Changes in ring-necked pheasants' (Phasianus colchicus) egg formation time, oviposition lag time, and egg sequence length due to ahemeral light-dark cycles.

A total of 108 pheasant hens was exposed to either a conventional 24-hr (14L:10D), an ahemeral 22-hr (14L:8D), or an ahemeral 26-hr (14L:12D) light-dark (L:D) cycle. Total lag time for each egg sequence was greater in the ahemeral cycles than in the conventional L:D cycle, resulting in significant (P less than .05) differences in egg formation times (EFT) or intraclutch intervals of 26.4, 25.8, and 27.5 hr, respectively. The EFT under the ahemeral 26-hr L:D cycle was synchronized (within 1.5 hr) with the length of the L:D cycle. This light cycle resulted in the longest egg sequences (average 8.5 eggs per sequence) produced under any of the three L:D cycle treatments due to a shorter pause in oviposition. Values were significantly (P less than .05) different from the average values obtained under the conventional 24 hr L:D cycle (4.9 egg per sequence) and ahemeral 22 hr L:D cycle (3.5 eggs per sequence).