Sage-grouse, © Stephen Ting/USFWS

A Tale of Two Chickens

Tim Male, Vice President of Conservation Science and Policy 

It was the best of times, it was the worst of times. For lesser prairie chickens and greater sage grouse, two very similar birds, things are trending toward the latter.  Greater sage grouse have disappeared from more than 50 percent of their range, and the prairie chicken from more than 86 percent of theirs.  Both are candidates for listing under the Endangered Species Act.  But the stark differences in federal goals for these two species highlight problems in how the U.S. Fish and Wildlife Service (FWS) is managing different species.

For some species that have not yet been added to the endangered species list, federal and state agencies, private landowners and businesses that might be affected by it sometimes make a last ditch effort to keep that listing from happening.  To prevent it, conservation efforts need to eliminate or reduce threats to the species, including the threat of having a population so small that it  could go extinct simply by chance. Below a certain number, the population can’t survive. The question is how biologists determine what that number is for each species.

Currently, there are up to 300,000-500,000 sage grouse on tens of millions of acres of western sage brush habitat.  The FWS determined that any population of sage grouse with fewer than 200 males, or a total of fewer than 500 birds, must be considered ‘at risk’ because the small population is inherently more vulnerable to extinction. They identified more than 40 populations that meet these conditions, and set goals for their conservation. The agency’s strategy calls for the smallest of these populations of sage grouse to be protected so that threats go down and numbers go up – a sensible approach, and one that should be applicable to most species under similar conditions.

The FWS’s conservation goals for the lesser prairie chicken, however, offer a stark contrast. There are currently an estimated 37,000 prairie chickens remaining – a far lower number than the sage grouse, and this out of a historic population of two to three million.  For this bird, the agency has hinted that the species is not “at risk” so long as it maintains a minimum of four “strongholds,” each consisting of 25,000-50,000 acres of habitat and just 6 male and 6 female birds.  Add that up and what do you get?  200,000 acres of habitat and only 500 birds in total. Although the documents also obliquely reference ‘additional strongholds,” it looks like they are setting this low threshold up as being enough conservation to avoid listing.  And even if additional strongholds are established, there would likely remain large, unaccounted gaps between the goals for the prairie chicken and those for the sage grouse.  Dan Ashe, Director of the Fish and Wildlife Service, stated that he sees this plan as having all the ‘right ingredients’ for conservation to make an endangered species listing unnecessary.

lesser prairie chicken

A lesser prairie chicken in New Mexico (Credit: Larry Lamsa)

As a scientist, it’s extremely difficult for me to understand any scientific rationale for the differences in conservation goals between these two very similar bird species.  Both species have generally similar diets, longevity, reproductive potential and breeding system.  How can one say that the sage grouse’s future depends upon having 20,000 birds in dozens of populations across 165 million acres of habitat, but at the same time state that prairie chickens only require 200,000 acres of habitat and 500 breeding birds in total? And, if the Service’s goals for the prairie chicken are scientifically valid, and a population of 500 means a species is neither threatened nor endangered, how can FWS even have considered listing the 500,000-strong greater sage grouse?  Those differences certainly look like the agency is setting expedient goals rather than scientific ones.

The Endangered Species Act is capable of achieving great things for species on the brink, but with taxpayer dollars funding their recovery it is important that the Act’s protections be applied to the species that need it most. It’s unfortunate that FWS has never set measurable standards that define what makes a threatened or endangered species, even though the IUCN, the State of Florida, New Zealand and other countries have already done so.  Those standards would be one step toward a more scientific basis for one of the most important wildlife questions the U.S. government faces: whether a species is or isn’t endangered.