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Healthy golden eagle fledgling

I’m holding a large, healthy golden eagle fledgling captured in late June.

Wow! Time has flown by this summer field season, and this entry is way overdue. There is so much to report regarding field excursions into Yellowstone and our ongoing golden eagle study. I’ll focus on golden eagles with this entry and catch up with Yellowstone grizzly bears and other topics in the near future. Cottontail and white-tailed jackrabbit populations are still in a low phase of their cycles, and that continues to have a big effect on our eagles.

Richard Jones and Nathan Horton with newly-banded golden eagle fledgling

Richard Jones (left) and Nathan Horton with newly-banded golden eagle fledgling.

Richard Jones just completed our final aerial surveys, and most nesting is complete; only a few active nests still contain nestling eaglets. Although most of our 65+ eagle territories were occupied this year, fewer than 20 pairs actually laid eggs. Of the eggs that successfully hatched, more than half have survived to leave the nest, but we found evidence that a few of these fledglings did not survive long. We don’t know for sure why these birds died, but it’s a good bet they were not getting enough to eat late in the season — there are surprisingly few prey remains in most nests, and some of the surviving fledglings we’ve banded have been malnourished.

Dead fledgling

This dead fledgling was found under its nest, apparently soon after fledging.

It is a tough time for golden eagles in the Bighorn Basin! We suspect this is typical of what happens when cottontails crash here; the eagles really do not seem to be able to switch to an alternate prey species! It will be interesting to see what happens as cottontails begin to increase in number again.

May 7: Fieldnotes from the Edge of the Wild

About to board a helicopter for an early April nest survey flight.

Our leased helicopter, with pilot Josh, research assistant Richard, and videographer Penny, about to board for an early April nest survey flight.

Greetings to all! Today (May 7,  2013) is much too beautiful to be inside, but here I sit in my office awaiting an upcoming phone conference. At least I can write about some recent experiences in the field and anticipate fieldwork later this week. On April 5 we completed early season aerial surveys to determine the status of golden eagle nests in our Bighorn Basin study area. Eagle chicks began to hatch around April 27.

This is the 5th year of our research program to determine the relationships between golden eagle reproduction and various environmental factors in the sagebrush-steppe habitat in the eastern margin of Greater Yellowstone.

An active aerie, with an incubating golden eagle!

An active aerie, with an incubating golden eagle!

At this point, the number of active nest areas is a bit higher than last year, but not nearly as high as 2009 and 2010, when cottontail rabbits were far more abundant in our study area. We’ve seen cottontails crash since 2010, and eagle reproduction has declined similarly. No clear understanding of why rabbit populations in some areas tend to exhibit repeated cycles of abundance and scarcity. Some studies indicate that abundant rabbits deplete and otherwise stress their food plants—possibly causing a significant reduction in nutrition value of the preferred plants, and thus inhibiting rabbit reproduction! Other possible explanations involve increased incidence of disease in a dense rabbit population or even a stress response of rabbits to too many other rabbits, thus inhibiting successful reproduction.

Drought is apparent from the air.

The winter drought was apparent from the air when we flew over the Bighorn Basin in early April.

We’re also finding that human activities have caused some eagles to abandon nest-sites, but it is difficult to separate out the effects of natural prey cycles and human-caused interference. It is the interaction of so many factors that makes ecology both an exciting and extremely challenging science! This is also the reason why long-term studies in ecology are so important: …given time, we are much better able to tease apart the effects of confounding factors, like weather, food availability, human activity, etc. on wildlife populations. We’re anxious to begin analyzing data at the end of this year to really begin to understand how the sagebrush-steppe ecosystem functions and what drives and threatens golden eagle populations in the American West. Stay tuned in the next several weeks for reports, photos, and video from the field reported by our Golden Eagle Posse volunteers and the rest of our research crew. In the meantime, get outside and explore the wild!

December 14: Fieldnotes from the Edge of the Wild

Responsibility and Credibility in Communicating Conservation Science to the Public

Rough-legged hawk

A melanistic rough-legged hawk (Buteo lagopus) recently captured and released by our Draper Museum team in the Bighorn Basin.

Last week was typical of scientific fieldwork involving the capture and marking of large raptors in Rocky Mountain winters―long hours of setting traps before dawn and waiting quietly in cold, windy conditions, punctuated by brief moments of exhilaration, immediately followed by attempting near-surgical precision with frozen hands while we secured, weighed, measured, banded, and released unhappy predators brandishing 3 – 4-inch, needle-sharp, talons! Our primary objective was to place colored, uniquely-coded leg bands on resident eagles to help us determine nest ownership and turnover in our long-term study of golden eagle nesting ecology in relation to human activity in the Bighorn Basin. But we also wanted to band some non-resident raptors such as rough-legged hawks, to help determine the specific breeding origin of these winter visitors to the Greater Yellowstone Ecosystem.

A winter wildlife trip

Participants in one of our winter wildlife field trips―often the most impactful conservation stories are those that people experience themselves.

Those long hours of waiting last week allowed me time to think more about the important role of natural history museums in our society, and the responsibility of working scientists to make the process and product of our work accessible to the public. I’ve been on the lecture circuit in 2012 discussing these topics and continue to refine my ideas from audience feedback at each venue. When I returned from the field this week and began trying to catch up on recent scientific literature, I came across a provocative editorial in the journal Conservation Biology. Kent Redford and colleagues contributed a cautionary piece about the importance of relying on rigorous conservation science when we (i.e., conservation scientists and other professionals) relate conservation stories to the public. We should celebrate the increased public attention and scrutiny conservation stories are generating these days and work doubly hard to ensure that our stories accurately reflect the most current, most rigorous science available. It is too easy sometimes, especially when synthesizing and “packaging” complex information into sound bytes, to over-interpret or sensationalize scientific information. While this practice can be immediately attention-grabbing, it can undermine the long-term credibility of conservation practitioners and conservation science if the story doesn’t stand up to careful scrutiny. To be effective in countering typical anti-conservation dogma regarding such topics as wolf reintroduction and management, and climate change, we must make certain that we aren’t propagating our own preferred dogma.

All of this brings me to the role of natural history museums and other similar institutions engaged in informal science education for the public. I believe we are in a unique position to inspire curiosity and excitement about the natural world through scientific discovery and help create responsible stewards of the spectacular biological diversity of our planet through our daily contact with lay audiences of all ages. It is therefore critical that we take this responsibility seriously and make certain that the exhibits, programs, media interviews, and publications we present to the public are engaging, relevant, and stand up to the strongest scrutiny.

For further reading:

  • Lomborg, B. 2001. The skeptical environmentalist: measuring the real state of the world. Cambridge University Press, Cambridge, United Kingdom.
  • Preston, C.R. 2012. “A new breed of museum for a new era of exploration: celebrating the tenth anniversary of the Draper Museum of Natural History.” Points West Fall 2012: 22 – 27.
  • Redford, K.H., C. Groves, R.A. Medellin, and J.G. Robinson. 2012. “Conservation stories, conservation science, and the role of the Intergovernmental Platform on Biodiversity and Ecosystem Services.” Conservation Biology 26: 757 – 759.
  • Vohland, K., M.C. Miambo, L.D. Horta, B. Jonsson, A. Paulsch, and S.I. Martinez. 2011. “How to ensure a credible and efficient Intergovernmental Platform on Biodiversity and Ecosystem Services.” Environmental Science and Policy 14: 1188 – 1194.

July 16: Fieldnotes from the Edge of the Wild

Bighorn Basin larkspur

A spectacular bloom of Bighorn Basin larkspur in June 2010–we’ve seen nothing like this in 2012.

Summer set in with a vengeance in the Intermountain West through much of June, after some cooling weather and rain at the end of May. Very dry and windy conditions fanned raging wildfires in Colorado, Montana, Idaho, and southern Wyoming during the past month. Somehow, we’ve escaped significant fires in northwestern Wyoming, despite the hot, dry conditions…so far. No two years are alike in this part of the world. The variation in occurrence and schedule of wildflower blooming is particularly intriguing. Depending on the combination of ambient temperature and the timing and amount of moisture, the sagebrush-steppe environment of the Bighorn Basin might be covered with lupine, penstemon, larkspur, prickly-pear, scarlet globemallow, and other brightly-colored native flowers in June. This year, we’ve seen only brief, sparse blooms. Many areas that were awash in color last year are lacking blooms at all this year.

Lark bunting

One of the many lark buntings we encountered in the Bighorn Basin after a mild, wet spring a few years ago.

Several years ago, with significant late April rains after a very dry winter, we were surprised to see especially lush growth of bunchgrasses and blooming larkspur, accompanied by a large breeding population of lark buntings! We’ve not seen anything like that the year before or since. I suppose the take-home message is that wildlife (both plants and animals), especially in the arid sagebrush-steppe ecosystem, is truly existing on the edge, with even minor variations in weather resulting in dramatic differences in occurrence, distribution, and abundance of some wildlife species.

Golden Eagles in our study area began nesting a bit earlier than average this year, and many of the young eagles have already fledged (left the nest). I’ve begun capturing and banding some of the eagles who have left the nest. An early review of our data indicates that rabbit populations were very low early in the year, and eagle nest occupancy and productivity were the lowest we’ve seen in the last four years. More on that after we complete analyses and present our results at scientific conferences this fall. Our citizen scientists, the Golden Eagle Posse, have continued monitoring successful nest sites this year. Here are a couple of excerpts from their recent weekly narrative reports:

2012 fledging

I’m holding one of our healthy 2012 fledglings, newly banded and ready to be released.

From Anne Hay and Richard Gruber on 19 June: The chick is now about 54 days old. The adult is standing at her favorite perch at the south side of the nest. The chick is out of the nest, down an incline, standing about 6 to 10 feet south of the nest. It is farther back from the cliff’s edge, unlike on Tuesday, and is standing in a safe location. The chick begins to eat at 11 o’clock. The feeding occurs for 14 minutes. At 11:39 a.m. the mother eagle begins to feed on a prey hidden from our view. This continues for 4 minutes when the mother returns to her ‘knob’ perch and the chick follows her. At 11:44 a.m. the mother moves to the north side of the nest and again, the chick follows her. Two minutes later the mother begins to feed the chick on some unknown prey. At 11:53 a.m. the female eagle stops feeding the chick and eats for about one minute. She moves to her knob perch and cleans her beak on the edge of the knob perch. We do see, during our observations, the chick preening and exercising its wings. While the soul may be willing, the flesh is weak…so fledging is still two to three weeks away.

And here is a report from Don Chaffey from the same nest on 01 July:  Since we know first flight for this chick is close, I wanted to follow up with another quick observation. At 6 a.m. no signs of life in nest area—no adults and no chick. 6:15: Adult flew into nest area, walked around area like it was looking for food. 6:20: The new fledgling flew into nest area, started vocalizing, then picked up some leftover food—looked like rabbit. It appears that our youngster has fledged at 63 – 65 days after hatching. It is darker in color than adults now and begging for food at a perch near nest.

We are continuing to keep tabs on the nests that still hold nestlings, and will provide an update for you in a few weeks. Until then, keep observing and keep learning!

May 25: Fieldnotes from the Edge of the Wild

Bighorn Basin site, mid-May 2012.

Bighorn Basin site, mid-May 2012.

Big Horn Basin site, mid-May 2011

The same Bighorn Basin site, mid-May 2011.

Wow! We finally got a break last week from the hot, dry spring weather with two days of rain, and today we have temps in the 30s and snow. What a difference a week makes. This was shaping up to be the warmest, driest spring in decades. Sometimes people forget to make the distinction between long-term climate change and day-to-day, season-to-season, and year-to-year weather fluctuations. Both are important to patterns of vegetation and animal behavior, but exert their influence on different time and geographic scales. Just to document year-to-year variation, I shoot photographs of several sites in our Golden Eagle study area in the Bighorn Basin on or about the same dates each year. Comparing my photographs of this May 16 with last year’s May 16 at one site shows how much drier we have been this year. It will be interesting to see how this recent wet spell changes things.

Golden Eagles are well into the nesting season, with the first eggs hatching in late April. Our citizen scientists, the Golden Eagle Posse, have been monitoring several selected nests since the first of May. Here are some excerpts from their weekly narrative reports thus far:

From Anne Hay and Richard Gruber, 01 May: We arrived at 1:00 P.M. to find an adult sitting on the nest. 5-minutes later the other parent arrived, but only stayed for about 4-minutes, then flew to the top of the ridge. The female then stood up, and fed on an unknown food source for a short time. We saw no signs of a chick, so we ask ourselves, “brooding, or incubating?” The female then spent most of her time lying down, with some feeding from this position. At 2:27 the female stood up and stretched. “We have a chick,” I exclaimed. A little head popped up, looking quite white in the sunshine. Mom left briefly, returning with pine boughs to add to the nest. She fed the chick for a couple of minutes, then continued to brood. At 3:01 the male arrived with what looked like a talon full of dry grass. The female looked as though she was calling out the entire time he was present, as we could see her mouth moving up and down, however, with wind gusting to 30 mph toward the nest, we could not hear her. 

A curious--and hungry--youngster

This curious youngster is ready for some food! C.R. Preston photo.

And here is a report from Richard Brady and Sharyl McDowell, 07 and 10 May: last week we reported two chicks on nest… Today only one at a time. Scanned rocks/cliff bottom etc. No baby eagle apparent. Chick appears to be 5-15 day old. Very white down. Moving around inside the nest, did not see second parent eagle. An eagle soared over the nest for a while, but there was no calling, it did not come in to perch and mom eagle did not leave the nest. Could have been an eagle from the airport nest out for some exercise. 5/10: Arrived at nest site in a 10~20 mph wind. Ascertained an adult eagle was sitting in the nest site. Absolutely no activity during our observation period. She at times did turn her head from left to right. No sighting of second eagle. The large antelope we have observed each time was present again but he also soon disappeared, seeking shelter from the wind. The other times we have visited this nest, we have seen and heard any number of smaller birds flying and calling. Today we did not observe or hear any of this activity. Conclusion: Birds don’t like to try to move around in the wind either.

Prey remains

Just a sampling of prey remains from one golden eagle nest last year. C.R. Preston photo.

This is an excerpt from last week’s report from Bud and Dale Schrickling: During the first observation period we were able to verify that there was a single chick in the nest. We witnessed a parent return to the nest and feed the chick. Our optics prevent aging the chick at this time due to the distance we are away from the nest. The second observation period was cut a little short due to bad weather. We intended to return later, but both were not well for a couple days.

And, finally, here is a note from Sammi Bray from 22 May: Arrived at nest at 1430, it was windy as crap so I did not stay due to poor observation conditions (could not even hold binoculars still; wind estimated at 30-40mph). No data sheet for this observation. Greenery was visible on nest, but no adults or chicks could be seen. There is no place to get a good line of sight into this nest that is not extremely far away.       

Well, some days are better than others. Hang in there Sammi!!

Our 2012 undergraduate intern from the University of Wyoming, Nathan Horton, is taking advantage of today’s nasty weather to stay in our lab and begin sorting through some of last year’s Golden Eagle prey remains we collected at the end of the nesting season, after youngsters fledged.  You’ll be hearing from Nathan in subsequent postings, and much more from our Posse as the eagle nesting season progresses. Stay tuned!

April 26: Fieldnotes from the Edge of the Wild

Golden eagle nest

This is just one of several golden eagle nests not occupied by eagles this year.

In my last blog post, I discussed trophic cascades and humility in the face of the complexity of nature. We’re in the midst of our field season conducting research on golden eagles in the Bighorn Basin now, and trophic cascades and humility are on my mind again! Of about 60 Golden Eagle nesting areas we’ve mapped in our study area, we can only confirm 20 that are active this year. Eagle pairs may refurbish one or more alternate nests in a given breeding season, but ultimately choose not to carry on with breeding activities. Presumably, this choice has much to do with food availability, though disturbance near the nest may also play a factor.

During the past two years, we’ve documented a population crash in cottontail rabbits and white-tailed jackrabbits; key prey for eagles in our area. If there is enough alternate prey available, we’d expect to see eagles maintain similar breeding rates while feeding on different prey. Although we’ve seen eagles take more ground squirrels, songbirds, snakes, and even pronghorn fawns, rabbits remain the chief prey, and the breeding rate and productivity of eagles have declined. Apparently, alternate prey is not available in sufficient abundance in our study area to completely replace rabbits in the diet. Scientists have been studying rabbit population fluctuations in different areas of the world, but the fundamental cause of these cycles remains unclear.

Cottontail rabbit

Cottontail rabbits are a key prey species for golden eagles and other predators in the Bighorn Basin.

One possibility is that high rabbit density tends to create stress for rabbits that reduces reproduction in some way. Another hypothesis is that high rabbit densities reduce food availability or affect plants in a way that makes them less nutritious or palatable to rabbits. Others point to the fact that high rabbit densities lead to an increase in predators preying on rabbits. And, of course, weather conditions may exert pressures on rabbit populations. As with most ecological puzzles, rabbit population fluctuations are probably caused by a combination of factors acting together. Because rabbits are such a core prey species where they occur, fluctuations in rabbit populations create widespread effects felt by predators, other prey species, and the plants that rabbits use as food. As we continue our long-term study of golden eagles in the Bighorn Basin, we’re learning much more about the interrelationships among all the inhabitants in the sagebrush-steppe ecosystem and how human activities influence these interrelationships.

Golden eagle pair

To breed or not to breed? That is the question for this golden eagle pair in 2012.

We’ve just completed our early season aerial surveys to determine eagle nesting activity, and during the next few weeks we’ll be conducting ground surveys to gather additional information. This year is shaping up to be unusual—warm weather has come early, and hot, dry conditions are forecast for the summer. It will be interesting to see how these conditions impact our eagles and the ecosystem. Stay tuned to this blog for updates and enjoy Spring!

March 2: Fieldnotes from the Edge of the Wild

I’ve often said that ecology is not rocket science…it’s far more complex. Ecology is the scientific study of the relationships of organisms to their physical environment and to one another. Sometimes these relationships are immediately obvious and intuitive, and sometimes they’re a bit more, well…complicated. Take the well-documented case of sea otters, sea urchins, and kelp “forests” in the North Pacific Ocean. Beginning in the early 1970s, ecologist James A. Estes, his students, and many subsequent researchers, revealed an intriguing set of relationships that help us understand the broad impact of top predators in an ecosystem. The discoveries arose from the patchy distribution of sea otters in the North Pacific. The fur trade in this region had left only a very small scattering of sea otter populations. Otters had been completely removed from some sites, while colonies in other sites persisted. Some populations were reestablished by translocations. This patchy distribution of otters set up a lucky natural experiment for Estes and his colleagues. They found that kelp forests and many organisms that depended on kelp forests had disappeared from areas without otters, but flourished in areas with otters. What do otters have to do with kelp? With additional observation and dozens of experimental studies, ecologists discovered that otters eat sea urchins, which in turn eat kelp as their primary food source. Where otters are absent, sea urchin populations increase 10 – 100 times! At these population levels, urchins eliminated most or all of the kelp, creating what are called “urchin barrens.” Where otters are present, they keep urchin populations down, and kelp forests flourish, supporting a wide variety of invertebrates, fish, and other organisms missing from urchin barrens. The story becomes even more complicated when we consider the differences in wave pattern and water chemistry between kelp forests and urchin barrens and what happens when killer whales are present to prey on otters. But the point is that predators like the sea otter can have a profound influence on an ecosystem through several levels. This ecosystem effect from top to bottom of an ecosystem is termed a trophic cascade.

Wolves were reintroduced to Yellowstone in 1995 after being absent for nearly 70 years.

We have our own, world-famous trophic cascade in the Greater Yellowstone region, discovered when the gray wolf was reintroduced to the region after being largely absent for nearly 70 years. In a study published last month in the international scientific journal Biological Conservation, William Ripple and Robert Beschta reported that wolves are profoundly changing Yellowstone from what it has been for the last several decades. Wolves have reduced elk populations and changed their feeding patterns, particularly in Yellowstone’s Northern Range. As a result, Ripple and Beschta say that aspen trees and willow shrubs are flourishing, bringing back beaver populations and improving habitat conditions for fish and some songbirds. For example, the authors found that along streams in Lamar Valley, 100 percent of the tallest aspen sprouts were browsed in 1998, compared with only 20 percent in 2010―less browsing generally means more trees to reach maturity. The estimated 6,000 elk that remain on the Northern Range (down from an early 1990s high of more than 15,000 individuals) behave differently with wolves present. These elk tend to avoid foraging in areas where they are more vulnerable to predation and don’t tend to forage in any one place very long. This has been characterized as the “ecology of fear.” Wolves have had other wide-ranging effects in Yellowstone, directly reducing coyote populations. Coyotes, in turn, impact prey populations and repress red fox populations. What do fewer coyotes and more red foxes mean to small mammal and songbird populations? And how do carcasses provided by wolves affect ravens, eagles, grizzly and black bears, and other scavengers? It’s clear that these scavengers benefit from carcasses, but it remains unclear how that will ultimately affect the size of these populations and their effect on other species. Like I said, ecology is complex.

Increased tree and shrub growth in Yellowstone's Northern Range may reflect a trophic cascade started by wolf reintroduction.

What lesson should we take away from this complexity? For me it is humility and the recognition that we still have so much to understand about nature and how she works. I have to chuckle a little at the folks who stand up at public meetings and stridently hold court in local bars expressing with great certainty their opinions on wildlife from their many years of observation. I’ve hunted wildlife of all sorts and observed nature for nearly 60 years now, and actively studied it professionally for more than 35; the more I learn, the more I realize I have to learn. The wonderful thing is that exploring nature and discovering her mysteries never ceases to amaze, inspire, and rejuvenate anyone who is really paying attention.

For further reading:

Terborgh, J. and J. A. Estes (eds). 2010. Trophic Cascades: Predators, Prey, and the Changing Dynamics of Nature. Island Press, Washington, DC.

Ripple, W. and R. Beschta. 2012. Trophic cascades in Yellowstone: The first 15 years after wolf reintroduction. Biological Conservation 145:205 – 213.

Welcome to ‘Fieldnotes from the Edge of the Wild’

Rainbow over the "edge of the wild"

Rainbow over the "edge of the wild"

Living and working in the Greater Yellowstone Area (GYA) is a wonderful privilege, complete with many spectacular rewards and more than a few challenges. We are in the last frontier of the contiguous United States, complete with beautiful, but rugged and unforgiving terrain, magnificent but dangerous grizzly bears, otherworldly and unparalleled geothermal features, constantly changing seismic landscapes, and, of course, the ever-controversial gray wolf. Here survives not only the Spirit of the American West, but also the ancient Spirit of America herself. But, we also belong to a culture that is on the move, always spreading our influence a little deeper into the frontier. Perhaps that is our nature. Our species has arrived at a point where our population and technology have far outdistanced our knowledge of their consequences to the last frontiers of our world.

Here in the GYA, we seem to have a love-hate relationship with the frontier. We pride Read the rest of this page »

2011 Field Notes: July 22

Rock ledge

Rock ledge with a more thank 65-foot drop to the ground.

22 July: At least one of our nests has a young eagle yet to fledge! This bird is at least 62 days old and reluctant to leave the safety of the nest. This nest is more than 65 feet from the nearest safe ground, so this youngster may be wise to hang on for a while.

Four eagles fledged last week from three different nests. We caught up with one of the fledglings perched on a large rock outcrop about 100 meters away from its nest. We watched it for about 30 minutes before it took flight!  It flew with strong wingbeats for about 250 meters, then began gliding and landed a bit awkwardly on a sagebrush-covered hillside across the canyon. The bright, white band on the tail and stark, white wing patches were clearly visible to us. Summer is in full swing now, with temperatures in the low-mid 90s most days.

Golden Eagle Posse member Anne Hay filed this report and photograph shortly after the Read the rest of this page »

2011 Field Notes: July 8

Big Horn Basin

Rugged terrain in the Big Horn Basin.

July 8: Summer has definitely arrived in the Bighorn Basin! Still a good deal of green and some wildflowers in bloom, but things are heating up and drying out. It was 93 degrees F. yesterday afternoon when several of us visited one of our successful eagle nests. The single fledgling left the nest more than two weeks ago, at about 54 days of age. She wasn’t quite ready for sustained flight yet, so she stayed in the rocks and sagebrush around the nest for several days before she finally took flight and left the immediate area. In the meantime, both parents continued to bring her freshly-caught prey. Our team began collecting prey remains in and around the nest to determine this family’s nesting food habits in 2011. Next week, I’ll post some photographs of this trip and what we discovered. Nearly all of the nestling eagles in our study Read the rest of this page »

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