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---2114655128-463263766-1347306261=:82586
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Hi Lance and All=0AThere is also the case of Black Ducks where the females =
stop here on their northern=0Amigration to raise broods and the males carry=
on to Labrador, perhaps mating=0Awith other females along the way. The mal=
es will return here in late fall and=0Awere once thought as a different spe=
cies. Northern Redlegs!=0AMallard employ a different pattern and the males =
flock up after the females=0Astart nesting. They will mate with any late br=
eeding females, blacks or mallards=0Athat may be around. Hence the crossbre=
eds.=0AI often wondered about Robins. They are plentiful here in spring=0Aa=
nd early summer, disappear this time of year and return in late fall.=0ALot=
s to learn.=0AEnjoy the rain=0APaul=0A=0A=0A=0A=0A_________________________=
_______=0A From: "Laviolette, Lance (EXP)" <lance.laviolette@lmco.com>=0ATo=
: "naturens@chebucto.ns.ca" <naturens@chebucto.ns.ca> =0ASent: Monday, Sept=
ember 10, 2012 4:29:30 PM=0ASubject: Re: [NatureNS] Intriguing question=0A =
=0A=0AHi James and others,=0A=C2=A0=0AThere are a number of strategies that=
birds use for southern migration. The case mentioned of Ruby-throated Humm=
ingbirds demonstrate the strategy of differences of fall migration timing o=
f adult males from that of and adult females and young, perhaps to reduce c=
ompetition for resources along the route. My observations of migrating adul=
t females and young on Brier Island show that the available resources there=
may be vigorously defended by individual, non-adult males. So while it may=
lessen competition it certainly doesn=E2=80=99t eliminate it. =0A=C2=A0=0A=
For raptors, males and females migrate together in loose associations and t=
heir size differences (females are significantly larger than males) that al=
lows each sex to exploit different sized prey. So rather than a timing diff=
erence it is a physiological difference that may enable the species to bett=
er exploit the available resources.=0A=C2=A0=0AOther examples that I can th=
ink of are Empidonax flycatchers where most adults migrate before young bir=
ds and warblers where there doesn=E2=80=99t appear to be much of a timing d=
ifference bet=0Aween males and females nor probably between adults and youn=
g. However, there may be an age specific difference in migration route sele=
ction or even in the type of migration that takes place. Minimal steps (or =
even a non-stop trip) for adults and multiple steps for young. =0A=C2=A0=0A=
Lastly there are species such as Blue Jays which are known to employ severa=
l different strategies. Some birds will overwinter, some birds will be shor=
t distance migrants and some will be long distance migrants.=0A=C2=A0=0AThe=
risks/rewards you=E2=80=99ve listed in your email are varied and would cer=
tainly provide good explanations as to why these varied strategies evolved.=
=0A=C2=A0=0AAll the best,=0A=C2=A0=0ALance=0A=C2=A0=0AFrom:nat=0Aurens-owne=
r@chebucto.ns.ca [mailto:naturens-owner@chebucto.ns.ca] On Behalf Of James =
Churchill=0ASent: Monday, September 10, 2012 1:49 PM=0ATo: naturens@chebuct=
o.ns.ca=0ASubject: EXTERNAL: Re: [NatureNS] Intriguing question?=0A=C2=A0=
=0AHi folks, =0ASome additional thoughts, from another non-expert, on a nea=
t topic...=0A=0AI'd add that if zugunruhe (loosely, impulse to migrate) and=
migration behaviour are not entirely genetically controlled (which seems t=
o be the case) males and females should be expected to experience different=
selective pressures in terms of timing of migration from breeding grounds =
to wintering grounds related to differences in costs and benefits to males =
and females of leaving vs. staying. =0A=0AThis might differ based on things=
such as the distance between breeding and wintering grounds, seasonality o=
f risk (food availability, climate/weather pattern=0As, predator abundance/=
distribution etc), mating system (as Chris and Rick allude to) physiologica=
l and/or genetic constraints and environmental/social conditions experience=
d on wintering grounds. I would guess, that these factors should also lead =
to differences in the relative timing between males and females among speci=
es but also among m/f of the same species in different geographic locations=
(i.e., no population-level selection; but perhaps depends on definition of=
'population').=0A=0ASince ruby-throats are polygamous, and males are repor=
ted as not providing parental care, there could be significant fitness bene=
fit to males of sticking around so they could achieve additional fertilizat=
ions with late-breeding or re-nesting females (not sure if there is any evi=
dence of this for hummingbirds?). But perhaps the potential benefit of this=
is outweighed by other factors such as resource availability during migrat=
ion, securing a good wintering territory, or physiological constraints.=0A=
=0Acheers, =0AJames. <=0Abr>
---2114655128-463263766-1347306261=:82586
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<html><body><div style=3D"color:#000; background-color:#fff; font-family:ti=
mes new roman, new york, times, serif;font-size:12pt"><div><span>Hi Lance a=
nd All</span></div><div style=3D"color: rgb(0, 0, 0); font-size: 16px; font=
-family: 'times new roman', 'new york', times, serif; background-color: tra=
nsparent; font-style: normal; "><span>There is also the case of Black Ducks=
where the females stop here on their northern</span></div><div style=3D"co=
lor: rgb(0, 0, 0); font-size: 16px; font-family: 'times new roman', 'new yo=
rk', times, serif; background-color: transparent; font-style: normal; "><sp=
an>migration to raise broods and the males carry on to Labrador, perhaps ma=
ting</span></div><div style=3D"color: rgb(0, 0, 0); font-size: 16px; font-f=
amily: 'times new roman', 'new york', times, serif; background-color: trans=
parent; font-style: normal; "><span>with other females along the way. The m=
ales will return here in late fall and</span></div><div style=3D"color: rgb=
(0,
0, 0); font-size: 16px; font-family: 'times new roman', 'new york', times,=
serif; background-color: transparent; font-style: normal; "><span>were onc=
e thought as a different species. Northern Redlegs!</span></div><div style=
=3D"color: rgb(0, 0, 0); font-size: 16px; font-family: 'times new roman', '=
new york', times, serif; background-color: transparent; font-style: normal;=
"><span>Mallard employ a different pattern and the males flock up after th=
e females</span></div><div style=3D"color: rgb(0, 0, 0); font-size: 16px; f=
ont-family: 'times new roman', 'new york', times, serif; background-color: =
transparent; font-style: normal; "><span>start nesting. They will mate with=
any late breeding females, blacks or mallards</span></div><div style=3D"co=
lor: rgb(0, 0, 0); font-size: 16px; font-family: 'times new roman', 'new yo=
rk', times, serif; background-color: transparent; font-style: normal; "><sp=
an>that may be around. Hence the crossbreeds.</span></div><div
style=3D"color: rgb(0, 0, 0); font-size: 16px; font-family: 'times new rom=
an', 'new york', times, serif; background-color: transparent; font-style: n=
ormal; "><span>I often wondered about Robins. They are plentiful here in sp=
ring</span></div><div style=3D"color: rgb(0, 0, 0); font-size: 16px; font-f=
amily: 'times new roman', 'new york', times, serif; background-color: trans=
parent; font-style: normal; "><span>and early summer, disappear this time o=
f year and return in late fall.</span></div><div style=3D"color: rgb(0, 0, =
0); font-size: 16px; font-family: 'times new roman', 'new york', times, ser=
if; background-color: transparent; font-style: normal; "><span>Lots to lear=
n.</span></div><div style=3D"color: rgb(0, 0, 0); font-size: 16px; font-fam=
ily: 'times new roman', 'new york', times, serif; background-color: transpa=
rent; font-style: normal; "><span>Enjoy the rain</span></div><div style=3D"=
color: rgb(0, 0, 0); font-size: 16px; font-family: 'times new roman', 'new
york', times, serif; background-color: transparent; font-style: normal; ">=
<span>Paul</span></div><div style=3D"color: rgb(0, 0, 0); font-size: 16px; =
font-family: 'times new roman', 'new york', times, serif; background-color:=
transparent; font-style: normal; "><span><br></span></div><div style=3D"co=
lor: rgb(0, 0, 0); font-size: 16px; font-family: 'times new roman', 'new yo=
rk', times, serif; background-color: transparent; font-style: normal; "><sp=
an><br></span></div><div><br></div> <div style=3D"font-family: 'times new =
roman', 'new york', times, serif; font-size: 12pt; "> <div style=3D"font-fa=
mily: 'times new roman', 'new york', times, serif; font-size: 12pt; "> <div=
dir=3D"ltr"> <font size=3D"2" face=3D"Arial"> <hr size=3D"1"> <b><span st=
yle=3D"font-weight:bold;">From:</span></b> "Laviolette, Lance (EXP)" <la=
nce.laviolette@lmco.com><br> <b><span style=3D"font-weight: bold;">To:</=
span></b> "naturens@chebucto.ns.ca" <naturens@chebucto.ns.ca> <br> <b=
><span
style=3D"font-weight: bold;">Sent:</span></b> Monday, September 10, 2012 4=
:29:30 PM<br> <b><span style=3D"font-weight: bold;">Subject:</span></b> Re:=
[NatureNS] Intriguing question<br> </font> </div> <br><meta http-equiv=3D"=
x-dns-prefetch-control" content=3D"off"><div id=3D"yiv296906609"><style><!-=
-=0A#yiv296906609 =0A _filtered #yiv296906609 {font-family:Calibri;panose-=
1:2 15 5 2 2 2 4 3 2 4;}=0A _filtered #yiv296906609 {font-family:Tahoma;pan=
ose-1:2 11 6 4 3 5 4 4 2 4;}=0A#yiv296906609 =0A#yiv296906609 p.yiv2969066=
09MsoNormal, #yiv296906609 li.yiv296906609MsoNormal, #yiv296906609 div.yiv2=
96906609MsoNormal=0A=09{margin:0in;margin-bottom:.0001pt;font-size:12.0pt;f=
ont-family:"Times New Roman", "serif";}=0A#yiv296906609 a:link, #yiv2969066=
09 span.yiv296906609MsoHyperlink=0A=09{color:blue;text-decoration:underline=
;}=0A#yiv296906609 a:visited, #yiv296906609 span.yiv296906609MsoHyperlinkFo=
llowed=0A=09{color:purple;text-decoration:underline;}=0A#yiv296906609 span.=
yiv296906609EmailStyle17=0A=09{font-family:"Calibri", "sans-serif";color:#1=
F497D;}=0A#yiv296906609 .yiv296906609MsoChpDefault=0A=09{}=0A _filtered #yi=
v296906609 {margin:1.0in 1.0in 1.0in 1.0in;}=0A#yiv296906609 div.yiv2969066=
09WordSection1=0A=09{}=0A--></style><div><div class=3D"yiv296906609WordSect=
ion1"><div class=3D"yiv296906609MsoNormal"><span style=3D"font-size: 11pt; =
font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Hi James and o=
thers,</span></div><div class=3D"yiv296906609MsoNormal"><span style=3D"font=
-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> =
</span></div><div class=3D"yiv296906609MsoNormal"><span style=3D"font=
-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">T=
here are a number of strategies that birds use for southern migration. The =
case mentioned of Ruby-throated Hummingbirds demonstrate the strategy of di=
fferences of fall migration timing of adult males from that of and adult fe=
males and young, perhaps to reduce competition for resources along the rout=
e. My observations of migrating adult females and young on Brier Island sho=
w that the available resources there may be vigorously defended by individu=
al, non-adult males. So while it
may lessen competition it certainly doesn=E2=80=99t eliminate it.=0A</span=
></div><div class=3D"yiv296906609MsoNormal"><span style=3D"font-size: 11pt;=
font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span=
></div><div class=3D"yiv296906609MsoNormal"><span style=3D"font-size: 11pt;=
font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">For raptors, =
males and females migrate together in loose associations and their size dif=
ferences (females are significantly larger than males) that allows each sex=
to exploit different sized prey. So rather than a timing difference it is =
a physiological difference that may enable the species to better exploit th=
e available resources.</span></div><div class=3D"yiv296906609MsoNormal"><sp=
an style=3D"font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(3=
1, 73, 125); "> </span></div><div class=3D"yiv296906609MsoNormal"><sp=
an style=3D"font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(3=
1, 73, 125); ">Other examples that I can think of are <i>Empidonax</i>
flycatchers where most adults migrate before young birds and warblers wher=
e there doesn=E2=80=99t appear to be much of a timing difference bet=0Aween=
males and females nor probably between adults and young. However, there ma=
y be an age specific difference in migration route selection or even in the=
type of migration that takes place. Minimal steps (or even a non-stop trip=
) for adults and multiple steps for young. </span></div><div class=3D"yiv29=
6906609MsoNormal"><span style=3D"font-size: 11pt; font-family: Calibri, san=
s-serif; color: rgb(31, 73, 125); "> </span></div><div class=3D"yiv29=
6906609MsoNormal"><span style=3D"font-size: 11pt; font-family: Calibri, san=
s-serif; color: rgb(31, 73, 125); ">Lastly there are species such as Blue J=
ays which are known to employ several different strategies. Some birds will=
overwinter, some birds will be short distance migrants and some will be lo=
ng distance migrants.</span></div><div class=3D"yiv296906609MsoNormal"><spa=
n style=3D"font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31=
, 73, 125); "> </span></div><div class=3D"yiv296906609MsoNormal"><spa=
n
style=3D"font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31,=
73, 125); ">The risks/rewards you=E2=80=99ve listed in your=0A email are v=
aried and would certainly provide good explanations as to why these varied =
strategies evolved.</span></div><div class=3D"yiv296906609MsoNormal"><span =
style=3D"font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, =
73, 125); "> </span></div><div class=3D"yiv296906609MsoNormal"><span =
style=3D"font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, =
73, 125); ">All the best,</span></div><div class=3D"yiv296906609MsoNormal">=
<span style=3D"font-size: 11pt; font-family: Calibri, sans-serif; color: rg=
b(31, 73, 125); "> </span></div><div class=3D"yiv296906609MsoNormal">=
<span style=3D"font-size: 11pt; font-family: Calibri, sans-serif; color: rg=
b(31, 73, 125); ">Lance</span></div><div class=3D"yiv296906609MsoNormal"><s=
pan style=3D"font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(=
31, 73, 125); "> </span></div><div style=3D"border:none;border-top:so=
lid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in;"><div
class=3D"yiv296906609MsoNormal"><b><span style=3D"font-size: 10pt; font-fa=
mily: Tahoma, sans-serif; ">From:</span></b><span style=3D"font-size: 10pt;=
font-family: Tahoma, sans-serif; "> nat=0Aurens-owner@chebucto.ns.ca [mail=
to:naturens-owner@chebucto.ns.ca] <b>On Behalf Of </b>James Churchill<br><b=
>Sent:</b> Monday, September 10, 2012 1:49 PM<br><b>To:</b> naturens@chebuc=
to.ns.ca<br><b>Subject:</b> EXTERNAL: Re: [NatureNS] Intriguing question?</=
span></div></div><div class=3D"yiv296906609MsoNormal"> </div><div cla=
ss=3D"yiv296906609MsoNormal" style=3D"margin-bottom:12.0pt;">Hi folks, <br>=
Some additional thoughts, from another non-expert, on a neat topic...<br><b=
r>I'd add that if zugunruhe (loosely, impulse to migrate) and migration beh=
aviour are not entirely genetically controlled (which seems to be the case)=
males and females should be expected to experience different selective pre=
ssures in terms of timing of migration from breeding grounds to wintering g=
rounds related to differences in costs and benefits to males and females of=
leaving vs. staying. <br><br>This might differ based on things such as the=
distance between breeding and wintering
grounds, seasonality of risk (food availability, climate/weather pattern=
=0As, predator abundance/distribution etc), mating system (as Chris and Ric=
k allude to) physiological and/or genetic constraints and environmental/soc=
ial conditions experienced on wintering grounds. I would guess, that these =
factors should also lead to differences in the relative timing between male=
s and females among species but also among m/f of the same species in diffe=
rent geographic locations (i.e., no population-level selection; but perhaps=
depends on definition of 'population').<br><br>Since ruby-throats are poly=
gamous, and males are reported as not providing parental care, there could =
be significant fitness benefit to males of sticking around so they could ac=
hieve additional fertilizations with late-breeding or re-nesting females (n=
ot sure if there is any evidence of this for hummingbirds?). But perhaps th=
e potential benefit of this is outweighed by other factors such as resource=
availability during migration, securing a good wintering territory, or
physiological constraints.<br><br>cheers, <br>James. <=0Abr><br><br>=
</div></div></div> =0A=0A</div><meta http-equiv=3D"x-dns-prefetch-control" =
content=3D"on"><br><br> </div> </div> </div></body></html>
---2114655128-463263766-1347306261=:82586--
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