Relationship between wing length and body mass in atlantic puffin chicks

Abstract.–Ages of Atlantic Puffin (Fratercula arctica) chicks are sometimes estimated by com-paring their wing lengths with a sample of known-aged chicks from the same colony. Thetechnique is reliable if the rate of wing growth is unaffected by variation in nutrition. Recentstudies suggest that wing growth may respond to food supply. I investigated variation in winglength in relation to chick age and mass during a period of reduced food availability. Winglength was correlated with mass at all chick ages, and wing growth over a 4-d interval wasrelated to change in mass over the same interval at most ages. Variation in wing length anddifferences between estimated and actual ages increased with age. Average ages of chicksbetween 5-50-d old were estimated satisfactorily, but estimates for chicks growing faster orslower than average were biased. Measurements from a representative sample of contem-porary, known-aged chicks are required to provide reliable, average age estimates. Largepotential errors for individual chicks poses problems for studies investigating individual be-havior.

Mich l S. Rodway, j. Field Ornithol., 68(3):338-347