Photoperiod and nesting phenology of whooping cranes at two captive sites

Increasing daylight is known to be a breeding stimulus in many avian species breeding in northern latitudes. This is thought to be true for cranes that breed in such latitudes including the Whooping Crane (Grus americana). For this reason, the captive breeding centers use artificial light to lengthen daylight hours, but no study has been done to look at the effect of such lighting on the reproductive season. We examined the past light cycles and breeding season results from Whooping Crane pairs at USGS Patuxent Wildlife Research Center and the International Crane Foundation. At Patuxent two lights were used to produce light of 170 lux in the pens. On average, photoperiod lights were turned on Feb. 17 (range Feb. 11-24). With two lights per pen, whooping cranes laid their first egg on average 10 days earlier than when one light was used and 16 days earlier than when no lights were used. At ICF the difference between lights on a pen and no lights was only 8 days difference in first lay dates, but still this was statistically significant.