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Index of Subjects --089e0115ea2eed641c0502a3307f Content-Type: text/plain; charset=ISO-8859-1 hi folks, Here is a recent paper summarizing host defense against cowbird parisitism in North America: HOST DEFENSES AGAINST COWBIRD (MOLOTHRUS SPP.) 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 > > -- James Churchill Kentville, Nova Scotia jameslchurchill@gmail.com (902) 681-2374 --089e0115ea2eed641c0502a3307f Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable <div dir=3D"ltr">hi folks,=A0<div><br></div><div>Here is a recent paper sum= marizing host defense against cowbird parisitism in North America:</div><di= v><br></div><div>HOST DEFENSES AGAINST COWBIRD (MOLOTHRUS SPP.) <br>PARASIT= ISM: IMPLICATIONS FOR COWBIRD MANAGEMENT<br><br>Ornithological Monographs, = 2005<br><div> </div></div><div><a href=3D"http://www.biosci.missouri.edu/a= vianecology/courses/avianecology/readings/Peer_BD_2005.pdf">http://www.bios= ci.missouri.edu/avianecology/courses/avianecology/readings/Peer_BD_2005.pdf= </a><br></div><div><br></div><div>Note, this opens a pdf.</div><div><br></d= iv><div>cheers,</div><div><br></div><div><br></div><div><br></div><div><div= class=3D"gmail_extra"><br><div class=3D"gmail_quote">On Tue, Sep 9, 2014 a= t 12:38 AM, Stephen Shaw <span dir=3D"ltr"><<a href=3D"mailto:srshaw@dal= .ca" target=3D"_blank">srshaw@dal.ca</a>></span> wrote:<br><blockquote c= lass=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left-width:1p= x;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1= ex">An interesting question is why host species at least in some cases do n= ot take countermeasures to turf out the egg(s) of the parasite.=A0 =A0At le= ast in one case, it is not a problem of clever cryptic coloration having be= en used to evade detection.=A0 The single cuckoo species we used to see in = UK often lays an egg in the nest of the hedge sparrow (dunnock).=A0 The sin= gle cuckoo egg is much larger than those of the dunnock, is often white wit= h brown spots versus always plain bright blue for the dunnock.=A0 Some bird= s, perhaps most, have good colour vision so there should be no problem in d= etecting an alien egg that is also twice the size.=A0 The newly hatched cuc= koo throws out all the dunnock's eggs, so the dunnock ends up not reari= ng any offspring of its own for that breeding cycle.=A0 This should be a st= rong evolutionary incentive to develop a defense.<br> <br> Presumably there must be some disadvantage attached to developing a simple = defense of detecting then removing an alien egg?=A0 I could see it