Estimated effects of age and sex on the fat-free body mass of autumn migrating Bluethroats Luscinia svecica svecica.

Bluethroat (Luscinia svecica) Science Article 9

abstract

If constant and size-specific values of the fat-free body mass are used for estimating the fat content of migrating birds, it is required that the fat-free body mass does not vary considerably between age and sex groups. To test this requirement, body masses of autumn migrating Blue-throats from different age and sex groups were analyzed when wing length and fat index had been compensated for. Age has significant effect on body mass among males (adults being 0.16 g heavier) while no other age or sex effects were observed. The impact of the observed situation on flight range estimates is discusssed.

Ellegren H., ARDEA 80 (2): 255-259.

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