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Birds by the number

June 1, 2021

Were I to guess how many individual birds live on earth, my first estimate would be 100 times the number of people, or a bit over a half trillion. That is above the mean of the probability distribution estimated by Australian scientists working from a variety of samples. (See diagram.) I am not surprised that the three most abundant species are the house sparrow, the European starling, and the ring-billed gull.

British scientists doing fecal bar-coding find that bird feeders in England have a surprisingly large effect on the species of birds that eat from them. (Cite.) That spurs the abundance of those species, such as the blue tit, relative to others:

We show that woodland bird species using supplementary food have increasing UK population trends, while species that do not, and/or are outcompeted by blue tits, are likely to be declining.

BirdPopulationsI suspect there may be other unintended environmental effects from growing that 150,000 tons of annual feed.

Philadelphia has decided to dim some of its skyscrapers during migration, after a few thousand birds flew into them last October. I don’t have much confidence that will significantly change bird numbers. But it might assuage the pedestrians who otherwise would walk by the carcasses.

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