Second North American Sea Duck Conference - Patuxent Wildlife ...

SECOND NORTH AMERICAN SEA DUCK CONFERENCE
HABITAT USE, TIME SPENT DIVING AND ENERGY EXPENDITURE
DURING WING MOLT IN BALTIC COMMON EIDERS
Magella Guillemette¹ and Patrick J. Butler²
¹Université du Québec à Rimouski; magella_guillemette@uqar.qc.ca
²School of Biological Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
Molt is an elusive phase of the annual cycle of sea ducks given their offshore habits. In this study
we present the first results aiming at quantifying flightlessness duration, dive budget, habitat use
and energy expenditure during wing molt of female common eiders (Somateria mollissima). Data
loggers were implanted in the body cavity of 20 females to record heart rate and hydrostatic pressure
(depth) every two seconds. The loggers were recording continuously for 220 days and were deployed
on Christians’ Island located in the Baltic during the nesting season of 2003. Flight frequency and
duration were assessed from elevated and constant heart rate and the absence of flight was used to
quantify the duration of flightlessness, which lasted 43 days in average. Using a period of three weeks
before and three weeks after the flightless period, we found that depth use did not vary in the course
of the study ranging from one and a half to two m in average. By cumulating all dives made during
one day, we determined that flightless eiders spent about 1 h diving each day in average, which was
not different from the before and after periods. Daily heart rate (in heart beats per day) increased 28%
from the before period to the middle of the flightless period and remained high afterwards. Similarly,
resting heart rate, defined as the minimum heart rate during the day, increased by 43% during that
period but with a tendency to decrease during the after period. Our study indicates that the energetic
costs of replacing flight remiges in female eiders are substantial although this was not associated with
any increases in diving activity. This suggests that females in this sample were loosing mass during
wing molt.
NOV. 7-11, 2005 ANNAPOLIS, MARYLAND, USA
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