Shiny invaders

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Shiny Cowbirds (Molothrus bonariensis) - female

These beautiful birds were first sighted on Curacao a little over a decade ago. The response of one of our colleagues, who was fast to identify the species, was a frantic hunting party. Armed with an air gun he shot several birds. What was going on?

These birds, identified as Shiny Cowbirds (Molothrus bonariensis), display the same reproductive behavior as the common cuckoo in Europe. These birds are brood parasites, which means they will not build a nest themselves, but simply lay an egg in a nest of another bird. After hatching, the chick will push the other eggs or hatchlings out of the nest. The unfortunate parents don’t have a clue and will raise the invader as if it is their own chick. Such behavior can be extremely damaging to an ecology that has not evolved a level of defense against it. Hence the actions of our colleague.

Shiny Cowbirds (Molothrus bonariensis) - male

How these birds ended up on Curacao we don’t know. That their nest parasitism is effective has unfortunately been observed. Several years ago we encountered a Trupial Kachó (Yellow Oriole – Icterus nigrogularis) in the process of raising a black chick. Not good.
On the other hand, we have not seen these birds as often as feared. Maybe the environmental harshness interferes with their survival skills. Let’s hope so.

 

 

 

 

Leon Pors

About Leon Pors

5 Responses to “Shiny invaders”

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  1. Rob Wellens says:

    To comprehend that shiny cowbirds are not to be compared to other invader birds i compared the cowbirds with lion fish. But maybe this was not a sufficient wise comparison. lion fish indeed needs other fish to survive and i really do hope it will come to a new balance between them in the future without to much irreversable damage.

    Shiny cowbirds on the other hand are not dependent on other nesting birds for their survival, because they also built their own nests to raise offspring!

    what does this mean: in the future there will not be any other bird species to be admired by our children on the island of curacao then the shiny invader. it has happenend on caribbean sister islands already. the impact was so severe that governements of these islands have asked the public to help catch the cowbirds and kill them humane. They tought the public how to or where to bring them to have governement bodies dispose of them.

    Yes, i agree, it is appaling to shoot off birds, especially for birdlovers as i consider myself one. it is not easy and it hurts even after 200 killed. it is the responsibility of everyone though, even birdlovers, to keep the population of cowbirds under control. we need to keep catching and killing them, have somebody else kill them or put them in cages. because of the hurt i tried the cages option, but in no time i had over 60 caught cowbirds, and still counting, in one cage. this was not humane anymore so …..

    With this i hope more people will understand that if the cowbird population is not kept under control by catching them, soon we will not have any other bird species to admire in our gardens, not even the other ‘invaders’. off course if there would be a solution other than catching and killing them, for instance by sterilising them, i would be very happy, but for now i do not see any other solution.

    as for the other invader birds, the seed competitors: my hobby is atracting as many bird species in my garden as possible without one making it impossible for the other to get near the feeders. For moffis and rufus-colared sparrows i have feeders with mesh wire around them with mesh size just large enough for birds of their size only being able to get to the food. every day over 20 different moffis visit my garden, together with several rufus-colared sparrows. for saffronfinch and house sparrow i have feeders with mesh wire the cowbird cannot pass through. for the bananaquit i protect the fruit with mesh wire only they can pass through and in such a way troupial and tropical mockingbird cannot disturb them. prikichis (caribbean parakeet), troupial, orange and yellow, and the tropical mockingbird feed on two meter long feeder cilos. pigeons and doves cannot feed from those; it even seems user unfriendly to the cowbird. the rest of the birds, the common ground dove, the white faced dove, the eared dove, the bare-eyed pigeon and all the other seed eating birds eat the leftovers on the ground where there are no feeders with left over catchers. i also have water containers hanging in my garden where the majestic, most beautifull, Red- necked pigeon comes to drink every day. i have never seen this big shy royal-looking pigeon eat leftovers under the feeders with the others or alone.

    as you can see my garden is for me as a birdlover a paradise. i will defend this paradise from desasters as shiny cowbirds ruining it, even if it hurts to use the only appalling method available for now. i also see it as my responsibility to help to keep this cowbird from ruining curacao as a bird paradise. If you and i do not take responsibility in this, at the end the balance will be that there will be only shiny cowbirds, beautifull as they are, and none of the other beautifull birds…..

    Rob Wellens

  2. bart de boer says:

    I don’t think it’s a good idea to go shooting the cowbirds. Frankly, I am appalled at the idea of shooting off 200 birds!! Yes, they are invaders but so are the house sparrow and the saffron finch, both seed-competitors for ‘our’ mofi. And what about the exotic parrots and ara’s flying around the island, also invader-species. The fact is that the fauna of out islands is made up of invaders some from centuries ago, others more recent ones. Every time a new species is introduced the resident fauna will have to adjust to this newcomer. So it will go with the cowbird: they may prevent some yellow troupials of procreating, but they will never finish them off completely because then they rob themselves from suitable stepparents for their chicks. At the end of the day a new balance will be found and the invaderspecies becomes part of the natural fauna.

  3. rob wellens says:

    Leon, maybe this clarifies why you might not have seen so many shiny cowbirds anymore, because by the time you wrote this article we had killed them. I live 5 houses down the road from where you (used?) to live, parallelweg 15.

    Salados,

    Rob

  4. rob wellens says:

    Hello leon, yesterday was the first time i was on your website and found myself reacting on an article michelle wrote on invasive species with a picture of a shiny cowbird.now i find your article about this beautiful but severe danger for other birdlife. We a friend of mine and i caught and killed over 200 shiny cowbirds until we did not get them in my garden anymore. For a while we did not see them anymore, but lately they are back and start to become a menace again. We used to catch them with a bird cage we hang in a tree and put broken dog rice in. The sliding door was attached to a thread which made it possible to operate the door from a large distance. The problem is this time i have no time to catch them this way anymore and am looking for a quicker way to catch more of these shy and very smart birds in one catch, like with a net for instance. try to shoot them is not an option because it will scare the prikichis, that feed and drink on my feeders, away for ever. I like to compare thisbird with the lion fish. If we let our guard down and do not keep them under control we will loose

    • rob wellens says:

      Hello leon, yesterday was the first time i was on your website and found myself reacting on an article michelle wrote on invasive species with a picture of a shiny cowbird.now i find your article about this beautiful but severe danger for other birdlife. We a friend of mine and i caught and killed over 200 shiny cowbirds until we did not get them in my garden anymore. For a while we did not see them anymore, but lately they are back and start to become a menace again. We used to catch them with a bird cage we hang in a tree and put broken dog rice in. The sliding door was attached to a thread which made it possible to operate the door from a large distance. The problem is this time i have no time to catch them this way anymore and am looking for a quicker way to catch more of these shy and very smart birds in one catch, like with a net for instance. try to shoot them is not an option because it will scare the prikichis, that feed and drink on my feeders, away for ever. I like to compare thisbird with the lion fish. If we let our guard down and do not keep them under control soon we will not see any other birds in our gardens anymore.

      Thanks for your article.

      Saludos

      Rob