I am not a birder. Yes, I can identify some of the unique birds that we see like robins, Canada geese, maybe some nuthatches and chickadees. But for the most part, I don't have the eye or the quickness to see the distinguishing features of some of the most common birds that fly about our neighborhood. When it comes to photographing them, well forget about it!
I was shocked recently when one of my acquaintances casually asserted that all sparrows should die. According to them, sparrows are an introduced species that are killing off our songbirds. I immediately questioned this statement, so let us examine this and determine its validity.
A case of unintended consequences
In 1851 the house sparrow (Passer domesticus
) was introduced into North America when eight pairs were released that spring in Brooklyn, New York. Additional numbers were introduced between 1872 and 1874 in Cincinnati. The plan was to control the insects that were damaging the grain and cereal crops.
Biological control of pests has been documented in China as far back as the 3rd century CE. This technique was being widely studied and implemented in the mid-19th century. Even today, we can read about the application of biological control with the release of genetically modified mosquitos to control Zika virus. Perhaps the most notorious unintended consequences happened with the release of Cane Toads in Australia in the 1940s. The toad went from an introduced species to a feral invasive species in just a few short years.
The house sparrow introduction has not been without its own unintended consequences. The house sparrow is an Old-World Sparrow of the order Passeridae. Allegedly brought in to control insect pests, the house sparrow is primarily vegetarian, adapted to eat nuts and seeds. This bird very successfully occupied North America and by 1898 was already being seen in Alberta. If you were to draw a map of North America and colour in the range of the house sparrow, you would find you filled in virtually everything south of the 60th parallel and even some range into the Northwest Territories.
Indeed, as my colleague feared, the ecological impact of this introduced species is primarily negative. I don’t believe the house sparrow actively kills other species; rather they displace native bird species, including robins, native sparrows and chickadees. You may have observed how aggressive flocks of house sparrows chase off the other bird species.
What have we learned from genomics
An international consortium of more than 200 scientists from 80 institutions across 20 countries is sequencing and comparing the full genomes of a significant number of bird species representing all major branches of modern birds. I expect the results of their studies will enhance our understanding of both the evolution and the ecology of birds over the next few years.
In a paper published on August 8, 2018 the authors led by Mark Ravinet Centre for Ecological and Evolutionary Synthesis, University of Oslo investigate the genomics associated with the house sparrow. Their interest in this sparrow has to do with it being labeled an anthrodependent species living in commensalism with humans. By comparing the genomes of the house sparrow with closely related Eurasian species they found that the ancestral population of house sparrows probably branched off during the Neolithic Revolution at the beginning of the spread of agriculture. Most significantly this study indicates that the gene AMY2A, a part of the amylase family, is linked to the adaptation to high starch diets found also in humans and dogs. The authors conclude that this rapid adaptation to a new niche ties the evolution of this bird species to the development of modern human civilization.
The house sparrow is also a model for comparing native populations with introduced populations regarding founder effects, genetic bottlenecks, selection versus drift, and the effects of epigenetics on phenotypic plasticity.
In the next blog
, I will discuss some of the local sparrows that contribute to Alberta’s biodiversity.
Links of Interest:
Signatures of human-commensalism in the house sparrow genome
Invasion genetics: Lessons from a ubiquitous bird, the house sparrow
You can also find me on