Free range hens are more productive and lay more eggs, according to research carried out by scientists at a university in Australia.
Researchers found that ranging hens could produce more eggs not only because they ranged, but because they seemed to have a more vigorous approach to life in general.
They said this unexpected insight into hen character emerged from one of the most ambitious chicken-tracking project ever undertaken.
The University of New England (UNE) research used electronic tags to track some 15,625 hens across five free range chicken sheds from the time a flock was placed in the hen house at 16 weeks of age to when they were removed at 74 weeks of age.
The researchers said the first major finding to emerge from the resulting data was that those hens who preferred to range outside began laying earlier.
They also produced about 15 percent more eggs at 22 weeks of age than those who prefer to stay inside.
The ranging study was led by Dr Isabelle Ruhnke, who said that in some operations, a one percent increase in egg output can translate to hundred thousands of dollars in extra revenue a year.
"A 15 percent difference in productive capacity is significant," she said. However, the research suggested that performance dropped off for the wider ranging hens at an older age.
At 72 weeks of age the early rangers laid 10 per cent less eggs than the hens that initially preferred to stay in the shed, Dr Ruhnke explained.
She added that those hens who remained in the shed tended to be more fearful. It was assumed that these birds felt safer under cover.
Chickens were descendants of jungle fowl, native to dense forest, she noted. Despite thousands of generations of domestication, some birds were likely to feel vulnerable under open skies.
"Now that we know that the hens that prefer to stay in the shed are less productive at an early age, what effect will it have if we train them to go outside?," asked Dr Ruhnke.
"Some producers are already trying new strategies to encourage more hens to move outside to see whether it lessens the numbers of stayers in the long-term, and increases overall productivity."
The findings will open up questions about chicken management, such as whether the practice of providing a single feed mix to all the hens in the shed, regardless of their range use, was inefficient.
"In addition to the current findings, rangers even increased their egg production if being fed a different diet that provided more nutrients," Dr Ruhnke said.
"If the rangers and stayers peak with their production at different times, as we've found, then producers can probably benefit from providing different feed mixes to the chickens often found outside, the lower feeders tiers of the shed, and those who rarely leave but stay on higher in-shed structures.
Feed can represent up to 70 percent of the cost of egg production, the UNE researcher noted.