In my last post, I talked about the usefulness of our robotic grouse for studying complex social interactions on the lek. This week we tried another method for modifying a male’s social experience– audio playback.
Male Sage-Grouse listening to our rock speakers.
We have a long history of playing back sounds to the Sage-Grouse. For the first several years our basic behavior studies were running along side the ‘Noise Project’, an extensive research program into the effects of noise associated with energy development on the grouse. The centerpiece of the Noise Project was playing back the sounds of two common noise sources (drilling sounds and road noise) from the Pinedale Anticline/Upper Green River area. We used fake rock speakers, possibly the same kinds you might have seen in a SkyMall catalog, to play these sounds at leks, and compare how many birds showed up and their behavior between the noisy leks and control leks that had. I’ll talk more about the results from this project in a future post.
We also used the speakers in 2011, this time as part of the basic behavioral research program. We’ve been interested in the importance of “courtship skills” in the males, and part of that is how attuned males are to changes in their social environment. Does a male change his courtship behavior a lot when a female gets closer, or not very much? Our first experiment with the fembot showed this was related to the success a male has in courting females.
One species used in our 2011 playback study: Pronghorn
Our experiment in 2011 was designed to look at another dimension of responsiveness- how attuned are males to the threat of potential predators? Here we chose alarm calls o f three different species that live with the sage-grouse: ravens, killdeer, and pronghorn antelope. We played these from the rock speakers and measured the strength of the grouses’ reaction, as well as how long it took them to resume their original behavior. Analysis is ongoing, so we don’t yet know how this sort of “ecological” responsiveness relates to their social responsiveness or their success on the lek.
Fast forward to 2013, and we’ve set up the speakers once again, this time to measure how males respond to other males. It would be great to have a robotic male, but as you can imagine, making a mechanical male that is realistic enough to give a convincing display would be a steep technical challenge (never mind making one sturdy enough to withstand an attacking male). Instead, we are playing back the sounds of male struts from the rock speakers to see how males respond to a simulated male at the edge of the lek. Anna has been putting together recordings with different call rates, so we can see if they are attuned to differences in the signals that males may be sending out. We’ve only just begun, but this will hopefully allow us to collect some interesting data on how males respond to other males while Gail puts together the new fleet of robots.
We also played a control vocalization– Horned Lark.
In other news, we observed the first copulation of the season yesterday! The breeding season has officially begun. Our earliest observation ever was on March 19th (in two different years), so we are on the early end of things.
Although we are based out of the University of California Davis, our field studies of Sage-Grouse take us to west-central Wyoming. This is one of the best places to find this species, with lots of good habitat for the grouse and other sagebrush specialists.
View from our camp, 2011
It’s also a stunningly beautiful place to get to work. Our camp looks out on the eastern face of the Wind River Range, a spine of the Continental Divide near Lander, Wyoming. Although we are less than an hour from town, we feel like we are in the middle of nowhere. We can see distant lights from Riverton, and a bit of city glow from Lander, but otherwise we have this patch of heaven almost to ourselves.
Driving through Nevada
The first challenge we face is simply getting all of our gear out to the site. This takes careful packing followed by a long drive through the lonely spaces of Nevada and Utah.
Work trailer arrives.
Once we’ve landed in Lander, the next step is to get the camp set up. Besides our RV, we have to rent a work trailer, as well as propane service. Thankfully we have electricity; there’s a line that runs the well pump for the cattle water tanks in the summer that we can use in the spring (the cows don’t come up until May when we are done with our research- we’ve been fortunate to coordinate with the local grazing leaseholders on this).
Propane tank arrives- nice to have heat, hot water, and cooking capability without having to run into town to fill canisters all the time.
Home sweet home.
Looking for tracks or poop on the lek.
Our first field technicians arrived on March 3rd, and the following day we were out at dawn looking for grouse on the leks. It’s still very early in the season- at least 2 weeks before the earliest sage-grouse mating we’ve ever recorded during our years out here. This means some leks will still be empty while others will have a few males starting to set up territories. Our first visit is to the most accessible lek called Chugwater Lek (in our area each display ground has a unique name). We didn’t see any birds, and a search of the lek surface showed no fresh sign. Our first birds didn’t show up here until March 7.
Scanning Cottontail Lek to count grouse.
Cottontail Lek is our largest lek, and on our first visits there we did find males starting to set up territories. This was the first chance for the crew to see the courtship display, and they were suitably impressed (just wait until they get to experience it from a blind down on the lek instead of a distant look-out point!) We were also treated to a large herd of pronghorn moving past in the early morning light. This was also a new animal for some on the crew. They are taking to the western wildlife quickly, although some are still getting used to the idea of a landscape without any trees!
Pronghorn Antelope near Cottontail Lek
Over the next couple of weeks we will be gearing up for our data collection, which will involve setting up a grid of stakes on the lek to help with territory mapping, installing microphone cables on the leks, starting to get photographs of the males to distinguish them, and hopefully capturing and banding some as well.
I’m kicking off my blog for the 2013 research season with a brief description of what makes sage-grouse such a great bird to study for someone interested in animal behavior and evolutionary biology.
Male sage-grouse courts a female.
One of North America’s most spectacular birds is also a species that not many people have seen. I’m referring to sage-grouse: I study the more widely distributed greater sage-grouse (Centrocercus urophasianus); I have yet to personally see the less common Gunnison’s sage-grouse (Centrocercus minimus), but that is definitely on my wish list. Given the spectacular plumage of a male sage-grouse in display, why are these birds so hard to see? A quick look at a female sage-grouse tells you the girls are built for crypsis- well adapted to blending in with their environment. For most of the year male sage-grouse also play the hiding game, so unless scared into flight they may pass unnoticed. Yet for a couple of months in winter and spring, males come into their traditional display grounds (called leks, from a Swedish word for “child’s play”) and put on one of the greatest shows on earth. These leks are often in fairly remote areas, and males typically attend them only in the early morning hours. Both of these reasons help explain why getting a look at this spectacle can be a bit of a challenge.
These unusual breeding clusters have captivated not only birders but evolutionary biologists as well. In about 90% of birds, both parents provide some care for the nestlings. In those cases, females are often choosing their mates at least partly on the material benefits they get from this partnership, whether it be the quality of the male’s territory or his ability to provision the female during incubation or the chicks once they’ve hatched. [Note- in many birds males and females mate outside of this pair bond, but that is a tale for another day]. Lekking species are therefore unusual among birds in that males don’t form a bond with their mate nor provide any child care. Scientists are still trying to unravel some of the puzzles that leks represent. Why do males cluster together to display, rather than searching around for females, following females around, or spacing themselves farther apart and defending larger territories like most other birds do? If males aren’t helping raise the kids, why are females so picky? What benefits do females get from choosing one male instead of another? And given that females often pick only a few among the many males on a lek, why do the “loser” males bother to stick around?
(This is a 3-hour time lapse video of the lek. The males appear as small black-and-white specks at the bottom of the frame)
Lekking animals also tend to be high on the charisma scale. Besides the spectacular sage-grouse and their cousins the prairie chickens and sharp-tailed grouse, other lek-breeders include some of the most beautiful and acrobatic birds out there, including birds of paradise, neotropical manakins, peacocks, cock-of-the-rock, some hummingbirds, and ruffs. When we see a species in which males are larger or more colorful than females, we presume these differences are related to an evolutionary process called sexual selection, where one sex- often the males- competes either directly for access to females or indirectly by producing the best advertisement among the other males. This certainly seems plausible for sage-grouse; not only are adult males almost twice the weight of females, but they have a range of specialized feathers, brightened skin patches, and other unique structures.
Male sage-grouse showing his inflated vocal sacs.
The distinctive air-filled vocal sacs are actually part of the digestive system; once inflated with air, powerful muscles just under the skin help move and shape the them during display. In spite of decades of research and routine collection by hunters, we are still finding surprising structures in these birds. Just recently we discovered that male sage-grouse have an almost songbird-like syrinx (sound-producing organ analagous to the human larynx) capable of producing two tones at once. All of this adds up to the bizarre appearance of the male that has presumably evolved through sexual selection- the males with the more elaborate versions of these unique features get to mate with more females and pass on more copies of their genes to the next generation.
These differences between males and females extend to courtship behaviors as well; males and only males have a characteristic “strut” display. A male’s strut serves to attract females to the lek from across the landscape, to woo females once they are on the lek, and most likely to help claim their small patch in the midst of all the other males. Each display lasts about two seconds and involves coordinated movements of the wings and body.
For sage-grouse, courtship is not just a visual spectacle. Males produce a variety of sounds during the strut display. The first two notes actually are not vocalizations at all, but instead made by rubbing stiff, pointed breast feathers against the inside of the wings. This is somewhat analogous to how crickets chirp. Making sounds with feathers may sound unusual, but it has evolved repeatedly in birds. Some common species in the Bay Area that do this include Mourning Doves (the ‘wee-wee-wee-wee’ made during take off) and Anna’s Hummingbirds (the loud chirp made at the nadir of the male’s dive display).
Spectrogram of a sage-grouse display. The two feather-produced 'swish' notes occur at about 2.6 and 3.6 seconds. The first low frequency 'coo' note is at 4 seconds, and is followed by the pop-whistle-pop at about 4.3 seconds. You can hear this in the video above.
The remaining notes are true vocalizations made by the syrinx, although unlike most birds they are made with the beak closed. These sounds start with a series of three low frequency ‘coo’ notes, and conclude with an up-down-up ‘whistle’ note sandwiched between two staccato ‘pops’. You can see these in the spectrogram- this is a visual representation of sound and you can read it much like reading music, with time progressing towards the right, pitch becoming higher towards the top of the figure, and the darkness representing something like loudness. Females may care about some very subtle differences in these sounds when they are looking for a high quality mate. Researchers have compared sound recordings of successful and unsuccessful males and found differences in the relative timing of the two ‘pop’ notes, and maybe the loudness of the whistle. What is amazing is that the differences between ‘Mr. Right’ and ‘Mr. Wrong’ are on the order of less than a tenth of a second. Females may have quite the ear when it comes to picking their mate!
That’s a quick introduction to sage-grouse in the spring. I feel extremely lucky to have heard and seen this show for the past several years as part of my research at the University of California, Davis. Along with Professor Gail Particelli, graduate student Anna Perry, and our intrepid field crew, we will be conducting research into several aspects of sage-grouse behavior and ecology from our field site just east of the Wind River Range in Wyoming. Over the next couple of months I’ll be discussing what it takes to set up a camp like this, how we use new technologies (including robotic birds!) to study courtship in this species, and review some of the conservation studies out of our lab. I hope you’ll join me for our 2013 field season!
For a variety of reasons including wanting to expand the size of our crew, we are looking for an additional one or two assistants for our rapidly approaching field season. Dates potentially a little flexible, but we really need people comfortable driving an ATV (even better if received agency training or certification). Feel free to contact me with any questions.
Anyway, here’s the revised advertisement:
FIELD ASSISTANTS (1-2) needed approximately March 3 – May 5 (dates potentially flexible) for investigations of the behavior and ecology of Greater Sage-Grouse near Lander, Wyoming and the scenic Wind River Range. The projects are part of a larger effort in Prof. Gail Patricelli’s lab at UC Davis to understand how sexual selection shapes sage-grouse display behaviors- see the following websites for more information (http://www.eve.ucdavis.edu/gpatricelli/) and (http://www.alankrakauer.org). Assistants will use video and audio recording technology to support an NSF-funded study of courtship dynamics and display plasticity on the lek. Duties include maintaining camera and acoustic monitoring equipment, observation of basic courtship behavior and lek counts, GPS surveying, habitat characterization, assisting in the capture of adult sage-grouse, data entry, and some computer and video analysis. Assistants must be flexible in their needs and comfortable living and working in close quarters in a remote field station, and able to work in adverse field conditions (mainly MUD and COLD). Work will be daily and primarily early in the morning, with afternoon and night work required as well. Applicants must have a valid driver’s license, basic computer skills, ATV experience (ideally with formal safety training or certification), and have succeeded in at least one field biology project in the past. Wilderness First Aid or First Responder, and prior experience spotlighting for sage-grouse, preferred but not required. Must be able to show proof of United States employment eligibility. Assistants will receive $600/mo plus room and board, but need to provide their own transportation to Lander and their own personal gear. Please send a cover letter, resume, and contact info (email and phone) for two (2) references to: Alan Krakauer, Department of Evolution and Ecology, University of California Davis, One Shields Avenue, 2320 Storer Hall, Davis, CA 95616, or preferably by email to ahkrakauer [at] ucdavis.edu. The positions will remain open until filled, and review of applications will begin immediately.
I guess it says something about how much we like field biology that, after a grueling season in Lander, Gail Anna and I are willing to go spend another week being field assistants on someone else’s project. On the way back west to California, we stopped at John Byers’ research site to help out with his long-term study of Pronghorn.
John is set up in a beautiful old house, quite close to the National Bison Range. The site is in a picturesque agricultural valley between the Mission Range and Sapphire Range in western Montana. Great views everywhere, and lots of wildlife. It helps that we arrived at probably the greenest time of the year, with spring in full surge all around us. The house is on a ranch with a few horses, cows, and a lot of cute fluffy sheep.
The field site itself is incredible- 30 square miles of rolling meadows and tall hills carpeted with purple lupines and big clusters of yellow mule’s ears. There are a few hundred bison, along with a lot of white-tailed deer and of course the monitored population of pronghorn. John and his recently-finished graduate student Erin know all the individuals, and much of our first week has been tracking everybody down and waiting for the females (does) to give birth. The first birthing date was unexpectedly late this year, but we did get to catch at least one before leaving.
Erin weighs the first fawn of the season
Our travels have also taken us to Yellowstone and Glacier National Parks- two of the truly spectacular places on this planet. Even if I don’t have an update specifically about those, I’ll definitely have some photos up on my flickr site.
