You’ve heard the story before, and it’s sobering: Once perhaps the most abundant vertebrate on the planet, a combination of unremitting exploitation and habitat loss reduced the Passenger Pigeon (Ectopistes migratorius) from billions to none in a few short decades in the late 19th and early 20th centuries.
A recent analysis by Hung et al. 2014 used multiple sources of evidence to challenge the notion that Passenger Pigeons had always been that abundant. Their analysis does not, however, question the oft-cited estimate of somewhere between 3 and 5 billion Passenger Pigeons in North America at their population peak in the 19th Century. Even the low end of that estimate is difficult to fathom, so I decided to do a little back-of-the-napkin calculating to get a bit of perspective on what it would mean to have at least 3 billion birds of one species flying around North America.
For estimates of bird population sizes, I turned to the Partners in Flight Population Estimates Database. This database is a compilation of abundance estimates from the North American Breeding Bird Survey with extrapolations to available unsampled habitat in the US and Canada. It is biased toward the species most likely to be sampled via the BBS (passerines and similar “landbirds”) so there are likely some other species that are more abundant than some of the species on the following list.
Naturally, we can carve up the methods for making these estimates nine ways to Sunday. That’s not my objective in this post. Instead, I wondered how many cumulative populations of our most abundant species here in North America it would take to get to 3 billion. So here we go. To roughly approximate the abundance of the low estimate of Passenger Pigeon in the 19th Century with North American landbirds today, we would need to add together every single . . .
- American Robin +
- Chipping Sparrow+
- Dark-eyed Junco +
- Savannah Sparrow +
- White-throated Sparrow +
- Red-eyed Vireo +
- Alder Flycatcher +
- Yellow-rumped Warbler +
- Song Sparrow +
- Red-winged Blackbird +
- Blue-gray Gnatcatcher +
- Brown-headed Cowbird +
- Mourning Dove +
- Swainson’s Thrush +
- Golden-crowned Kinglet +
- Northern Cardinal +
- Ruby-crowned Kinglet +
- Yellow Warbler +
- Common Yellowthroat +
- House Sparrow +
- Horned Lark +
- Orange-crowned Warbler +
- Western Meadowlark +
- Indigo Bunting +
- Tennessee Warbler.
There you have it. Passenger Pigeon was once at least as abundant as our top 25 most abundant landbirds today, combined.
The Waterthrush Blog 
Reblogged this on The Waterthrush Blog and commented:
Some perspective on how large a number 3 billion is. It’s the low-end estimate of how many Passenger Pigeons we once had in the USA, and it’s the amount by which overall North American bird populations have been reduced since 1970.
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