Monday, November 30, 2009

Fence collisions and sage grouse

Making headlines across the West of late is a two-page preliminary report issued by a Wyoming Game and Fish Department biologist noting that barbed wire fences pose a collision hazard to Greater Sage Grouse. The U.S. Fish and Wildlife Service is expected to meet its court-ordered February deadline to determine if sage grouse should be granted Endangered Species Act protections, so the report will come into play there. Those who oppose livestock grazing on public lands are also latching onto the report as another reason to rid the western range of its agricultural industry, and its associated fences.

But everyone might be reading more into the report than it merits. WG&F biologist Tom Christiansen noted it all began when two separate falconers provided incidental reports that grouse had been injured or killed on the top wire of certain fences located near important grouse areas. The area is just to the southeast of where we ranch, in the border area of Sublette and Sweetwater counties. This area is believed to have one of the largest concentrations of sage grouse on the planet. It’s falconer Steve Chindgren’s stomping grounds (the falconer who is the subject of Rachel Dickinson’s Falconer on the Edge).

According to Christiansen’s report, “One of these falconers subsequently began marking such fences with aluminum beverage cans in a volunteer effort to reduce these mortalities.”

The WG&F study sought to quantify the level of sage-grouse fence strikes and mortalities and test whether marking devices could effectively reduce collisions in a cost effective manner that was not visually intrusive. There are two large grouse leks (traditional breeding grounds) in the area, located within just a few miles of a range fence, and the region also winters at least a few hundred grouse. The fenceline became the study area, with its three strands running nearly five miles.

Here’s the pretreatment scenario: In the two and a half years prior to treatment, observers documented evidence of wildlife fence strikes and mortality while driving immediately adjacent to the fence. They found evidence of 170 bird strikes/mortalities and two pronghorn mortalities. Confirmed greater sage- grouse accounted for 146 (86%) of the 170 strikes/mortalities documented. The other 22 observations included four waterfowl, five raptors, two passerines, one shorebird, and 12 unknown birds.

Researchers then marked ¼-mile sections of the top wire of the fence with FireFly bird diverters or homemade markers that are similar to those used in other areas to reduce lesser prairie-chicken fence mortality. In the next year and a half, collisions were once again observed, with seven grouse strikes in marked sections, and 47 strikes (36 sage grouse) in the unmarked sections. The research suggests the fence markers (all types combined) reduced bird collisions by 70 percent over unmarked sections, or reduced sage grouse collisions by 61 percent.

The study is ongoing, with the previously unmarked sections of the fence being marked, and vice versa. Markers are being changed as well, with highly reflective tape added to the white markers to increase visibility in winter months.
Although we’ll know more once the study is complete, what we know now is this: not every fence is a problem. Those that tend to cause problems include one or more of these characteristics:
1) are constructed with steel t-posts,
2) are constructed near leks,
3) bisect winter concentration areas, and/or
4) border riparian areas.
WG&F is developing guidelines for prioritizing what fences need to be marked to reduce grouse collisions, and is in the process of making markers available to ranchers at no cost.

Meanwhile, Jim and I took at drive out to the fenceline study area last week, and found one collision event – a sage grouse. There were a few grouse feathers on the top strand next to the marker, and grouse feathers in a heap on the road. But the grouse was gone – quick work for a predator.

What the research effort does not mention or address is that golden eagles and other birds of prey have been known to drive their prey into fences and other obstacles to injure or kill them – it’s a hunting tactic. I watched a grouse forced into a flying crash into a willow stand in August, but Rant the guard dog was watching the birds as they came over. He was quick and he ended up with the stunned grouse, which was sorry luck for the avian hunter that had orchestrated the successful maneuver.


Matt Mullenix said...

Cat those remains look particularly like the work of a hawk's plucking. As a falconer I am very aware of fence danger to hawks and prey (my present hawk has been hung badly on barbed wire, twice), but I would say that prey (at least rabbits and small birds) are more likely to use fences as evasive barriers than are hawks likely to use them as proxy killers.

It is very clear from the falconer's viewpoint that prey make speed for fencelines and hawks merely contend with the barrier as best they can.

That said, I have also witnessed 2 hawk chases on jackrabbits in which the jack clearly did not see a fence and slammed into it full speed--both times fatally. It was unclear whether the hawks intended this, but they certainly took full advantage.

Anonymous said...

Jackrabbits also run for fences when pursued by dogs. The dogs don't chase them there, the jacks head there to scrape the dogs off. As a matter of fact some dogs learn to force the jacks away from the fence.

Birds often crash into cover to get away from a pursuing raptor. It is a last ditch effort to avoid capture, not a desired effect from the raptors standpoint.


Retrieverman said...

I've not seen a cock Greater sage grouse or a Gunnison grouse displaying, but is one of my dreams.

I love this footage, which was taken by a camera modified as a grouse hen "fembot":

Rachel Dickinson said...

I had the opportunity to drive to some fence lines with Steve Chindgren and to hang flattened cans along a section of fence in a traditional sage grouse wintering area that Steve had found evidence of bird strikes on. I could certainly see how the grouse could plow into the top wire of an almost invisible fence when they are just gathering speed as they take off . I give Steve a lot of credit for bringing this to the attention of Wyoming Fish & Wildlife and for heading out there on his own for several years in a row to hang the cans.

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