Pennsylvania Game News - February 2020 - 62

bird population - had been lost since
1970, when the population was estimated at 10 billion.
Even Rosenberg was surprised by
the results, telling Pennisi he expected
to see rarer species disappearing, but
common species increasing to make up
for those losses.
Over 90 percent of the birds lost -
2.5 billion birds - came from 12 bird
families. The sparrow family topped
the list with a loss of 862 million birds,
40 percent of them Savannah sparrows
and eastern towhees, and 20 percent of
them song sparrows.
The warbler family - down 618
million - sustained the second-highest
loss. Canada warblers were down 60
percent; Wilson's warblers, 50 percent;
and Cape May warblers, 30 percent.
The blackbird family also recorded
heavy losses at 440 million. Most surprising was the red-winged blackbird,
the species always thought to be our
most-common native bird. There 2018
population of 170 million compares to
260 million in 1970. In addition, 60
percent of bobolinks and about 50 percent of common grackles disappeared.
The lark family - down 182 million - and the finch family - down 145
million - were next on the list. Finch
losses included 90 percent of evening
grosbeaks and 40 percent of common
redpolls and purple finches.
Other sizeable losses included swallows, nightjars and swifts - down by
nearly 50 percent, and shorebirds -
down 37 percent.
As a feeder-watcher, I wasn't surprised by the steep decline of evening
grosbeaks. I haven't heard or seen one
in decades. But I found it more difficult
to grasp the lower numbers of other
backyard birds.
62

The study found one in four blue
jays and rose-breasted grosbeaks had
disappeared, as did one in three Baltimore orioles, dark-eyed juncos and
white-throated sparrows.
After seeing dark-eyed juncos and
white-throated sparrows crowd at my
feeder area last winter, I was especially
surprised at their decline.
Blue jays, too, seemed abundant as
usual, and First Field supports several
pairs of breeding song sparrows every
year.
But as study co-author Adam Smith,
a biostatistician for Environment and
Climate Change Canada, points out,
because the declines are gradual, we
tend to forget just how abundant these
birds used to be.
That's true even for house sparrows
and European starlings, which have
sustained losses of 70 percent and 50
percent, respectively, since 1970.
The study found the greatest bird
loss had occurred in eastern North
America.
Forests across the continent have
lost a billion birds. In eastern forests,
17 percent of birds had been lost; in
boreal forests, 33 percent.
Grassland bird numbers had fallen
by 53 percent - a decline of 700 million
birds - primarily due to habitat loss
from the intensification of agriculture
and development.
"These bird losses are a strong
signal that our human-altered landscapes are losing their ability to support birdlife," Rosenberg told Gustave
Axelson, editorial director of Living
Bird, in an article.
Still, all was not gloom and doom.
The researchers credited things like

Pennsylvania Game News - February 2020

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