A Tale of Two Finches

This photo was the beginning of an very interesting story.  Or, maybe, several stories. One about identification, one about animal behavior, and one about how incredibly difficult it can be to find what seems like pretty simple information.  Lets start at the beginning.

 Last week, I spotted these two birds on the rail outside my living room window.  They were there for quite a while, and I was able to get plenty of photos.  I've had lots of finches around this year -- and the colorful Goldfinches stand out.  The flash of yellow in the trees always gets my attention.  When I uploaded the photos, though, I was a little baffled.  Just who is that second bird handing out with the Goldfinch?

First, I should tell you I blew the identification even on the most obvious bird.  Looking at my photos, and looking at descriptions in the birding guides, I concluded that the dark discolorations on his back were the olive coloring that is characteristic of female Goldfinches.  Strike one.

Then, I started looking at the second bird.  Well, it's not a sparrow.  It's not a female House Finch (the beak is way to small).  What is it?  There have been a lot of Pine Siskins around this year -- and you can clearly see that small beak -- so naturally I considered that.  It didn't look like any of the Pine Siskins I've seen though.  And it didn't look like any of the photos I could find in my guides or online.  So?  Finally, I decided that it must be a juvenile Siskin.  Strike two.

So I sent my photo off with my best guesses to my friend Kevin, who's the naturalist at the PAWS Wildlife Center.  And it turns out I was totally wrong.  If you look at the photos, the Goldfinch is clearly male.  He has the little black cap on his head (which always reminds me of Moe from the Three Stooges).  The dark spots are because he's molting, just coming into his full spring colors. 

And the second bird.  Well, it turns out, she's a female Pine Siskin.  Yep.  In both cases I had the species right and the specifics wrong.  I've lost count of what strike that is, but I'm probably out.

However, Kevin had a question.  Which opens up the second part of the story:  "Were these guys part of a larger flock, or were they just hanging out together?"

I don't really have the answer to that .  There has definitely been a large flock of Siskins around for the last month or so.  They're beginning to thin out a little now, but there are still plenty of them here.  And there have been a number of Goldfinches around too -- not flocks of them, but I have often seen two or three in the cherry tree at the same time, which has never happened before this spring.  But for the time I was watching them -- which must have been about half an hour -- these two were hanging out together on the rail, eating.  It was just them, and when they left, they left together.  Circumstantial evidence at best.  But it turns out that Goldfinches and Pine Siskins, being closely related, and having a tendency to intermingle, can occasionally interbreed.  "You might have an interesting inter-species romance going on in your yard," Kevin wrote. 

Well, "inter-species" is a phrase that always gets my attention.  I'm a sucker for all those photos on the web of different animals who become friends.  And I'm fascinated by the whole topic of inter-species communication.  So naturally, I love the idea of a mixed romance going on right outside my window.  I went looking for more information on the web about interbreeding in finches and hybridization in general.  Turns out, it's a very big field.  A couple of years ago, National Geographic ran an interesting article on the role that hybrids might play in evolution -- how they could actually lead to the creation of new species.  It might be much more common than scientists thought, especially among insects like butterflies.  But what I couldn't find were any photos of Goldfinch/Pine Siskin hybrids, although the possibility was mentioned in several sources.  (And I discovered interesting facts along the way -- such as:  The Goldfinch is sometimes called the "wild canary" and they have been interbred with domesticated canaries to create pet birds.)

But mostly, the topic of hybridization raised more questions  than it answered.  For instance, under what circumstances would an animal be attracted to a member of another species?  It would seems, even in closely related species, like Goldfinches and Pine Siskins, individuals of another species would lack the markers that would activate attraction.  But as the National Geographic article suggests, there could be an evolutionary advantage to occasional interbreeding -- freshening the gene pool for instance, or allowing for new kinds of adaptations.  I have to wonder if, as climate conditions continue to change and that change accelerates, we might see more of these kinds of "wild" evolutionary strategies.  It would be worth exploring.

Which brings me to the final part of the story.  I wondered whether Goldfinches and Pine Siskins were closely enough related that their offspring would be fertile.  Many species (like horses and donkeys or lions and tigers) can interbreed, but the offspring is infertile -- a mule.  And so I started looking for what I thought was a simple piece of information: how many chromosomes do Goldfinches and Pine Siskins have?  Is it the same number or different?  I assumed that in today's world, with genomes being decoded left and right, it would be a relatively easy question to answer.  I was wrong.  I couldn't find it.  The librarians I talked to couldn't find it.  And the experts haven't returned my emails.  So I don't have that "simple" fact to pass on.

If anyone out there know more about Goldfinch/Pine Siskin hybrids -- especially if you've seen photos -- or about finch genetics -- I'd love to hear from you.

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