From the Audubon Society website:
Audubon’s unprecedented analysis of forty years of citizen-science bird population data from our own Christmas Bird Count plus the Breeding Bird Survey reveals the alarming decline of many of our most common and beloved birds.
Since 1967 the average population of the common birds in steepest decline has fallen by 68 percent; some individual species nose-dived as much as 80 percent. All 20 birds on the national Common Birds in Decline list lost at least half their populations in just four decades.
Update: Hmm; the article didn’t seem all that convincing. It had that “of America’s best tasting gums, Trident is sugarless” feeling, as if what they were actually trying to get across was different from what they were allowed to literally say.
So I looked at the referenced technical report.
We see two different measures of species trend, one called BBS and one called CBC. I didn’t look into the meanings of these, but they correlate well. There is also a reliability score. Both on the high reliability trends and on all estimated trends:
The number of species increasing in abundance exceeds the number in decline!!!
Species trends are divided into rapid increase, moderate increase, stable, moderate decrease and severe decrease. One slice through the data looked at those with reliability index of score of 2 or 3 on a scale of 0 to 3 on both measures, with 3 being most reliable. Using the BBS measure, we see 41 species in rapid increase, 38 in increase, 31 stable, 24 in decline, and 22 in rapid decline. Similar numbers for the CBC measure.
Similar numbers are seen on various other measures. I didn’t cherry pick. Look for yourself.
Is this bad? Maybe. Maybe more stability should be expected.
Is the situation obviously bad? Not really from the point of view of the birds. It is nasty form the point of view of the nature of public discourse, though.
I am not saying I am sure there is no problem, but the technical report certainly requires a different exposition than the Audubon website provides. In fact I would suggest their implied position is at odds with their report.