Here's the latest update on the progress I have made during my first field season of my master's thesis project in Raptor Biology studying the Northern Goshawk. This post covers weeks three and four. I have previously posted an introduction, a summary of the first week, and a summary of the second week.
As expected, we have become more and more busy as the new protocols come online and as access to new territories occur. Although at the end of week 4 we can still only access 13 of the original 23 historic territories I plan to work in. I am eagerly hoping that next week opens up new opportunities.
Lauren and I were joined for three days by another volunteer Michelle, a former student of mine. She provided excellent field support and likely learned a great deal. Dusty and Mike joined us in the field for the camera installation as well. I have a couple of other volunteers joining during the next few weeks and possibly for the session after that. Some are former students and others are friends considering a career in biology. It's great to have the extra help.
The new week enabled access into five previously unvisited territories (due to snow and mud), bringing my total accessible territories to 13. This quickly delivered two new occupied nests, for a total of four. Lauren and Michelle discovered the first, and I discovered the second. On the nest that I discovered it looked as if the female was sitting very high on the nest. This can often mean that nestlings have hatched. As I watched a small white head popped out from under the female. Nestlings! The first observed of the season. Very cool! This would lead to this nest being the first to be installed with a nest camera (story below).
One of the new techniques for this week is the use of broadcast call stations. This procedure consists of playing the goshawk alarm call and then listening for a response. This procedure is not used until the first of June as the goshawks don't generally respond until after the chicks have hatched. June 1st is the average hatching date in my area. Our first day using the new technique was productive as both Lauren and I had aggressive responses to the call backs. I had a female aggressive vocal response as she flew toward me calling. Lauren had an aggressive male response in another territory. Unfortunately, neither response has yet lead us to a new nest. We have yet to give up on these territories though. As we have the areas localized, if there is a nest, it could be close. Another aggressive female response later in the week did lead to new nest discovery (fifth of season).
|Volunteer Michelle broadcasting goshawk alarm call.|
|Fifth nest of season, this one located in Lodgepole Pine.|
A core premise of my thesis is the relationship between prey abundance and goshawk nest success. One of the mechanisms I hope to use in a series of prey surveys in each nesting territory. These prey surveys will be used to generate a general prey abundance measure of the territory which can be used for comparison between successful and unsuccessful nests. The method I chose to use is called distance sampling along line transects. Each historic goshawk territory has four 750m lines randomly placed within its bounds. For each round of surveys we will walk one of the 750m transects, noting any potential prey observed - Ground Squirrels, Chipmunks, Robins, Grouse, etc, and measuring the perpendicular distance from the transect with a laser rangefinder. These measures will be used to generate detection probabilities and ultimately estimate prey abundance for the each territory. I had hoped that I could do each round across all 23 territories within a period of three to four days. As mentioned earlier, I do not yet have access to many territories. Regardless, I chose to complete the first round on the 13 territories I did have access. New procedures often bring many new learnings. The first challenge was the two inches of new snow on the ground the morning that we began. I walked 500 meters before seeing my first potential prey item. This was in an occupied territory as well! Learning number two is that 30 minutes after sunrise, does not mean the sun has risen on the territory. As a result, I have shifted the surveys later in the morning - 30 minutes after sunrise in the territory, not what the calendar says. It is way too early to look at the data, but I can say there was no initial obvious correlation. We will initiate the second round of surveys next week on the 13 territories and hopefully the first round in some new areas.
The story of the week is definitely the installation of the first nest camera. This was scheduled for Wednesday as the nestlings were estimated to be 8-10 days old. A lot of coordination was required to get the gear in place, invite my climbing coach down to the area, and to align our schedule around the weather so as to minimize exposure to the nestlings during the camera installation. It looked like it could all come together.
We staged the gear about 100m from the nest. We completed the last bit of training on the spot, then it was time to make a decision. We needed 2 hours of clear weather, at least no rain, to proceed. The fog was rolling in, but there was no immediate threat of precipitation. We made the decision to go. The four of us (myself, Lauren, Dusty [climbing coach], and Mike [Dusty's student]) all had our roles. I would climb, Dusty would coach, Lauren would belay if needed and coordinate the camera once I reached the nest. The camera is installed in the nest, but the recorder and battery are at the end of a 200 foot cable. This allows for remote battery and tape exchange without disturbing the nest again. Mike would take pictures, assist on demand, and yell a warning when a goshawk was about to take my head off! A very important task! We gathered the gear and moved toward the tree.
About 80m from the nest the male goshawk issued the alarm call! Dang! I had hoped he was miles away hunting. I would have to deal with two angry parents from the start. I approached the tree, rapped the sling around and left the ground. The female left the nest and the clock was started. We hoped to be out of the territory within an hour.
It was hard not to just watch in admiration as the parents flew through the forest heading to attack me, but I had a job to do. Up I went.
This tree proved much more difficult than the training tree. I guess the training isn't over yet. The hardest move is getting around the nest. I planted an anchor at the base and attempted to move up and over the side. I worked up over the lip and FALL #1! Yikes! A dead limb broke... Nothing gets your attention like taking a fall 30+ feet above the ground. I hugged the tree and tried to recover my senses and my wind. This is hard work! The clock was ticking, but I forced myself to relax and take my time. I worked the move again... FALL #2! Wow, getting tired. Focus... I rapped the limb again and wrenched myself up over the rim and into another anchor. I was there and ready to work. What?!? Only one nestling. I had expected three or four. Five was not out of the question. Only one. It was big, not 8-10 days old, but 14-17 days old. I guess measuring age by the amount of fecal material on the nest rim doesn't work when there is only one nestling. I placed my fleece jacket over the nestling to protect it from exposure and help it to relax. Not that it would relax with the parents' alarm calls flying by my head.
I hoisted the camera up and began the installation. On the ground the monitor failed. Dang, I would have to align the camera on sight alone. It was done.
As I was setting up my rappel, one of the adults flew over the nest and snatched my fleece coat covering the nestling! Off through the woods it went! Unbelievable! Mike went running after and eventually returned with the jacket. I set up my rappel and got out of the tree. We quickly grabbed the gear and retreated as far as possible. Without the monitor, I cannot ensure the camera settings are correct. I hit record and we left. High def, low def, motion activated or always on. Who knows... We get what we get... I will find out Monday...
I was cooked. Exhausted from the stress and the effort to climb the tree, I needed a break, but there was still work to do. We existed the territory in 55 minutes - ahead of my time allotment. It seemed like a blur of confusion and chaos, but even with the falls and equipment malfunction, we got our job done and mostly right. The camera monitor was the only real problem. It's a great team I work with! It is an honor to work with them.
Field work is always presenting new challenges. The setback of the week was the broken motorcycle. After finding the nest with nestlings, Lauren volunteered to perform prey surveys in that area in the hopes of stopping by the nest and seeing the nestlings. Little did she know when she volunteered, that it would be a balmy 26 degrees in the morning and the motorcycle was the only vehicle to get there! She was undeterred. Adding to the challenges was a couple of new inches of snow on the ground. She headed off for the slippery cold ride as Michelle and I climbed into the heated truck. Six hours later when our work was done, we would learn of Lauren's fate. The roads were very snowy and slippery which quickly turned into wet and slippery after the sun came up. Not the ideal conditions for a motorcycle. The bike unavoidably slipped into a rut and the chain came off. Six miles from camp on a dead end road. What a beautiful morning for a walk! While Michelle and I were performing prey surveys and call stations, Lauren was hiking the muddy road back to camp. Just before arriving back at camp, the first person she saw was the man, Rick, from the neighboring camp who Lauren had made friends with the night before. He offered to help, took her to the bike and got it back on the road. When we returned later in the day, Lauren was sleeping on the ground next to the bike in camp. Next on the agenda was a bike repair in Twin Falls! On Saturday I took it to the shop. Standard answer - sometime next week. I tried to politely reemphasize my urgency - it was a work bike and the only way I could get my study complete. Well, maybe they would get to it later in the day. Ok, I will wait. This was not the answer he was expecting. They decided to put it on the rack right then. About an hour and a half later, I was headed back into the hills! Thank you to Kevin at Adventure Motorsports!
The Week ahead
The week ahead brings much of the same, but on a larger scale. More nests to find, more prey surveys to do, and more cameras to install! Hopefully with access to new territories. It will be a busy, but wonderful time. For the next ten days we will have a second field assistant and possibly one or two other volunteers spending time in the field.
One of the things I love about field work, is you come across many different surprises and discoveries. Such as spooking up a deer or an elk while walking through the woods. I actually logged an elk at 60m during a prey transect! Ok, maybe a goshawk can't take an elk, but I wrote it down anyway. Lauren saw a Moose, and I had a Badger. Coyotes, Beavers, White-tailed Jackrabbits, you name it.
Since we spend a lot of time looking for nests, we have a high probability of find them. To add to our five Northern Goshawk nests, we have found an occupied Red-tailed Hawk nest (with nestling), an occupied Cooper's Hawk nest, and an occupied Common Raven nest (with nestlings). The most surprising was the American Robin nest that I discovered when my face was about 2 feet away and the female Robin flushed from the nest! Scared the crap out of me!
Another surprise was having a Northern Saw-whet Owl fly right by me mid-day and perch in a tree.
Unfortunately, one thing we are likely to see a lot more of is dead raptors. Once raptors fledge, their chance of survival greatly diminishes. Over 50% will likely die during the next 3 or 4 months. While not a raptor, this fledgling Raven didn't do so well.
You can tell it is a fledgling as its feathers were still growing. An adult will only replace a few feathers at a time, whereas a fledgling will still be growing all of their feathers. This fledgling Long-eared Owl also met its fate. I found this right after watching an adult Long-eared Owl fly by.
Yes, only a geeky biologist photographs the dead things he finds...
With that, I have a few days off an then its back to work. Prey surveys, nest cameras, new territories, it feels like a whole new project. I can't wait to get back out there!