Posted by: soniahs | January 10, 2011

Flockalypse redux

Today, I’m revisiting my recent blog post on the “Flockalypse” to try to shed some light on what scientists mean when they say that large numbers of birds being killed “happens all the time.” I’ve seen this phrase in the news a lot lately, and I want to point out that it does not mean that scientists think that these types of deaths are “okay.”

Instead of taking “happens all the time” as a dismissal of the importance of mass bird die-offs, let’s look at as recognizing that many, many birds are killed every day from causes that are directly related to human activity. How many? Well, that’s hard to estimate, for a couple of reasons. One big reason is that many of these deaths occur at night, and night-roaming scavengers quickly dispose of the evidence.

Here’s one estimate of numbers. A 2005 paper by Wallace Erickson, Gregory Johnson, and David Young (“A Summary and Comparison of Bird Mortality from Anthropogenic Causes with an Emphasis on Collisions“) estimates that 500 million-1 billion birds are killed each year in the U.S. alone from human-related causes. This includes:

  • Collisions with buildings – 550 million (58.2%)
  • Collisions with power lines – 130 million (13.7%)
  • Cats – 100 million (10.6%)
  • Cars, trucks, etc. – 80 million (8.5%)
  • Pesticides – 67 million (7.1%)
  • Communication towers – 4.5 million (0.5%)
  • Wind turbines – 28.5 thousand (less than 0.01%)
  • Airplanes – 25 thousand (less than 0.01%)
  • Other sources (oil spills, fishing by-catch, etc) – did not estimate

While recent large mortality events have been in the news, the point I want to make is that a constant level of bird deaths occurs constantly due to human-related factors. These are large numbers. One in six bird species worldwide is threatened with extinction, because of the factors listed above plus things like habitat loss, invasive species, and climate change.

The endangered Florida Scrub-Jay (byVvAndromedavV, wikipedia.org)

Looking at this list, you should be able to see a number of ways that we can work to prevent at least some of these deaths. Things like making windows and other structures more visible to birds, keeping cats indoors, and minimizing use of pesticides are all crucial to the survival of many species. (For more info on some of these efforts, see the American Bird Conservancy’s site.)

So, can public attention to the recent dramatic bird deaths be used to spark wider awareness of what we can do to prevent the constant slow preventable deaths of birds? Hopefully, it can- and many science communicators are trying to get the word out. Human population growth and natural resource use, habitat loss and invasive species, along with global climate change, are ever-increasing threats to the survival of many species. We should try to prevent this constant rate of attrition whenever we can.


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  1. [...] as well as a pupping spot for endangered Hawaiian Monk seals. The fence is intended to keep predators from slaughtering these ground-nesting birds. A few dozen nest here each [...]


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