Sunday, July 31, 2011

Plucking the data for the verdict

The data analysis has begun! Now that my first field season of studying Northern Goshawks in the Sawtooth National Forest is complete, I have started to analyze the data. This will involve watching 3 months worth of video and performing many elaborate statistical procedures. The first analysis I have chosen to focus on is determining the prey abundance in each of the Northern Goshawk territories. These values will be used in further calculations in future steps of my analysis. Here I present what I hope is a simplified description of the process. Don't be frightened, I will try to make it as straight forward as possible.

For background on this project, these links to previous posts might be useful:

One of my key thesis questions is whether or not prey abundance influences Northern Goshawk nest occupancy and success. Further, which prey items have the greatest influence. The first step, and the step summarized here, is focused on prey abundance. This data was gathered by performing linear transect surveys within each historic Northern Goshawk territory. As each survey is performed, we logged the perpendicular distance of the prey item from the transect "line" by measuring it with a rangefinder. Prey could be detected by sight or sound. My field partner Lauren and I walked 96 transects, each 750 meters long, noting each prey item we detected and its distance from the line. Each goshawk territory had four of these transects randomly placed within its bounds. We tried our best to spread the surveys out over the nine weeks of the project, but late access to a number of territories prevented this. We also attempted to ensure that each of us performed two surveys in each territory. Scheduling also prevented this, but we were able to ensure that we each of us covered at least one of the surveys in each territory. This procedure resulted in 507 observations of prey items along with a number of non-prey items - coyotes, deer, elk, moose, cows, Red-tailed Hawks, Common Ravens, etc.

The theory behind this process assumes that it is easy to detect prey items on the line, but "detection rate" decreases with distance from the line. 0 meters is easier than 20 meters, which is easier than 40m, etc. Once a full set of data is collected, you would expect more detections near the line, dropping off with distance from the line. In fact the method assumes that the detection rate is 100% on the line and drops off from there. 100% detection on the line is rarely possible, but the procedures are fairly robust against some violation of this assumption. Mathematically a function can be applied to the data which models the observations recorded and this can be used to estimate abundance within a given area. Don't worry if you are a little lost. It's complicated, but should be more clear as I present the results below.

I am using a more sophisticated approach within the process which allows for the inclusion of covariates. Covariates consist of any conditions which might change the detection of the animals. The method I used allows for covariates to influence the scope of the detection function, but not the shape. In my case, this assumption is valid. An example of a covariate is the day of the year. We would expect some prey to be more or less abundant or more or less easily detected as the season progresses. Thus, the day of the year the individual survey was performed is probably the most common covariate used in this type of study. Time of day is a second covariate I am evaluating. It seemed like some prey was more easily detected later in the day. Who performed the survey is an important factor. Lauren and I have different experiences, knowledge, and recognition of prey species. Thus, the method allows for adjustments to be made based on who performed which survey. For example, I emphasized strongly to Lauren to "mind the line". In other words, she should devote a large amount of focus on detecting all animals on the line and less away from the line. It is clear from the data that she did this. I, however, have lower detection rate on the line than 10-20 meters away. Ooops. The great news is that our two surveys combined together look great! There are other biases influenced by who performed the survey. For example, I detected Green-tailed Towhees by sight and by call, but not by song. Lauren detected by sight only. The procedures are robust in handling these differences as long as who performed the survey is considered as a covariate. The 4th covariate I am evaluating was recorded on each observation as to whether the animal was seen or heard. The data show what you might expect that observing animals by sight is limited to those closer to the line, where observing by sound extends out much more evenly to about 50 meters. The last covariate deals with the distance of the survey that was performed in open sage/grass versus in forested habitat. Remember the surveys were laid out randomly across the landscape. This one is tricky as we were often walking in sage by a forest stand where the bird was observed. We did not record the habitat of each observation, only the structure of the transect. Next year I may collect more detailed habitat information.

After entering all of the data, the first step in the process is referred to as exploratory data analysis (Thomas et al. 2010). In this process, the data is checked against the assumptions and the covariates are evaluated for importance. This used a fairly complicated model selection procedure called Akaike Information Criterion (AIC). This method has become the standard in ecological research and is one I used in my undergraduate research (Miller et al. 2011). The good news is that unless performing the research you don't have to understand the method, only how to interpret the results. The process is to calculate an AIC value for each combination (or only the relevant combinations) of covariates. In our case, all of the covariates appeared to be relevant. Five covariates produced 32 combinations including the model with no covariates. The AIC score represent how well that model or combination of covariates fit the data that was recorded. Essentially choose the model with the lowest AIC value. Sometimes you could choose a model with an AIC within 2 points which includes fewer covariates (within 2 points is considered roughly equivalent. Generally fewer covariates are better, but AIC does penalize the use of too many, so most people just choose the lowest AIC. I should note the AIC value is meaningless except for comparison between models using the EXACT SAME data. Blah, blah, blah, I hope that wasn't too much theory...

So after entering all of the data, I started the model selection for the covariates. I have chosen to process birds and mammals separately as they are generally detected in different ways, are detected at different distances, and are of different size and thus could have different impact on the diet of goshawks. Also note that we are only including prey items for goshawks. We did not count small warblers of which a nestling goshawk would have to eat 40-50 a day. While goshawks may occasionally eat small prey, that prey is not likely to have an important impact on nest success. For birds we included robins, woodpeckers, doves, tanagers, towhees, bluebirds, blackbirds, and grouse. Mammals included ground squirrels and chipmunks. The following table shows the mammal output for the top models. Note the smallest AIC is at the top. Most AIC tables, like this one, include a delta AIC which performs the math for you. The top model is 0 and the delta AIC indicates the AIC difference from the top model.

Name # params Delta AIC AIC
Mammal Time Who 3 0.00 393.12
Mammal Julian Time Who 4 0.93 394.05
Mammal Time Who Seen 4 1.25 394.37
Mammal Time Who Sage 4 1.83 394.95
Mammal Who 2 1.90 395.02
Mammal Julian Time Who Seen 5 2.05 395.17
Mammal Julian Time Who Sage 5 2.80 395.92
Mammal Who Sage 3 3.22 396.34
Mammal Time Who Seen Sage 5 3.24 396.35
Mammal Who Seen 3 3.50 396.61
Mammal Julian Who 3 3.70 396.82
Mammal Julian Time Who Seen Sage 6 4.05 397.17

Here we can see the top model for Mammals only uses the time of day of the survey and who performed the survey, dropping the other potential covariates and simplifying the model. The bottom line is that ground squirrels were more easily detected later in the day and Lauren and I detected them differently. The analysis of bird detections chose a model using the day of year, who performed the survey, whether they were seen or heard the bird, and the amount of survey performed in open sage/grass versus forest. Excellent.

Now lets see how the data look once they are adjusted by these covariates, extreme values are truncated, and data is grouped into 10 meter buckets to smooth the curve. Mammals came out looking exactly like it should, as illustrated in the graph below! The sampled data is in blue and the "fitted curve" is in red. The fitted curve will be used to estimate abundance in each territory.

Sampled mammal data (blue) and fitted curve (red).

This may not look exciting, but it is absolutely awesome! This illustrates that my survey method worked. Not only did it work, it worked great! I was ecstatic when I first saw this. As scientists we like to find significant results, but we like even more to implement methods that when executed produce valid results. This did just that!

The avian results, as illustrated below, are not quite as clean due to a "training and assumption" issue in our field methods. The only issue is the increased detection probability near 50m. As you can see from the curve below, it had little influence on the fitted model and falls well within the bounds of the methodology. The end effect is potentially a slight under estimate of abundance within each territory, applied consistently across all of my territories. Since I am using abundance as a relative measure, the end effect is irrelevant.

Sampled bird data (blue) and fitted curve (red).

Thanks for sticking with me. All of this work simply leads us to the conclusion that the method works, the data is valid, and abundance estimates produced can be used in the next steps of my analysis. It is often the case that more work is required to prove the method than to interpret the results.

Now, on to the real results. I categorized each of the goshawk nesting territories as either "no occupied nest detected", "occupied nest that failed", or "occupied nest that successfully fledged young". Calculating mammal and avian prey abundance in each of these territories, we can compare the results between these categories. Mammalian prey abundance did not have a significant impact on nest occupancy or nest success. This is a bit of a surprise as we know from the not yet quantified camera footage and personal observation, that goshawks in the South Hills do eat a lot of ground squirrels.

Mammalian prey abundance in goshawk territories categorized by success - not significant.

A significant result would occur if the bar height of one bar fell outside of the "whiskers" on another bar. The bar represents the expected value and the whiskers represent the range within the true value should fall with 95% confidence. If a bar were to fall outside the 95% confidence of another category, we could call it significantly different. In this case none of the bars fall outside of the whiskers of any other bar. The whiskers on the "breeding, nest failed" bar are larger since there are only two territories in this category. Fewer samples result in larger uncertainty and a wider range of possible values. But, the avian prey results are significant!!

Avian abundance is a significant predictor of nest success!.

If you think I was excited before, this is outstanding! This illustrates that avian prey abundance in successful and breeding/failed territories are both significantly different than avian prey abundance in territories where no nest was detected. Although, the abundance between successful and failed nests is not significant. This far exceeds my expectations for my first field season! Awesome!

Why might avian prey abundance be significant while mammals are not. I will leave most of this for the discussion section of my research publication, but a likely answer is that nest occupancy is determined by two factors - past breeding success and prey abundance in February/March when the territories are chosen. Ground squirrels are unavailable in Feb/March and thus don't likely influence initial occupancy. Past success is dependent upon many phases including early spring, breeding season, and the post fledging dependency period (time after birds fledge but before they are independent from their parents). During this later period ground squirrels begin to estivate (summer hibernation) and the goshawk diet has to shift back to birds. Thus, birds early and late may possibly be the limiting factor to success. This theory would be consistent with my results. If you made it this far send me an email or post a comment so I know that this write-up was valuable.

I should note these results are still preliminary and I have months worth of further work and analysis to do. I will plan to provide other analysis updates as I make progress. I plan to present these results and the next few analysis steps at the annual Raptor Research Foundation conference in Duluth MN in early October (their logo is even a goshawk!).

Thursday, July 28, 2011

Blinded by science

Actually, the title should read blinded by bad assumptions while in the field performing science! I have previously written of my adventures studying Northern Goshawks in the South Hills of the Sawtooth National Forest of Idaho. In the previous reports I have noted the discovery of a dead male goshawk in one of the nesting territories we were studying. Well, not so fast...

One of the nesting territories of my study remained inaccessible until very late in the season due to snow. Once we did arrive in the territory, I quickly received a response from a adult female goshawk. Her response was consistent with the presence of a nest very close. The presumed nest stand was fairly small, but after numerous searches we failed to find a nest. However, the female goshawk was easy to find in the same stand day after day.

One day Lauren found a pile of feathers about 150m from where we usually found the female. The feathers were definitely raptor feathers and seemed consistent with a goshawk, although we did not have a feather reference with us.

Feathers discovered in the South Hills.

Due to the territory where the feathers were found and the proximity to the female goshawk, we assumed this pile of feathers belonged to the male goshawk of the territory. This one assumption played a critical role in our interpretation of the female goshawk behavior as I will illustrate below. However, upon further inspection...

Returning home after the season, I accessed the online feather atlas to confirm the identity of the feather owner. They unfortunately do not have male goshawk feathers available, but do have adult female feathers.

Hmm. We have a problem here. The colors don't match, but goshawk colors vary significantly. The shape seems a bit off as well. But the size is the real issue. Our collected feathers are longer than these female goshawk feathers. In most raptors, including goshawks, the female is larger than the male. In goshawks the female can be 15% larger. I would expect male goshawk feathers to be shorter... Well, there is only one other gray raptor in this area. The male Northern Harrier.

Well, that is better, but what about those assumptions...

We observed the female goshawk in the stand on six different days. On each occasion we were there for at least an hour searching and watching her behavior. This behavior was interpreted through our assumption of the male being dead. For example, if the male was dead and the female had a nest with live nestlings she should be hunting most of the time. In our case, she was perched in the stand on every occasion of our visit. This was inconsistent with a nest full of hungry nestlings. On the other hand, if the male was out hunting all of the time then the female could remain back to guard the nest stand. This could be consistent with a nest full of nestlings.

Another challenge in the South Hills is that we would occasionally hear a goshawk call which was unfamiliar. This unique call was omitted from most references regarding goshawk communication. On one occasion the female issued this call and flew like a rocket over my head and to the edge of the stand. With the assumption of the male being dead, I could not explain this behavior. Maybe stand defense? I was confident that her response was not directed at me, but I had previously seen her respond to a Common Raven, but not in this manner. Upon further research I have found one description of a female "dismissal call" which is issued by the female to the male, often as the male delivers food. Could I have witnessed a male prey delivery and not even recognized it? This would be a indication, although not a firm confirmation, of a nest with live nestlings in the area. I have yet to find a recording of the "dismissal call" to confirm this, but we have heard three other females give the same call, on each occasion the male was also present. Once again, the assumption of the male being dead and my lack of experience with the "dismissal call" clouded my interpretation in the field. Yes, experience does matter! 

Next week I hope to return to the stand one more time. By this time any nestlings should have fledged, but would still be expected to be in the area. Nestlings are easily identified by their begging calls. Begging calls would allow me to classify the territory are a successful nesting territory even without finding the nest. Otherwise, it will remain as "occupied".

Next year I will definitely have more resources in the field including a printed feather atlas!

Monday, July 18, 2011

Trends in the data...

As a research biologist I am always looking for patterns in the environment or in the data that I collect that could lead to new conclusions and knowledge about the species we study. Usually these patterns are mostly hidden from view and we rely on statistics to tease them out. During my recent field season I noticed a very strong trend regarding the six non-failed goshawk nests were were monitoring at the end of my seventh week in the field. It appeared that the late spring weather might have had an impact on the number of nestlings. The earliest hatching nest (as determined by the age of the nestling) only had a single nestling, where the two latest hatching nests each had three!. A plot of the six nests looks like this...

Northern Goshawk nestling counts by hatching date for first six nests discovered.

Look at that amazing trend line. Not surprisingly with a pattern like that the trend is very significant. A simple regression has a p value less the 0.001 and an r-square of 0.95. This is unheard of in ecological research. To have such a strong p-value and r-square value with only six points is amazing. This was definitely looking like a strong conclusion. I looked through my research summaries (Book: The Goshawk by Robert Kenward) for other research with the same conclusion. I didn't find any. While this book is not comprehensive, it is nearly so. I became more optimistic that we might be on to something.

During week eight, we performed our job too well. We discovered two more occupied nests and these two did not fit the mold. Adding these two points into the analysis produced a picture that looks like this... (new points in red)

Northern Goshawk nestling counts by hatching date for all eight nests discovered.

The statistical significance goes right out the window... The p-value rises to 0.27 and the R-square drops to 0.06. The only trend remaining in the regression line is almost entirely influenced by the first point.

The lack of significance does not mean that early season nests didn't faced unique challenges affecting brood size, it just means that this study cannot conclude that there is a correlation.

Brood size by hatch date is not part of my thesis, but it might have been nice to have a freebie significant result. Anyway, I would rather have the two new nests for my thesis, which is challenged by sample size, than concluding brood size is related to hatch date.

Sunday, July 17, 2011

Mission Accomplished!

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 field season weeks 8 & 9. Previous posts in this series:

The end of my first field season studying Northern Goshawks has arrived. Well, sort of... I have a one day trip to the area I still need to make. The last trip, not scheduled for a few weeks, will allow me to remove the final nest camera and to perform habitat surveys around the nest trees without disturbing the nestlings/fledglings. I can't believe it is mostly over. I am relieved yet at the same time disappointed. It has been a fantastic experience which I will clearly miss. But, by all measures it was a highly successful season! And for that I am tremendously grateful! It could not have occurred without the support of many.

On my final day in the field, while still amped up on adrenalin from climbing a nest tree, I focused my creativity on poetry. A 40 minute motorcycle ride can do that to a person. Here are my two works of art!

To the South Hills Goshawks I bid you adieu,
I enjoyed our time together probably much more than you,
May the ground squirrels by plenty,
and the Flickers be plump,
I will see you again next May for my thesis year 2!
There was a young goshawk affectionately known as Chuck,
when I climbed the nest tree to band her I definitely had to duck,
for the parents were screaming,
and attacking with rage,
but Chuck just stared and said, "Hey, what the ...?"

Yah, yah, yah, I'll stick to field work...

Adult Goshawk.

The season

My early season concern regarding the late spring weather was eventually alleviated. My hope was to discover at least eight occupied goshawk nests. With a couple late discoveries, I ended the season with ten! The early season weather also presented many transportation and access challenges which I have documented in previous posts, but through some long hard days, we managed to get back on track and catch up. We even completed a couple of the stretch goals for the season!

Now comes the long process of analyzing the data. Three months of video footage, data from 100 prey transects, observations from ten goshawk nests, interim reports to write (due in September), final reports to write (due in December), posters to create for presentation to the Raptor Research Foundation annual conference (October), applying for additional funding through grants, and then revising plans for next year. Wow, somehow I feel the work has just begun!

Three nestlings approximately 25 days old.

Goshawks everywhere

One of the new developments during this final field session was a significant increase in the number of sightings of goshawks. As the nestlings age the adult female goshawks are free to spend more time out hunting. This essentially doubles the number of birds visible. This is great, but it can also be frustrating. Visiting a territory a half a dozen times, finding an empty nest, performing multiple prey surveys, systematically searching for nests, performing call broadcasts covering a 577 hectare plot, all with no detections. Then, on the final visit to the territory while riding out on the motorcycle, I watch an adult goshawk fly into the nest stand. Unbelievable! Could I have missed a nest? Could this territory really be occupied? Should I go back and search some more? Probably just a roving adult out on a hunt far from their territory. If this was one isolated incident, maybe it wouldn't be so bad. When it happened again in another territory and then again in a third... well... Hmm... I guess that is why we have a formal protocol.

The case of the mistaken identity. We came to know a particular female goshawk quite well. In a late territory we finally gained access to we had an adult female response to our call playback. The stand was reasonably small, but we were unable to find a nest. There had to be a nest. We discovered a pile of raptor feathers nearby. With goshawks on the brain, we assumed it to be a the adult male. The female could be a widow. Each day we returned, we were able to easily relocate the female in the stand. But the location of a nest and its status remained a mystery. After spending time in the stand on five different days, we gave up on that territory for this year. I still believe there was a nest, but her actions seemed inconsistent with it still being successful, especially being a lone adult. Upon returning home and having access to resources such as the feather atlas, we discovered the feathers to be a male Northern Harrier and not a goshawk! Ooops! This changes our interpretation of the female's behavior. Possibly there is still a successful nest in the area.

One highlight observation occurred one evening while sitting on the porch of our cabin. An adult goshawk swooped by 20 feet in front of us at eye level and flew off through the trees. How cool is that! We travel all over the forest in search of these birds every day and here it was right in front of us.

37 day old nestlings, 4 days before they fledged.

Research on goshawks has occurred off and on in the South Hills over the past 20 years. Most studies, mine included, have focused on the same historic territories. One of my stretch goals was to discover a new territory. With the late spring weather I had all but given up on this, but our progress in the last few weeks re-opened the door. Through the use of GIS techniques I had mapped out the historic territories and analyzed the attributes of those, focusing more on the most successful nesting areas. I combined this with other literature on goshawk preferences and produced an algorithm for discovering new territories. Applying this algorithm to the entire South Hills I came up with seven potential locations. Last week I finally had an opportunity to visit one of them and boom, within an hour I had a detection. Within two more hours I had found an occupied nest with three nestlings! I also found two alternate nests in the area. My sample size just increased and I delivered a new territory to the forest service for future monitoring. I hadn't been this excited since finding my first nest on the first day. It got even better when Lauren reported a detection in the third new area we explored. Unfortunately we did not find a nest there but will return to check it out next year. The other four potential territories will have to wait for next year.

Adult Goshawk.

Nest stand structure and health

Visiting the various territories you definitely get a strong feel for the preferences of goshawks. A number of studies have shown their preference for a thick canopy cover with a relatively open understory. In fact, ground cover in the form of shrubs has a negative correlation with occupancy. Thus, mature Aspen with few saplings and mature Lodgepole with few saplings and shrubs are the places we most often find nests.

The problem with many of the historic nesting territories is that they are progressing beyond the mature stage and cycling back to a young forest. The older mature trees are dying off and often being replaced by young saplings. The result is that the nest stand may become unattractive to goshawks for another 20-30 years. This can be a natural cycle for Aspen. Bark beetle attacks are also killing off the mature Lodgepole pine, also forcing a reset to the succession and causing the stand to lose attractiveness to goshawks. While the primary focus of my study is on the prey relationships, I am also measuring the nest stand structure and health. It may just be coincidence, but one of the failed nests I was monitoring was once an excellent stand for goshawks, but I would no longer choose it for occupancy. Over 1/3 of the mature Aspens are dead and the stand is almost impenetrable due to Aspen saplings everywhere. A few of the Lodgepole Pine stands have been attacked by bark beetles and may be completely gone within 5-10 years. The forest service has a general plan to actively manage stand succession ensuring adequate availability of each successional stage. I have initiated discussions with them on how to integrate goshawk territories into that planning. This is a very exciting opportunity to have a positive impact on the conservation of this species.

Miscellaneous musings

The story of the watch. One funny thing that happened in the South Hills occurred when I was installing a nest camera in one of the trees. Lauren thought she saw a curved twig fall that I had somehow broken off. Later when back at the truck I stopped to see what time it was. Where was my watch? Apparently during the climb the watch had come off my arm. It would now be stuck in the tree for some time. Every morning at 6:00am the goshawks would be awoken by the alarm on my watch. Talk about investigator disturbance! Three weeks later when I would re-climb the same tree to band the nestlings, there it was half way up, hanging on a branch. I can now say that the watch is back in my possession enabling the goshawks to sleep in for the remainder of their nestling phase.

When climbing the nest tree to band the young, we often find prey remains or in some cases whole prey waiting to be eaten. In the same nest that I lost the watch, I found a dead juvenile American Robin sitting in the nest bowl. As I proceeded to band the young, I was discovered by the adults and they began their barrage of attacks. Nothing serious at this nest, simply protests and fly-bys (versus direct attacks to my head that has occurred in other nests). Anyway, at one point the adult male flys up and lands on the nest rim about 2 feet away. I notice that he is carrying another juvenile American Robin. It is possible that these were taken directly from the nest. It is known that Accipiter hawks, of which the goshawk is one, will return to the same source once they discover the nest of a prey species. In two other nests we found whole Belding's Ground Squirrels. It takes a lot of prey to feed a nestling. In other studies, each nestling consumes about 3/4 of a pound of prey a day.


The project has been a fantastic educational experience and I can't wait to get on to analyzing the data. That will be after a short vacation filled with other outdoor activities. But I will miss the daily routine and the fleeting relationship I have had with the wild goshawks of the South Hills. I am sure it happens to all researchers, but my admiration for the goshawks and the challenges they face has only increased with my time. I cherish every observation, even the three occasions that resulted in blood being spilled (mine of course). Back home I keep thinking of the individual birds. Is "Chuck" still slowly expanding his range from the nest (last observed about 100m from the nest tree)? Does the lone female really have a nest? Will it be successful? Two adult males observed were previously banded. Where did they come from? My research is all about the big picture and the population as a whole, but my interactions were all with individuals and I will remember every one.

Two and a half years ago I left a high paying job to spend time working on this in the outdoors. I can honestly and unequivocally say that it was one of the best decisions of my life. While my field work is done for this year (except for the follow up day), I will be working on other projects this fall, most notably banding migrating raptors at Boise Peak. It's a great project, but it's not like working on my own. That will have to wait until next year when I once again return to the South Hills. In the mean time it is all about analyzing the results.

Saturday, July 16, 2011

It takes a village...

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. Previous posts in this series:

Northern Goshawk Adult. South Hills, Idaho.

No, I am not raising a child (reference to African proverb), but a thesis project is a large and challenging undertaking. My specific research has been supported in many ways by many individuals and organizations. I hesitate to list individually, as I am likely to omit an important contributor or two. I apologize in advance if I do. However, here are some of the contributors which helped make my first field season a success.

Financial Support

The Minidoka Ranger District of the Sawtooth National Forest is the primary financial supporter of this research. The Northern Goshawk is a local management indicator species and thus understanding the health of the population and filling in the picture of the goshawk's role in the ecosystem is critically important to them. In addition to the direct financial support, the forest service also provided a cabin within the study area, which was critical especially during the snowy portion of the season and access to important equipment such as an ATV, GPS units, call broadcast units, emergency radios, etc. Support also included GIS data and other coordination activities. This project could definitely not proceed without their support and commitment. Dena, Tom, Jill, Bonnie, Karen, Kirby, Amanda, the trail crew, the fire crew, the recreation crew, ... they all at one point or another crossed our path and helped with something. What a great organization!

Natural Research LTD awarded me the 2011 Mike Madder's Field Research Award! This competitive award provided additional funding which was used to purchase the digital nest cameras which are critical to my core research questions. I thank them for offering this award and their commitment to the advancement of science in Mike Madder's name.

Rob Miller & Karyn deKramer. I would like to be able to say that all project funding came from outside sources. Unfortunately, that is not the case. This project has faced many challenges requiring funds beyond the core budget. Our personal motorcycle also racked up over 1600 miles within the study area. I am grateful that we have been able to cover the required expenses and keep the project on track.  I especially thank Karyn for her willingness to share in our support.

Equipment and Support.

This project requires a significant amount of equipment: ATVs, trucks, nest cameras, batteries, GPSs, Rangefinders, climbing gear, etc.

Boise State University's Raptor Research Center provided logistical support, access to a truck and most of the equipment used by the program not provided by the forest service. In many cases they outlay-ed money to repair and replace dated equipment. Dr. Fuller, Kathy and Nikole are a pleasure to work with and have consistently exceeded my expectations in helping me as my project faced challenges.

The Idaho Bird Observatory initiated the discussions which led to this project and provided consultation, contracting, etc. Jay and Greg are a great team to work with and I admire their work to provide opportunities to students such as myself.

Inovus Solar donated a number of rechargable batteries which were used to power the remote nest cameras used in my study. This updated technology increased the feasibility of remote cameras and decreased travel time required in the field to replace them. They worked great!

Greg Kaltenecker not only dedicated his time in the field and the consulting mentioned above, but also contributed gasoline to the cause which helped keep the field crew moving from territory to territory. The study area consist of over 125,000 hectares. From our central location this includes a 20 to 25 mile radius. This is a lot of ground to cover with at least weekly visits to each of the 24 territories.


There were many volunteers through the season. First and foremost, Lauren, who worked long hard days from the beginning through the end. Nine weeks of hiking steep hills, through thick brush and inpenetrable ceanothus, snow, Belding's Ground Squirrel guts, and most importantly, putting up with me! I am forever indebted to her.

Others joined for days up to a week. Some left relieved their time was over, but most left wanting more. Karyn, Jay, Heidi, Dave, Carol, Cathy, Cristen, Uri, Kerry, Nicole, Jeri, Michelle, Dusty, Mike, and Grant, all spent time with Lauren and I in the field. Some provided training, some searched for goshawk nests, some found goshawks nests!, some helped with nest camera installation, etc. Many helped feed the crew as well. Wow, how to thank them all? How did I ever find such great friends?

But it didn't all happen in the field. Advice, perspective, and just listening when I needed to talk. My thesis committee, Jay, Marc, and Jen, all fielded questions via email, text message, and/or phone. I am sure they fear my name appearing on their caller ID! Other goshawk researchers also provided advice via email, some I have never met. Kristin, Susan, and Jack, to name a few, provided insight into how to search for nests, specifics on some of the areas within the South Hills, and in some cases just moral support. It was all appreciated.

I review this list of names and organizations in awe. How did I ever assemble such a team? How will I do it again next year? Some had never heard of a Northern Goshawk before seeing one in the field. They are great people who care deeply about our environment, it's conservation, and what it has to offer. I am honored to call each of them my friend, even the one's I have never met. Thank you!

Saturday, July 02, 2011

End Game

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:

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.

Nest Cameras

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).

Prey Surveys

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.

Nestling Banding

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.

Chuck protesting my arrival.

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.

Starting the climb.
Nestling looking over the rim.
30 foot climb.
Banding two 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! 

The locals

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.

Almost Done

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.

A sea of wildflowers!

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.