I'm confused, should we really be surprised that crossbills are feeding
on something other than one species of conifer?
Call me a skeptic. I'm ok with the idea that some crossbills have
different calls. But does that translate into diet isolation and
reproductive isolation? How would we know?
Sure, maybe some crossbills prefer certain types of cones/species based
on where they originated. But are we suggesting that they will refuse
to eat something else when their main source of food is limited?
Something tells me that is not the case.
Where is the evidence that crossbills will only feed on a certain
species? Maybe they prefer a species, but where is the evidence they
are this isolated or specific to one species?
Furthermore, where is the evidence that they are this reproductively
isolated? How do we follow crossbills of different types around as
they wander and document that these different groups are not criss
crossing and not breeding with each other? How do we know in the vast
stretches of Canada and Alaska and North America that crossbills always
only breed with their own calling kind? How do we know that their
calls are not more plastic than some may think? Where is the genetic
evidence that they are completely or nearly completed isolated?
Maybe I'm just ignorant. Maybe I don't read enough scientific papers
on these matters. Maybe I'm just out of touch.
But I'm skeptical.
I have a hard time believing that a hungry crossbill won't eat anything
that isn't the supposed cone their call is associated with. If that is
the case, when their crops fail, how the heck do they move hundreds if
not thousands of miles eating nothing to find the cones that suit their
call type? Wouldn't they starve long before that? It's like saying
Myrtle Warblers don't eat myrtle berries because all they eat is
insects, or they don't eat insects cause all they eat is myrtle berries.
Maybe all these red crossbills are really just one species with
different calls, and not mutiple species with different calls.
No need to answer me, I'm just expressing a different perspective on
this. Maybe we shouldn't be surprised at crossbills feeding on alders,
or whatever cone is available to eat. Maybe they are just HUNGRY?
Cheers
Dave Lauten
skeptic
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