Date: October 13, 2016
Source: University of Toronto
New U of T Scarborough research
has found adult ruby-throated hummingbirds choose to pack on significant weight
in the four days before their long migratory flights south for the winter.
"Many different birds fatten
up before they migrate, but we wanted to know what specific strategies hummingbirds
use to fuel up prior to migration," says associate professor Ken Welch.
"It turns out that
individual hummingbirds make individual decisions -- some fatten up for long
flights, while others stop and fuel along the way."
]
Welch and masters student Lily
Hou developed a unique system to track and weigh hummingbirds in the wild
before migration using radio frequency identification tags. Each bird had a
microchip and were weighed each time they landed on a balance attached to the
feeder.
They found hummingbirds that
fatten up spent more time at feeders in order to gain weight rapidly, in some
cases putting on as much as 35-40 per cent of their body mass in the four days
before migration. They also found that no juvenile birds were fattening meaning
that those choosing to fatten up had made the migratory trip at least once.
"This suggests fattening
could be a learned behaviour and it's based on experience," says Welch. He
adds the findings add to a growing body of research suggesting that for some
birds their pre-migration strategies are affected by age and experience.
Birds generally use two
strategies when it comes to preparing for migration. One prioritizes fattening
to allow a more direct flight in order arrive at the wintering grounds quickly.
The other involves shorter flights, stopping and feeding along the way.
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