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Just to clarify my earlier statement on this subject, I don=E2=80=99t =
doubt that birds carry the Hemlock Woolley Adelgid or the Black-legged =
Tick. Rather, I am suggesting that this fact doesn=E2=80=99t explain why =
infestations occur in some places and not in others. Spring bird =
migration occurs over a broad front in the northeast and all areas =
should be equally or more affected than Nova Scotia by bird transports.
=20
Both the Bay-breasted and Blackburnian Warbler cross the Gulf of Mexico =
in spring. The most concentrated spring migration occurs in the Ohio =
River Valley and much of the St. Lawrence River Valley. Since the winter =
range of the Blue-headed Vireo extends into the southeastern United =
States, its spring distribution is somewhat more eastward oriented and =
concentrated through the Appalachians, Maine, Maritimes and southern =
Quebec.
=20
You might be interested, Donna, in this paper that was published just =
last week: Toenies, M. J., D. A. W. Miller, M. R. Marshall and G. E. =
Stauffer. 2018. "Shifts in vegetation and avian community structure =
following the decline of a foundational forest species, the eastern =
hemlock." The Condor 120(3): 489-506. I hope such studies have begun in =
Nova Scotia, and we should try to see that such studies are initiated if =
they haven=E2=80=99t been already.
=20
John
=20
=20
From: naturens-owner@chebucto.ns.ca <naturens-owner@chebucto.ns.ca> On =
Behalf Of Donna Crossland
Sent: Sunday, June 17, 2018 20:09
To: naturens@chebucto.ns.ca
Subject: Re: [NatureNS] Lyme disease
=20
It's worthwhile questioning the ability of spring migrants to spread =
insects, such as the hemlock woolly adelgid (HWA). Invariably it's us =
humans who are the direct/indirect original vectors of introduction (and =
this is the case with HWA as well). I am interested to learn more about =
the spring migration routes of species such as Bay-breasted and =
Blackburnian warblers, as well as Blue headed vireo, and other high =
canopy gleaners of insects in hemlock stands. =20
I understand that HWA has been migrating more or less steadily toward =
northern Maine over the past decades, slowed somewhat by some of the =
colder winters. Everything points to it reaching there eventually. =
Since the pest consists of "all females", HWA needs only one new =
individual to start a whole new population. (We can only hope this =
could lead to part of its vulnerability.) =20
HWA needs to actually land on hemlock. I am not certain that NB has a =
lot of hemlock at the border, but it likely features much less than it =
once did, given the species sensitivity to fire, land clearance and =
clearcuts. (My research in eastern NB indicated a precipitous decline =
in expansive hemlock-dominated stands beginning in the early 1800s.) =
There may be much less hemlock to become infested with HWA in NB than in =
southwestern NS where some impressive hemlock stands remain. Other =
plausible theories for HWA dispersal vectors to NS were from high wind =
events and nursery stock. Birds seemed more likely to me, especially =
given the extremely small size of HWA and its ability to stick fast to =
feathers.
It's heart wrenching to watch.
Donna Crossland
=20
On 2018-06-15 8:07 AM, John Kearney wrote:
Hi David and all,
That=E2=80=99s a very good question. I=E2=80=99ve heard the same reason =
given for why we have the Hemlock Woolley Adelgid in Nova Scotia but not =
in northern Maine and New Brunswick. I=E2=80=99m not aware of any =
evidence indicating that more spring migrants fly to Nova Scotia than =
Maine or New Brunswick.
John
=20
From: <mailto:naturens-owner@chebucto.ns.ca> =
naturens-owner@chebucto.ns.ca <mailto:naturens-owner@chebucto.ns.ca> =
<naturens-owner@chebucto.ns.ca> On Behalf Of David
Sent: Thursday, June 14, 2018 17:10
To: <mailto:naturens@chebucto.ns.ca> naturens@chebucto.ns.ca
Subject: [NatureNS] Lyme disease
=20
Dear All,
In the July issue of Maclean's (p.17) are interesting data on Lyme =
disease incidence in Canada. The much higher incidence in NS, 21.5 times =
as high as the average incidence in the other nine provinces, is =
attributed to "climate and the large number of migratory birds carrying =
ticks from the US."
I don't follow why NS would be hit the hardest.
Yt, DW
=20
=20
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