[TN-Bird] Re: thoughts on Bill Pulliam's BBS data graphs of Wood Duck and Black-throated Green Warbler
- From: "Boves, Than James" <tboves@xxxxxxx>
- To: "littlezz@xxxxxxxxx" <littlezz@xxxxxxxxx>, TN-birds <tn-bird@xxxxxxxxxxxxx>
- Date: Thu, 13 Oct 2011 14:12:55 +0000
Interesting to think about these local patterns in comparison to range-wide
patterns. Are global patterns the same or different to TN changes? How many TN
changes represent range shifts vs. true declines/increases? For instance,
American Redstart has shown no change range-wide (1966 - 2008) vs. Bill found a
65% decline in TN. What do these differences mean?
I've attached a recent paper that summarizes rangewide BBS results from
1966-2010.
Than Boves
Knoxville, TN
________________________________
From: tn-bird-bounce@xxxxxxxxxxxxx [tn-bird-bounce@xxxxxxxxxxxxx] on behalf of
Bill Pulliam [littlezz@xxxxxxxxx]
Sent: Thursday, October 13, 2011 9:05 AM
To: TN-birds
Subject: [TN-Bird] Re: thoughts on Bill Pulliam's BBS data graphs of Wood Duck
and Black-throated Green Warbler
It's interesting to me that the discussion here has been entirely about
declining species, and especially about a species whose decline is already
well-known. Of course the species that are in trouble are a major concern.
But the biggest message I got from the BBS data in total was about the
increases. Raptors have skyrocketed. The non-neotropical migrant forest birds
have increased dramatically as well. The median for all 104 species that had
enough data to give meaningful statewide trends was an increase of 66%. Let's
not forget the good news!
About the declines -- I found some surprises in the list of species that had
dropped sharply. Four of the top five are well known: Bewick's Wren (-100%),
Loggerhead Shrike (-90%), Golden-winged Warbler (-89%), and Northern Bobwhite
(-78%). But nestled among these is also Yellow Warbler at -87%. Nine more
species showed drops of greater than 50%: Common Nighthawk (-78%), Gray
Catbird (-71%), House Sparrow (-70%), American Redstart (-65%), Eastern
Meadowlark (-61%), Northern Flicker (-58%), Common Grackle (-58%),
Whip-poor-will (-52%), and Orchard Oriole (-52%).
And again to keep the context, while 14 species showed drops of greater than
50%, 37 species showed increases of more than 100% (i.e. double). One native
species was almost entirely extirpated (Bewick's Wren), one native species
became a widespread new member of our breeding avifauna (Tree Swallow).
Bill Pulliam
Hohenwald TN
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