abundance estimates for 9,700 bird species. Proceedings of the National Academy of Sciences of the United States of America.

It is a watershed study, and one that will undoubtedly provide more insight to ornithologists and ecologists, most especially as it pertains to protecting species and habitats.

For amateur naturalists in Hometown Weekly’s communities, it is perhaps most immediately interesting in that it allows us to situate our own sense of commonness against a wider global perspective.

In some ways, the numbers affirm our everyday reality. For example, we see the house sparrow, European starling and ring-billed gull daily in our travels - I’d likely encounter all three simply by parking my car at Needham Center station and walking a couple blocks to Town Hall - and they are estimated to be the three most abundant global bird species, with populations of 1.61b, 1.28b, and 1.22b, respectively. The ubiquitous American robin is 11th overall with 561.2m individuals, and the rock pigeon, which inhabits our urban landscapes and highway overpasses, comes in 20th with 285.8m.

From there, it begins to get a bit more interesting, upending some of our preconceived notions of the ho-hum and the unique.

On a daily basis, we are likely to see more individual black-capped chickadees in our lawns and woods than we do Northern cardinals or mourning doves. Despite this, there are estimated to be significantly more cardinals (204m) and mourning doves (239.5m) than Massachusetts’ state bird (112m).

The bananaquit (27m) and bar-tailed godwit (24m), which sound like a probiotic yogurt and an insult lifted from the BBC, are in fact a rainforest-dwelling songbird and a wader that migrates between Australia and Siberia - and both are estimated to be more numerous, globally, than the tufted titmice (19.6m) and white-breasted nuthatches (19.5m) we can’t avoid around our bird feeders.

The sacred ibis (17m) of the Upper Nile, which played a special role in the art and religion of the ancient Egyptians, is more numerous than the great blue herons (13m) that stalk the waters of Bird Park or Channing Pond; tell that to your kids as they ooh and aah at the ibis’ likenesses painted on mummies in the MFA. Incidentally, the heron fills a similar niche in our ecosystem as the ibis does in its own.

A vagrant black-chinned hummingbird (9.7m) at a feeder once inspired a spit-take from me, and I still treasure the vivid memory of a scarlet tanager (6.2m) I briefly glimpsed as a small child; it turns out that the wild turkeys (4.86m) that harass cars on Clapboardtree Street are a rarer sight than both, all things considered, as are the belted kingfishers (3.7m) I’ve observed hovering over Meeting House Pond.

The yellow-billed oxpeckers (2.65m) perched on the back of wildebeests and zebras in Attenborough-narrated documentaries? They’re about as rare as the ospreys (2.66m) I see diving for fish along the Connecticut coast on my train rides to New York.

You’d need to head to Panama, Nicaragua or Costa Rica to see a striking crimson-fronted parakeet (2.25m). The Eastern whip-poor-will (1.77m), famously called from the cliffs behind Pine Hill by Sherborn birding legend Eliot Taylor, has the smaller population - and is more elusive, for that matter.

A boat, mosquito netting, and high tolerance for extreme humidity are prerequisites if you want to encounter the mangrove cuckoo (1.76m), whose spotted tail I used to admire in Audubon books as a child. Yet, the ruffed grouse (1.76m) I once saw in my youth, puffed out in full mating display, was just as rare, from a population perspective.

If you’ve seen a Vanuatu whistler (893,944), chances are it’s because you’ve escaped to a South Pacific paradise. Those who’d prefer to eschew the 24-plus-hour flight, however, can find the rarer Eastern screech-owl (762,610) whinnying in the woods behind their houses.

It is not difficult, looking out one’s back window every day as one does, to grow numb to the singular habitat we happen to inhabit. Poring over the PNAS dataset and getting lost in its catalog of over 50.5 billion individual birds, one begins to realize just how wide a world we live in - and just how exotic home is.

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