R.S.Brown 1968 Fairy Tern McKean Island 20 Oct. Worked at Fairy Tern nests on the high SW walls and the entire large central complex of walls. Data as follows: Egg SDY MDY LFY Imm. Total 20 Oct. HSW Walls 2 2 - 4 20 Oct. CC 17 2 2 26 24 Oct. NW Circular Wall 5 1 2 8 TOTAL 24 6 4 2 38 20 Oct. All eggs were measured as follows: 38.2 x 29.6 38.2 x 29.4 38.7 x 30.7 38.8 x 31.2 38.9 x 30.9 39.0 x 30.0 39.2 x 30.2 39.5 x 30.3 39.5 x 31.6 39.6 x 29.9 40.1 x 29.9 40.9 x 31.1 41.0 x 30.3 41.0 x 31.4 41.5 x 30.4 42.1 x 31.2 42.1 x 32.2 43.8 x 33.2 44.0 x 39.7 Total 19 Stage of Incubation Fr. VSC 1. VSC 2. SE MI Yolken 20 Oct. 4 1 1 4 5 4 Total 5 1 1 5 6 4 Total 19 Egg measurements, 24 Oct 40.0 x 31.0 39.9 x 31.1 38.2 x 29.2 40.1 x 33.4 40.6 x 31.3 R.S.Brown 1968 Fairy Tern McKean Island 20 Oct. Measurements of the culmen from appared skin (free of down or feathers) to tip of upper mandible were taken on all chicks. The individuals were first visually placed in an age class and then measured. SDY MDY LFY Imm. 20.5 mm. 23.0 mm. 25.2 mm. 27.5 mm. 14.0 mm. 24.1 mm. 26.1 mm. 26.3 mm. 24.1 mm. 24.3 mm. 25.4 mm. 24.8 mm. 24.2 mm. Hence by visual placement, there is some overlap between individuals in the middle down young and large feathered young classes, and very close measurements in the large feathered young and immature groups. A larger sample could no doubt join a better series in which to calculate lower and upper limits to the various age classes. However, individual variation will probably make this criteria invalid; hence I can see no reason for maintaining some age-class method which utilizes measurements, but it will allow a field worker to utilize the same visual methods we use in that one unfamiliar with aging this species can check himself with some concrete measurements. All young were banded 7/12-57244-55. One egg was known to be laid on 18 Oct, High SW walls.