To the casual observer, the castoffs of the digestive process of the greater sage-grouse may simply be considered poop.
But to the bird's researchers, they are proving to be valuable nuggets that contain elusive information about its population levels.
That's the upshot of recently published research conducted by Colorado Parks and Wildlife, working in cooperation with Colorado State University and the U.S. Geological Survey and focused on the isolated Parachute-Piceance-Roan greater sage-grouse population in Garfield and Rio Blanco counties.
The research used DNA analysis of grouse fecal droppings collected in snow to estimate populations during the winters of 2012-13 and 2013-14. Researchers say that while the method, known as non-invasive, genetic mark-recapture analysis, has been used to estimate populations of a number of wildlife species, this is the first time it has proven feasible for estimating greater sage-grouse populations.
That is important because of the longstanding challenge the species has posed to researchers trying to calculate their numbers, something crucial to managing their habitat and determining what level of protection they require. State agencies and other parties have been working to keep the bird from requiring listing for federal protection under the Endangered Species Act.
Typically, greater sage-grouse can be hard to detect and thus count, said Brett Walker, an avian researcher for CPW and a co-author of the study, principally authored by Jessica Shyvers, a former PhD student at CSU. The birds generally try to escape the notice of predators, but during the spring mating season the males lose their inhibition and strut at lek sites, or breeding grounds, to try catch the attention of females.
As a result, biologists long have relied on counting males at lek sites during the spring to estimate population numbers. But while that method helps track changes in male sage-grouse abundance and distribution over large areas, Walker said it's not as good at accurately estimating abundance at a given time, and especially the numbers of females, which are key to healthy greater sage-grouse populations.
Genetic mark-recapture analysis is a high-tech version of a traditional biology tool that involves capturing and marking animals with bands, transmitters or another device, then later capturing more animals and seeing how many were previously caught. A low proportion of marked animals being recaptured indicates a high overall population. Walker said statistical modeling can be used to analyze recapture numbers and estimate populations.
For the greater sage-grouse, the approach involved collecting feces and analyzing the DNA on it to identify individual birds, then collecting more feces later the same winter to see how many samples belonged to previously identified birds in order to estimate population numbers.
As it happens, the study ended up determining that greater sage-grouse numbers in the Parachute-Roan-Piceance population more than doubled over the course of a year, to 745 birds.
Walker said over the long term, rangewide greater sage-grouse numbers have decreased, as has their range.
"But it's like a lot of other game birds. You can have boom years and bust years. We just happened to capture one of these years when it was a real boom year," he said.
He said some of the highest greater sage-grouse numbers in Colorado were recorded from 2014-16 but their numbers have decreased since then, including in the Parachute-Piceance-Roan population.
That population overlaps natural gas resources locally, and Garfield County commissioners have pushed for more accurate mapping of the bird's range so conservation efforts don't unduly limit drilling activities. ExxonMobil/XTO Energy, which holds natural gas assets in the Piceance Basin, provided most of the funds for the recently released study, which can be found at onlinelibrary.wiley.com/doi/abs/10.1111/ibi.12768.
Walker says the genetic analysis approach to population counties could be particularly important when it comes to dealing with isolated greater sage-grouse populations subject to changing habitat and land use, such as the Parachute-Piceance-Roan birds.
For that reason, it could have important applications for management of the Gunnison sage-grouse, which is federally listed as a threatened species. Its main population is in the Gunnison Basin but several small populations are located elsewhere, including in Mesa County.
For now, however, cost is a limitation in using the genetic approach. Walker said those costs range from the DNA analysis itself to other expenses such as field crew operations, housing, and snowmobile operations and repair. But he hopes that over time, thanks to advances such as increased automation, the costs will come down to the point that the approach is widely used in greater sage-grouse management.
It's far easier on the birds than catching and marking them would be. And while one might think dealing with samples of pellet poop is not so pleasant work for researchers, Walker described the pellets as "essentially little green Cheetoh-looking things" that consist almost entirely of the sagebrush material the birds eat, with some genetic material on them.
"I've got a bag of them in my office. They smell great. They smell like sagebrush. It's not gross poop or anything like that," he said.