Cowbirds Cause Chaos
By Hayley Birch
It’s one thing dropping your kids off round the neighbours’ house for the afternoon while you bugger off shopping. However, it’s quite another to come back and, upon finding your sprogs playing out in the street, lob a brick through the window.
But in a roundabout way, this is exactly the course of action that the adult cowbird takes. Neighbours who refuse to look after a cowbird’s chicks are cruising for a bruising.
Brown-headed cowbirds are essentially parasites, imposing their offspring on warblers and other unsuspecting species of bird – rather like cuckoos do. Jeffrey Hoover and his colleagues at the Florida Museum of Natural History spent four years studying the feathered fiends.
They found that 56% of warblers that kicked cowbirds eggs out of their nests were later the targets of “mafia” style reprisals, having their domiciles wrecked by the angry parents.
According to Hoover, it’s the girl birds that really get in a flap. “The female cowbirds are the running the mafia racket at our site,” he commented.
But cowbirds aren’t just thugs, they’re devious with it.
By destroying a nest from which her eggs have been rejected, a female cowbird leaves herself just enough time to cook up another egg before the warbler builds a new one.
Then it’s simply a case of slipping it in there while the surrogate mother is eyeing up some juicy worm.
If mother warbler knows what’s good for her, she’ll presumably keep schtum. However, it might be difficult explaining the new addition to Father.
It’s pretty much like waking up to an extra pair of eyes staring at you over your cornflakes. “Darling, I was sure we only had three when we went to bed…”
Want more hot science from Hayley?
Image: Chris Young/University of Florida
But in a roundabout way, this is exactly the course of action that the adult cowbird takes. Neighbours who refuse to look after a cowbird’s chicks are cruising for a bruising.
Brown-headed cowbirds are essentially parasites, imposing their offspring on warblers and other unsuspecting species of bird – rather like cuckoos do. Jeffrey Hoover and his colleagues at the Florida Museum of Natural History spent four years studying the feathered fiends.
They found that 56% of warblers that kicked cowbirds eggs out of their nests were later the targets of “mafia” style reprisals, having their domiciles wrecked by the angry parents.
According to Hoover, it’s the girl birds that really get in a flap. “The female cowbirds are the running the mafia racket at our site,” he commented.
 |
| The female brown-headed cowbird - vicious bully or just protecting The Family? |
By destroying a nest from which her eggs have been rejected, a female cowbird leaves herself just enough time to cook up another egg before the warbler builds a new one.
Then it’s simply a case of slipping it in there while the surrogate mother is eyeing up some juicy worm.
If mother warbler knows what’s good for her, she’ll presumably keep schtum. However, it might be difficult explaining the new addition to Father.
It’s pretty much like waking up to an extra pair of eyes staring at you over your cornflakes. “Darling, I was sure we only had three when we went to bed…”
Want more hot science from Hayley?
Image: Chris Young/University of Florida
Share this
