Discuss: The Fall of a Sparrow

“They did not arrive…” is not telling the whole truth.  Perhaps they did not “arrive” (from some other place) in their NATIVE* range, but they are considered invasive pests in the areas to which humans DID bring them (e.g., the Americas)—places that they would not have arrived without direct human intervention.  This species “may evict native birds from their nests and outcompete them for trophic resources.”  “Early in its invasion of North America, [this species] began attacking ripening grains on farmland and was considered a serious agricultural pest.”

Let’s not glamorize an invasive pest species (outside its native range)!

-pt

(*Its native range—i.e., where it evolved—is “Eurasia and northern Africa,” according to Global Invasive Species Database [a product of the Invasive Species Specialist Group of the IUCN, an internationally-respected group of scientists].  http://tinyurl.com/2wj84z)

In response to Phillip: Humans in North America are also an invasive species. So are lots of other organisms (some rodents, bacteria, domesticated animals etc). So, saying an organism is an invasive species is not much of an argument.

Likewise, “native species” is not necessarily of particular value. As a biologist, I can tell you that many species become extinct and are replaced by other species. For example, the horse which evolved in the Americas became extinct in North America after it had invaded Eurasia. Good thing they did not get rid of the horse.

What seems to be important to humans is first of all to find out why a given species is decreasing significantly in numbers. The decline of House Sparrows in Europe suggests there has been a change in the environment. One possible change in the environment given by the author is the spread of an avian influenza virus to House Sparrows.

I think that any successful species can be considered a “pest species” if and when that organism gets in the way of humans.

So how do you define “invasive species”? Are humans “invasive”? Are domestic cats “invasive”? Do we apply that term only to species we’ve introduced that we subsequently regret having introduced?

What I am saying is that the term ‘invasive species’ is descriptive only. Species commonly invade one area or another. Some use birds and hitch a ride. Others use humans or arrive accidentally. There are always consequences when a new species arrives in an area in which it was previously not present.

I have difficulty with saying that invasive species are bad or good. That says more about the speakers values.

Mystery of their Badges

I thought I saw some research a few years ago which suggested the “badges” indicated a hierarchy of dominance among males which manifested itself in who was allowed primary access to food.

I’m sure the article I saw suggested an almost military ranking order depending on size of the said badge or shield.

I read the book, “Providence of a Sparrow” by Chris Chester in which the author and his wife share their house with a sparrow.  I’ve been fascinated by these creatures ever since.  I believe we take it for granted that sparrows will always be around.  This is probably another wakeup call that something is amiss in the environment.

Sparrows are a fixture in my neighborhood and the article describes them very well.  They’re hard working, cheerful,and ever present.  I’d hate to see them leave.

Difficult toppic, Philip touches on the clasic definition of “invasive” species, but at what point should it no longer be an invasive? They have been around for quite some time now, why not just leave them alone and accept that fact, at least that is what I am trying to do. May be we should focus on another “invasive” and parasitic avian like the brown-headed cowbird and the impications that is is now coast to coast in the US, when historically it never used to be. To me that is a deeper, darker and more far reaching problem than a house sparrow.

While I was a graduate student at the University of Kansas in the early 1960’s my major advisor, Richard Johnston, studied the evolution of the House Sparrow in North America.  He demonstrated in a series of papers, the first one appeared in Science, that the species had experienced morphological change in just a few generations in response to natural selection caused by various ecological differences.  For example, sparrows in Edmonton Alberta were darker and larger than sparrows inhabiting desert areas of the Southwest (responses ecologists know as Bergman’s and Allen’s Rules.) Johnston’s work helped to advance the thinking of evolutionists that change can occur more rapidly than once thought.