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Wilson’s Warbler http://www.utahbirds.org/birdsofutah/BirdsS-Z/WilsonsWarbler.htm
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There are approximately 450 native
migrating bird species that
for at least part of the year reside in Canada, but where do they go when they aren’t
in the
True North Strong and Free? If you ask just about anyone, they’ll tell you that
birds fly south for the winter, but where exactly is
south? South could be as close as the next city, the USA or as far as Tierra Del Fuego. Also
do they make stops on their way to this “south” and do they mix with
other populations? The
truth is there isn’t much information on where many migrating species go or the
route they take to get there.
But why should we care where they go when they
leave Canada, they seem to always come back in the spring. The truth is not all
birds are coming back, there has been a marked decline in the population size
of many migrating neotropical bird
species. As the leading cause of species loss, humans need to figure out
whether these bird populations are facing stressors in their breeding,
wintering, stopover range or some combination of the three
so we can help manage them. The first step in doing this is learning
the birds’ migration route.
The effort to understand the movement
patterns of birds began in North America during the 1800s when the famous
ornithologist John James Audubon started tying silver string to the legs of
eastern phoebes, Sayornis phoebe, to
see if individuals that left in the fall returned in the spring. Of all the
birds Audubon marked, 2 returned in the spring. This little experiment
transformed into the bird banding/ringing program we know today with different coloured
metal bands replacing
the pieces
of silver string.
Though the bird banding program has been
essential to the understanding of bird ecology, life history and migration it
is has one major flaw. This flaw is that banded birds must be
spotted again
and it’s
estimated that only 1
in 10,000 banded birds are recaptured, leaving a large data gap. So
why use bands, why not use GPS tracking devices? Well, they do for larger birds
but
for many bird species the size and weight of a tracker is too much of stress so a better
solution is needed. This solution is up and coming from Dr.
Kristen Ruegg’s lab
at UCLA and it has been dubbed The Bird Genoscape Project.
Ruegg and company have taken on the task of
creating a protocol that will allow them to identify where a migrating bird has
come from by using just a feather. To get a full comprehensive understanding of
this protocol please refer to Ruegg et al. 2014 but I’ll briefly explain their methods
here: Variation in DNA is what makes individuals unique
but a huge portion of an organism is actually shared with
the individuals
of the same species. As groups or populations of a species become more isolated
and
breed with
other individuals in their populations more, the
populations start to diverge, this is population differentiation. Individuals
in a breeding population will be more similar to each other than to other
populations.
The UCLA team used the concept of
population differentiation to find the small bits of DNA, called single
nucleotide polymorphisms (SNPs), that are unique to each breeding population, a
genetic fingerprint some might say. For their study they looked at
the Wilson’s warbler, Cardellina pusilla,
taking small blood
samples
from
individuals in each breeding population and each population’s genetic
fingerprint was made.
With a genetic fingerprint for each
breeding population Dr. Ruegg and
her collaborators were able to collect feathers from Wilson’s warblers across
North America and identify where it came from with an 80-100% success rate. So
a feather collected in Colorado in the late fall could be traced back to the
British Columbia breeding population, meaning Colorado is a stop off point.
This solves the major problem that banding had; you don’t need to come in
contact with the same bird to get information, any bird in the species will
work.
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From Ruegg et al. 2014. Each colour depicts a
breeding population, arrows are stopovers and circles are wintering grounds
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An interesting finding from
UCLA’s study was
that there are 6 breeding populations of Wilson’s warblers opposed to the 2-3
that biologist previously thought and that 3 of the breeding populations
actually share a wintering ground and flight path. Two of these three breeding
populations are stable but one population is declining, suggesting the cause of
decline stems from the declining population’s breeding ground. If the issue
stemmed from the wintering ground of the flight path, the other populations should
be affected too.
So what’s next? Ecological managers now
know where the issue is likely originating from for the Wilson’s warbler but
still need to identify the root cause. As for The Bird Genoscape
Project, Dr. Ruegg has
moved on to
repeating
this study with the
American
Kestrel. There is
also
work being done with museum samples to see if ranges and flight paths have shifted with
time. It’s looking like The Bird Genoscape Project can only get bigger,
spreading
to more migrating bird species and become an essential tool for bird
conservation just as bird banding did in the past.
For more information see:
Ruegg K.C., Anderson E.C., Paxton K.L., Apkenas V.,
Lao S., Siegel R.B., Desante
D.F., Moore F., and Smith T.B. 2014. Mapping migration in a songbird using
high-resolution genetic markers. Molecular Ecology 23:5726-5739.
Kristen’s interview with Podcast Eye’s on
Conservation is available on iTunes
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