Thank you Christopher for the links.
I agree that the curve on your link is compressed horizontally but it shows the 
same pattern I described before. Even the curve of each specific habitat is 
showing this pattern.
Look at (fig 1, A and B) on page 12 from the full study and you will see that 
each habitat has the U shaped curve (or reversed bell shape). The Boreal 
Forest's curve, for example, becomes completely flat in the last few years.
Birds numbers' decline should be more severe in the last couple of decades when 
the enveronmental changes are more severe.  On the contrary, the decline 
recently becomes less steeped than in the early stages of the study when the 
conditions were more favorable.
It would be interesting to know why this paradox is happening.
I am suggesting the presence of other factors that play role here. For example, 
birds might have some ability to adjust to adverse conditions in order to 
survive and thrive. Finidng the answer could provide help in the fight to save 

Sent using Zoho Mail

 ---- On Mon, 23 Sep 2019 10:51:04 -0400 Christopher T. Tessaglia-Hymes 
<> wrote ----
 > Hi Shai and Gus,
 > Here’s a link to the 2019 State of the Birds: 
 > At the above link, the front page shows a graph depicting the actual data 
 > from 1970 to present. The x-axis is compressed relative to the one appearing 
 > in Living Bird and the online graphic 
 > (, so the curve in 
 > the State of the Birds report appears to have a sharper decline; although, 
 > there was a minor increase about a decade ago, which helped level out the 
 > line. Also of note, the y-axis depicts thepopulation change (in billions of 
 > birds) by way of negative values.
 > The full Science article is below, although, I’m not certain if those 
 > outside of a university setting will have full access:
 > Hope these links are helpful.
 > Sincerely,Chris T-H
 > On Sep 22, 2019, at 1:12 PM, Shaibal Mitra <> 
 > wrote:
 > Hi Gus,
 > I really think it's just an artifact of the way the figure was made, and not 
 > something with a complicated biological explanation. To me it looks like a 
 > simple function that illustrates the entire estimated decline from 10 to 7, 
 > as though the current population size was the end point. In other words, the 
 > graphic looks like the exponential loss of 3 billion birds, starting with 
 > all of the 3 billion birds that used to exist, to the zero of those birds 
 > that remain today.
 > Shai
 > _______________________________________
 > From: Gus Keri []
 > Sent: Sunday, September 22, 2019 12:35 PM
 > To: Shaibal Mitra
 > Subject: RE: [nysbirds-l] Fwd: News Alert: North America has lost 29% of its 
 > birds since 1970, study finds. Experts blame habitat loss, pesticides, light 
 > pollution and cats.
 > Hi Shaibal,
 > I took into consideration the possibility of exponential  decline but it 
 > didn't look like that.
 > If you calculate the decline in relation to the absolute number of birds at 
 > the beginning of each decade, the difference is more remarkable.
 > Here is the percentage of decline for each decade alone:
 > By the end of the 70s: 12%
 > By the end of the 80s: 9%
 > By the end of the 90s: 7%
 > BY the end if the 2000s: 4%
 > By now: 1-2%
 > I don't know if birds are finding a way to adjust with all the environmental 
 > changes that are taking place, or there are other factors involved.
 > Sent using Zoho Mail
 > ---- On Sun, 22 Sep 2019 12:01:35 -0400 Shaibal Mitra 
 > <> wrote ----
 > Hi Gus and all,
 > The curve in the link has the shape characteristic of exponential decline at 
 > a constant rate. It has the properties you describe, with the amount of 
 > absolute loss diminishing in the recent years, because the population itself 
 > is getting smaller all the time. I suspect that this graphic is not to be 
 > taken literally but instead is a simple, fitted function meant to express 
 > the overall rate of loss that was estimated over these decades.
 > Best,
 > Shai
 > ________________________________________
 > From: 
 > [] on behalf of Gus Keri 
 > []
 > Sent: Saturday, September 21, 2019 6:57 PM
 > To: Anne Swaim
 > Cc: NYSBIRDS-L-for posts posts; Birding alert, ebirdsNYC, Birding alert
 > Subject: Re: [nysbirds-l] Fwd: News Alert: North America has lost 29% of its 
 > birds since 1970, study finds. Experts blame habitat loss, pesticides, light 
 > pollution and cats.
 > The shape of the curve on the graphic in the above article is very 
 > intriguing to me. It starts with a steep decline in the first couple of 
 > decades and plateaued toward the last few years.
 > The curve suggests that more than 75% of birds losses happened in the first 
 > 25 years (betwween 1970 and 1995) and less than 25% of the losses took place 
 > in the last 25 years(from 1995 to present).
 > The fact that habitat loss, climate changes and other adverse environmental 
 > changes are worse in the last 25 years compared to the previous period 
 > suggests other factors are at play to slow down the decline of the total 
 > population.
 > Does anyone have any explanation for this contradiction?
 > Sent using Zoho Mail
 > ---- On Fri, 20 Sep 2019 07:18:43 -0400 Anne Swaim <> 
 > wrote ----
 > The unformatted PDF version of the study is now openly linked on Cornell 
 > Lab's website 
 > here:
 >  also linked from accompanying Living Birds article 
 > here:
 > Anne SwaimSaw Mill River
 > On Thu, Sep 19, 2019 at 9:29 PM Anne Swaim <> wrote:
 > Further on this topic: someone just passed along a PDF of full text of the 
 > study.
 > Reply off list, if a copy would be of interest.
 > Anne SwaimSaw Mill River
 > --Christopher T. Tessaglia-Hymes
 > Field Applications Engineer
 > Center for Conservation Bioacoustics, Cornell Lab of Ornithology
 > 159 Sapsucker Woods Road, Ithaca, New York 14850
 > W: 607-254-2418   M: 607-351-5740   F: 607-254-1132
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