Friday, October 3, 2014

Darwin: Cliff Swallows displacing Barn Swallows?

A few days ago, I found this passage in the second edition of Origin "We see this in the recent extension over part of the United States of one species of swallow having caused the decrease of another species." 

I wasn't familiar with this story and I had no idea what species were involved. As a wonderful coincidence, I happened to discuss my blog with another Darwin-phile and she was able to uncover the species identity by referring to Darwin's expanded version of Origins

Here's the same part in the expanded version:

“If one species of Swallow were to increase we might expect that other Swallows would suffer more than other birds; & so it seems to be, for with the late curious increase in parts of the United States of the Hirundo fulva, the Barn swallow has decreased.”

And the footnote associated with this is: Dr. Brewer in N. American Journal of Science. vol. 38 p. 392. 

Unfortunately, I don't have access to this online but Hirundo fulva is the Cliff Swallow. So we have the species identified but I have not heard of competition between Cliff and Barn Swallows. As their name implies nesting habitat is mostly different. Anyone? 

And I realize I don't have pictures of either species. Blugh. 


  1. I cannot find anything on this, but intuitively, it strikes me that this is less about inter-species competition than anthropogenic disruption, given the propensity of both species to exploit human structures.

  2. It's hard for me to imagine a decrease in barn swallows for any reason (other than pathogens) at the time of the reference when barns (and houses with porches) were probably much more widespread than now. I could see the reverse of Darwin's statement given the current status of both species.

  3. Although it should be noted that the time of reference is the front end of mass urbanization; beneficial to cliff swallows, which might explain the noted increase. (But that would not, in theory, affecting barn swallows one way or another).

  4. Is it though? When I think cliff swallows I think bridges and barn sides not paved streets and parking lots. But what was mid-19th century urbanization? Mostly horses and backyard chickens, right? So maybe cliffs did like "urbanization." My guess is that this wasn't based on any data other than a local observation. BTW, there was a cliff colony in the small Pocono community of Blakeslee, PA on the side of a CVS that was then power-washed off. A bit depressing

  5. 19th-century urbanization was essentially about factories, tenement residences, bridges, and filthy, muddy streets - lots that the cliffs could exploit!