Abstract
Male Redheaded Buntings were exposed to constant darkness (DD) or short days (8L : 16D) after long-day (15L : 9D) photostimulation for either 15 or 30 days. Eight long-day photostimulated birds in two groups were maintained on the same treatment (15L : 9D) ; also, photosensitive birds in groups of four were exposed to DD and 8L : 16D. The birds continued on 15L : 9D maintained fattening and increased body weight. Fattening was never induced in the photosensitive birds exposed to DD or 8L : 16D; instead, a depletion in fat depots (P<0.05, P<0.02) occurred in those exposed to DD. Further, the long-day photostimulated birds (either for 15 days or 30 days) transferred to DD or 8L : 16D showed similarly reduced body weights, indicating that the effect of DD or 8L: 16D in Redheaded Buntings is not dependent upon the number of days of long-day exposure prior to these schedules. The results appear to be consistent with the Bünning-Pittendrigh avian external coincidence model.
