Thursday, June 23, 2011

Black Flies, Bachelors, and Technology Woes

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 five and six. Previous posts:

The project has been progressing very well. We have accomplished more during the past two weeks than during the first four weeks. The melting snow, day by day makes our jobs easier, but also opens up new territories where work needs to get done. The learning continues to progress at a rapid rate and I am more and more optimistic about the project. Both Lauren and I continue to improve our skills as well. I am more and more comfortable in the tree climbing arena, with four climbs under my belt. On a personal convenience front, we now have water in the cabin! It arrived just in time for the hot sweaty weather. Unfortunately, 1,000 of our friends on ATVs have also arrived, but I guess we can't claim the entire place to ourselves any longer.

Working in the field

One of the most important things I like about field work is being in the field exploring and working to interpret what the surroundings have to say. There are some researchers who can simply take data from field assistants and synthesize it into research manuscripts without ever getting their feet dirty. I am not one of those. I believe the data is critically important, but I often get the interpretation from my experiences and observations which were not designed into the protocol. For my undergraduate research, which has just hit the presses in the Journal the Condor, it was instrumental that I participate in the bird banding and raptor counting to get a sense for what answers I should be looking for in the data. It is when the data agrees and disagrees with personal observations that can drive to the next set of questions.

One of the questions we are looking into in the South Hills is whether this population of Northern Goshawks are doing well. Additionally, I am looking into what influences within the environment, most notably prey availability, may be influencing that success. Whether prey is the primary influence, will have to wait for my thesis, but there are other theories out there. One theory is that this population is not doing well. In a ten year study documented by Kaltenecker et al. 2004, there was no evidence that goshawks raised in the South Hills returned to breed there. General raptor life history would predict that male offspring would return to their natal area to breed. A potential cause of no returning nestlings could be high mortality to a black fly blood parasite which attacks the nestlings and the female while on the nest. I am not studying blood parasites, but I can attest to the black fly as a potential vector. On the third nest I entered, the nestlings were covered in black flies. A few other nests I have observed have had similar issues. Maybe next year I will recruit an undergraduate researcher to look into the parasite issue.

17 day old goshawk nestlings from nest #3 w/ Black Flies

We have also observed adult male goshawks in three territories where our protocol has yet to find an occupied nest. Of course, it is possible that we have just not found the nest; we will continue to monitor those areas. In another territory a sub-adult female was on a nest, usually a sign of a shortage of females. Is there a shortage of females in the area? A sub-adult female breeding and possibly three bachelor males? Is the blood parasite killing offspring? Is this a healthy population? So many questions... For now mine are focused on the population structure and the prey influences on this equation.

Nest Cameras

One of our main tasks are the installation of nest cameras. These cameras will enable a quantification of the prey consumed. They will also provide insight into other interesting behavioral aspects of a nestling's life. But first the cameras have to get up the tree.

Climbing nest tree #3 to install camera.

One of the most unsettling things for me about tree climbing is working over the branches. The harness is set up with two slings around the tree. When you reach a branch you put the second sling over the top and release the first sling. That release step, removing the only protection you have been using to hold on the tree, takes very careful consideration. The new sling must be attached and locked correctly. With eight to ten sling swaps per climb, there is ample opportunity for mistakes. I remain as focused as I can, take my time, and double check every move.

The first look into the nest.

Holding cable in my teeth while aligning camera. Note black flies on nestlings.

I align the camera in the tree while Lauren looks at the monitor below and provides instructions on how to adjust the alignment. The camera units are set up so that batteries and memory cards/tapes can be exchanged 200 feet away so that subsequent disturbance to the nest is minimized.

Double checking the configuration and video feed when back on the ground.

The focus, effort, and adrenaline take its toll. I am on a high for about an hour, then I want to nap away the afternoon...

It will take months to sort through the video I am capturing, but it doesn't take long to find interesting behavior. At age 4 days the nestlings begin to defecate over the rim of the nest. This 15 second video of a 10 to 13 day old nestling provides a great example.

But as I mentioned earlier,my focus is on prey. Here is a 25 day old goshawk walking around the nest then eating a chipmunk (meal starts about 40 seconds in).

Nature does know how to deliver surprises. Once I put my head over the rim of nest #2, this is what I saw.

Dead Nestling in nest #2.

The cause of death is not determinable. Sometimes nestlings are killed by their nest mates to decrease competition for food, but there was no sign of that here. Maybe starvation? The clutches are smaller this year than in previous studies, so resources could be more scarce. Unfortunately the dead nestling was gone before the camera was fully operational (12 hours later). We therefore do not know if the female removed it or if it was eaten. Few resources are wasted in nature.

The cameras are complicated technology for the outdoors. While they provide tremendous insight, they have been the source of frustration and have not worked out as well as planned. I had originally planned six cameras. Due to the battery recharge challenges, I scaled that back to 5 cameras. Two of these are analog units that only record for a day and a half at a time. I replace these batteries every two days. I have three digital units which can last a week on a battery charge. Unfortunately, one of these recorders died while operating in nest number one. I replaced it with my last available unit the day before I discovered a new candidate nest. I still have one analog unit, but this new territory is 2 hours each way by motorcycle. It would take far too much time to replace the battery every other day. So here I am with three cameras installed, each providing about 75% of the daylight hours. The TV monitors used to align the camera and configure the recorder has only worked on one of our three installs, requiring more followup to get the system fully functioning. I will defintiely be re-evaluating choices at the end of the season. For now, I hope the three units keep working for a few more weeks.  


Before heading into the field I have heard many stories of individuals getting attacked by goshawks. This usually occurs when 50 meters or closer to the nest tree. After my first encounters I was beginning to believe that these stories were overly exaggerated. While climbing my first tree, the two adults protested and flew toward us, but only brushed me with a wing twice. During the second camera installation, the female perched nearby, never even bothered to leave her perch. She didn't issue the first alarm call until I was three steps up the tree! On climb number 3, while the female made many flying approaches, no contact was ever made. What was all of the excitement about? Well, I would find out the hard way.

I was completing a prey survey in a new territory which had not yet been searched. Searching would be my task for the afternoon. I was 600m from where my information had told me the historic nest location would be. Just as I finish the survey a male goshawk issued the alarm call to my right. The female shot up out of the forest! I got the nest! I move in to find the tree and check on nestling status. The adults flew toward me while screaming their call. I ducked to the side, stayed close to trees, etc. I could see the nest and could see the evidence of nestlings (fecal marks on the ground). I quickly turned to retreat. Within moments the alarm calls ceased then wham!! my head gets knocked forward. I picked up the pace and got out of there. I touched my head... OUCH! Hmmm... Blood...

I like the full foot print of talons on the right.

The adults do get more aggressive as the nestlings get older. On Wednesday I reclimbed nest #1 to band the nestling. While I was only brushed twice during the first climb, the second climb produced a dozen direct hits from the female. She was able to hit me once just below the helmet to scratch the back of my neck! I will definitely turn up my collar for the next climb. The warnings from the ground crew are very important, "incoming!", so I am not in a critical climbing move when she's coming in.

Helmet ringer!

The Beginning of the End

The project is now six weeks complete, with only 2-3 weeks remaining. The end of the field season is no longer an abstract concept, but a huge boulder rolling down the hill. We constantly rearrange tasks to make them more efficient. We make decisions based largely on minimizing time. We hike double time through the sage to fit one more prey survey in before the 11:30am cutoff the protocol specifies. Right now, it looks like we will make it. Barely...

Other Observations

The other wildlife observations have taken a back seat to goshawks in recent weeks. Notable are many observations of moose including a few new moose calves. The bull elk are herded up and in full velvet. The mule deer are prevalent and the bucks are spectacular. More coyotes, badgers, beavers, and cougar tracks. Red-tailed Hawks, Turkey Vultures, Short-eared Owls, Golden Eagles, Northern Harriers, Cooper's Hawks, Sharp-shinned Hawks, etc.  The South Hills are definitely a special place to have as a study area.


This session we had a number of volunteers join us in the field. Uri, Nicole, Kerry, Jeri, Cristen, Dave, Carol, Cathy, and Karyn all spent time hiking through the woods with Lauren and I, taking notes, and carrying gear. Uri had the honor of finding a nest which we had spent days looking for. Dave, Carol, Cathy, and Karyn all fixed us dinner on different evenings to try and keep us from withing away (I am down 6 pounds in 6 weeks!). It is great to have such excellent family, friends, and volunteers.

Lauren, field assistant Superstar! The next climb is hers!
Dave and Carol, excellent Idaho Bird Observatory volunteers. Thanks for Dinner!
Cathy, excellent volunteer, photographer, and cook!

1 comment:

Debbie Courson Smith said...

Fascinating. Thanks for sharing the story/video/pics/war wounds.