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Dec 8, 2016

Hummingbird migration ~ adults versus juveniles

Photo by BarrytheBirder
Henry Nicholls writes in The Guardian Online this week that migration-based research shows Ruby-throated Hummingbirds adopt a mixed strategy regarding pre-migration feeding habits.   Some adults choose to fatten up in North American before heading to Central America wintering grounds, by gorging on feeders to increase their body mass by more than one third.   Juveniles do not appear to do this, so probably fall behind as they stop and feed along the way.   In my Ontario backyard, all the 'hummers' leave on southern migration at the same time, usually within a 24 to 48 hour period.   I find it difficult to distinguish between a well-fed adult bird and a partially nourished juvenile.   During the migration, the adults indubitably leap-frog ahead of the juveniles, which stop to nourish themselves as required.
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