Dullness an advantage when it comes to survival - at least for birds

In the bird world of parenting, it is a matter of survival of the dullest, according to new international research led by Deakin University.

The new study of survival of bird eggs found that when male parents refused to do the incubation day shift, it wasn't because they felt it was their partners' work, or because they were lazy, but rather because their bright colours make them easily-spotted by predators while the sun is up.

In fact, according to the team led by Deakin University conservation biologist Dr Mike Weston, male birds not only do their share of the incubation duties, but they take over the work during the night shift.

"The bright colours of many male birds are impressive to the human eye, but they are also attractive to predators," Dr Weston said.

"And when they are incubating their eggs, they are literally like sitting ducks, increasing the chance they will betray the location of their offspring to predators.

Deakin PhD candidate, Kasun Ekanayake said the idea of survival based on parental colour was first floated in science more than a century ago, but it had never been fully tested, in part because males and females differ in many other aspects apart from colouration.

"So we wanted to test just how true this theory actually was," Mr Ekanayake said.

The research team, a collaboration between Deakin's Centre for Integrative Ecology, within the School of Life and Environmental Sciences, and conservation group BirdLife Australia, set up models of brightly coloured Australian red-capped plover and placed them next to nests.

"We discovered that nests looked after by the duller female model survived better than those attended by the male model during daylight hours," Dr Weston said.

"We found that the female advantage was only noticeable during the daylight hours when ravens, which rely on vision to find prey, were active.

"At night, when foxes were roaming through the breeding site, nest predation occurred regardless of who attended them. And we know that foxes rely on scent to find their prey."

"Our research confirms the theory that until now has not been proven; birds are smart enough to let the less conspicuous females do the incubation shift during daylight hours, when visibility makes it harder for the males to hide from their predators."

The research, The bright incubate at night: sexual dichromatism and adaptive incubation division in an open-nesting shorebird, is published this week in the prestigious Proceedings of the Royal Society B journal.

"Despite being well camouflaged, red-capped plover eggs make popular snacks for local predators such as ravens and foxes.  Ravens find red-capped plover nests during daytime using their superior vision whereas foxes usually find nests during the night making use of their excellent sense of smell,", Dr Weston said.

Study co-author, Dr Clemens Küpper, now at Austria's University of Graz, said the team then studied the incubation pattern using video surveys of red-capped plover nests.

"Perhaps not surprisingly, the plover behaviour looks to have evolved to deal with the threat of nest detection," Dr Küpper said.

The researchers next plan to quantify the benefits of bright colouration in this species.