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!
and
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.

Conclusion

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.

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