Eagle Owls Send Sweeter Valentines When Moon Is Full

January 21, 2010 by Ted Goodman report
Eurasian Eagle Owl (Image: Wikipedia)

(PhysOrg.com) -- Placing a tracking device on breeding owls with a wing span large enough to cover eight humans lined up side-by-side, is not a walk in the park. But, funded by a grant from the Spanish Ministry of Science and Innovation, four biologists from Spain, Finland, and Portugal sought to find out how the Eurasian Eagle Owl's (the Bubo bubo) communication behavior is affected by moonlight. The study is one of the few that have looked at intraspecies communication of nocturnal birds and the findings provide further evidence lunar cycles affect the behaviors of animal species.

From 2003 to 2008, the researchers trapped and radiotagged 26 breeding eagle owls - 14 males and 9 females) from breeding sites in southwestern Spain. (Owls were caught with mist nets, and the radio transmitters only weighed 30 grams, less than about 3 percent of the owl’s own weight.) Every measure known to the research team was taken to avoid disturbing the adult owls or their infants. They continuously radio-tracked every person even remotely near the owls for the period of the study, and saw no adverse reactions from the owls.

The researchers traced two unique communication behaviors of the Eurasian Eagle Owl: vocal communication and visual communication. These behaviors were observed during five phases of the moon: new moon, waxing/waning crescent, first/third quarter, waxing/waning gibbous and , under good .

Phases of the moon. (Image credit: PLoS ONE)

As you might have guessed by the title of this article, the Eurasian Eagle Owl is turned on by moonlight. The brighter the moon, the more frequent the calls. But along with the owls' vocalizations is the moon’s affect on the owls’ visual communication.

Eagle owls have white patches of soft feathers under their beaks that they show only when vocalizing. So, as the moon gets brighter, and the eagle owls are calling to their mates more frequently, so do these owls climb to higher perches where they can be more easily spotted.

The researchers also learned that the eagle owls communicate similarly at dusk and at dawn to when the moon is full, and suggest that this is because the amount of ambient light at dusk and dawn are about the same as a moonlit night.

The puff of white feathers under the eagle owl's beak only shows when the owl is calling. (Image: Wikipedia)

It is possible that the largest owl in the sky with the best vision doesn’t have to worry about too many predators. It can afford to strut its stuff at night.

But not all nocturnal birds or animals can afford to be so boisterous in the moonlight. For many of them, it’s time to lay low.

Explore further: Owls' dawn and dusk concerts promote visual communication

More information: Moonlight Makes Owls More Chatty, Plos ONE, www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0008696

Related Stories

Owls' dawn and dusk concerts promote visual communication

April 8, 2009

Reporting in the online, open-access journal PLoS ONE April 8, Vincenzo Penteriani and Maria Delgado of the Estacion Biologica de Doñana, Spain, describe the evolution of white throat badges in association with dawn and ...

Spotted owls facing extinction in Canada

May 18, 2007

Officials in the Canadian province of British Columbia have ordered all regional spotted owls to be collected to prevent the birds from going extinct.

SF State scientists expose new threat to spotted owl

May 28, 2008

A new study provides a baseline distribution of blood parasites and strains in Spotted Owls, suggesting a more fragile immune health than previously understood for the already threatened Northern and California Spotted Owls.

Recommended for you

Blueprint for shape in ancient land plants

December 9, 2016

Scientists from the Universities of Bristol and Cambridge have unlocked the secrets of shape in the most ancient of land plants using time-lapse imaging, growth analysis and computer modelling.

Protein disrupts infectious biofilms

December 8, 2016

Many infectious pathogens are difficult to treat because they develop into biofilms, layers of metabolically active but slowly growing bacteria embedded in a protective layer of slime, which are inherently more resistant ...


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.