Date: 9/22/19 10:12 am From: Shaibal Mitra <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.
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.
From: Gus Keri [<guskeri...>]
Sent: Sunday, September 22, 2019 12:35 PM
To: Shaibal Mitra
Cc: NYSBIRDS (<NYSBIRDS-L...>)
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.
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.