Jp. Swaddle et Ms. Witter, THE EFFECTS OF MOLT ON THE FLIGHT PERFORMANCE, BODY-MASS, AND BEHAVIOR OF EUROPEAN STARLINGS (STURNUS-VULGARIS) - AN EXPERIMENTAL APPROACH, Canadian journal of zoology, 75(7), 1997, pp. 1135-1146
The physiological and energy costs of avian molt are well documented,
but indirect consequences such as changes in flight performance have r
eceived less attention. Here, we report two experiments that investiga
ted flight performance, body mass regulation, and behavior in captive
starlings (Stumus vulgaris). In the first experiment, we found a U-sha
ped change in take-off escape performance during natural molt: birds a
scended at the shallowest trajectories during midmolt. Birds' body mas
s was also reduced during molt. In the second experiment, we manipulat
ed the plumage of starlings to simulate different stages of flight-fea
ther molt. This allowed us to separate the aerodynamic costs of feathe
r loss from the physiological costs of feather synthesis normally asso
ciated with plumage growth. Through observations of flight (take-off,
aerial maneuverability, and level flapping-flight speed) and behaviora
l parameters, we demonstrated that birds in simulated molt have reduce
d night performance and reduced body mass. These birds also decrease t
he time spent performing energetically costly activities and seek area
s of relative protection. In the longer term, some aspects of performa
nce return to pretreatment levels, implying compensation for the pluma
ge manipulations. Our results demonstrate. that molt incurs significan
t functional costs that may play an important role in the adaptive rad
iation of molt strategies and molt patterns observed in avian species.