Wednesday, April 7, 2010

More Greater Sage-Grouse

Last weekend I found myself once again up early and out the door to get some sage-grouse photos at a nearby lek.

Earlier in the week I was out counting birds at a few leks for work, but this time the lek viewing was for fun.

I am not sure that I will be able to get much lek counting in this year with other work commitments, but I have an excellent crew (Matt and Marisa) to ensure the leks assigned to us get counted. We cooperate with Montana Fish, Wildlife and Parks and their great bunch of biologists and a recently retired biologist to ensure that all the known leks in Valley County get counted at least once and preferably three times during the next month or so.

Early in the season there are lots of fights as the males jockey for the best spots on the lek.

This is what it is all about for the males. About 12 females wandered into the lek and watched the males displaying. I am not sure how many times they visit the lek before copulating with the male of their choice but it must be more than once - I didn't observe any copulations during the course of the morning.

A couple of years ago I blogged about a sage-grouse study that I had initiated with Dr. Dave Naugle of the University of Montana (you can read that post here).

Jason Tack, the graduate student selected to conduct the research (photo above from the 2008 trapping effort) recently finished his thesis on that work. Below is a link for his full thesis (click on the title for the PDF) and the abstract of his findings.


Implementing conservation in the face of unprecedented landscape change requires an understanding of processes and scales that limit wildlife populations. We assessed landscape-level processes influencing sage-grouse (Centrocercus urophasianus), to a migratory population in the Milk River Basin (MRB), northeast Montana, USA, and south-central Saskatchewan, Canada. A regional analysis of leks (e.g., communal breeding sites) documented that populations impacted by the increasing extent of agricultural tillage, roads, and energy development out to spatial scales larger than previously known. Using bird abundance as a novel way to evaluate human impacts revealed relationships that would have been missed had we not incorporated lek size into analyses. For example, large leks are 4.5 times less likely to occur than small leks when agricultural tillage fragments 21% of land within 1.0km of breeding sites. Sage-grouse in the MRB met or exceeded demographic rates of stable or increasing populations, and thus, are not likely the cause for annual declines. Spring and summer survival of radio-marked females was higher in 2008 (0.91), than in 2007 (0.55), the year we documented an outbreak of West Nile virus. Nest sites in the MRB had lower shrub cover (15%) than range-wide estimates (15-56%), and overall shrub cover instead of sagebrush cover, was a better predictor of nest-site selection. Plains silver sagebrush (Artemesia cana cana) made up half of total shrub cover (7.1%) at nest sites, suggesting that other shrubs compensate for lower sagebrush densities in the MRB. We discovered the longest migratory event observed for sage-grouse, with females travelling 40km to120km from breeding to wintering areas in Wyoming big sagebrush (A. tridentata wyomingensis) habitats in Montana. Habitat may be sufficient to maintain a small population in the MRB, but its ability to persist through time and to buffer against stochasticity is depressed now that this once-large population has become small and isolated. For example, impacts of disease are compounded when acting on fewer individuals and working synergistically with fluctuations in growth rates. Consequently, conservation of sage-grouse in the MRB will depend on maintaining the current habitat base, and on restoring sagebrush-dominated grasslands currently occupied by agricultural tillage.
I hope that the results of Jason's work will lead to effective conservation efforts in both the U.S. and Canada to help ensure that this unique population of migratory (120 km or 75 miles!) birds continues to occupy this special part of the northern Great Plains.

Earlier this week I was able to participate in another capture effort on the same lek. This time we are using GPS tags on the birds that will collect the birds locations every 4 hours and then download the coordinates once a week to the university where a new graduate student will expand on Jason's work.

Orin and I remove a male from under the net.

This time only the two females we caught received the transmitters (note the well camouflaged transmitter on the bird's back - good job Rebecca!). There will also be a few tagged males this time around as well because the harnesses used this time will not interfere with breeding activities.

After the usual suite of samples and measurements were taken the birds were turned loose with their new hardware we hope will provide us with a more detailed description of the habitat use and movement patterns particularly during their migration and during winter.

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