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Why Cowbirds Lay Eggs In Other Birds’ Nests
Posted on Tuesday, May 24, 2011 by eNature
Eastern Phoebe nest with Brown-headed Cowbird egg
Eastern Phoebe nest with Brown-headed Cowbird egg
© Galawebdesign

After reading a recent blog entry about brood parasitism in cliff swallows, a number of readers wanted to know more about the well-known sort of brood parasitism practiced by cowbirds.

If a vote were taken tomorrow to find the most popular bird in the country, it’s doubtful that the cowbird would win. That’s because the cowbird has the nasty habit of laying its eggs in other birds’ nests.

It all started back in the days when American Bison ruled the Great Plains. At that time a rather nondescript grayish or black bird followed the herds around, feeding on seeds in the abundant supply of buffalo excrement. Settlers on the plains came to calling these animals buffalo birds.

But since the birds depended on wandering herds for food, they needed to wander as well if they wanted to survive.

The problem, of course, is that wandering birds can’t tend their nests. So the buffalo birds decided to leave their young in the care of other birds, an arrangement that seemed to work, at least from the buffalo birds’ perspective.

Then, during the 1800s, the prairies and buffalo disappeared, replaced by pasture and cattle. But the birds remained and started keeping company with cows instead of buffalo, eating insects in the grass, ticks on the livestock, and seeds and grain. The buffalo bird eventually became known as the cowbird.

Today there are two native cowbird species in North America, the Bronzed Cowbird of the Southwest and the Brown-headed Cowbird common in most of the United States and Canada. Both species still lay their eggs in the nests of other birds, which is to say that both maintain the parasitic tradition of their ancestors, much to the dismay of bird lovers and conservationists.

The main reason people find the cowbirds’ behavior objectionable is that it threatens biodiversity.

Cowbirds as a whole lay their eggs in the nests of more than 200 other species of birds. And in most cases, because these birds tend to be smaller species, the young cowbirds come to dominate the nests, pushing out the other young or hoarding the food. The result is that the two cowbird species thrive at the expense of hundreds of others.

More about the Brown-headed Cowbird »

More about the Bronzed Cowbird »

Cliff Swallows practics brood parasitism in a different way. »



Do cowbirds imprint on “adoptive” parents? How do they know they’re cowbirds? Is this a case of nature over nurture in cowbirds? Just wondering ...

Posted by Cath on 5/24

My husband and I HATE these things.  Several yrs ago, we embarked on our own personal cowbird eradication program—-even though it seems to be an illegal activity, thanks to an outdated law that is still in place.  At any rate, we kept up with the # that we killed each year, starting with 64 the first year and decreasing each year until for the last 3 years we have only briefly seen 2 or 3 on our place.  As a result, the population of warblers, wood thrushes, vireos, and cuckoos has just exploded around.  It is truly an etheral experience at first light when they all begin to sing.  I hope someone in our govt. will wake up and see what a detrimental effect these parasites are having on our wonderful songbird populations and allow us to legally blast the suckers to kingdom come!

Posted by Carolyn on 5/24

I know they come in ~ in spring and there are dozens of them , a real pain ! I’ve worked very hard on getting an area for the Blue Birds,Orioles ,blue Jays and such . When these cowbirds come in the food is gone in hours , and I have 7 feeders out so its bothering to see this . I didn’t know how destructive they were with laying eggs in others nest - - what a shame ! Guess I’ll have to correct this problem if I want to keep the normal birds coming back !

Posted by Ronald on 5/25

I abswolutely hate these birds!  I have tried to find a food they don’t like, and frankly I don’t think there is one.  I chase them from my feeders as soon as I see them.  The other birds are learning I’m only chasing the cowbirds, and they no longer fly off.  Wish I could absolutely get rid of them in my yard for good.  Any suggestions?

Posted by Suzanne on 5/25

Bird haters? Really? Don’t they deserve to live? They can’t help their behavior, they are born that way.I can’t believe the one person that was bragging about how many cowbirds they have killed.You people need to get a grip and stop hating Gods creatures.

Posted by Stacie on 5/25

I agree with Stacie. The cowbirds habits are out of survival instinct.

Posted by Cheryl on 5/25

When I first started feeding and watching the birds we had a nest in one of my hanging baskets. My husband and I could not figure out why one of the young ones was so much bigger than the others. I then discovered the story of the cowbirds. How many times I wish I could have someone else take care of my brood…lol (I really do love my children and would not have given them away at anytime) I enjoy all of the birds that come to my yard and enjoy telling the story of the cowbirds. I find nature exciting and truly enjoy all of the little facts as I learn about them.

Posted by Lil on 5/25

These birds will thrive in a field and field edge habitat.  The real problem is that human “development” had broken up deep woods habitats, where the warblers and song birds would normally live, into small sections of woodlands so the cowbirds have access to the nest of the songbirds all around the edges and into the woods. If you are living in a habitat that was once woods or fields you have invaded the habitat of the songbirds before the cowbirds.

Posted by megan on 5/25

This is definitely a controversial issue. I agree with Stacie and Cheryl in that we should respect the cowbirds, but we should not allow them to run rampant. I believe that we should use controlled killing, so that they do not force some species of endangered birds into extinction.

Posted by LeeAnne on 5/25

I agree with Stacie… people need to get a grip!  Stay out of nature.  It has a way of taking care of itself.  Man only messes it up.  Look at the Asian beetle problem we now have because someone decided that God wasn’t doing a good enough job.  Animals take care of themselves a lot better than man does.  Eventually something in nature will come along to ease the problem of these parasitic birds.

Posted by Sue on 5/25

Another thing to keep in mind is the Migratory bird Act of 1918. This act prohibits doing just about anything to a bird listed. The cow bird is listed.

Posted by Cheryl on 5/25

These birds are created as are other living creatures - they just want to eat, have their babies and live.  They are sentient beings - which should be enough protection but if not - there is a LAW.

Posted by Jan on 5/26

It’s ridiculous to ‘hate’ a bird species for following its genetic imperative. Cow Birds are as legitimate a part of nature’s interconnected strategies as any other bird species.  They just do what they’ve evolved to do. The greater threat to other birds and biodiversity in general is habitat loss, pollution, climatic disruption… all human induced threats. Humans are the ones who ‘run rampant’ over nature, yet some have the gall to judge birds in a sort of popularity contest. We need to respect nature’s intricate and interesting mechanisms for survival and not read our own rapacious behavior into other species.

Posted by k green on 5/26

Stacie!  How about cockroaches?  Don’t they deserve to live?
After all, they are only doing what nature demands.  So, Stacie,  next time you see a cockroach,  be sweet!

Posted by Joe Davajon on 5/26

We have too many starlings, do cow birds like to leave eggs in their nests? They are an introduced spieces not natives of north america.

Posted by lyndad on 5/26

It seems to me that when the European settlers wiped out the bison for sport and hides, they upset the natural balance of the prairies.  The ripple effect of this is that some displaced species (cowbirds) are now wiping out other species.  Regardless of whether we “love” or “hate” cowbirds or bluebirds or song sparrows, we have an obligation to do our best to restore the balance that existed before our forefathers did their damage, and do it based on careful study and on the best - albeit imperfect -  knowledge we have and as humanely as possible.

Posted by Marianne on 5/26

I bet Carolyn you would stand in line with the people who shoot, poison, and trap wolves and Grizzly Bears. Its the mentality that if it is not in your realm that if it doesnt fit into your standards of how things should be Lets Kill It. They are just doing what genetic predisposition tells them to do. I agree get a grip, get a life and let things be.  I certainly wouldnt brag about it.

Posted by Kathleen Finch on 5/26

I agree that those who express rage at cowbirds, and want to eradicate them in a fury, are unjustifiably anthropomorphizing them by imposing a characterization of malevolent motives on the birds’ *natural* behavior. Cowbirds are a *native* species, and have co-existed in North America with all the other native species here for countless millennia.

But I also think that those persons who piously proclaim that we should simply trust in nature, that our actions can only make things worse, and that we should never harm any of “God’s creatures,” are indulging in a naïveté that incorrectly fantasizes that inaction will render themselves pure and blameless.

As other writers have noted, European settlement has enormously changed the ecology of North America. Before Europeans arrived, most of the birds that cowbirds were in contact with, and whose nests they parasitized, had evolved *with* cowbirds, and had natural defenses to this brood parasite. (Their possession of such defenses is obvious from the fact that those birds hadn’t gone extinct.)

It is, however, a huge problem that modern settlement of this continent has vastly expanded the cowbirds’ range, and put them in contact with many birds that are not adapted to them, with devastating consequences for those species. (Kirtland’s warbler is one of the prime examples.) Those who sanctimoniously maintain that we must not interfere with nature, and must not harm its creatures, are arguing from a faulty premise. We *have* interfered with nature—already, and for centuries.

And inaction now does NOT mean we are doing no harm. By exposing to cowbird parasitism, bird species that are not adapted to dealing with it, we are harming those other birds, as surely as if we were going around and throttling their nestlings.

I think some control of cowbirds is necessary to protect certain species of birds. It’s done legally, for example, on the Michigan breeding grounds of Kirtland’s warbler. Nevertheless, it’s also true that cowbirds are a protected species under the Migratory Bird Treaty Act of 1918 (16 U.S.C. §§ 703 through 712). So if individuals kill cowbirds, or remove their eggs from nests, without special federal authorization, they’re breaking the law, and running the risk of federal prosecution.


Cath astutely asked whether cowbirds nestlings imprint on their host parents, and how they eventually know that they’re cowbirds. The answer is that they do *not* mature to think that they are warblers, cardinals, or whatever their host was. Once they leave the nest, they quickly start keeping the company of other cowbirds, and seek other cowbirds as mates.

But although the mechanism of *how* they “know” that they’re cowbirds has been the subject of considerable research, there’s still no consensus on what that mechanism is.

Posted by Brian Urban on 5/26

The BHC is a real threat to the existence of other bird species.

In response to the assertions of BHC natural behavior, these birds are one of the primary reasons the Golden-cheeked Warbler and the Black-capped Vireo are endangered, and, other neotropical passerines are so diminished in numbers.

I’ve been part of USFWS programs to eliminate the cowbird threat to endangered Golden-cheeked Warblers and Black-capped Vireos.  I suspect one would NOT be prosecuted for offing these birds.

Where endangered species are threatened there are ways to eliminate cowbirds. They may deserve to live, but that doesn’t give them the right to eliminate three or four other eggs or fledges of the natural parent bird.

Habitat fragmentation is the reason they are so bad. The BHC is an edge species.  The problem is that much of our woodlands
have edges that meet in the middle. Thus there’s few place safe left for other birds.

I’ve found here in Texas that BHCs like millet. Remove that and you may not see as many.  But you may lose your painted Buntings and other buntings as well.

i’m pretty sure BHC won’t eat black oil sunflower seeds. Or Milo.

Can we refrain from the asinine aspersions and ad hominems please?

Posted by Tim Jones on 5/26

Brian, That is very well said and well thought out. I agree with you for the most part. Control of the cowbird should be “contoled” by those with the knowledge of where they are doing damage. For example, several years ago we had problems with black headed vultures killing newborn calves. Yes, the Black Headed Vulture will kill live prey, the Turkey Vulture will not. We were almost to the point of contacting the Game Warden for a control, but something in the environment changed and the problem ceased and we did not have to go that route.

This seems to be a hot topic ..... <grin>


Posted by Cheryl on 5/26

As there are neither rights or wrongs in the natural world such concepts are irrelevant to any discussion of the cowbird’s behaviour.

Posted by Cornelius J. McHugh on 5/26

As our population expanded for agriculture and living space the woodlands of the U.S. have been broken up into small disconnected sections to where these open land birds have more perimeter access to the woodland song bird species. Since we will never see the expansive woodlands as in the past, to correct this situation, something else must be done to save our other birds. Being it is a federally protected species temporary permit tags could be issued to shoot a specific number of cowbirds to reduce the population without decimating them.

Posted by John on 5/26

Too many comments to read. so someone may have already said this, but having cattle at one time, these birds are a blessing. That’s all I can say. I no longer have cattle and live in the sub of Ohio, I dont see these guys anywhere in the subs.

Posted by Jen on 5/26

oh yeah… and during the time we had cattle I had a veggie and flower gardens. I had ever bird that was from this area. The cowbird did it’s job and the other birds came to the gardens.

And one suggestion I have on feeding birds, plant gardens. Dont feed them in the warm weather. They dont need it then, they need it in the winter.

Posted by jen on 5/26

Brian and Tim; Excellent, thoughtful, and accurate responses. I live and work with a federal land agency in the Minnesota Northwoods and BHC are not a problem in large, intact forests. However, outside of large, public forests urban and rural sprawl along with numerous other cumulative effects such as expanding cell phone towers, wind farms, winter range deforestation and irresponsible cat owners to name a few, are taking their toll on our neo trops including the black throated blue, baybreasted and cerulean warblers. If society values conservation of rare species, which they do, management actions such as BHC localized control is necessary. The issue is about populations and not individuals. If the BHC were a threatened species and robins were a primary cause of their demise, I’d be an advocate of robin control.

By the way Carolyn, what methods did you find most effective in reducing your local population?

Posted by Bruce on 5/26

I have lived in GA since 2003,love birds and have 12 bird feeders and numerous bird houses.  I have counted 42 different species of birds on my deck and in my back yard including the cowbird.  As far as their eating habits go, they eat right beside my other birds. The only birds that chase off the others and eat all the food are the Grakles and one Mocking Bird, he thinks he is king. But the birds have learned to send one in to distract the Mocking Bird while another goes in to eat. The Grakles come in, in huge flocks.  As far as the cowbirds laying their eggs in others nests, I must have pretty smart birds, because they just push the cowbirds eggs out. Sooo it seems to me that nature can protect itself. As mad as I get at the Grakles, I have never even thought of killing them.  God created these birds as he did you. And has given them the knowledge needed to survive just as he has you and me.  And he is STILL the ONE and ONLY GOD.

Posted by Katheryn P on 5/26

Why am I always incensed by the venom spewed by self-styled “environmentalists” against those who know and explain?

Y’all, anger achieves nothing.  Understanding and response in accordance with reality is what is required.  If you are furious that man’s “encroachment” on the “natural order of things” has disturbed the status quo—venting your fury does no good, none at all. In fact, it does harm; it alienates those who might have otherwise joined the cause.

Brian Urban’s explanation is on point.  Now, if you have a possible, realistic (emphasis on that word) solution/correction/alteration to propose, state it.  Otherwise, your irrationality harms the cause.

While we’re at it:  Every species seeks to enhance its existence, survival, and success, albeit at the expense of others.  The only species that consciously worries about retaining or restoring a balance is man.  So, if you really just want to ascribe blame for species exitinction:  It began well before man was the dominant species.  More species have gone exitinct through natural competition than others than exist today, and man had nothing to to with that.  Is man’s behavious today accelerating that process?  Probably.  Is it not in the Earth’s best interest to continue that?  Define your terms.  Is it natural?  Well, as loath as you may be to hear this:  It is.  We behave like every other species:  Compete for personal and species survival, at any expense to others.

Now is it in man’s best interest to interfere with that natural process?  That is a matter of faith, not science.  Man’s best interest, independent of nature’s balance or lack thereof, would be best served by contolling man’s overpopulation of the Earth.  Not “encouraging”, but literally “controlling.”  Indeed, I would hazard the guess that the optimum herd size for mankind, worldwide, is about 10% of what it is today.

And you are going to achieve that how?  Destroy all antibiotics, reintroduce man’s “predators”—such as smallpox, bubonic plague?  Or regulate births, forcing any without permission of the herd who become pregnant to abort?

Face it.  Recycling, restoring nature’s balance, minimizing greenhouse gas emissions, reducing dependence on fossil fuels—all those actions are treating the disease while the pandemic rages on.

Until you are ready to subscribe to reality, all those activities serve only to satisfy your desire to believe that you are “doing something.”  In reality, you’re just serving to satisfy your need to feel you are making a difference, to feel good personally. 

In short, you are just jerking off.

Posted by Gary on 5/26

Megan hit the nail on the head.

Posted by Lisa on 5/26

OK so I read more… I totally agree with Megan (above) about WE are the ones that are screwing things up. We took and are taking their world away from them and many other creatures. I myself seen harmony among these birds and other birds.

I lived in the country on 300 acres. I discovered more birds from the garden than ever at a feeder!

To this day, I still have gardens to attract birds and NO feeders. Plan a natural garden for your area for all seasons, you’ll be surprised at all the different birds that come together and each bird has it’s reasons to be there.

Put one food out there… then you got a fight between species!
You’re just asking for it.

Posted by jen on 5/26

Thank you Brian Urban.  I hereby pronounce you Brian Wilderness!  You have helped clarify a tricky issue of cow bird parasitism. In any case…are we humans not also parasites?

Posted by Evelyn on 5/26

Some people talk too much. When you live it yourself then you should speak. Are you one that is a diseased person?

Posted by jen on 5/26

I’m glad that Katheryn has taken such interest in her yard birds, and has observed them and their behaviors so carefully. In the course of this, she has observed that birds nesting in or near her yard push cowbird eggs out of their nests. If she read the previous posts, she knows that ornithologists have long been aware that some bird species have behaviors that defend against cowbird parasitism.

Other birds, however, do not. Those that do *not* are birds that, prior to European settlement, had ranges or habitats that coincided little or not at all with those of the cowbird.

A bird species’ ability to defend its nest against cowbird parasitism has nothing to do with the application of intelligence—the mental assessment of a novel situation and the devising of a solution. It is a matter of behaviors that are innate to some species, and not to others, irrespective of problem-solving intelligence.

Katheryn says that “it seems to [her] that nature can protect itself.” Can nature protect itself from the damage caused by modern industrial society? Had humans not intervened in the Michigan nesting territory of the Kirtland’s warbler to suppress the population of brown-headed cowbirds (which had not existed in great numbers in that area prior to European settlement), and to cultivate the specialized habitat (stands of jack pines between 5 and 20 years old) required by nesting Kirtland’s warblers, the bird might well now be extinct, or on the brink of extinction. In this case, the assertion, “nature can protect itself,” is utterly unpersuasive.

By the same token, did God give the Kirtland’s warbler “the knowledge [it] needed to survive”? One may make the argument that God did give the bird what it needed—in its original ecology. But that’s not the relevant question, if we’re interested in the survival of the species into the future. The evidence is clear that God did not give the Kirtland’s warbler the knowledge it needs to survive, unaided by humans, in an ecology drastically altered by modern society.

These warblers do not have behaviors that enable them to defend their nests effectively against cowbird parasitism. Before federal wildlife authorities commenced cowbird suppression programs on the Kirtland’s warbler nesting grounds some 40 years ago, 75% or more of the nestlings that the warblers were fledging out of their nests were *cowbirds*.

The evidence is unequivocal that the warblers would not survive unaided by humans. And *that* is much more compelling than a belief—indifferent to facts gathered through objective observation, but based instead on dogmatic faith—that because God made this animal, its survival requires no action from us.

Kirtland’s warbler presents a drastic case of harm to a species by cowbird parasitism. But it is not the only one. Other species are being seriously undermined by the expansion of cowbird range and habitat. (Not starlings; they’re cavity nesters, and cowbirds parasitize cup-type nests out in the open.)

This is not the cowbird’s “fault”; they’re functioning in their natural habitat, behaving in their natural way. Humans, and modern industrial society, have created these problems. But an awareness of those facts does not logically compel a conclusion that we must never ever try to do anything to mitigate the damage that we have caused, to protect a vulnerable species against another one that threatens its survival, to prevent the destruction of the diversity of the natural world.

These are difficult, complex issues. But that’s no reason to refrain from grappling with them. Solutions may not come easily, nor always feel completely satisfactory. But we are more likely to address these problems effectively if we apply our God-given intelligence, than if we are complacently satisfied with faith-based platitudes.

Posted by Brian Urban on 5/26

I mistyped:  Treating the “symptoms” while the pandemic/disease rages on.  jen, read it again:  The disease isn’t personal; it’s endemic to mankind as a species.

Evelyn:  “parasite” as used here could be dependent upon your perspective.  Every carnivore could be categorized as a “parasite” by its prey.  But that’s not the dictionary definition.  A parasite lives in/on the body of its host and draws nourishment therefrom physically, not metaphorically, harming the host in the process.  If no harm is caused, it probably is closer to symbiotic but is not parasitic.  Pilot fish live in the company of sharks, live off the shark’s leavings, but are not attached to the shark and cause it no harm and therefore are not parasites.  Remora attach themselves to the shark but are symbiotic with it.

In the case of cowbirds and their eggs . . . not sure what the etymologically correct term is, but I don’t think it’s “parasite”.

Posted by Gary on 5/26

The description of cowbirds as “brood parasites” is conventional among ornithologists. (See <>.) I’m satisfied that it’s technically accurate.

The word “parasite” carries normative baggage in general usage. But ornithologists’ use of the word to describe cowbirds’ nesting behavior implies no value judgment.

Posted by Brian Urban on 5/26

I absolutely hate those people who hate birds.  One year my wife and I decided that anybody who killed a bird (other than for food) should also die. 

Our first year we killed 36 adolescents (35 boys and 1 girl) who got bb guns over the holidays and 16 adults who didn’t like birds.  After 10-15 years the songbird population exploded.

You see, by killing the majority of our towns young males the human population decreased.  By killing the humans, that needed to keep so many cattle, which helped the cowbird thrive, we naturally eradicated the source of the cowbirds food source. 

This is of course all jest as I have never murdered anybody… but Carolyn does belong in jail.

Posted by Ray on 5/26

My God what is wrong NOW!! The cowbirds I have act no different or eat no more than ALL of the other birds I have that come to my feeders daily! In fact they actually have a beautiful song and a really neat mating dance that they do!! I have 17 other species that come every day too and they don’t have as near a pretty song and I sure don’t see them doing mating dances! ALL BIRDS HAVE A PECKING ORDER. The Cardinal will run the smaller birds like the Finches and Sparrows off. The Bluejay will run the Cardinal off and so on, but to this day I still have never seen a Cowbird be agressive or run even the smaller birds off!!!

Posted by Debbra on 5/27

Joe, you can’t compare a bird to a cockroach not only are they completely different animals but the one is also a disease carrier that invades our homes. I do believe Stacie is right on about these birds and Marianne is also right about mans role in the events that have taken place to cause these birds to migrate and adapt as they have. These birds are also eating a lot of harmfull insects as do most all other birds so why would anyone want to just kill them and why hate them? Birds are a joy to watch and their antics can at times be thrilling.

Posted by Yelta on 5/27

Oh man did I stir up a hornet’s nest!  I want to thank Brian Urban for your most excellent explanation and insights on the problems with allowing the BHC to run rampant in areas where some species have no defense against them.  Also, I would like to thank Tim Jones, John (hunting tags) and Bruce for being voices of reason.  The BHC is not indigenous to the eastern deciduous woodlands where I live and when I see a flock of 30 to 50 of them in a pasture about 2 miles from my home, I can’t help but think about all the little vireo, wood thrush and warbler babies that will never enter the world because of their parents’ broods being parasitized by the BHC.  Oh, and BTW, I’ve decided that I don’t hate the actual bird, it is what the BHC is doing to so many of our indigenous species that I find so distressing.

I also realize that we humans are responsible for the BHC invasion, but that doesn’t mean that we should just say, “woe is me”, or make excuses like, “they’re God’s creatures”, or “they’re just doing what is natural to them”, and do nothing to try to protect our threatened native species.  All these threatened indigenous species of the eastern deciduous woodlands are “God’s creatures”, too, so are we to just allow an overpopulation of a non-native species to wipe them out?  I personally love John’s idea of the temporary hunting tags or season for controlling the BHC and would love to know where and how to go about obtaining a permit.

In response to Bruce, the BHC only comes into our woods in early spring when the neotropicals are just beginning to nest.  We bait them on the ground with small seeds and shoot them from the kitchen window using a 22 rifle with a scope.  If there are mulitples on the ground, we shoot the females first in case they are already a fertilized egg repository.  It has been tremendously successful.  We have been so surprised at the explosion of our woodland bird population since we embarked upon this project.  We had never even seen or heard a white-eyed vireo until we began to eliminate the BHC from our immediate area.  And yes, we know that it is illegal according to the almost 100 year old Migratory Bird Act that was enacted before the BHC began to threaten our indigenous species, but we feel that we have to do something, even if it is only in our little corner of the world.  Oh, and Ryan, if I do have to go to jail, it will be because I shot some poor misguided pseudo environmetal do-gooder who would obviously rather deprive future generations of the joy and magic of a wood thrush song than have the courage to take steps to control a non-native bird whose overpopulated presence threatens their very existence.

And yes, Gary, it absolutely does make me feel great to wake up to the nothing short of joyous,  miraculous songs of numerous vireos, wood thrushes, and warblers that I know have been able to do “what nature intended for them to do” and raise their own babies instead of a brood-parasite imposter.  Do some of you “OMG, she’s killing birds” people even know what our threatened species look or sound like?  They don’t just show up at feeders, you have to look for them, usually with binocs or a spotting scope.  I for one am not willing to deprive my grandchildren of the priviledge of seeing and hearing our native birds in their natural habitat rather than some zoo’s aviary by being misinformed, squeamish, or just plain foolish.

And in response to Kathleen, I happen to like wolves, grizzlies, and all manner of wildlife and might be tempted to shoot at any human that is shooting at them.  We live in big-time hunting country, and my husband doesn’t even hunt.

When we built our home in the middle of these blessed woods, we went to great pains and extra expense to leave the forest intact and share this space with what God put here before us.  I feel it is my responsibility as a steward of His gift to maintain this little area as the sanctuary for woodland birds that it has always been.

Posted by Carolyn on 5/27

EXCELLENT points and perspectives, Megan and Gary!
It’s ironic how, even in ecology and conservation circles, NO ONE wants to address the looming problem of human overpopulation. Every time I see a male cowbird chasing a yellow warbler away from its nest, I’m reminded of how *I* chased away so many species from their homes when I built mine.  :(

Posted by Kathryn on 5/27

I was reminded by a plant friend, what is a weed? A plant that grows where MAN does not want it to. I guess Cowbirds are in that same category.

Posted by Lee on 5/27

Thank you both, Brian and Carolyn for teaching more about cow birds than I ever thought there was to know. and thank you Ray for being so funny. All these comments bring home a central theme for guiding human behavior - consume less.

Posted by Evelyn on 5/27

Cowbirds didn’t “decide” to leave their eggs in other birds’ nests.  I think you meant to say, those cowbirds that practiced parasitism thrived to reproduce better than those that reared their own chicks.  It’s an evolutionary adaptation, whether we humans like it or not.

Posted by David on 5/27


Well put. We humans tend to anthropomorphize animal behavior.  That’s an error.  Animals don’t analyze and then make rational decisions.  They just do what works, without wondering about why it does.  And if their environment has changed faster than the natural speed of their ability to adapt —it doesn’t, and they become extinct.

Interesting exercise:  Can you think about an idea, an event, an expectation, a behaviour, a response, without thinking in “language”, without thinking in words?  We’re the only species that does so.  (As far as I know. . .)  Even the cleverest “Seeing Eye” guide dogs don’t think, “Oops, that awning support is too low, I’ll take my master around it.”  But they do do it, even in situations for which they were not explicitly trained.  How they do so has always fascinated me.

So for the cowbirds.  What they did when they followed bison migration just happens to work even better with confined cattle herds. 

Which does not mean that we who changed their environment should not attempt to adjust the imbalance that resulted.  Go, Carolyn!  Leave a few, though, just go for balance, don’t go for extinction.

Posted by Gary on 5/27

It must have been the bit about jerking off.

Posted by Cornelius J. McHugh on 5/27

Eat the cowbird! They taste really good with orange-raisin or orange currant dressing. Yummy, especially the breast and legs.

This is not a joke or a prank. I discovered the tastes of many small birds growing up at the southern end of the great plains. Cowbird and blackbird are my favorites.

Of course they don’t compare favorably to the larger migratory game birds but they are good to eat.

Posted by Dr. Electro on 5/27

It seems as if some here may need to go back and take Biology 101.  I was able to take a Bio class that taught about population densities and the delicate balance of populations of both predators and prey. 

The students were able to play with a computer program that allowed the user to adjust the predator and prey population numbers.  For example, you could enter “200” rabbits and 6 wolves for a location.  Once these numbers were entered it would run through a simulation of population growth over time.  In most of these instances, the populations eventually became eradicated. 

If you start with too many wolves, they kill off all the prey, have no food, then die.  No more rabbits, no more wolves.

If you start with too few wolves, there is a huge population growth of the wolf population because of over abundance of food.  This leads to overpopulation of wolves which kill off all the prey.  The wolves then have no food and die.  No more rabbits, no more wolves. 

While the predator/prey relationship is not exactly the same here, I suspect that something similar could happen when you have some misinformed backyard birder trying to wage a 2 man war against the BHC on their.  I am not against the controlling of a population providing it is something organized and planned, like hunting tags. 

Carolyn writes “Oh, and Ryan, if I do have to go to jail, it will be because I shot some poor misguided pseudo environmetal do-gooder who would obviously rather deprive future generations of the joy and magic of a wood thrush song than have the courage to take steps to control a non-native bird whose overpopulated presence threatens their very existence.”

Well Carolyn, everything about that statement proves that you don’t have your facts straight.  My name is Ray, not Ryan.  Had you taken the time to re-read you would have known this.  There is a law against shooting this bird.  You should be in jail now as you have already broken the law, not because you are going to kill someone.  What future generations are going to benefit from your 2 man war?  Have you appointed a person to continue to keep the BHC population in check when you die or is their population going to explode as a result of your misinformed decisions to take the law into your own hands?  Perhaps Gary, who applauds your efforts, will set up a sanctuary on your land and hire people to continue your efforts?

Posted by Ray on 5/28

assuming the story as correct how broodparacitism can b explained in other birds which are many.for example koel from india.we do not know origin of its habit.can anybody throw light?

Posted by digambar gadgil on 5/28

The gal killing the cowbirds is kinda like ethnic cleansing… weird. Can’t believe a human being could possibly think that’s the right thing to do???? I mean, who put you in charge of altering Nature? wow - what a jerk. Hopefully you won’t decide your neighbor is too close and start taking care of them!

On another note:  I’m in the Eastern part ofthe country and the cowbirds are not so much a problem as groups of crows, grackles, and their ilk.  Safflower is a tremendous help in keeping so many from your yards and feeders.  It’s a high fat seed, so good for the birds. It has a different taste to the birds, so when switching over to it there is a good deal of scattering to the ground and then it’ll settle down once they realize it’s the only seed being offered. BTW it needs to be the only seed out there - do not mix it with other seeds. You can continue to feed the American Goldfinch with “thistle” (industry name is Nyjer*) as they won’t bother that, nor were the squirrels.

To the gal who said not to feed the birds in warm weather:  birds will always eat bugs and natural first before coming to a feeder.  Having a feeder
up guarantees bug control in your gardens, as well as safety for all the nesting birds in terms of not needing to go far for food. Seed from feeders is only 20% of a birds diet.

Posted by Grace on 5/28

We have Cowbirds too, I’ve found feeding my other birds close to my house near my windows keep the Cowbirds from the feeders. My cats know to leave my birds at the feeders alone. But they also know I allow them to have the Crackels & Cowbirds, because they’re more of them. Don’t ask me how my cats know what I’m telling them, they just know. & they eat & feed them to their kittens. I also have sucksion cup feeders for the Hummingbirds on the windows too.

Posted by Lois on 5/28

On second thoughts, it is more likely to have been my reference to $adistic $arah.

Posted by Cornelius J. McHugh on 5/28

We can’t just go around and kill whatever animals we don’t like.  Especially since we are the ones who are getting rid of their habitat.  How would it be if humans acted that way?

Posted by C J on 5/28

Really Carolyn.. You don’t like these birds so you KILL them????? Unbelievable!! What kind of a person are you? I wish I were your neighbor, you can bet that I would make sure you paid for your actions. You and your husband are disgusting human beings. God help you.

Posted by Jeanne on 5/28

I apoligize, I love nature also, but I’ve planted 2 new trees last year & 5 this year. Give to Arbor Day Foundation, have vegetation for Butterflies, & birds. I’m a Birder & my Pine Trees & Cedar Trees are full of Birds in my area. I feed & water year round both my pets, & the birds that come to my feeders at my windows, & trees. I don’t kill anything, but my cats know not to bother my birds at feeders & waters. However I say nothing to them about the Cowbirds & Crackles, there 100’s of them & they only catch one if it’s in the garden in the yard. The Crackles do however rule the Pine Tree every year, I do love watching them build nests. They are loud, but they soon all leave & the song birds are heard again. The Mourning Doves also like that very large double Pine Tree. The cats don’t bother those Doves or Northern Mockingbirds. Those don’t come to the feeders. They do like the Misters I have out for all the birds. The horses, cows & Peacock come to that also on the outside of the fence of my yard. I live outside city limits 10 miles from town.

Posted by Lois on 5/28

Lois, I wasn’t responding to you, I was responding to “Carolyn” who along with her husband, shoot these birds.
I understand that cats will kill birds. I don’t like it, but it is a fact of life.
You mentioned the cats feeding the birds to their kittens…don’t you get your cats spayed/neutered? It’s very important because there is a problem with cat overpopulation. If these cats are strictly outdoor cats, they still should be neutered. T.N.R is term used for trap/neuter/return. Stray cats are trapped and neutered and then allowed to roam freely.
check out

Posted by Jeanne on 5/29

Jeanne, Thanks for your Info. My son has a feed lot & all his friends have cattle also so they take those that don’t stay with me to control their feed barns of snakes & mice. I’ve never had too many cats, in fact some times I’ve too few. I also have family & friends that know others that want them for pets. We vac. all yearly as our newphew is a Vet. & he’s here reguarly to check them for their needs. & for those that go to the barns when he checks our sons cattle & his friends too. Our exterminator takes care of other pests, but not my caterpillers or butterflies,or hornets(my birds love hornets, I’ve videoed a F.Summer Tanger clear out a nest of some that had a nest in one of my bird houses, she did it one at a time) I strictly watch for him to not bother their habitat. I really care about what happens in my world, but my world starts where I am & where ever I am. When I can help, if it’s in my power, I do it, one thing at a time & then move to another, it works for me. I have no problem that doesn’t get solved, as I ponder it at all angles & try to make a choice that want hurt me or what’s around me. I don’t expect others to agree. I just know what I like & what I’ve allergies to. I can’t have poison ivy or scorpoing (cats also control the scorpoins) in my yard or home. & about the Cowbirds, watch if you can how the Bird family takes care of all their little ones, they don’t care if one is different, & he/she doesn’t care they are different, they’re just happy they are together until they part there ways to go make their own families. Thanks again, I listen to advice & is another angle before choices. Oh, yes our Vet. nephew has neutered, I didn’t like his choice on my dinning room table. He only did it once, I made sure from then on I went to the clinic. You are a very smart & caring person!!! Thanks Again!!

Posted by Lois on 5/30

Carolyn is doing the right thing.

When man has upset an ecology so that a natural species balance is destroyed and there is no prospect of restoring that ecology—we will not bring back thundering herds of migrating bison—the best that can be done is to use “other means” to maintain balance.  Almost invaruably that means “managing the population” of one or more species, and that management—it’s called that, and not as a euphimism, but as an accurate description of the goal of the process—involves death, since we can’t prevent births among the runaway species.

This is an issue I have with those who would simply demand that “nature” be “restored.”  In rare situations—such as wetlands compromised by prior generations who believed that swamps were useless and ugly and converting them to “nice” was a boon—the injured ecology actually can be restored, albeit at a very hich cost.  But that is not generally available.

After being anti-gun and essentially anti-hunting (“you kill Bambi?!?”) for most of my life, I lived in Montana for five years.  I learned that my earlier attitudes were prejudices—I had pre-judged with neiher knowledge nor experience.  Montana hunting is not an “open season.”  Every person wishing to hunt must get a permit that is specific, by species, sex, location and months—from a pool of permits constructed exactly each year, from game census, to maintain a healthy population given the wild lands that remain and the man-influenced proportionality among those species.  It works.  It’s honest—the permits are issued by lottery, they cannot be sold or given as gifts or transferred except within the immediate family.  Even the Governor would have to win one in that lottery.  And it works.

Re hunters:  Almost every Montanan I met—right or quite far left, owned multiple guns.  Many were simply part of their collection, like others collect motorcycles or postage stamps.  Those that were used to hunt only rarely were involved in trophy kills; the vast majority of the hunting weapon families hunted for the pot.  (I knew one family that told me they hadn’t bought red meat in twenty years.  Not a single trophy on the walls.  Gave me an elk temderloin.  Yum!!!  Beef is now boring.)

So, rebalanacing nature?  Wolves were reintroduced in Montana and are doing well.  I had one harrowing midnight; just as I was falling asleep, a pack not more the 40’ from my window howled.  I went traight up!  They are loud!  And it was chilling!  The reason they were there was that deer were constantly trying to find breaks in the fence surrounding my formal garden—all those yummy flowers—so the deer scent was highest on those paths around my fence.

OK, then, death by wolves; classic as nature’s way of maintaining the deer population.  Would you increase the wolves further, reduce man’s involment?  Can’t.  Wolves pull down the weak, and there are few weaker than a young calf; there goes ranching as an industry.  Eve more germane:  Why should the wolf be able to hunt for food, as his species has always done—and not man, who has done it even longer? 

And it is inhumane!  A deer surrounded by a wolf pack is helpless.  The wolves start to eat as soon as she is down—without waiting for her to die, just ripping at the soft parts.  Given that deer must die to maintain a population that the vegetation can support . . . personally, I’d prefer a quick bullet by man than being eaten by wolves.  I found a deer with a broken back—cause unknown—outside the fence one evening, and knew her fate.  I’m not a hunter, but I did what was needed.

Don’t introducee wolves OR allow hunting?  Death by startvation.  The main difference between that and the wolves is that it initially doesn’t hurt as much, but it eventually does, and lasts a lot longer.  By the end of a colder winter, when all the easy food is gone . . . I’ve stood an arm’s length away from a buck in late spring, his new antlers not yet full and still in velvet, as he was stripping bark from a bush for nourishment, for there was nothing else available (this was in Shenandoah NP, not Montana), he was so hungry and desparate for nourishment I could have touched him and he would not have stopped.

In summary:  Most ecological changes wrought by man cannot be undone.  The best we can do—and the morally correct thing to do, if you are one that cares about such stuff—is to provide the natuaral species population regulation that our changes destroyed.  And, almost invariably, that involves killing. 

To close with a cliche, to you nature lovers who are too squeamish to deal with that reality—stay out of the kitchen, let others deal with the heat—but, please, stop denigrating those willing to take the hard but correct road.  They practice rather than preach, and what they do is necessary and effective.  Praise them.

Posted by Gary on 5/30

Gary, laws are there for a reason. Carolyn is breaking the law. Just because “you” think so, it doesn’t mean Carolyn is doing the right thing.

Posted by Jeanne on 5/30

I’m feeding pigeons. Not a cowbird in sight.

Posted by Dr. Electro on 5/30

Sorry Gary, I guess everything I learned while getting a degree in Animal Science was wrong and your and Carolyn are correct.  I see I was wrong in posting my earlier comment on population control because you lived in Montana for 5 years.  Those 5 years definitely trump all documentation about Biology, research done on animal population densities, and the many years of work done by those who have devoted their lives to studying nature. 

To restate my argument in more basic terms: It is OK to have human intervention as it was human intervention that caused the problem.  Without humans now helping populations survive, many more species would be extinct as a result of our expansion. 

It is NOT, however, OK intervene in an unorganized fashion.  A married couple going taking the law into their own hands and eradicating a population of birds from their area is not a viable means to population management.  The problem with doing so is the unknown outcome of their actions.  Who is going to manage the BHC population when Carolyn goes blind and cant hit her target or when she dies?  Is the BHC population going to explode when she dies? 

If you believe there is a problem with the current system: develop a plan, organize an action, petition change.

If you feel the BHC is that big of a problem, contact some of those who have devoted their lives to Ornithology.  Get in touch with the people who run this website or the Cornell Lab of Ornithology.  Let them know of your plan to kill BHCs and see if you can get support.

Posted by Ray on 5/30

Nice one Ray. Big thumbs up.

Posted by Cornelius J. McHugh on 5/30

I used to have cowbirds at my lake house in WC OH.  One time I removed a large egg from a finch nest in my porch wreath. I had no qualms at all doing it. For some reason the cowbirds have moved on.
House sparrows are a menace to other birds,too, especially bluebirds.  My son is a ranger with the Army Corps of Engineers and one of his jobs is to check bluebird boxes at his park and clean out any sparrow nests he finds.  These nasty birds come in and build their messy nests over the top of bluebird nests after pitching out any eggs or babies already there.  In many areas the bluebirds are endangered because of this.

Posted by Kathie on 5/31

Apropos of Kathie’s post: Cowbirds and house sparrows (sometimes called “English sparrows”)—and starlings, as well—present threats to other birds, but the ecological and legal issues presented by these various species are not the same.

House sparrows (“HOSPs”) and starlings are invasive, exotic species introduced to North American by humans in the last 150 years or so. They are alien to the New World ecosystem.

Cowbirds, as has been discussed exhaustively in this thread, are native to North America. European settlement of North America has, however, drastically changed the continent’s ecosystem, opening up vast new areas as habitat more favorable to cowbirds, and thus newly exposing many species of birds to cowbirds’ brood-parasite reproductive behavior. Some of those species have proven particularly vulnerable to cowbirds’ use of their nests, and their populations have greatly suffered as a result.

HOSPs (and starlings and rock pigeons) are not protected by federal law (nor are their nests or eggs), because they are non-native species.

Cowbirds *are* a native species, and they and their eggs are protected by federal law.

I don’t propose that this end any conversation. We should, however, make the correct distinctions, lest the conversation veer off into comparing apples and oranges.

Posted by Brian Urban on 5/31

Brian’s last comment opens a different question and points out the difference between what is legal and what is logically correct.  The threat that unfettered reproduction by invasive species represents to native species is accepted as real, in law and in science.  The question then is, what is the correct response—independent of the legal issues—when an ecological change (man made or not—nature comes with its own cruel changes) results in a single native species presenting the same level of threat to the other native species within the same ecology?

I simply maintain that the “best” man can do is to pursue restoring balance, on the presumption that that balance existed successfully for millenia until man changed the ground rules and, therefore, that balance is desired.  (Which can also be argued; for this thesis, accept it as axiomatic, please.)  To do so, man should use the most efficacious methods.  If that means plinking with a .22, so be it—with the full understanding that many are offended whenever anyone fires a weapon at any living creature independent of motive or goal, and also with the understanding that that action is contrary to law. 

Which suggests that the law should provide for exceptional circumstances, and that such circumstances exist in this instance, else this thread would not exist . . .

Until/If ever the law is changed, should we slavishly allow strict adherence to it to continue its detrimental effects on that balance, even to the elimination of species from a local ecology?  I maintain, no.

I could start citing the hundreds of laws we’ve had—and changed—that unfairly disadvantaged segements of population, human and otherwise, but let’s not go there, we’ll get bogged doen in metaphorical equivalence arguments.

Posted by Gary on 5/31

Ray & Brian grin

Posted by Jeanne on 5/31

Can’t believe all the cowbird haters!! I LOVE these birds-they have such strange and unique calls-they are one of my favorites at the feeder. And seriously this is the way nature has made them-how do you fault a creature for something they can’t control.

Posted by Cheryl on 5/31

Cheryl, I so agree. The first time I saw these birds they were doing a strange mating ritual. One male was trying to scare off the others and had his wings spread out. I had such an interesting time watching all of this. It actually took me a long time to find out what kind of bird they were, and after reading about them I was even more intrigued.

Posted by Jeanne on 5/31

Ivorybilled Woodpecker and Passenger Pigeon

How about less malls and business parks instead
more forest rejuvenation? Such venom toward the
Grackles & Crows!Blue Jays are part of the Crow
Family also does that mean eradicate them along with the Cowbirds?The Eurasian House Sparrow sure
was a wise addition to North America.Set up Bluebird houses to increase their numbers in between venting rage toward Cowbirds who simply
took advantage of European expansion to increase
their numbers.

Posted by NorthsideRasta on 6/2
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