Abstract:
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Marginal coverts are often neglected in passerine moult studies due to their small size and large
number. Here, we document eight moult components of this group of wing coverts in a House
Sparrow population from Barcelona in 2018–21: timing, growth rate, intensity, speed, duration,
sequence, extent and barb density. We also tested the influence of various intrinsic and
extrinsic factors on marginal-covert moult. Our adult population started marginal-covert moult
on 29 July and finished it on 29 August, with the moult of hatch-year birds delayed 13 days in
relation to the moult of adults. Growth rate of the largest marginal covert increased significantly
with its size but did not differ between sexes. Intensity of marginal-covert moult replacement
was not constant during the moult progress, which took 32 days on average. Moult sequence of
marginal coverts started with the proximal feathers, proceeded distally replacing the central
rows and was completed toward the front and rear rows. Moult extent was complete except in
one case. Size of the largest marginal covert increased with calamus width, but not significantly,
and barb density decreased with feather size, but not significantly, and neither measure differed
between sexes. Comparison with published results indicated that growth rate is lower in
marginal coverts than in primaries and rectrices, whereas barb density is greater. Linear
regression of marginal-covert size on both growth rate and barb density can be used to predict
growth rate and barb density of flight feathers in the House Sparrow. |