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

SECOND NORTH AMERICAN SEA DUCK CONFERENCE
MORPHOLOGICAL AND PHYSIOLOGICAL ASPECTS
OF TAKEOFF APTITUDES OF FEMALE COMMON EIDERS
IN PRE-LAYING PERIOD
Jean-François Ouellet, Magella Guillemette, and Pierre Blier
Department of Biology, University of Quebec at Rimouski, 300 allée des Ursulines, Rimouski, QC,
G5L 3A1, Canada; jean-francois_ouellet03@uqar.qc.ca
The pre-laying period is often associated with an improvement of body condition of females. An
extreme case is observed in the common eider (Somateria mollissima). The pre-laying period in female
common eiders is characterized by an important increase in body mass caused by follicular growth
and the accumulation of body reserves. This weight gain results in dramatic, sex-specific takeoff
impairment. Heavy females are frequently observed failing attempts to take off in still air conditions.
We investigated how the locomotor apparatus of females responds to this mass increase and tested
the hypothesis that pre-laying female common eiders compensate in order to diminish or retard
their takeoff impairment. We addressed our question at three organizational levels: i) measurement
of flight morphology, ii) weight of flight musculature, and iii) measurement of the activity of key
enzymes of aerobic and glycolytic capacity in two locomotor muscles and one structural muscle. All
measurements were performed on individuals of both sexes collected around Bicquette island, Quebec,
Canada, a large colony found in the St. Lawrence River estuary. Our results indicate that, by the
means of phenotypic plasticity and physiological compensation, females adopt strategies enhancing
lift production at different organizational levels. However, these strategies do not fully offset weight
gain effects. Compared to the larger males, females showed a similar wing area, a hypertrophy of flight
musculature, and maintenance of an energy metabolism pathway in pectoralis muscle. The pectoralis
muscle of females with higher wing-loading further compensates for their weight gain. Females seem
to have reached the upper limit of metabolic power, suggesting the existence of a glycolytic capacity
threshold (reflected by body mass-specific pectoralis LDH activity) to takeoff aptitudes in large birds.
These results demonstrate that the maintenance of flight aptitudes is an issue of tremendous importance
for pre-laying female eiders.
NOV. 7-11, 2005 ANNAPOLIS, MARYLAND, USA
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