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I happen to have purchased a sale copy of Turner and Rose (1989) "Swallows
and Martins of the World" years ago and never had occasion to use it till
now.  I haven't seen the bird yet, but after seeing David Wright's photos
I'd like to share some info from the book.

I understand Kenn Kaufman has suggested the possibility of the southern
South American species White-rumped Swallow, which resembles Mangrove.
I've also seen the names Chilean and Tumbes thrown out there.  First,
"tumbes" or variations of the same does not appear in Turner and Rose's
index, so I can't comment on that one.  Second, this bird is clearly not a
Chilean Swallow, because it has a clear white supraloral line; T&R state
that Chilean can easily be separated from White-rumped (and by implication
from Mangrove) by "lacking the white streaks above the eye."  I would
think this would also eliminate Violet-green (especially in conjunction
with the continuous white rump and upper tail coverts).

Some of David's photos clearly show that the supraloral lines join in a
clear, continuous band above the bill.  For the White-rumped Swallow, T&R
state that these white streaks "...usually meet above the bill."  They do
not make this statement for Mangrove Swallow (but it might be conservative
to consider this omission to be agnostic rather than diagnostic), but they
do state for Mangrove: "The lores are black with a narrow white line above
and a narrow black line below them."  Dark auriculars have been mentioned
and are apparent in the photos.  This would also appear to rule out
Violet-green.

One other consideration is size.  From T&R, it seems that White-rumped
Swallow is about the same size a Tree Swallow, and Mangrove Swallow ought
to be noticeably smaller:

Tree     13 cm; wing 115-119 (female, male);  wt. 20 g (range 16-25)
Wt-rump  13 cm; wing 116 (no sex. dimorph.);  wt. 19 g (17-21)
Mangrove 11 cm; wing 94-97 (female, male);   wt. 14 g (10-16)

I know that David Simpson has commented that the bird did not appear more
"slender" (I don't recall anyone saying the bird was noticeably smaller
than the Tree Swallows--did anyone notice that?).

Brad
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Brad Bergstrom, Ph.D., Professor           TEL  229-333-5770 /-5759
Department of Biology                      FAX  229-245-6585
Valdosta State University                  e-mail: [log in to unmask]
Valdosta, GA 31698-0015                    Home: 229-333-0743
           Home Page-- http://www.valdosta.edu/~bergstrm/
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