Where Winter Wrens and Pacific Wrens Meet, But Never Greet

Lynsey Kitching


Ever been out sitting on your porch or hiking along the Tumbler Ridge Point trail in the morning and heard what seems like a symphony coming from the tree tops and bushes?

Well, this is because Tumbler Ridge is home to many different species of birds, in fact it is one of two great areas in the whole world where eastern and western bird species meet. This is called a contact zone.

Darren Irwin, who runs the Irwin Lab at the department of Zoology at the University of British Columbia (UBC) says, “Tumbler Ridge is in the heart of one of the two great west/east bird contact zones in the entire world. The other one is in central Siberia and I spent a lot of time there during my thesis work in the late 90s. I was studying these birds called Greenish warblers. It turned out that in central Siberia there are these contact zones for east and west species. It became my specialty to study those.”

In 2004, Irwin was hired for a position at UBC and decided he needed to find an area to study closer to home.

He began studying books and reading about different types of birds in Canada. “What I noticed was there were a lot of eastern bird species and a lot of western ones. The range limits of those species tended to occur in western Canada in this general area,” explains Irwin.

Not known too much about western Canada, because he grew up in California, Irwin decided to hit the road and go see, or rather, hear for himself.

“I decided to pick one species of interest, and I was interested in winter wrens. One reason is because they occur in Asia and Europe, so I already had some experience with them in Asia. The winter wren is the one who gets the farthest north. They breed in old mature forests and are often called the pinnacle of song complexity in birds,” explains Irwin.

Up until this point, the winter wrens were divided into two sub-species, but previous workers had noted they sounded different in the east and the west.

“I decided to drive around western Canada, it was great fun,” explains Irwin, “I would stop the car and listen to the birds wherever I went. Then I said, I need a place where these [the eastern and western wren] come together. Are these two forms of wren the same species or not? Do they blend together? It was quite hard. They aren’t very prominent across the landscape in this area.”

However, just to the east of Tumbler Ridge, Irwin made a big discovery. After having looked at an online birding map, provided by Mark Phinney, President of the South Peace Bird Atlas Society, Irwin saw that most wrens were seen in the Peace region around the Quality Creek area.

“There was a big red dot on the map. Well, that happens to be just east of Tumbler Ridge. So I said, ‘I have to go there.’ I went and I found this wonderful trail, the Quality Creek hiking trail. I sat down for a rest at the top of a hill and I heard a wren at the bottom of the hill singing. I listened and it was an eastern form. I wandered around a little more and across the road I heard another wren, and it was the western form. They sounded different.”

Irwin then setup a net to try and catch the wrens. He used a speaker with an iPod to attract the male wrens.

“When you sing a song to a male bird, they get very angry and think another male has come into his territory, want to come investigate and you can catch him in the net…Here I almost caught a black bear,” laughs Irwin, but at last the birds were caught, and given bands so they can be identified later.

Irwin explains the two birds (the eastern wren and the western wren) look pretty similar, with only a slight difference in colouration, but other than that, they are very similar. But, if you hear them, they sound quite different.

“Eastern ones are a little more melodic, the western ones a little more high strung and staccato. It is those high versus low frequency trills that I was listening to,” describes Irwin.

He then decided to do a full study. “Are they different enough in this area that we could call them different species?” he asked.

Irwin explains female birds prefer long complex songs, because it points to the general health of the male, and their parental upbringing. This is important because as Irwin says, “If songs become different between two groups, they may not interbreed anymore.”

The team then did some DNA testing to see how many differences there are in a segment of mitochondrion DNA from one individual to another.

Irwin explains the results, “In the western group there are at most two mutations separating the birds. In the eastern there is one. Between those groups there are 65 changes between them. This indicates these two groups that sound different are highly divergent genetically. They last shared a common ancestor a long, long time ago. We confirmed that result with nuclear DNA sequencing. As different as they are in song and genetics, they still do look very similar.”

This is called a Cryptic species.

So, what next?

Irwin explains, “We declared the western form as a different species. We submitted to the American Ornithologists’ Union an official recommendation to declare the western form a separate species. They agreed with us to consider the pacific wren and winter wren as separate species.”

This happened in 2010.

Tumbler Ridge can claim they were the site where this was discovered. I think that is kind of cool,” says Irwin.

This speciation isn’t always the case with different types of birds in the area. For instance, the morning warbler and the McGillivry warblers, the east and west versions, do interbreed in the area.

So Tumbler Ridge being a very special place in the world in terms of being a contact zone for birds has the potential to spark the interest of tourists. “In terms of tourism, I think the birding potential, to attract people here, is quite high. Where else can you go to get so many eastern and western species in one small area,” explains Irwin.

But, in order to keep the diversity of bird species around town, Irwin explains we must be able to balance forestry and conservation, as migratory birds are the most effected by human impacts.

“Migration is genetic; two groups of wrens, two different places. The pacific wren migrates down to the coast of the Pacific Northwest, and the winter wrens living side by side in Tumbler Ridge take a much longer trip to the Southeast US. This is showing their ice age history, they are showing us this is where I lived during the ice ages. These migratory patterns are a geological phenomenon,” Irwin continues, “The wrens don’t occur everywhere on the landscape; you have to work very hard to find them. You have to find the patches of dark green, old forest, trees that have naturally fallen down. They live on spiders and other insects. We need to protect some of that old forest, a lot of them [the forests] are [protected], but I just want to draw your attention. There is lots of clear-cutting going on in the Tumbler Ridge area, we all need wood, but I just want to encourage a balance between forest extraction and protection of the really old patches of forest you have.”

So how does this speciation of birds fit into the Geopark for Tumbler Ridge?

Irwin explains, “When I look at the distribution of birds, I see the impact of geology in the songs they sing, the migratory behaviours they have, their genetics, their plumage, where they live, it’s an impact of the geology. Part of it is the mountain range, which is a natural barrier between eastern and western populations. How exciting it would be for this Geopark idea to catch on because I think it would bring a lot of attention here in many ways.”