Friday, May 25, 2012

Oh, What a Great First Week it has Been!

Last Sunday brought the official kick off of my second field season studying Northern Goshawk (Accipiter gentilis) breeding ecology within the Minidoka Ranger District of the Sawtooth National Forest. This study is the core of my thesis work in the Raptor Biology Program of Boise State University. The first few days could not have been more different than last year! Last year we arrived to 2 feet of snow on the ground with more coming down. This year it was near 80 degrees Fahrenheit and very dry and dusty. As you might imagine, progress came much more quickly this year!

The 2012 Team Goshawk: Lauren (a.k.a. the Traitor), my field assistant from last year, moved on to a new endeavor more in line with her future studies. As a result, I have hired two new undergraduate students for the 2012 team - Emmy and Mike. They had a great week learning about goshawks, driving ATVs, navigation in the forest, GPS use, and my specific survey protocols. They have already proven their enthusiasm and abilities to be great assets to the team!

Emmy performing a trial prey survey in mixed terrain.
Mike performing trial prey survey in open habitat.

Searching for Nests: We use a number of different techniques for discovering occupied goshawk nests. Prior to the first of June, we use passive methods of simply searching through the forests. During last years field season we discovered more than 60 nest structures that could possibly be used by goshawks. During our first week, we visited 57 of these structures to check for goshawk presence. Six of these were occupied by goshawks and two were occupied by Red-tailed Hawks. While searching these, we found a seventh occupied goshawk nest which was previously undiscovered. Wow, by the third week last year I only had two confirmed goshawk nests and could only access about a third of my study area! In fact, we discovered the first three nests this year within three hours of returning to the field! The first three nests we checked were all occupied!

Occupied goshawk nest - sub-adult female (note tail extending from nest).

If you followed my progress last year, you might remember the story of Chuck. Chuck was the first nestling I observed, was the first nest tree that I climbed, and the first nest camera that I installed. I was saddened to view Chuck's old nest tree. It has been pushed over by other broken trees to the point it is no longer usable. Hopefully we will discover the adults nesting again somewhere nearby.

Chuck's old nest.

Last year we found that one nest tree had been cut down by firewood collectors. Luckily, it was not occupied at the time, but it had shown that it had been visited by a potential user (fresh greenery had been added to the nest). After discussion with the wildlife biologist of the forest, we decided to mark these important resources to help prevent future destruction. Thus, we have so far installed 24 signs to help raise awareness of the importance of the nest trees. We skipped the trees which are currently occupied (to minimize disturbance) and those that are so far degraded to not be of much future value.

Wildlife sign installed on nest trees.

After the first of June we will return to the territories where an occupied nest has not been confirmed and try to detect goshawks using a call broadcast. This consists of a three minute protocol at each point where we play a recording of a goshawk alarm call, then listen/watch for a response. This will be performed at points 300 meters apart throughout all appropriate habitat out to a distance of 1700 meters for the historical nesting location. This can consist of up to 35 call points per territory. That will take up a big chunk of our time over the coming weeks.

If that isn't enough, I have also predicted high quality habitat for nesting using Geographic Information System Analysis. This resulted in another 250 locations to perform call broadcasts which are outside of any known historical nesting territory. Last year this yielded one additional confirmed territory and one possible territory (had a response, but no nest was found). That's over 500 call points to complete!

Nest Cameras: I will once again be installing nest cameras in three nests to help identify and quantify prey deliveries to the nest. As the top diet choice of goshawks in many parts of the world, tree squirrels, are naturally absent from the South Hills, quantifying the goshawk diet in this unique landscape will be one of the main chapters of my thesis. I expect the first installation will occur during the next two weeks.

Prey Surveys: The second chapter of my thesis relates prey abundance with nest occupancy and success. To evaluate the prey abundance, we will perform six 750m prey surveys randomly placed within each territory. These surveys are walked point to point while recording each potential prey item observed (birds and mammals). The distance to the prey item is recorded using a laser rangefinder. These values are then integrated into a Distance Sampling analysis to produce prey abundance estimates for each territory. With 150 prey transects to perform, we will be in excellent hiking shape by the end of the season! That's a minimum of 140 miles of hiking for just the prey transects, all off-trail through whatever the landscape presents!

One of the great things about field work is discovering the things you don't expect to see. While searching for nests this last week, I found a large nest which could belong to a Bald Eagle. This was a surprise and not located in what I would consider ideal habitat for Bald Eagles. While still investigating the possibilities, what I do know is that a large group of adult Bald Eagle feathers were scattered across a 15m radius around a nest tree. These are assumed to be molted feathers as they were fresh, none were damaged, and they were clean on the shafts (no flesh remaining). There was also about 10 times more fecal splatter around the base of the tree than I have observed around any goshawk tree. There was no sign of birds in the area. It's a fun side project to investigate.

Sampling of Eagle feathers with GPS for size comparison.

Next week we will once again hit the field to complete our first official prey surveys, continue monitoring occupied nests, begin camera installation preparation, and start with call broadcasts. By the end of the week, we could have our first camera installed. I expect another fruitful week!

Saturday, May 19, 2012

Bears, Badgers, and Other Creatures of Yellowstone National Park

It is worth noting that in all of our (Karyn and I) Yellowstone adventures I have been reporting on over the past few days, we did not spend all of our time observing wolves and birds. There was a wide variety of other wildlife present to help entertain and in some cases, challenge us.

Yellow-bellied Marmot. Yellowstone River Canyon. Yellowstone National Park.

Bears. Many people travel to Yellowstone in the hopes of seeing bears. If you spend much time there, you will be definitely be successful. We saw lots of bears. We had dozens of sightings. In most cases these were Grizzly Bears which we could observe from a distance across the Lamar Valley. Most every evening one to three Grizzlies would be out and about. We watched as one chased a bison heard far up canyon. I was amazed at how far they could run. I had always expected them to be limited to short, fast bursts of power. There were reports of a few grizzlies with cubs of the year (COYs), but we would only see one such family. Luckily, we didn't find any on our hikes.

Black Bear. Slough Creek. Yellowstone National Park.

Black bears were another case. We would find Black Bears during two of our hikes. Luckily, no contact was made. During the Garnet Hill hike, we came upon some hikers who has just spooked up a black bear and its cubs right next to the trail. They were fairly alarmed. We crossed the stream to climb up on the opposite hillside to see what we had to deal with. It was a black bear with two yearling cubs and didn't seem too upset.

Black Bear and Yearling Cubs. Garnet Hill. Yellowstone National Park.

She was so alarmed that she rolled over onto her back and started nursing the cubs. I was surprised that she would continue to nurse yearlings. As one friend pointed out, what a great observation on Mother's Day! Anyway, we gave her as much room as possible and continued on our way.

Black Bear nursing yearling cubs. Garnet Hill. Yellowstone National Park.

On our final hiking day, we headed down to the confluence of Slough Creek and the Lamar River to get a closer view of a Bald Eagle nest. We sat up on a hill over the river to look into the eagle nest on the other side. Karyn glanced down to see another bear lounging in the shade next to the river. What a great place to hang out on a hot day

Black Bear. Slough Creek. Yellowstone National Park.

My field studies into the dynamics between Northern Goshawks and Belding's Ground Squirrels have raised my awareness of this critical raptor prey source. There are no Belding's in Yellowstone, but the Uinta Ground Squirrel has taken its place as the primarily mammalian food source for raptors.

Uinta Ground Squirrel. Slough Creek. Yellowstone National Park.

These guys are everywhere, watching for threats and giving off their ubiquitous alarm call.

Uinta Ground Squirrel. Lamar Valley. Yellowstone National Park.

But the threats to ground squirrels are not limited to aerial predators. One of my other favorite animals (how many times can I say that...) is the American Badger!

American Badger. Lamar Valley. Yellowstone National Park.

As you can tell, Spring is a great time in the park. I just got back, but I can't wait to go again.

Chipmunk (Yellow-pine Chipmunk?). Near Mammoth. Yellowstone National Park.
Wapiti (Elk). Madison River. Yellowstone National Park
Pronghorn. Lamar Valley. Yellowstone National Park.

Friday, May 18, 2012

Spring is the Time for Birds in Yellowstone

Late spring is a great time for birds most everywhere in the northern hemisphere, and Yellowstone National Park is no exception. Karyn and I just returned from the park a few days ago and here is a highlight of what we observed.

Mountain Bluebird. Slough Creek. Yellowstone National Park.
Loggerhead Shrike. Lamar Valley. Yellowstone National Park.
Townsend's Solitaire. Lamar Valley. Yellowstone National Park.
Savannah Sparrow. Slough Creek. Yellowstone National Park.
Lark Sparrow. Lamar Valley. Yellowstone National Park.
Pink-sided Dark-eyed Junco. Garnet Hill. Yellowstone National Park.

But it was not all about songbirds. There are many raptors in the park as well. We reported 60 sightings to the Yellowstone Raptor Initiative. This list consisted of only our first sightings of a particular species in a given area. We observed occupied nests for Bald Eagles (2), Red-tailed Hawks (3), Osprey (2), and many paired up American Kestrels.

Bald Eagle just captured a Uinta Ground Squirrel. Lamar Valley. Yellowstone National Park.
Red-tailed Hawk dispute. Lamar Valley. Yellowstone National Park.
Red-tailed Hawk and Golden Eagle. Garnet Hill. Yellowstone National Park.
Osprey. Lamar Valley. Yellowstone National Park.

The list of bird families continued with some other of my favorites. The Harlequin Ducks weren't at their usual hangout, but we were lucky enough to spot them on our way into the park.

Harlequin Ducks. Madison River. Yellowstone National Park.
Eared Grebe. Trout Lake. Yellowstone National Park.
Spotted Sandpiper. Slough Creek. Yellowstone National Park.
Sandhill Crane. Blacktail Plateau. Yellowstone National Park.

Wolves and the Battle for Territory in the Lamar Valley

It has been a difficult year for the wolves of Yellowstone National Park. There is a general rule that mild winters favor prey species at the expense of predator species. We don't know if this year's mild winter was the cause, but only two of the wolf packs in Yellowstone have denned this year. The result will most likely be a decline in the wolf population within the park.

The two wolf packs within the park with pups are busy doing what wolves do: hunting prey and delivering as much as possible back to the puppies during the period of their most demanding energetic needs. The wolf packs without pups are probably confused as to their true purpose. For a wolf, the annual cycle is defined by the breeding season and the following nine months of leading the puppies to adulthood.

At least one of the Yellowstone wolf packs have decided to use their time without pups to seek out new territory. The Mollie's pack have moved from the Pelican Valley in the southern part of the park into the prime habitat of the Lamar Valley in the north. Providing the Mollie's pack with additional advantage in this endeavor is their number, currently 14 wolves, their size, the largest wolves in the park, and their ferocity. The Mollie's have killed wolves in nearly every pack they have encountered. As the only pack in the park that regularly take bison, the Mollie's definitely know how to throw their weight around.

The Lamar Valley was once the domain of the famous Druid Peak wolf pack of which many nature TV programs were created. Until recently it was the domain of the Lamar Canyon wolf pack which conveniently moved into the Druid Peak den site after the Druid pack dissolved. The Lamar Canyon pack consists of nine or ten wolves trying to feed an unknown number of pups.

Lamar Canyon Alpha Female. Yellowstone National Park.
Lamar Canyon Alpha Female. Yellowstone National Park.

The Lamar Canyon pack may just lay claim to the best wolf territory in the lower 48 states. Apparently the richness of this valley has not gone unnoticed as the Mollie's wolf pack, after roaming many parts of the park, appear to have settled here for good. As mentioned, they are a formidable group always on the prowl and appear to always be in a hunting formation. The Mollie's were heading east...

Mollie's Wolf Pack - 13 of the 14 wolves. Yellowstone National Park.

The next morning we were watching the Lamar Canyon pack on an old bison kill. The kill had been taken over by two grizzly bears. The Lamar's were trying to take it back without success. In fact one of the bears appeared to be sleeping on the carcass! We received word that the Mollie's were on the move in our direction. I usually try not to take sides, but I had to root for the Lamar Canyon pack as they were desperately trying to raise the next generation. I also wasn't sure a fight to the death was high on my list of things to observe.

There were six Lamar wolves present. Upon seeing the Mollie's, two yearling Lamar wolves took off, leaving the four adults to defend the territory and their honor. At first it appeared that the Mollies would pass on by, about a half mile away. But the Lamar wolves couldn't have it. They ran toward the invaders. About half way there they apparently saw the size and number of their foes as their chase turned into a retreat for their lives. Four wolves ran at their fastest speed, two to our left and two to our right, being chased by 14 Mollie's. Wow.

Lamar Canyon pack on the run.
Lamar Canyon pack on the run.
Lamar Canyon pack on the run.

I am not sure why the Mollie's stopped the chase, but they quickly circled and celebrated, tails in the air. Maybe they weren't in the killing mood today or maybe it was the hundreds of people and cars lining the road they would have to cross. The Mollies are less accustomed to people, whereas the Lamar's must cross the road every day from their den site to the core of the valley. Anyway, the fight was over for now, but something tells me that this is far from settled.

Mollie's wolves celebrating the chase.

Even the grizzly bear on the carcass took note, although the 14 wolves could not take the carcass from him! That is commitment.

Mollie's wolves disturbing a grizzly bear on a carcass.

One of the Lamar Canyon wolves that swam to our right took up position on the hillside near us to howl and howl in distress. For more than 20 minutes.

Lamar Canyon wolf howling in distress.

We moved over a small ridge to decrease the pressure on the wolf. After another ten minutes of howling, he/she once again came toward us, crossing just above. He/she occasionally stopped to howl again. Interesting the wolf was within 50 meters and never actually looked directly at us. He/she looked at the invaders, back to the den, and back to the invaders. A little while later it crossed over the ridge and out of sight.

Lamar Canyon wolf howling in distress.
Lamar Canyon wolf howling in distress.

Later that day, while we were off hiking, there was yet another conflict. The alpha female was in deep, deep trouble forcing her to bail off a cliff into the river. Later in the day she appeared to be ok. The next day the Lamar wolves were observed hunting north of their den and the Mollie's had retreated back to the west. The situation was averted for now.

Thursday, May 17, 2012

A Story of Bison, Wolves, and the Raging Lamar River

The theme of our (Karyn and I) visit to Yellowstone this year seemed to be Wolves and Bison. Each season of the year brings unique dynamics between the species, especially between predators and prey. As our visit coincided with bison calving season, bison were one of the major themes of the week (I will describe the other themes in a later post). In the Lamar Valley I expect the focus will shift to elk as the elk calving season kicks off in the next few weeks.

With two wolf packs occupying the Lamar Valley, we had ample opportunity to observe wolves both morning and evening. It was one of the richest watching experiences of all of our visits to the park in both quantity of observations and diversity of events.

To observe the Lamar Valley pack, the area near the confluence of Soda Butte Creek and the Lamar River provided the best opportunities. As the Lamar Canyon wolves den nearby, they have a fairly constant presence in the area. Climbing the hill north of the road provides spectacular views of the valley and aids in observing wolves hidden by sagebrush, tall grass, and the undulations of the landscape.

Confluence of Soda Butte Creek and Lamar River. Yellowstone National Park.

Bison. Hundreds of Bison occupy the Lamar Valley. For the most part, healthy adult Bison are out of reach of even a large wolf pack. Only one wolf pack in the park, the Mollie's Pack, regularly attack bison. Even during calving season, most bison have little to fear. In a past visit we have watched a single adult bison successfully defend her calf against a pack of six adult wolves. On this visit we watched numerous small groups of bison successfully defend a calf from a pack of 14 wolves! Unlike elk, bison exhibit group defense in the face of predators such as bears and wolves. However, we did observe one repeated threat that was unexpected. Even more unexpected was the magnitude of the threat. The threat: losing calves during river crossings.

Bison and calf crossing Lamar River, Yellowstone National Park.

Bison are herbivores which eat grass, small forbs, and occasionally shrubs. The landscape of the Lamar Valley is covered in sagebrush, grass, and forbs. From our viewpoint, it looked rather homogenous on both sides of the river. Indeed, the bison spend significant time on each side of the river. However, they often are observed crossing to the other side. As the saying goes, the grass is always greener... During these crossings the vast majority of the calves are successful. Even most one or two day old calves can swim the raging river. However, sometimes they don't make it. Those that don't are often swept downstream to be deposited on a river island or on a far away shore, left to slowly starve or more quickly succumb to predators. So why do they take the risk? I don't know but expect there is some evolutionary justification. It is possible that this early test of strength can determine a calf's future success. If the calf is not strong enough, maybe the mother is better off saving her resources for the next breeding season. It is harsh, but nature often is. As Jacob Dylan says, "the tyranny of nature's plan."

Our first morning in the Lamar Valley we were watching a pack of wolves on a carcass across the valley. We were also watching a stranded calf wandering around and around and around a small island. There was no adult anywhere in sight. We could only imagine that it was tired, hungry, and very confused. I wondered how long it would take for a predator to find it.

Stranded bison calf on island. Yellowstone National Park.

Little did I know that my question would soon be answered. As we descended the hill to our car so that we could move down valley, a friend pointed out the alpha male of the Lamar Canyon wolf pack. He was sitting next to the river watching the calf.

Alpha male, Lamar Canyon Wolf Pack. Yellowstone National Park.

Wow. Here we were just under 100 meters away... He rose and entered the water...

Alpha male swimming to island in Lamar River, Yellowstone National Park.
Alpha male approaches stranded Bison calf. Yellowstone National Park.

The calf appeared unaware of it's fate. From my observations deer and elk have an innate fear of predators, but apparently bison do not. I am sure this ties directly into the adult response which is for an elk to run and a bison to challenge. Anyway, the calf just watched as the wolf approached.

The final approach. Yellowstone National Park.
The takedown. Yellowstone National Park.

I would like to say that the kill was fast and painless, but it took a bit longer than I had expected. Regardless, the suffering of the calf was ended and the Lamar Canyon pups would be fed. Somewhere in the long chain of evolution, the available bison gene pool was just slightly altered for the better. The next generation will be slightly better swimmers...

The wolf ate some of the calf on the island before carrying, with difficulty, the carcass back across the river toward his den. What a prize a partially complete carcass would be for the four or five week old pups waiting there. This would augment their usual diet of breast milk and regurgitated meat.

Bison calf is carried back toward the den. Yellowstone National Park.

The outcome is not always the same. On another day we watched bison crossing the river. The first calf made it across successfully, but the second was washed far down stream away from it's mother. In addition, the calf appeared to panic and returned to the wrong side of the river. From our high observation point we could watch the whole drama play out. The mother appeared to have assumed that the calf made it across. She ran from calf to calf trying to find her offspring. She crossed back to the other side, searched, and crossed again continuing to search. The calf was moving too. The calf moved up the hill from bison to bison searching for its mother, but ended up moving farther and farther away. The mother crossed the river to search three more times! Time passed by and the distance between them was not getting any shorter. We were convinced the reunion would not happen. She crossed again and started heading in the wrong direction...then the right direction...then the wrong direction... It was agonizing to watch as we could see the whole hillside. They moved closer together, but a low ridge separated them. Finally the distance was short enough that their calls could be heard. Both animals ran at full speed to each other. The calf immediately started feeding. The whole drama lasted nearly 40 minutes. We didn't watch to see if they swam the river again.

Another day, another calf. We were now noticing stranded calves more and more often. Another was stranded on an island near the road. We could not bring ourselves to sit and watch. The day passed. It was there as we exited the park that evening. It was there as we re-entered the next morning. The photographers set up to catch it's fate. That evening it was still there with no signs of its mother. What happened next was unbelievable. We were not in attendance, but some other wolf watchers we know passed on the story. In the evening a yearling wolf from the Lamar Canyon pack noticed the calf. It crossed over and tried to attack the calf by the neck. This failed. It then grabbed it by the nose and pulled it to the ground. At this point the calf must have let out a wail as the mother, far uphill from the melee, came at full speed to its defense chasing the wolf away. With the wolf on the run, the calf immediately started nursing. Wow, lost for two days and then rediscovered at the final instant the animal could be saved. Amazing. The Lamar Canyon wolf pups would not be having bison this evening...

I can't stop thinking about all of these dynamics... Why do bison swim the river so often if the risk is so high? What could be the evolutionary benefit? It likely improves the swimming ability of the species, but does it benefit the individual female? It would be fascinating to study this more...if I wasn't up to my neck in bird research...