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Inside the $45 packet were five feminized, photoperiod seeds from Gogol’s Oregon farm, and they can be purchased with no more hassle — or stigma — than anything else at C&S Garden Center.

The LWD1 mutation thus makes barley virtually insensitive to photoperiod, which in turn makes cultivation in various latitudes and marginal environments with sub-optimal growing conditions possible.

"Moreover, biological factors that are known to affect birth seasonality -- such as photoperiod exposure, temperature, humidity, and availability of food -- also depend on socio-demographic characteristics, since different social groups are exposed to these biological factors to varying degrees," Professor Borrell, a social epidemiologist at the City University's Department of Epidemiology & Biostatistics, Graduate School of Public Health & Health Policy, says.

To time this arrival for the highest likelihood of conditions favorable to reproducing, a migratory bird tracks each day’s light length, or photoperiod, says Marilyn Ramenofsky, a behavioral endocrinologist at the University of California, Davis, who specializes in birds.

A day’s photoperiod seems to tie to the initiation of breeding steps, but by the time of the year when birds are returning, they are no longer sensitive to changes in day length, she adds.