Brood Parasites: "One of These Eggs is Not like the Others" by Alicia

Brown-headed cowbird
Source, Rob & Ann Simpson/VIREO
While browsing through an online group's page, I came across a picture someone had posted of a nest. The nest had 4 eggs in it. 3 were colored 1 uniform color while the 4th egg was speckled. There were many people that speculated that the 4th egg belonged to a cowbird, and should therefore be removed. This struck me as strange (honestly, I was a bit horrified), as I had always been taught to leave 'mother nature' alone, especially when it comes to nests.

This particular speckled egg probably belonged to a brown-headed cowbird. Brown-headed cowbirds are what we call a "brood parasite," which means it lays its eggs in the nest of another species. It's not just birds that exhibit this reproductive behavior, but this phenomena also occurs in insect and fish species as well. Other birds that lay eggs in other species nests are cuckoos, the village indigobirds in Africa and the black-headed duck.

Eastern phoebe nest with brown-headed cowbird egg

It's quite clever actually from the aspect of the cowbird.... The female cowbird hops in a nest of say a cardinal or sparrow, removes one of the eggs (or in some way damages it, sometimes eating it), and replaces it with one of its own. The host species comes back to the nest, finding the same amount of eggs, typically, and then the host bird raises all the baby birds together...never realizing that "ones of these birds is not like the other."

Here's actual video of a brown-headed cowbird laying an egg in a Northern Cardinal's nest (via


In many cases, depending on the species, the brown-headed cowbird's gestation is shorter, which means that the baby cowbird hatches first, before the other eggs in the nest--getting mom's full attention, and food, for a time. In some cases (but not always) the larger cowbird baby could threaten or even kill the other babies in the nest. This, I'm sure, is why some people think it's "helpful" to remove the egg. 

The brown-headed cowbird specifically, is credited with threatening the numbers of several songbird species. Not great news if you're a birder who enjoys watching songbirds, right? (I would put myself into that category). But hopefully we can all agree that 'mother nature' is a complex lady, that we have yet to thoroughly understand...and sometimes she can be downright cruel!

Most of us have the impulse to 'help'--myself included.  So then the question becomes: should we or shouldn't we play 'mother nature' and remove the egg?  The! Not because I say so, but because the law does. The brown-headed cowbird, along with 800 other species, are protected by the Migratory Bird Treaty Act of 1918, which protects these types of nests from human interference...the bird, dead or alive, its feathers, and its nest.

"The Migratory Bird Treaty Act of 1918 (MBTA) a United States federal law, first enacted in 1916 in order to implement the convention for the protection of migratory birds between the United States and Great Britain (acting on behalf of Canada). The statute makes it unlawful without a waiver to pursue, hunt, take, capture, kill or sell birds listed therein ("migratory birds"). The statute does not discriminate between live or dead birds and also grants full protection to any bird parts including feathers, eggs and nests. Over 800 species are currently on the list." source

You can find the entire list of protected bird species on the website for the U.S. Fish and Wildlife Service. The list includes many of Rockport's beloved bird species including the Whooping Crane, the Rosette Spoonbill...and some more seasonal visitors you might find at your backyard feeder, such as the Indigo Bunting and the Baltimore Oriole.

The penalty? "...a person, association, partnership or corporation which violates the Act or its regulations is guilty of a misdemeanor and subject to a fine of up to $500, jail up to six months, or both. Anyone who knowingly takes a migratory bird and intends to, offers to, or actually sells or barters the bird is guilty of a felony, with fines up to $2,000, jail up to two years, or both." source

"In some states, such as Michigan and Texas, permits can be obtained to trap cowbirds to protect endangered species like Kirtland’s Warbler, Golden-cheeked Warbler, and Black-capped Vireo." source

Many have concluded that the species directly above, and others, are being threatened by more than just the even more imposing threat: the loss of habitat. While you might 'like' one bird over another, due to its beauty, melodic song, etc., we mustn't forget that every species has its own place in the world, its own purpose...yes, even the cowbird. It might not always be clear to us what that is, but be sure that everything is connected. When we begin to tamper with nests, or relocate one species to favor another, we could reputably alter the delicate balance. Personally, I would rather put major efforts and focus into preserving habitat, first and foremost, and then let 'mother nature' do the rest.

Other countries have similar protective laws in place to protect such bird species including Canada, Mexico, Russia and Japan. In the last decade, there has been a proposal to update the list, including adding 152 species.

"In the 24 August 2006 edition of the Federal Register, the U.S. Department of the Interior's Fish and Wildlife Service proposed adding 152 species, removing 12 species, and correcting/updating the common or scientific names of numerous others." source

So in conclusion, hands off. Let 'mother nature' do her incredible, mysterious work. ...sit back and enjoy!

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