Hawks win, doves pay for being odd

Apr 13, 2012 By Pete Wilton
Juvenile goshawk hunting by Thermos. Credit: Wikimedia Commons

(Phys.org) -- In a crowd, looking different can be dangerous, at least if you’re a pigeon.

A new study from Oxford University has examined the so-called ‘oddity effect,’ in which predators preferentially attack different-looking individuals within a group - presumably because it enables them to focus on a single target within a confusing, moving mass.

To test whether this hunting strategy actually pays off for the predator in terms of enhanced reproductive success, Christian Rutz of Oxford University’s Department of Zoology studied urban goshawks preying on feral pigeons in the city of Hamburg, Germany.

A report of his research is published in Current Biology.

In feral pigeons, most individuals are grey-blue but many flocks contain a few white birds.

"Goshawks are specialist bird hunters, and in urban environments, their preferred prey is the feral pigeon," says Christian. "When attacked by a raptor, pigeons seek safety in numbers and form a tight flock. Goshawks struggle to single out a suitable victim in such flocks, but by focussing on an odd-coloured individual, they seem to be able to enhance their attack success."

Adult goshawk with pigeon. Credit: Johan Krol

But, Christian explains, like other skills this hunting strategy is something young birds have to learn: "Male goshawks apparently hone their hunting skills over their first few years of life. As they get older, they become not only better pigeon hunters in general, but they also get increasingly selective for odd-coloured individuals."

Importantly, the study found that those hawks that master this selective attack strategy are the best breeders:

"An efficient hunter can provide a lot of food to their offspring," Christian comments. "In goshawks, the most selective pigeon hunters initiate their clutches very early in the season and raise young of excellent body condition."

This finding leads to an intriguing question: why doesn’t this selective hunting drive rare white pigeons to extinction?

"Feral pigeons apparently prefer to mate with partners who are of a different colour to themselves," Christian notes. "Thus, white pigeons may risk paying the ‘ultimate price’ for being conspicuous, and get killed by a hawk, but they are preferred mating partners of their much more common grey-blue counterparts and seem to enjoy reproductive advantages whilst alive."

The work may encourage studies in other species to move beyond simply recording success rates in predators attacking swarming prey, to examine explicitly how different attack strategies may affect a predator’s reproductive performance. 

Explore further: Green spaces don't ensure biodiversity in urban areas

Related Stories

Pigeons never forget a face

Jul 03, 2011

New research has shown that feral, untrained pigeons can recognise individual people and are not fooled by a change of clothes.

Raptors guard S.African World Cup stadium

May 28, 2010

A South African World Cup stadium has turned to birds of prey to chase out rogue pigeons and rats in an anti-pest strategy that favours raptors above the pitch instead of poisons.

Like monkeys, pigeons can put numbers in order

Dec 22, 2011

(PhysOrg.com) -- Pigeons are on par with primates in their numerical abilities, according to new University of Otago research appearing in the leading international journal Science.

How the 'street pigeon' got its fancy on

Jan 19, 2012

Pigeons display spectacular variations in their feathers, feet, beaks and other physical traits, but a new University of Utah study shows that visible traits don't always coincide with genetics: A bird from ...

Pigeon 'backpacks' track flock voting (w/ Video)

Apr 08, 2010

(PhysOrg.com) -- Pigeon flocks are guided by a flexible system of leadership in which almost every member gets a ‘vote’ but the votes of high-ranking birds carry more weight, a new study has shown.

Recommended for you

'Divide and rule'—raven politics

8 hours ago

Mythology has attributed many supernatural features to ravens. Studies on the cognitive abilities of ravens have indeed revealed that they are exceptionally intelligent. Ravens live in complex social groups ...

Science casts light on sex in the orchard

Oct 30, 2014

Persimmons are among the small club of plants with separate sexes—individual trees are either male or female. Now scientists at the University of California, Davis, and Kyoto University in Japan have discovered ...

Four new dragon millipedes found in China

Oct 30, 2014

A team of speleobiologists from the South China Agriculture University and the Russian Academy of Sciences have described four new species of the dragon millipedes from southern China, two of which seem to ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

hyongx
not rated yet Apr 13, 2012
"Feral pigeons apparently prefer to mate with partners who are of a different colour to themselves,"
Perhaps they know that keeping the oddly colored pigeons around helps their own chances of success. Or perhaps that behavior is a product of programming to support genetic diversity within the species, also a good thing.

As far as physorg goes, this article does an above-average job of not making wild extrapolations to humans.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.