JAN 09, 2017 11:10 AM PST

Parasitic Cowbirds Plan Criminal Acts Just Like People Do

WRITTEN BY: Anthony Bouchard

A specific type of bird known as a cowbird is quite the tricky little schemer, and some scientists are comparing their sneaky behavior to that of a human criminal, who sits in wait until the time is right to strike.

Cowbirds, which come in different varieties, are parasitic types of creatures, and that’s because they lay their eggs in other songbirds’ nests to trick the songbird into raising their young for them.

The shiny cowbird is a type of brood parasitic bird that was involved in this study.

Image Credit: Michel Giraud-Audine

According to a study published in the journal Behavioral Ecology and Sociobiology, which takes a closer look at the behavior of two particular kinds of cowbirds including the screaming cowbird and the shiny cowbird, these creatures carefully study their nest targets just before laying their eggs, just like a criminal would study their target before making a hit.

Once the host birds, which in this case were baywings and chalked-browned mockingbirds, leaves their nest, cowbirds will flutter over to the nest they intend to parasitize and lay their own eggs to camouflage in with any existing eggs that are already there.

Cowbirds won’t lay eggs if there aren’t already any eggs there, as it would raise suspicion of the nest’s owner. They also won’t lay the eggs if the eggs that are already there have been there too long, as it could lead to problems for the baby cowbird when the incubating bird loses interest in caring for it after its other eggs have all hatched.

For the research, Romina Scardamaglia, a behavioral ecologist at the University of Buenos Aires, and her colleagues tagged a grand total of 41 different cowbirds among the two different species and tracked their movements.

They found that screaming cowbirds were about twice as much more dedicated to ensuring their eggs’ survival than shiny cowbirds were. They were traced visiting back to the nest where they laid their eggs, or returning to the scene of the crime, on average 27 times, while shiny cowbirds only did so about half of that frequency.

Based on what the researchers knew about shiny cowbirds, this was probably a good thing. Shiny cowbirds have a nasty habit of poking small holes in the host’s eggs so that they won’t hatch. This helps ensure that the parasite eggs hatch and that the host will take care of them. They likely avoid nests after laying their eggs to prevent pecking holes in their own eggs, which are hard to tell apart.

As villainous as these brood parasitic birds’ behavior sounds, that’s how they happen to survive. Their behavior isn’t particularly good for the survival of the host species, but despite how destructive the behavior of these two species of cowbirds is, they don’t come close to that of the North American brown-headed cowbird, which repeatedly destroys the host’s nest if they fail to take care of and hatch the parasitic eggs.


Without a reasonable doubt, human criminals are not the only ones in the animal kingdom capable of working out devious planning to ensure their scheming goes according to plan. They’re also not the only ones to return to the scene of the crime. It seems that even some species of birds replicate similar behavior to get their dirty job done.

Source: Science Mag

About the Author
  • Fascinated by scientific discoveries and media, Anthony found his way here at LabRoots, where he would be able to dabble in the two. Anthony is a technology junkie that has vast experience in computer systems and automobile mechanics, as opposite as those sound.
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