Saturday, April 12, 2008

Another Grouse Morning

Friday morning and I was up and out the door again bright and early (well, not so bright but definitely early!). Another couple of Greater Sage-Grouse leks to count and collect feathers on. We had a pretty good thunderstorm move through to the north on Thursday night but I really wanted to get out so I figured if the roads were bad I would turn around and head back to the office. The roads were actually pretty good and I wound up getting to both leks I had hoped to survey.

One was my favorite lek I have been surveying for last few years. It has been down by about half this year as have a number of other leks but there are others that are right about where they were last year. We are not sure what the cause of this is but West Nile Virus is certainly a potential cause.

The other lek is one of the most difficult ones to survey because of the need to drive a good distance on a pretty poor road (well two track trail would be a more apt description). But it is worth the drive because it is the largest lek in the area with 52 males displaying this week. That number should go up a bit in the next week or so as the young males start to attend the lek.

This is a portion of the large lek. There are about 21 males displaying in this photo.

I also stopped by another lek on my way back to town. There were no birds on the lek or in the area and although it was a bit late in the morning, there should have been some birds lingering in the area since this is pretty close to the peak breeding time (there were more females than males on the first lek I surveyed). I headed out to the lek to collect some feathers and there was plenty of sage-grouse "sign" at the spot.
Although they are hard to find in this large landscape without having the birds present, when you do stumble on a lek it is pretty unmistakable - there is grouse poop all over the place like light green Cheetos littered on the ground, with occasional dark patches where it looks like someone spilled tar. The tar patches are another type of fecal matter that expels the toxins ingested from the sage plants the birds eat exclusively in the winter. The ground is also trampled down in the center of the lek and there are usually a number of feathers scattered around - a byproduct of occasional fights between the displaying males.
After I gathered the feathers I could find I headed back towards the road and then I found this a short distance from the lek and I knew why there were no birds there this morning.

This is a pile of Greater Sage-Grouse feathers. If you click on the photo to make it larger you can make out the head lower left of center in the photo. Look for the yellow combs above the eye.

The most likely culprit, a Golden Eagle, based on evidence at the scene of the crime. Very little of the grouse was left. Only a piece of the pelvis, the head and lower mandible, and feathers remained. There was one large mute (eagle poop) streaked through the middle of the feathers.

Leks can be a dangerous place for these birds. Much like I know to go to these traditional areas to count grouse, predators also learn to return to the leks looking for a meal. Although this may seem like a very high cost to showing up on a lek or even evolving a mating system that exposes individuals to such a high cost, the benefit is related to the nature of these birds and the landscapes they live in. In such large open areas, a female may never find a male to mate with if there was no place where they could reliably be found and even then she would have no way of assessing mate quality. The lek centered breeding system enables these birds to find each other regularly and also the females can assess mate quality by the location of the males on the lek, with presumably better quality males occupying the central areas of the lek. Predation risk can also be mediated by the number of animals looking for predators on the leks although the vigilance is presumably greater in the females since the males usually concentrating on beating each other or gaining a mating opportunity. Sounds about right.
I also found a small Sharp-tailed Grouse lek on my way home. I hope to find another lek closer to home to get some more photos of this prairie grouse species. They are much more active dancers than the sage-grouse and much more pugnacious too.


ArtSpot Gallery said...

I'm glad that you put the Greater Sage-Grouse feathers photo up. Although it may be thought somewhat morbid, it's a beautiful composition and part of life.
See you soon,

Max said...

It is amazing how fast a lek clears out when a golden eagle passes overhead. I have seen males display a few meters away from a coyote, but they do not mess around with goldens.