It is time to stop quivering in our boots in pointless fear of the future and just roll up our sleeves and build it.
- Ray Pierrehumbert

Friday, June 15, 2007

Widespread decline in US bird populations ????

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.


Anonymous said...

This story was published two days earlier on,

Anonymous said...

At least over here in northern Europe habitat destruction and change of agricultural land use has changed the populations a lot from the fifties or so. For example sparrows are much more rare nowadays because of changes in agriculture. But of course they probably were rare too before humans settled the place.

Climate change has done a lot too, of course.
One big proxy for climate change is the migration dates, and it's nicely independent of many other phenomena.

Birdwatching has become very popular nowadays here, among folks of all ages.

Michael Tobis said...

Nice to see Quark Soup back in business.

Is it the same guy? He used to write essays and not just act as a news filter, but it looks to be a very good news filter.

I'm not sure if "this story was publsihed earlier" was meant as criticism, but if so you don't understand blogs. The story was not published by Quark Soup, but by the Audubon Society.

Calling your attention to it is meant as a service and an effort to advance the conversation. No claim to precedence is expressed on links to external articles by myself or QS.

EliRabett said...

This is going to sound very strange, but there is a bird population explosion near our house in Washington, DC. It is actually quit nice

Michael Tobis said...

Note for clarity: the previous comments were made before the update, i.e., before I saw the contradiction between the press and the actual study.

EliRabett said...

The cbc is the christmas bird count, you can read about it at The bottom drop down menu show counts on various species. Interesting to me was the one on doves. In the last couple of years we have begun to see some morning doves, nice birds. They seem to be increasing their range.

bbs is breeding birds survey.

You can read why there is concern at

"The wide variety of birds affected is reason for concern. Populations of meadowlarks and other farmland birds are diving because of suburban sprawl, industrial development, and the intensification of farming over the past 50 years.

Greater Scaup and other tundra-breeding birds are succumbing to dramatic changes to their breeding habitat as the permafrost melts earlier and more temperate predators move north in a likely response to global warming. Boreal forest birds like the Boreal Chickadee face deforestation from increased insect outbreaks and fire, as well as excessive logging, drilling, and mining.

The one distinction these common species share is the potential to become uncommon unless we all take action to protect them and their habitat. Browse the species and learn what you can do to help. "

IEHO, this is a thing you need to know a lot about before having an opinion as to whether, like 1066 it is good or bad, or neither

Michael Tobis said...

Eli, I have little doubt that there are real issues. I am not taking a position on whether the state of the bird population is good or bad, improving or deteriorating. I am taking a position on how science gets reported.

While I remain surprised by the actual results of the survey I am no expert on the matter and have little to say about it. My point is that I am very disappointed by what is apparently a manipulative approach taken by the Audubon society in representing the results of the study.

They need to explain why the total bird population is apparently increasing, and how likely the proportion of species in decline is to be outside the bounds of (much as I hate to say the dreaded words it's hard for me to avoid) natural variability.

Just because such a story is harder to tell doesn't give them the right to misrepresent by omission the actual results of the actual research.

We can't sensibly decide anything if we are constantly at the mercy of spin doctors.

Adam said...

"They need to explain why the total bird population is apparently increasing"

Is it though? I haven't read it in detail, but I didn't see total numbers listed anywhere except this bit:

"Since 1967 the average population for the common birds in steepest decline has fallen 68 percent, from 17.6 million to 5.35 million."

If the populations for the birds in steepest increase are smaller, then the total population will be in decline.

For instance, in the UK there has been a very successful Red Kite breeding programme that has led them to become quite common in some areas. However that increase is vastly dwarfed by the decline in Starlings. Obviously you'd need to total all the changes for all species to know which way it goes.

Finally, it seems to me that if an organisation that is interested in conservation and species diversity, then they will highlight step declines as they would want to prevent any further decline in those populations. If other species are increasing, nothing needs to be done. The population of birds is not some monolithic entity, in the same way that mammals aren't.

It's a bit like saying why worry about the decline in otters when the population of rats is growing.

Or you could say why worry about X genocide when the population of China in increasing - but that analogy fits less well.

Michael Tobis said...

Adam, "The population for the birds in steepest decline has declined steeply", which is what the statement amounts to, is not a statement about which one should take any alarm.

Is that really surprising? Under what conditions would it be untrue?

If you go to the actual report you will have to read carefully and patiently, rather than superficially and credulously. If you do that, you will see that more species are increasing than decreasing. (Did you do that?)

That is the big news from the report, because it is scientific evidence that is contrary to expectations. What it means is another matter, but it is something we need to think about.

Why hide good news? If birds are increasing we shouldn't go around with a gloomy sense that they are in decline! Can't we use this to say that conservation measures can succeed?

We need to learn (or, if Al Gore is right in his book "Assault on Reason", we need to remember) how to make decisions on evidence, not feelings. Feelings can be manipulated, but evidence is evidence. Anyone manipulating feelings at the expense of evidence is doing the wrong thing.

It is hard for me to see the statement you quote as anything short of manipulating feelings at the expense of reason.

I would be happy if the Audubon Society would at least elaborate on their statements. As it stands the public statements amount to cherry picking not morally different than the Idsos "climate record of the week" which says that the fastest cooling weather stations are not warming, and implies that as a consequence global warming cannot be real.

Selecting data is a central trick of lawyers' science and it is very destructive whether or not you happen to think it is applied in a good cause.

Adam said...

Maybe I didn't explain myself very well, but my quote was to point out the only bit that I found that mentioned actual numbers.

"If you do that, you will see that more species are increasing than decreasing. (Did you do that?)"

Yes I noticed and addressed it in my comment. As I said, that tells us nothing about total bird numbers and even so I think that's a bit irrelevant. So what if there are a few more Eagles if Sparrows become extinct?

As I said, I believe it's a fallacy to lump all birds together as one group. They have different roles within the ecosystem, for one reason. As I said above, it's the same as saying that who cares if otters die out because there's loads more rats around.

I get your point about not mentioning that some species are doing well, but they're probably more bothered about species loss, and think that if you want to help arrest a (to some) fairly alarming decline in the numbers of some species of birds then you ought to highlight the ones in danger of complete collapse?

Michael Tobis said...

Adam, if that was "the only bit you saw that mentioned actual numbers" you were looking at the press release and not the scientific report.

Please get back to me after you look at it.

Adam said...

I've re-read it a bit more carefully now, and I still can't see anything that tells me what the population is say for the Mute Swan now and 40 years ago, thus what the actual population change is. I also can't find the bit that tells us that the actual population of birds is increasing/decreasing/staying the same (more bird species increasing is not the same thing). This may be me missing something obvious.

There is a section on the website ( that's based on Table 10 in the report that does mention actual bird figures (eg Northern Bobwhite has declined by 25.5 million in 40 years), but as they don't do this for all species it's difficult to compare with the actual numbers of those birds that are increasing in numbers.

Also, the report itself states (on P9) that they are interested in species loss: "We are interested in identifying common birds in decline (Table 10)." One assumes that that is because the main effort is to try and halt species decline.

Using the BBS numbers you quote. If all the species listed in the BBS in decline were to die out, that would be nearly one third of the species included (156 / 46).

I guess we'll not agree whether this is the correct way to go about things or not, but it just seems to me that the Audubon Society seem to want to highlight the twenty bird species most adversely affected to try and arrest their decline.