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 week seven. Previous posts:
- Introduction: The Study Begins
- First week: First week starts with a bang, ends in snowy frustration but renewed optimism
- Second week: Two weeks in, three weeks behind...
- Third and fourth week: Project is Rolling Now
- More on fourth week: The Tale of the Stolen Jacket!
- Fifth and sixth week: Black Flies, Bachelors, and Technology Woes
Finally we have gained access to all of the historic territories in the South Hills. Not all roads are open due to snow, but we have fairly direct access to most areas with a few minor detours. This next week I expect it all to be available. With the new territory access, we are zeroing in on possibly the ninth occupied nest of the season. In this last territory we received a "vocal female approach" in response to a goshawk call broadcast. That usually means an occupied nest within 200m. The two other times I have witnessed this type of approach, we eventually found the nest. Eight nests is a good sample size, but nine would be better!
We continue to make progress on the prey surveys and completing our search protocol in unfinished areas. Lastly, we have started banding nestlings and continue to maintain the three nest cameras which I have installed.
The three nest cameras I have installed (had hoped for five), will be used to quantify the diet of Northern Goshawks within the South Hills. My proposal mentioned that the South Hills lack tree squirrels which have been shown to be the top diet choice of goshawks around the world. Additionally, Lauren will be researching nestling behavior using the same video footage. It is a tremendous resource. While I have not looked through the hours of video, nearly every file I open has some interesting behavioral aspects. I can't wait to discover all of the interesting content included within. Here is a age sequence of the first nestling with a nest camera. This nestling was affectionately named "Chuck". In general we do not name our study individuals, but when I posted my facebook status my fancy Droid phone spell checked the message and changed "Chick" to "Chuck". The name stuck. The short video covers ages of 14 days, 20 days, 28 days, and 35 days old of the same nestling (Chuck).
As I have mentioned in previous posts, the primary focus of my thesis is on the predator-prey relationships of Northern Goshawks. To accomplish this we are performing prey surveys in each of the 22 historic territories, independent of whether the territory is occupied or not. The method used is Distance Sampling along line transect. In each territory I have randomly placed four 750m transects. To complete a transect, we walk the 750m and note the perpendicular distance from the line to the prey item. This distance is measured using a laser rangefinder. We count Robins, woodpeckers, ground squirrels, etc. While we occasionally find other prey species such as White-tailed Jackrabbits or Ruffed Grouse, I won't have sufficient sample size to estimate their abundance. The perpendicular distance is entered into a statistical function which uses detection probability to produce an abundance estimate, with confidence intervals, for each territory. This means that you cannot look at the list of prey items seen and estimate abundance. Abundance is a function of both number seen and distance. I remain skeptical but optimistic that I will find a significant result. Some surveys in occupied territories have produced a huge list of prey items, while others have not. Also, all four surveys must be looked at together as the survey routes are placed randomly across different habitat types. To complicate matters I will also include the date, time, and whether the survey was performed by Lauren or myself. These "co-variates" will try to account for the differences in prey presence/detectability through the season, at different times of day, and the fact that Lauren and I will see/detect different species/individuals, etc. The calculations are very complex indeed. It's a good thing that there is a special software program called "DISTANCE" which will do most of the heavy lifting. It will be another couple months before I know for sure what I have got.
Another challenge with the prey surveys is that they are randomly placed across the landscape, not on trails or roads. In fact, they cannot be placed on trails and roads as this would bias the results. The effect is that they sometimes lead over cliffs, head straight up the mountainside, pass straight through impenetrable shrubbery (Ceanothus!) ,are miles from the nearest access point, or a combination of these. This last week while hiking in the deeper canyons in the south, some surveys required hiking to the bottom of the canyon to start, completing the survey by hiking straight up the other side, hiking back across to the vehicle, then moving to the next territory to repeat. It was our toughest week to date.
Regardless, this past week we did get caught up on surveys, completing three in each of the territories. Next week we will complete the remaining.
Last week's post included some photos of my first experience banding nestlings in the nest. As you can imagine, the nestling "Chuck" was not pleased with the encounter.
Here is the video sequence of the banding as captured on the nest camera.
It was quite a challenge hanging in the tree, working on the bird, all while the adult is attacking me. This week, my field partner Lauren climbed and banded her first nestlings.
Lauren was a bit luckier than I as the adults did not attack her. In fact both adults were away hunting for the first half of the banding process. One adult returned with some prey, probably the male, called out and then flew off. The female would have likely put up a stronger defense if she was around. Lauren had a small challenge on the descent as her feet had fallen asleep while at the nest. We often rappel out of the nest, but this tree did not have a suitable rappel anchor. Lauren therefore had to downclimb the tree with her feet asleep. I am happy to report that while it wasn't pretty, she made it down safely! Next week we will be climbing two more nests to complete nestling banding. One of the nesting areas has been very heavily defended by both adults (see reference to "scalped" in previous blog post!). The defense is so strong that we have yet to see or count the nestlings. I will definitely be wearing armor for that!
One of the interesting aspects of field work is interacting with other people in the field. For the first half of the season we rarely saw other people. The South Hills are now crowded with people providing numerous opportunities for interactions, both positive and not so positive.
The first group were three men on a beer break one afternoon. We stopped to say hello. After informing us that anyone from Boise must be lost (Boise State logo on side of our truck), they proceeded to inquire about our work. Raptors? Hawks? "They taste good!" Better than those black ones with the red heads (Turkey Vultures). We enjoyed the laughs. They then invited us to their cabin for a beer drinking contest. My guess is that Lauren, I, and six friends would still lose! Nice guys, they even told us where they keep the beer! As he said: "20 minutes in the spring water and the mountains turn blue!" (reference to Coors Light labels that change color when chilled). We are contemplating paying them a visit next week, although we have no illusions of the beer drinking contest...
The sound of gunfire is not uncommon in the South Hills. It is very unsettling when you know that you are probably the first person the people with guns have seen in hours. They do not expect you to be there. When people are traveling by ATV and shooting high powered rifles out of hunting season, I am not sure what to expect. They clearly were not sighting their rifles or target practicing, unless their targets were moving as there were a series of gunshots, they would move, a series more, etc. Hmmm. On the topic of guns, I found myself one morning on a prey survey walking into an area where kids were shooting pellet guns. Pellet guns don't make much noise, so I as completely surprised. I kindly requested that they pause until I had cleared the area. They looked at me like I was from another planet! But they didn't shoot me so I guess that was good...
Trying to help. Lauren also had an interesting encounter. In the middle of nowhere in the Southern part of the South Hills, she sees a dog. No one to be seen for miles in any direction. She stops the ATV and calls the dog to see if she could help. Suddenly a woman comes over the hill and asks what she was doing messing with her dog. Apparently, the explanation still didn't settle her down.
The bottom line is that there are many great people out there and a few that aren't so great. It is always wise to stay alert.
Next week we head back out for our last ten days in the field. We will be busy and I expect it to fly by. It's hard to imagine that the end is almost here. But our schedule is dictated by the birds and the seasons. Chuck will likely have fledged by the time we return if he hasn't done so already. The other nestlings will not be far behind. The odds are stacked against them all. An estimated 70% will not live until June of next year. 80-90% will not live to see their second birthday when they will first mate. But those that do will be all the stronger for it, as will their offspring. I hope that some of these nestlings will be the ones to make it. The leg bands that we have applied will help to tell their story. Lets hope its a good one.
Of course, the end of the field season only means the start of the analysis. Over the next six months I will be watching video, analyzing data, writing reports, creating posters, and presenting results at conferences. Then begins the work of modifying procedures for my second field season on which it will all start again.
It's hard to imagine my days (21 years!) working in the high tech industry. This world is so far from that one. I cherish every day of this new encore career, even the cold, wet, miserable ones and the hot, dry miserable ones! Look for another update in a couple of weeks time.