HWI Science Staff

HWI Science Staff

Friday, 10 March 2017 07:11

Gunsight Mountain, Alaska: 2017

March 7th marked the start of HawkWatch International’s second annual spring migration count at North America’s northernmost migration site: Gunsight Mountain, Alaska!

Cold but clear weather highlighted the first few days of counting with temperatures reaching -4 degrees Fahrenheit (-20 Celsius), not an uncommon occurrence in interior Alaska this time of year.  March 9th saw the first migrant Golden Eagle pass by the site, the first of many more to come.  Last season we counted 1,163 of these early northern migrants so we’re hoping for another good year!  In total we counted 3,143 migrating raptors of 13 species in 2016.

Our counters this season are Frank Nicoletti, a seasoned hawk watching veteran who many know from Hawk Ridge in Duluth, Minnesota; and Frank Simeone, who helped break the single-season Golden Eagle record this past fall at our Commissary Ridge, Wyoming HawkWatch site.  We’re thrilled to have both these gentlemen on board for what should be an exciting season.

We’ll continue to post updates throughout the spring, but as always, daily count totals can be viewed here.  Just click on “Latest count data."  You can also find more information about this site, including the 2016 Annual Report, at http://www.hawkwatch.org/migration.  

Tuesday, 21 February 2017 10:25

Swainson's Hawk-like Rough-legged Hawks

We are approaching the time of year in western North America when late wintering Rough-legged Hawks and early arriving Swainson's Hawks can be present at the same time. Particular Rough-legged Hawk morphs can have heavy bibs with lightly marked bellies and appear very Swainson's Hawk-like. This fact reminded us of a a great blog post shared by Jerry Liguori last year on this very same issue: http://hawkwatch.org/blog/item/848-swainson-s-hawk-yay-or-nay

An excellent thing to keep in mind as Swainson's Hawks begin trickling back north from their wintering grounds in South America!

Tuesday, 14 February 2017 15:58

Where Do Canadian Ferruginous Hawks Winter?

Blog by Jesse Watson

In early October we blogged about the Ferruginous Hawk project one of our biologists has been involved with in southern Canada.  At that time, we posted a map showing where Ferruginous Hawks tracked from their breeding ranges in Alberta and Saskatchewan were located along their fall migration paths.  Fast forward 4 months and we have a much better picture as to where these hawks have spent their winters and how they got there.  Many of the Canadian breeding Ferruginous Hawks tend to winter in the region between northern Texas and southern Kansas but some winter in New Mexico, Nebraska, and a few other states.  Of note are the hawks wintering in Mexico, California, and Idaho.  Although it is widely known Ferruginous Hawks winter in Mexico, only a few from this study have moved so far south. Similarly, only one of the tracked hawks has crossed the Rocky Mountains and wintered in California.  Finally, the hawk wintering in Idaho is the first in this study to do so and is also the most northern wintering Ferruginous Hawk from the study.  As spring approaches keep your eyes to the skies for migrating raptors and maybe if you’re lucky you’ll spot a Ferruginous Hawk headed north!

In June 2016, Jesse Watson, HWI’s Research Biologist and current University of Alberta student, led a team of researchers in capturing and attaching satellite transmitters on 5 breeding adult male Ferruginous Hawks in western Canada as part of an ongoing research effort.

Friday, 16 December 2016 09:54

GPS Tracking of Rough-legged Hawks

Rough-legged Hawks spend the winter throughout southern Canada and the United States, and yet scientists still know surprisingly little about the basic movement patterns of this relatively common arctic-breeding raptor.

One reason we know so little is that Rough-legged Hawks are thought to be “broad front” migrants, meaning they are not typically counted in large numbers along ridges that concentrate many other North American raptor species during fall and spring migration. Recent advancements in GPS-tracking technology have allowed increased understanding of avian movements, and Jeff Kidd of Kidd Biological, Inc. in California has been leading a collaborative effort to increase our knowledge of Rough-legged Hawk movement behavior.

Since 2014, Kidd’s group has deployed 55 GPS transmitters on Rough-legged Hawks in western North America, collecting more than 100,000 GPS locations along the way. HawkWatch International is partnering with Kidd to deploy GPS transmitters on wintering Rough-legged Hawks in Utah to gather movement information from a broadening western landscape.

To date, 4 GPS transmitters have been deployed on Utah Rough-legs during the 2015/16 and 2016/17 winters. GPS location data from Utah will be combined with data from birds wintering across western North America to provide the first comprehensive study of Rough-legged Hawk movement ecology. An exciting effort and one HWI is thrilled to be a part of!

Wednesday, 05 October 2016 15:38

Ferruginous Away - Migration is on!

Blog by Jesse Watson

Raptor migration is in full swing and nothing is more exciting than observing thousands of hawks headed towards their wintering grounds (or breeding grounds in the spring).  One North American raptor species that we don’t often hear about during migration is the Ferruginous Hawk.  Although a few are observed each season among several of our sites, they are counted in no-where near the same numbers as other Buteos.  This is because these hawks migrate along a broad-front (wide open areas) rather than along the tight corridors (mountain ridges and coastlines) with which we typically associate migrating hawks and hawkwatch sites

Since 2010, the University of Alberta has been studying the Ferruginous Hawk which is listed as Endangered in Alberta and Threatened throughout Canada.  Research has focused on a range of questions with the intent of gaining a better understanding of the species current status, as well as determining if and how Ferruginous Hawks are affected by continued development in the Canadian prairies, a breeding stronghold. 

Now you’re probably wondering how this all ties in with migration.  Part of the research effort at the University of Alberta has focused on the movement behavior of breeding adult male hawks and if those behaviors are affected by development.  To answer these questions, we are using satellite telemetry to track when, where, how and under what environmental conditions these hawks are moving throughout their breeding ranges, and we continue tracking these hawks after they leave their breeding grounds in August-October.  These migration data open the door for answering numerous questions about migration patterns, fall/winter ranges, potential hazards away from the breeding grounds...and they are just plain cool!

Currently, we are tracking 18 hawks including 5 from 2016 as they fly south for the winter.  Check out the U of Alberta’s Wild49 Lab Blog here for other posts about Ferruginous Hawks, Broad-winged Hawks, and owl species being studied within Canada, and be sure to check back here over the next few months to see where these hawks end up for the winter.  Lastly, if you are lucky enough to spot a migrating Ferruginous Hawk this season, make sure to keep an eye out for a transmitter antenna on the birds back in addition to leg bands!

In June, 2016 Jesse Watson, HWI’s Research Biologist and current University of Alberta student led a team of researchers in capturing and attaching satellite transmitters on 5 breeding adult male Ferruginous Hawks in western Canada as part of an ongoing research effort.

This blog post was written by Caitlin Davis who, together with Rya Rubenthaler (both have worked at our Goshute raptor migration site in NV the past 4 fall seasons), are the two official hawk counters for HawkWatch International's hawk migration count at Gunsight Mountain, Alaska. Up to date count totals can be seen at www.hawkcount.org/Gunsight by clicking on the "Latest count data" link.
Greetings from Gunsight Mountain, Alaska! Rya Rubenthaler and I (Caitlin Davis) have been here since March 7th, conducting the first standardized migration count at the site. The highlights have included large numbers of Golden Eagles in March, peaking at 229 in one day, hundreds of amazing Harlan's Red-tailed Hawks, and over 200 dark and light morph Rough-legged Hawks. We've also counted over 50 Northern Goshawks. Later migrants are starting to move through in higher numbers now, including Sharp-shinned Hawks and Northern Harriers. We saw our first falcon on Saturday: a Merlin who was chasing a flock of Lapland Longspurs. We're still hoping for that Gyr!
We had a great time with the Anchorage Audubon Society and Mat-Su Birders at their annual Gunsight get together this past weekend. Thanks for the food and laughs! We hope to see everyone again soon as the season picks up.

On March 7th, 2016 HawkWatch International began the first full-season of spring raptor migration counts at North America’s northernmost migration site: Gunsight Mountain, Alaska. This snow covered, valley migration site is nestled between the towering and glacier covered Chugach and Talkeetna Mountains. These two mountain ranges act as a natural funnel channeling migrating raptors through the Tahneta Pass.

Best known as North America’s premiere destination for viewing the Harlan’s subspecies of Red-tailed Hawk, Gunsight Mountain also has the potential to be one of North America’s largest Golden Eagle and Rough-legged Hawk migration sites. HawkWatch International conducted 2-weeks of exploratory counts in April 2015, counting nearly 1,400 migrating birds of prey and setting the stage for a full-season of spring counts in 2016.

Thanks to generous support from the Eppley Foundation for Research and Anchorage Audubon Society, the 2016 spring season will have 2 full-time experienced hawk watchers counting migrants from March 7 – May 15. Nearly 400 migrating raptors, almost entirely Golden Eagles, have already been tallied at the site.

March is Golden Eagle season at Gunsight Mountain, with generally distant views of the eagles over the Syncline Mountains to the north and west. Every once in a while however, one will pass directly overhead on their way to breeding grounds in the western Alaska Range. According to GPS tracking data from Alaska Department of Fish & Game, some of these Golden Eagles wintered as far south as New Mexico, while others winter as far north as the Yukon Territory; an incredible latitudinal span of winter ranges!

March is also a good time to see migrating Northern Goshawks, as well as migrant and resident Bald Eagles. Resident Northern Hawk Owls also frequent the tops of Black Spruce along roadsides near the count site. As we near peak Golden Eagle migration, we are eagerly wondering just how many eagles we will count this historic first season at what must surely be one of North America’s most unique, and beautiful, migration sites.

More Gunsight Mountain Information:

Monday, 23 February 2015 00:00

Wacky Weather and Early Breeding Activity

The harsh east coast winter has been getting much of the press, but in the western half of North America this has been one of the warmest winters on record. As a result, I've recently heard several people say something along these lines: "I've noticed some early breeding activity in my local bird species, but I'm worried about them nesting too early and leaving themselves open to nest failure because of late winter or early spring storms." Is this a legitimate concern? Lets do a quick review of the scientific literature and see what we can come up with.

First and foremost, birds are nesting earlier than they used to. An example of this can be found around Boise, Idaho where the local American Kestrel population is nesting approximately 21 days earlier than it did 20 years ago (Steenhof and Peterson 2009). These same Kestrels tended to nest earlier after warmer winters (Heath et al. 2012).

For many bird species, early arrival to the breeding grounds means you secure a higher quality nesting territory and have a better chance at being reproductively successful; i.e. raising nestlings to fledging age. This has been shown in both Merlins (Espie et al. 2000) and American Kestrels (Steenhof and Heath 2013). By nesting early, birds may also avoid raising nestlings during those sometimes brutally hot summer days that in some species like the Golden Eagle, can result in nest failure from heat exposure (Steenhof et al. 1997). 

So nesting early is good right? Well, as our concerned citizens mentioned above, nesting too early may result in increased nest failure due to late winter/early spring storms. The scientific literature is just beginning to show some evidence for this as the earliest breeding White Storks in Poland actually suffer higher rates of reproductive failure, possibly because of increased exposure to cold weather (Janiszewski et al. 2013). 

What's the bottom line here? Climate change! Climate change is happening, and it is having reproductive consequences for many bird species.

Now what can we do about climate change? This is a question that is difficult to answer, but a colleague of mine offered up a great suggestion: Write to your Congress person and let them know that climate change is real. Several links below discuss how to find, contact, and write you congress person. Another thought: next time you are comtemplating driving hundreds of miles to chase a rare bird sighting, maybe consider carpooling, or even not going as vehicle emissions are one of the leading causes of increased Carbon Dioxide in our atmosphere. Remember: increased Carbon Dioxide because of human activity is one of the biggest reasons why our climate is changing so rapidly.

Scientific Literature Cited:

Espie, R.H.M., Oliphant, L.W., James, P.C., et al. 2000. Age-dependent breeding performance in merlins (Falco columbarius). Ecology 81: 3404-3415.

Heath, J.A., Steenhof, K., Foster, M.A. 2012. Shorter migration distances associated with higher winter temperatures suggest a mechanism for advancing nesting phenology of American kestrels Falco sparverius. Journal of Avian Biology 43: 376-384.

Janiszewski, T., Minias, P., and Wojciechowski, Z. 2013. Reproductive consequences of early arrival at breeding grounds in the White Stork Ciconia ciconia. Bird Study 60: 280-284.

Steenhof, K., and Heath, J.A. 2013. Local recruitment and natal dispersal distances in American kestrels. Condor 115: 584-592.

Steenhof, K., Kochert, M.N., Mcdonald, T.L. 1997. Interactive effects of prey and weather on golden eagle reproduction. Journal of Animal Ecology 66: 350-362.

Steenhof, K., and Peterson, B.E. 2009. American kestrel reproductive in southwest Idaho: annual variation and long term trends. Journal of Raptor Research 43: 283-290.

Tuesday, 27 January 2015 00:00

Wintering Concentrations of Eagles

Winter is a critical time of year for all raptors, including Golden Eagles. Limited food resources and freezing cold temperatures result in high mortality rates, and as a result, many congregate in high densities around areas of increased food availability.

Hawkwatch International has found a Golden Eagle winter “hotspot” in south-central Utah where eagles congregate in truly impressive numbers. Watch the video clip below of ~9 Bald and Golden Eagles soaring together from this area. Several of HWIs juvenile Golden Eagles outfitted with GPS transmitters in the West Desert have spent their winter in this area, as have several juvenile Golden Eagles with GPS transmitters from other states (Nevada, Oregon). Check out the map of GPS points (Figure 1) from one of HWIs West Desert eagles for a sense of how this bird has been using the landscape in south-central Utah since November 15, 2014.

This particular area contains pristine sagebrush habitat that sustains large populations of jackrabbits, the preferred prey of many Golden Eagles. Jackrabbits have a propensity to be struck by cars at night, and the resulting road kill provides a bountiful food source for these wintering eagles. It’s a dangerous and competitive game they play: locating and consuming road-killed carcasses before other eagles get to them. At the same time they must carefully avoid being struck by high-speed vehicular traffic. If you ever see an eagle, or any other raptor in or near a road, PLEASE SLOW DOWN.

Unfortunately, some eagles, especially juveniles, do not make it through the winter months. Mortality factors are wide ranging and include things like vehicle collisions, lead poisoning, electrocution, and starvation. If you should happen to discover a deceased or injured Bald or Golden Eagle, DO NOT disturb the animal and call your state fish & game agency or the U.S. Fish & Wildlife Service. They will treat the deceased eagle and the area surrounding it as a crime scene.

HWI will continue studying this winter eagle “hotspot” to fully understand its importance in the life-history cycle of Golden Eagles. It will help us track population trends but also identify significant mortality threats to wintering eagles.

Please comment and let us know if you have seen significant winter concentrations of Bald or Golden Eagles in your area. What do you think attracts them?

Wednesday, 14 January 2015 00:00

Midwinter Raptor Survey Update

January 15th, 2015 marks the mid-way point of our Winter Raptor Survey season. Our citizen scientists have been conducting vehicle surveys 1-2 times per month since November 15th along pre-determined routes all across Utah and southern Idaho.

27 surveys have been conducted along 10 different routes to date. Many of these routes are conducted through rural and agricultural areas historically holding the highest densities of winter raptors in Utah. Wintering raptors, particularly Buteos, are attracted to these areas because of their high prey densities.

HWI citizen scientists have counted an astonishing 2,294 raptors this winter! We’ll continue to track raptor numbers and distribution changes until March 15th when our winter season is officially over. At that time we’ll have a complete report of our 2014-15 Winter Raptor Survey field season.

Until then, enjoy these raptor photographs taken during our Winter Surveys. 


Total Raptors




Red-tailed Hawks


Sharp-shinned Hawks


Rough-legged Hawks


Cooper’s Hawks


American Kestrels


Peregrine Falcons


Ferruginous Hawks


Turkey Vulture


Northern Harriers


Short-eared Owl


Bald Eagles


Unidentified Buteos


Golden Eagles


Unidentified Falcons


Prairie Falcons


Unidentified Accipiter




Unidentified Eagle


Great Horned Owls


Unidentified Raptors

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