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November 2007

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From:
Bill Whan <[log in to unmask]>
Reply To:
Bill Whan <[log in to unmask]>
Date:
Fri, 30 Nov 2007 10:08:02 -0500
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Well, a good question. If you want intriguing answers, you might want to
look at the Partners in Flight database, with query for Ohio available
at  http://rmbo.org/pif_db/laped/PED3.aspx  .  All bird population
estimates have their quirks and failings, but this one, based mostly on
recent Breeding Bird Survey routes, boasts an enormous bank of data
collected in comparable standardized ways. Its shortcomings are well
enough known that results can be adjusted in an attempt to minimize them.
        Because it uses BBS data, it counts only breeding landbirds. Its
estimate of the total number of them in North America?  Five billion,
which, it is pointed out, roughly matches the population of a single
species--the passenger pigeon--in historical times.
        A search for Ohio produces plenty of thought-provoking numbers. In
order to understand them more fully, it is necessary to read the
introductory material, which explains the categories and all the
adjustments and various reliabilities of the data.  You can click the
column heads to get ranked versions. Some numbers that jumped out at me
included:
        --American robin commonest breeder in Ohio, more than starlings or
house sparrows or grackles.
        --the ten breeders with highest percentages of global numbers in Ohio:
     cerulean warbler 13.4, blue-winged warbler 13.2, Henslow's sparrow
7.8, Acadian flycatcher 6.1, field sparrow 5.6, chimney swift 5.3, gray
catbird 5.1, Cooper's hawk 4.6, scarlet tanager and yellow-throated
vireo 4.5. We hear about the cerulean all the time, but not about the
blue-winged. Cooper's hawk?  Acadian flycatcher? Field sparrow? Swift? Wow.
        --among other interesting population estimates: bald eagle (70),
Bewick's wren (80), black vulture (180), blue grosbeak (3,000),
blue-headed vireo (170), common nighthawk (6,000), eastern screech-owl
(4,000), golden-winged warbler (60), least flycatcher (1800), loggerhead
shrike (300), mourning warbler (1), northern harrier (1100), osprey
(50), prothonotary warbler (300), purple finch (6,000), vesper sparrow
(150,000), western meadowlark (200), and no numbers for dark-eyed junco
or short-eared owl at all. Some of these are explained by changes since
the '90s. Bewick's wrens and loggerhead shrikes and golden-wings have
all but disappeared here; bald eagles have continued their recovery,
ospreys have been successfully reintroduced, and protho warblers are
more successfully supported.  The blue grosbeak and northern harrier
numbers seem kinda high; do we really have anywhere near 1500 breeding
pairs of the former and 550 of the latter? The vesper sparrow number may
surprise many people who don't listen for them. Anyway, just some stray
thoughts; have a look at the numbers (and read the user guide) and
you'll have plenty of your own.
Bill Whan
Columbus


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