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Hi James, Steve, Randy & All, Sept 10, 2014
This is a variation on the theme of predation so mechanisms of =
predation will apply.
And, as noted by Paul L. Herrington (The phenomenon of predation =
Amer. Sci.51(2):180-192, 1963) ""Nature's way is any way that works"". =
In this essay he condensed 60 years of vertebrate predation research to =
12 pages so the original has a high content/fluff ratio. But condensing =
further-- "I regard the outstanding source of error in appraisals of =
predator-prey relationships as confusion of the fact of predation with =
the effect of predation." and "Watch out for compensations in attempting =
to distinguish between what does and does not count."
All sorts of compensating adjustments can kick in but perhaps the =
most direct is reduction of intraspecific competition. With fewer host =
young in a given area, competing for finite resources, their survival =
rate will be increased.=20
But in any case, brood parasitism will tend to cull the offspring of =
potential parents who are less aware and, if this poor awareness has a =
genetic basis then, over many generations, awareness of the host species =
would improve.=20
Yt, Dave Webster, Kentville
----- Original Message -----=20
From: James Churchill=20
To: naturens=20
Sent: Tuesday, September 09, 2014 11:59 AM
Subject: Re: [NatureNS] Brood parasites
hi folks,=20
Here is a recent paper summarizing host defense against cowbird =
parisitism in North America:
HOST DEFENSES AGAINST COWBIRD (MOLOTHRUS SPP.)=20
PARASITISM: IMPLICATIONS FOR COWBIRD MANAGEMENT
Ornithological Monographs, 2005
=
http://www.biosci.missouri.edu/avianecology/courses/avianecology/readings=
/Peer_BD_2005.pdf
Note, this opens a pdf.
cheers,
On Tue, Sep 9, 2014 at 12:38 AM, Stephen Shaw <srshaw@dal.ca> wrote:
An interesting question is why host species at least in some cases =
do not take countermeasures to turf out the egg(s) of the parasite. At =
least in one case, it is not a problem of clever cryptic coloration =
having been used to evade detection. The single cuckoo species we used =
to see in UK often lays an egg in the nest of the hedge sparrow =
(dunnock). The single cuckoo egg is much larger than those of the =
dunnock, is often white with brown spots versus always plain bright blue =
for the dunnock. Some birds, perhaps most, have good colour vision so =
there should be no problem in detecting an alien egg that is also twice =
the size. The newly hatched cuckoo throws out all the dunnock's eggs, =
so the dunnock ends up not rearing any offspring of its own for that =
breeding cycle. This should be a strong evolutionary incentive to =
develop a defense.
Presumably there must be some disadvantage attached to developing a =
simple defense of detecting then removing an alien egg? I could see it =
if the parasite's eggs looked very similar to those of the host -- the =
defending host bird then might remove some of its own eggs by mistake, a =
disadvantage. At least for the UK cuckoo this is not the case: the eggs =
are easily distinguished from those of most host species'.
Is there a plausible explanation for this, and is it a general =
phenomenon? If parasitism of the dunnock by the cuckoo were a very =
recent development, it could be argued that the dunnock has not yet had =
time to evolve countermeasures, but this sounds a bit lame. Have any =
N. American brood parasites (cowbirds?) developed eggs that mimic those =
of their hosts -- is there a general rule for this, where the UK cuckoo =
is an exception? My guess is that 97% of the folk on NatureNS are =
birders of some ilk, so someone out there must have an answer.
As a related afterthought, bird books in the UK in the 50s-60s used =
to describe the nests, eggs and nesting habits of birds, not just their =
plumage. I haven't seen this here in the Sibley, Petersen etc recent =
era in Canada/USA or I could probably have answered the cowbird question =
myself. I presume the main (and valid) reasons are now to discourage =
any interest in egg-collecting or nest-disturbing, by simply not giving =
out any useful information?
Steve (Hfx)
________________________________________
From: naturens-owner@chebucto.ns.ca [naturens-owner@chebucto.ns.ca] =
on behalf of Randy Lauff [randy.lauff@gmail.com]
Sent: Monday, September 8, 2014 2:03 PM
To: NatureNS
Subject: Re: [NatureNS] Brood parasites
Our own Black-billed Cuckoo normally builds its own nest, but will =
sometimes brood parasitize other species.
They avoid wiping themselves out in the same way carnivores do...too =
many carnivores, not enough prey, many carnivores starve, prey rebounds, =
carnivores increase. This is a basic explanation...there's a lot to =
this.
Randy
_________________________________
RF Lauff
Way in the boonies of
Antigonish County, NS.
On 8 September 2014 13:49, Gerald =
<naturens@zdoit.airpost.net<mailto:naturens@zdoit.airpost.net>> wrote:
I hope brood parasites is the correct term for birds that lay their =
eggs
in the nest of a different species.
Are there such parasitic bird species who can also build their own
nests? How do they avoid becoming so successful that they wipe out =
the
hosts and thereby themselves?
--
Gerald
--=20
James Churchill
Kentville, Nova Scotia
jameslchurchill@gmail.com
(902) 681-2374
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2014.0.4765 / Virus Database: 4015/8177 - Release Date: =
09/08/14
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charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META content=3D"text/html; charset=3Diso-8859-1" =
http-equiv=3DContent-Type>
<META name=3DGENERATOR content=3D"MSHTML 8.00.6001.23588">
<STYLE></STYLE>
</HEAD>
<BODY bgColor=3D#ffffff>
<DIV>Hi James, Steve, Randy & All, =
=20
Sept 10, =
2014</DIV>
<DIV> This is a variation on the theme of predation so =
mechanisms of predation will apply.</DIV>
<DIV> </DIV>
<DIV>
<DIV> And, as noted by Paul L. Herrington (The =
phenomenon=20
of predation Amer. Sci.51(2):180-192, 1963) ""Nature's way is any way =
that=20
works"". In this essay he condensed 60 years of vertebrate predation =
research to=20
12 pages so the original has a high content/fluff ratio. But =
condensing=20
further-- "I regard the outstanding source of error in appraisals =
of=20
predator-prey relationships as confusion of the fact of predation with =
the=20
effect of predation." and "Watch out for compensations in attempting to=20
distinguish between what does and does not count."</DIV>
<DIV> </DIV>
<DIV> All sorts of compensating adjustments can kick =
in but=20
perhaps the most direct is reduction of intraspecific competition. With =
fewer=20
host young in a given area, competing for finite resources, their =
survival rate=20
will be increased. </DIV>
<DIV> </DIV>
<DIV> But in any case, brood parasitism will tend to =
cull the=20
offspring of potential parents who are less aware and, if this poor =
awareness=20
has a genetic basis then, over many generations, awareness of the host =
species=20
would improve. </DIV>
<DIV> </DIV>
<DIV>Yt, Dave Webster, Kentville</DIV></DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; =
PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px"=20
dir=3Dltr>
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: =
black"><B>From:</B>=20
<A title=3Djameslchurchill@gmail.com=20
href=3D"mailto:jameslchurchill@gmail.com">James Churchill</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Dnaturens@chebucto.ns.ca=20
href=3D"mailto:naturens@chebucto.ns.ca">naturens</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Tuesday, September 09, =
2014 11:59=20
AM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> Re: [NatureNS] Brood=20
parasites</DIV>
<DIV><BR></DIV>
<DIV dir=3Dltr>hi folks,
<DIV><BR></DIV>
<DIV>Here is a recent paper summarizing host defense against cowbird=20
parisitism in North America:</DIV>
<DIV><BR></DIV>
<DIV>HOST DEFENSES AGAINST COWBIRD (MOLOTHRUS SPP.) <BR>PARASITISM:=20
IMPLICATIONS FOR COWBIRD MANAGEMENT<BR><BR>Ornithological Monographs, =
2005<BR>
<DIV></DIV></DIV>
<DIV><A=20
=
href=3D"http://www.biosci.missouri.edu/avianecology/courses/avianecology/=
readings/Peer_BD_2005.pdf">http://www.biosci.missouri.edu/avianecology/co=
urses/avianecology/readings/Peer_BD_2005.pdf</A><BR></DIV>
<DIV><BR></DIV>
<DIV>Note, this opens a pdf.</DIV>
<DIV><BR></DIV>
<DIV>cheers,</DIV>
<DIV><BR></DIV>
<DIV><BR></DIV>
<DIV><BR></DIV>
<DIV>
<DIV class=3Dgmail_extra><BR>
<DIV class=3Dgmail_quote>On Tue, Sep 9, 2014 at 12:38 AM, Stephen Shaw =
<SPAN=20
dir=3Dltr><<A href=3D"mailto:srshaw@dal.ca"=20
target=3D_blank>srshaw@dal.ca</A>></SPAN> wrote:<BR>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: rgb(204,204,204) 1px solid; MARGIN: 0px 0px 0px =
0.8ex; PADDING-LEFT: 1ex"=20
class=3Dgmail_quote>An interesting question is why host species at =
least in=20
some cases do not take countermeasures to turf out the egg(s) of the =
parasite. At least in one case, it is not a problem of =
clever=20
cryptic coloration having been used to evade detection. The =
single=20
cuckoo species we used to see in UK often lays an egg in the nest of =
the=20
hedge sparrow (dunnock). The single cuckoo egg is much larger =
than=20
those of the dunnock, is often white with brown spots versus always =
plain=20
bright blue for the dunnock. Some birds, perhaps most, have =
good=20
colour vision so there should be no problem in detecting an alien =
egg that=20
is also twice the size. The newly hatched cuckoo throws out =
all the=20
dunnock's eggs, so the dunnock ends up not rearing any offspring of =
its own=20
for that breeding cycle. This should be a strong evolutionary=20
incentive to develop a defense.<BR><BR>Presumably there must be some =
disadvantage attached to developing a simple defense of detecting =
then=20
removing an alien egg? I could see it if the parasite's eggs =
looked=20
very similar to those of the host -- the defending host bird then =
might=20
remove some of its own eggs by mistake, a disadvantage. At =
least for=20
the UK cuckoo this is not the case: the eggs are easily =
distinguished from=20
those of most host species'.<BR><BR>Is there a plausible explanation =
for=20
this, and is it a general phenomenon? If parasitism of the =
dunnock by=20
the cuckoo were a very recent development, it could be argued that =
the=20
dunnock has not yet had time to evolve countermeasures, but this =
sounds a=20
bit lame. Have any N. American brood parasites =
(cowbirds?)=20
developed eggs that mimic those of their hosts -- is there a =
general=20
rule for this, where the UK cuckoo is an exception? My guess =
is that=20
97% of the folk on NatureNS are birders of some ilk, so someone out =
there=20
must have an answer.<BR><BR>As a related afterthought, bird books in =
the UK=20
in the 50s-60s used to describe the nests, eggs and nesting habits =
of birds,=20
not just their plumage. I haven't seen this here in the =
Sibley,=20
Petersen etc recent era in Canada/USA or I could probably have =
answered the=20
cowbird question myself. I presume the main (and valid) =
reasons=20
are now to discourage any interest in egg-collecting or =
nest-disturbing, by=20
simply not giving out any useful information?<BR>Steve=20
(Hfx)<BR>________________________________________<BR>From: <A=20
href=3D"mailto:naturens-owner@chebucto.ns.ca"=20
target=3D_blank>naturens-owner@chebucto.ns.ca</A> [<A=20
href=3D"mailto:naturens-owner@chebucto.ns.ca"=20
target=3D_blank>naturens-owner@chebucto.ns.ca</A>] on behalf of =
Randy Lauff=20
[<A href=3D"mailto:randy.lauff@gmail.com"=20
target=3D_blank>randy.lauff@gmail.com</A>]<BR>Sent: Monday, =
September 8, 2014=20
2:03 PM<BR>To: NatureNS<BR>Subject: Re: [NatureNS] Brood=20
parasites<BR><BR>Our own Black-billed Cuckoo normally builds its own =
nest,=20
but will sometimes brood parasitize other species.<BR><BR>They avoid =
wiping=20
themselves out in the same way carnivores do...too many carnivores, =
not=20
enough prey, many carnivores starve, prey rebounds, carnivores =
increase.=20
This is a basic explanation...there's a lot to=20
this.<BR><BR>Randy<BR><BR>_________________________________<BR>RF=20
Lauff<BR>Way in the boonies of<BR>Antigonish County, NS.<BR><BR>On 8 =
September 2014 13:49, Gerald <<A =
href=3D"mailto:naturens@zdoit.airpost.net"=20
target=3D_blank>naturens@zdoit.airpost.net</A><mailto:<A=20
href=3D"mailto:naturens@zdoit.airpost.net"=20
target=3D_blank>naturens@zdoit.airpost.net</A>>> wrote:<BR>I =
hope brood=20
parasites is the correct term for birds that lay their eggs<BR>in =
the nest=20
of a different species.<BR><BR>Are there such parasitic bird species =
who can=20
also build their own<BR>nests? How do they avoid becoming so =
successful that=20
they wipe out the<BR>hosts and thereby=20
themselves?<BR><BR>--<BR>Gerald<BR><BR></BLOCKQUOTE></DIV><BR><BR =
clear=3Dall>
<DIV><BR></DIV>-- <BR>
<DIV dir=3Dltr>James Churchill<BR>Kentville, Nova Scotia<BR><A=20
href=3D"mailto:jameslchurchill@gmail.com"=20
target=3D_blank>jameslchurchill@gmail.com</A><BR><A=20
href=3D"tel:%28902%29%20681-2374" target=3D_blank =
value=3D"+19026812374">(902)=20
681-2374</A><BR><BR><BR><BR></DIV></DIV></DIV></DIV><A></A>
<P align=3Dleft color=3D"#000000" avgcert??>No virus found in this=20
message.<BR>Checked by AVG - <A=20
href=3D"http://www.avg.com">www.avg.com</A><BR>Version: 2014.0.4765 / =
Virus=20
Database: 4015/8177 - Release Date: =
09/08/14</P></BLOCKQUOTE></BODY></HTML>
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