Abstract

Reproduction and molt are costly processes in avian life histories. These two fitness-related traits are expected to be under one of physiological trade-offs. Age-related molt is known to be higher in young birds than that in adults presumably due to the cost of reproduction in adults. The present study partially replicated a previous study using a non-invasive method of seasonal wing feather loss instead of capture-inspection for molting progress in oriental storks (Ciconia boyciana). We first examined characteristics of the known six wing feather types (i.e., primaries [P], primary coverts [PC], secondaries [S], secondary coverts [SC], and tertials [T]) from two specimens with four wings. Results were utilized as references for further investigation. We then collected a total of 3,807 wing feathers shedded by 61 captive storks for one year and classified them into six wing feather types based on the reference with structures of vane (i.e., how asymmetrical) and calamus (i.e., how rigidly attached to skin) of wing feathers. Our results indicated that annual losses of all six-type wing feathers decreased with increasing ages, ranging from 29% to 58% for PC, alula, SC, P, S, and T in order. Our results were also comparable to those of a former study, suggesting that the pattern of age-specific molt might be associated with the cost of reproduction in adults. However, juveniles might shed more wing feathers with low quality formed during the previous development stage than older birds.