The first week of my master's thesis field season studying Northern Goshawks was a mixture of stress and anxiety, ecstatic discoveries, frustration, and disappointment. A year's worth of planning all came together for a successful week that fell short of expectations. I was not surprised by this. Last week I posted a quote predicting that my plans would undergo significant challenges and it indeed came true. The good news is that we did make progress (discovered two occupied goshawk nests), we learned along the way, gained renewed confidence in my field methods, and we have a renewed plan of attack for next week.
My study area is in the South Hills, a portion of the Sawtooth National Forest located south of Twin Fall near the Idaho/Nevada border. Since the study is partially funded by the Sawtooth National Forest, they have generously provided us lodging in the small cabin picture below located on Rock Creek in the South Hills. My field assistant Lauren, myself, and other occasional volunteers will be staying there. It sure was nice the first week as the outside temperature dipped to 16 degrees and snow was falling much of the time.
For the first few days Lauren and I were joined by Karyn (my wife), by Jay (Idaho Bird Observatory Research Director and my thesis committee chair), and Heidi (Idaho Bird Observatory researcher and BSU Graduate Student). After our arrival in the South Hills and an evening cleaning the cabin, which had been closed up all winter and possibly for a few years, we headed out on the first morning to find our first goshawk nest. I had been given rough coordinates for a number of historic goshawk nest locations and we chose one which looked to be easily accessible.
While it snowed much of the night, the first morning was clear and cold. The cold crusty snow enabled us to hike without snowshoes. We worked our way toward the expected nest location. Once we were within 100 meters of the assumed location, we split up and began the detailed search. Just one minute after splitting up I looked up and right there in front of me was the nest! It was occupied! I can honestly say that I haven't felt that excited in some time. It was such a rush. Three years of preparation for this new career, one year of planning on this project, and less than one hour in the field and I was staring into an occupied nest! I used hand signals to tell the others I had found the nest!
Wow, this was easy. Only 24 other historic territories to go. As you might expect, it doesn't always work like this. We moved on to the next territory. This involved a one mile hike on snow, occasionally post-holing, followed by a thorough search of the area. With five people for two hours we were not able to find a nest. Finding this particular nest in this territory was supposed to be easy. We decided to move on as we could ask for more specific directions later from individuals who had been to the nest. That afternoon, in a third territory, we again failed to find the historic nest. Some of these nests haven't been looked at in the past eight years. The original GPS coordinates could be as much as 200 meters off. This might not sound like that great a distance, but in dense forest, post-holing in snow, the effort to find a single nest in a single tree is definitely considerable.
A new days brought new nest searches. Unable to cross the ridge due to deep snow we drove for 2 hours around the outside of the forest to gain access to the west side of the mountain range. On the drive we saw a male goshawk perched on the ridge. We bailed out of the truck to observe and mark the location.
Our first search of the morning was rewarded with our second occupied nest! Jay discovered this one. Surprisingly, this nest was occupied by a sub-adult female (one year old bird). Sub-adult females are able to reproduce, although sub-adult males usually are not fertile. I am definitely liking this morning success. Should we just take the afternoons off?
In second territory search on the west side of the mountain we were able to find the historic nest, but unfortunately it was not occupied.
|View over territory.|
|Lauren scanning for nests.|
|Jay and I overlooking territory as the clouds roll in.|
The lack of an occupied nest caused some lapse of focus as Lauren and Heidi started inspecting the lichens on the rock, which was also covered in Marmot scat. Do you think a goshawk could eat a marmot? Hmm.
The storm hit as we headed back to the cabin for a meeting with the wildlife biologist from the forest service. In fact, I had driven this road three days in a row and it had snowed there every day.
On the third day it was left to Karyn, Lauren, and I as Jay and Heidi had their own projects to get on to. With new information we returned to a territory from the first day. The three of us systematically searched the area again for 2.5 hours. We did find an unoccupied nest, but it mostly likely belonged to a Red-tailed Hawk as it was near the top of the tree and open where goshawks prefer to nest under the canopy.
A few days before we had seen an adult male goshawk fly from a stand of trees about 700 meters from our documented nest location. Karyn suggested that we go search there. I said no as we have a search protocol which would eventually take us there, but we first had to find the historic nest. As the fog came in and the snow decreased visibility we headed in for the morning. I would later receive updated information from the forest service that in recent years the nest has been located in that very stand of trees that Karyn proposed searching. I guess Karyn has earned a significant number of "I told you so's". We will head there first thing next week!
With limited road access, the amount of snow on the ground, and a forecast of more snow in coming days, we made the decision to abandon our work for the rest of the week. We will return on Monday, hopefully to better access and higher productivity. This first week was filled with the excitement of finding the nests, with frustration of only being able to access about 1/4 of the study area, and relief that I believe my field methods in general are going to work. I am now excited to return to the area on Monday morning.
With the amount of time we spend in the field, we are able to observe other wildlife as well. One species of unique interest in the South Hills is the South Hills Crossbill. This bird is a sub-species of the migratory Red Crossbill which has taken up permanent residence in the South Hills. There it has evolved a unique morphology which has resulted in it being proposed as its own species.
The South Hills lack tree squirrels, so the South Hills Crossbill has taken over the role of the pre-disersal seed predator of Lodgepole Pine. As a result the Lodgepole Pine has developed a unique defense in its cone structure to protect against the Crossbill seed predation instead of the usual squirrel seed predation. In the evolutionary arms race, the Crossbill has in turn developed a unique bill structure to overcome these new defensive mechanisms. This has driven the bill structure of the South Hills Crossbill to be different from the standard Red Crossbill. These birds are abundant and easy to see in the South Hills. Interesting stuff!
We have seen and heard many other bird species and have watched the increased emergence of the Belding's Ground Squirrel which are key prey items for the Northern Goshawk. I look forward to our return to the field early next week.