. The Canadian field-naturalist. 1979 DUNN: Black Tern Nestings 281 100 80 E E 60 - 40 20 1—I—I—I—I—I—I—r—I—1—I—I—I—I—I—I—I—I I r 4 --. —1—I—I—I—I—I—I—I—I—I—I—I—I I I r- 0 5 10 15 AGE (DAYS) 20 Figure 3. Development of feathers in Black Tern chicks (total length, including sheath). Legend as in Figure 1. Upper bars indicate length of 9th primary, lower bars show outer rectrix growth. believed to be caused by predation or faulty fencing. The chick that was underweight throughout the growth period stayed inside the fence the longest. Delayed fledging of underweight Common Terns was noted by LeCr
. The Canadian field-naturalist. 1979 DUNN: Black Tern Nestings 281 100 80 E E 60 - 40 20 1—I—I—I—I—I—I—r—I—1—I—I—I—I—I—I—I—I I r 4 --. —1—I—I—I—I—I—I—I—I—I—I—I—I I I r- 0 5 10 15 AGE (DAYS) 20 Figure 3. Development of feathers in Black Tern chicks (total length, including sheath). Legend as in Figure 1. Upper bars indicate length of 9th primary, lower bars show outer rectrix growth. believed to be caused by predation or faulty fencing. The chick that was underweight throughout the growth period stayed inside the fence the longest. Delayed fledging of underweight Common Terns was noted by LeCroy and LeCroy (1974). I originally thought disappearances of young represented first flights, but the last occurrence took place while the nest was under observation. The chick flapped its wings and barely hopped the fence, then swam away. Exact age of fledging is undetermined, but must be close to 19 d. Baggerman et al. (1956) said flight first occurred 3 wk after hatching, but Cuthbert (1954) felt it was closer to 25 d after hatching. Black Terns are very similar to other temperate- nesting species in both egg and growth characteristics, even though other species studied to date are primarily piscivorous and nest along marine shores rather than in marshes. Acknowledgments This study was supported by the Frank M. Chapman Memorial Fund in 1975, and in 1976 by the National Research Council of Canada. The Long Point Bird Observatory provided facilities, a canoe, and numerous assistants. I particularly thank Erica Nol for extensive help in field work, and Marshall Field for aid in designing traps and giving access to unpublished banding records. Literature Cited Baggerman, B., G. P. Baerends, H. S. Heikens, and J. H. Mook. 1956. Observations on the behaviour of the Black Tern (Chlidonias n. /7/ger(L.)), in the breeding area. Ardea 44: 1-71. Bergman, R. D., P. Swain, and M. W. Weller. 1970. A comparative study of nesting F
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