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Hi,
To add to what John has written and leaving aside 'vagrant' birds, individu=
als of many species that are seen in winter in Nova Scotia may be non-migra=
tory residents or they may be migratory individuals from areas to the north=
and northwest of the province. This may be their normal over-wintering are=
a. Bald Eagles in the Sheffield Mills area are a good example of this.
Also, a given species can engage in several migration strategies. Blue Jays=
are known to partake in long range and short range migration as well as ov=
er-wintering.
Of course without human intervention, the ability to find and exploit the l=
imited food options available during a Nova Scotia winter is necessary for =
a species ability to take advantage of the over-wintering option. As John i=
ndicates, a bird may change its strategy, if it's in a condition to do so, =
if environmental factors change during the course of the season. A winter o=
f heavy snow may bury food that is often available to over-wintering, groun=
d foraging birds like White-throated Sparrows. A poor fruit year will limit=
the ability of birds like American Robins to stick around.
All the best,
Lance
Lance Laviolette
Glen Robertson, Ontario
From: naturens-owner@chebucto.ns.ca [mailto:naturens-owner@chebucto.ns.ca] =
On Behalf Of John Kearney
Sent: October 17, 2017 8:16 PM
To: naturens@chebucto.ns.ca
Subject: EXTERNAL: RE: [NatureNS] Nocturnal migration for the 1st Week of O=
ctober
Hi Keith.
Very good questions. Yellow-rumped Warblers are long-distance migrants but =
are interesting because they are known to migrate south not only in the aut=
umn but also in the winter. Studies in New England have shown that Yellow-r=
umped Warblers will move further south in the middle of a severe winter and=
not do so during a mild winter. One therefore has to wonder if Yellow-rump=
s wintering in coastal Nova Scotia die off during a cold snap or depart for=
warmer climes.
There is some evidence from tagging and observational studies that Yellow-r=
umped Warblers don't like to cross large bodies of water. I tend to think t=
he Yellow-rumps that I'm detecting at Cape Forchu recently are a mixture of=
birds that were travelling southwest over Nova Scotia and others that were=
displaced by wind from the west, but in both cases are now heading west-no=
rthwest over the Bay of Fundy.
Indigo Buntings nest not that far from us and could have been driven here b=
y weather from the west or perhaps are young birds exploring new territory =
as this species is undergoing range expansion.
American Robins winter mainly in the southeastern USA from Delaware south. =
The ones that winter here tend to concentrate in coastal areas with good be=
rry crops. Last winter we had a fluky late winter invasion in southwest Nov=
a Scotia of robins that appeared to be from the Delaware region and dropped=
here and on Cape Cod by a weather bomb. These birds seem to have returned =
south again after the event.
Black-capped Chickadees are said to undergo periodic eruptions of juvenile =
birds rather than having true migration. I will detect a few Black-capped C=
hickadees every year in my nocturnal recordings in October. However, one mo=
rning in Antigonish County along the Northumberland Strait I had 800 Chicka=
dees literally fall from the sky around me. They all flew northeast and a f=
ew minutes later came back and flew southwest.
Song Sparrows have migratory populations in the north of their range (like =
Nova Scotia) but have sedentary populations in the southern part of their r=
ange. It is believed our Song Sparrows leap-frog over the sedentary populat=
ions to winter in the southern USA. But obviously there is a sedentary comp=
onent to our population as well.
John
From: naturens-owner@chebucto.ns.ca<mailto:naturens-owner@chebucto.ns.ca> [=
mailto:naturens-owner@chebucto.ns.ca] On Behalf Of Keith Lowe
Sent: October-17-17 16:20
To: naturens@chebucto.ns.ca<mailto:naturens@chebucto.ns.ca>
Subject: RE: [NatureNS] Nocturnal migration for the 1st Week of October
I see a lot of Yellow-rumped Warblers (YRWA) have been pulling out lately.=
Has their even been any studies done on the successfulness of the species =
that only partial migrate? So many YRWA migrate I don't know if is consider=
ed a partial migrant or not. I would guess about 2% give or take of the coa=
stal YRWA from Halifax to Cape Sable stay along with a few stragglers elsew=
here. It would be interesting to know how many actually stay and if the one=
s that over-winter are mostly ours or did they came from further north or t=
he interior. What percentage survives compared to what percentage survive a=
nd return of the ones that migrate?
And ditto for other partial migrates. How many Song Sparrow over-winter? 10=
%? Robbins 2%? Black-capped Chickadees, I hesitate to guess 50%?
John, or anyone else that wants to weigh in, I know most of the birds are o=
utgoing. Were those Indigo Bunting likely incoming? Or overshoots heading b=
ack?
Keith
Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=3D550986> for Window=
s 10
From: John Kearney<mailto:john.kearney@ns.sympatico.ca>
Sent: Tuesday, October 17, 2017 3:21 PM
To: naturens@chebucto.ns.ca<mailto:naturens@chebucto.ns.ca>
Subject: [NatureNS] Nocturnal migration for the 1st Week of October
Hi All,
Nocturnal migration was down again during the 1st week of October at the tw=
o Yarmouth County monitoring sites. Details can be found at these two links=
:
Carleton: http://johnfkearney.com/Carleton_Yarmouth_County_2017.html
Cape Forchu: http://johnfkearney.com/Cape_Forchu_Yarmouth_County_2017.html
The low numbers at both sites suggest that birds are beginning to cross the=
Bay of Fundy rather than make a longer journey across the Gulf of Maine to=
avoid weather conditions such as stronger winds.
Rare or uncommon birds for the week included Indigo Buntings, Field Sparrow=
, and Clay-colored Sparrow.
John
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