Craighead Beringia South Craighead and Craighead Raptor Census 2014 Annual Report

Beginning in 1946, Frank and John Craighead surveyed a 12 square mile area on and around Blacktail Butte in Jackson Hole, Wyoming and searched for all nesting raptors. The objective of the original study was to learn as much as possible on the ecology of raptors by taking a community-based approach. The Craighead brothers collected information including first date birds were seen on territory, nest initiation rates, number of eggs laid, number of young fledged, prey selection and many other important factors pertinent to raptor ecology. The results of their work were published in the book, “Hawks, Owls and Wildlife” which is still considered a definitive text on raptors and raptor ecology. Since the initial effort in the late 1940’s, the study area has been re-surveyed multiple times to track the changes in the raptor community. In 2014, we began the most recent phase of the project which is slated to last through the 2015 nesting season. Our primary questions of interest for the current phase are 1) how has the raptor community changed over the last 70 years in Jackson Hole, Wyoming and 2) which environmental factors explain documented change? To answer our questions of interest, our objectives for the current phase of this project are to: 1. Determine the density of nesting raptors 2. Determine the species richness 3. Estimate prey availability 4. Determine productivity of nesting raptors in the study area 5. Determine factors influencing selection of nest sites Our overall goal is to assess the fluctuating health of our ecosystem by tracking changes to raptor populations. It is important to note that we did include Common Ravens (Corvus corax) and American Crows (Corvus brachyrhynchos) in this study since Common Ravens were included in the initial research project. American Crows were not present in the study area during the initial phase but are now common and therefore we included their nests in our monitoring effort.

Methods The study area where we conducted our work is identical to the historic study area. It was first delineated using the public land survey system and encompassed 4 sections east to west and 3 sections north to south. Each section is equal to 1 square mile so the study area is approximately 12 square miles or 31 km2. The eastern boundary includes Blacktail Butte and the west boundary includes portions of the Snake River flood plain and the sagebrush-dominated flats south of Windy Point (Figure 1). Elevation in the study area ranges from 1950 m to 2345 m. The study area includes the town of Moose, a low density housing development south of Moose and a few scattered houses on the northeast side of Blacktail Butte but that is the extent of development. Land ownership in the study area is primarily the National Park Service (Grand Teton National Park) with some private land in the southwest corner.

As per the historic methods, during the current phase we searched the entire study area as thoroughly as possible. Our territory and nest searching began in early April with our primary focus initially on finding owls. We would have preferred starting earlier but it was not logistically possible in 2014. We used broadcast calls to elicit responses from territorial owls (Anderson 2007). We surveyed at stratified, random locations 300-500 m apart throughout the forested regions of the study area. At each call point, we used two calls; the first was a Northern Saw-whet Owl (Aegolius acadicus) and the second was a Great Horned Owl (Bubo

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Figure 1. Map of study area including boundaries for Grand Teton National Park and the National Elk Refuge.

virginianus). We spent 5 minutes after each call for a total of 10 minutes at each call point. By playing the Northern Saw-whet and Great Horned Owl calls, we also had the potential to elicit responses from other owls such as Long-eared Owls (Asio otus), Northern Pygmy Owls (Glaucidium californicum), Great Gray Owls (Strix nebulosa) and potentially Flammulated Owls (Otus flammeolus) and Boreal Owls (Aegolius funereus; Crozier et al. 2003). Once an owl was

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detected, the direction and distance was recorded so we could approximate the location of the responding bird for follow-up nest searches.

Figure 2. Locations of historic nests and nests found in 2014. Historic nests are transparent and shown for comparative purposes. The projected eyrie location for the Peregrine Falcon is based on the location where the pair was seen copulating and showed signs of nesting although incubation was never confirmed. The location representing the Cooper’s Hawk is where we searched for a nest based on the response to the broadcast call but we did not find a nest or young. AMCR is American Crow, AMKE is American Kestrel, COHA is Cooper’s Hawk, CORA is Common Raven, GGOW is Great Gray Owl, GHOW is Great Horned Owl, NOHA is Northern Harrier, OSPR is Osprey, PEFA is Peregrine Falcon, RTHA is Red-tailed Hawk, SSHA is Sharp-shinned Hawk, and SWHA is Swainson’s Hawk.

We began nest searching in April for the early nesters in the study area, the Red-tailed Hawks (Buteo jamaicensis) and Common Ravens (Corvus corax). We targeted territories and nest sites for both species that has been previously documented in other years of monitoring initially and then expanded our search as needed. Since 1992, we have documented 92 Raven nests and 45 Red-tailed Hawk nests within the study area (Figure 2). These were the areas that were initially targeted for nest searching. We also searched locations without known nesting territories or nest sites by scanning with optics for the presence of either species with optics.

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As raptors came back from migration, we broadened our search efforts. Being in the field every day, we had the ability to track when new species arrived and concentrate search efforts accordingly. Our most common technique remained visiting areas with historic nest sites regardless of species and glassing for long periods of time since there is some affinity to territories over time. If birds were seen, we would make the appropriate effort to find a nest based on the behavior of the birds. If no birds were seen on an initial visit, the area was often revisited several times until we were sure there were no birds present.

We also spent ample time searching areas with no known nest sites. In areas without known nest sites, we would also glass large areas to look for the presence of raptors or we would conduct systematic nest searches. For systematic nest searches, we typically had multiple observers moving through an area listening and looking for any raptors, ravens or crows. If birds were seen, we again spent as much time as necessary searching for a nest which typically occurred over repeated visits. In addition to passive nest searching, we also conducted broadcast surveys for accipiters specifically. For accipiter surveys, we targeted forested areas and used a similar approach as for the owl surveys where we played a Sharp-shinned Hawk (Accipiter striatus) recording followed by a 5-minute waiting period and then a Cooper’s Hawk (Accipiter cooperii) followed by a 5-minute wait period. Broadcast surveys for accipiters were done at pre- determined points but also opportunistically. When an accipiter was located, we searched the area thoroughly to look for nests. Accipiters typically to respond to broadcast surveys when they are close to their nest (Rosenfield et al. 1988) so search effort was usually centered on the location where the accipter responded to the broadcast call.

We were not able to find all nests during the nest initiation or incubation period, so some nests were found when young were present. Typically, we found nests with young during targeted searches in areas where we did not find a nest earlier and thought there was a nest present. Once a nest of any species was found, we re-visited the nest at least once per week until the nest failed or the young fledged. We considered any young greater than 80% of fledging age to have fledged (Steenhof and Newton 2007).

Beginning in 2014, we also began assessing prey base. We felt prey base is an important factor that may regulate population dynamics of raptors in the study area and therefore it was worthwhile to estimate the annual variation of population abundance. To estimate relative density of Uinta ground squirrels (Urocitellus armatus) colonies, we conducted active burrow transects based on the recommendations from a previous pilot study (Chalfoun et al. 2000). Burrow transects were 50m long by 10m wide. Because there are many other important prey sources, we are also set small mammal trapping grids to assess the densities of other small mammals including Peromyscis spp. and Microtus spp. among others. We used Sherman traps (H.B. Sherman Traps, Tallahassee, Florida, USA) to live trap the animals. Traps were placed in grids consisting of 25 traps in a 5x5 pattern with each trap 10-m apart. We placed 2 grids in each major habitat type, 1) coniferous dominated forest, 2) riparian, 3) sagebrush and 4) grassland for a total of 8 small mammal trapping grids. Traps were checked twice daily, once in the morning and once in the evening. All captured animals were given a unique identifying shave and color combination which was applied with non-toxic markers so we could identify each individual that was previously captured. All traps were monitored for 3 mornings and 3 evenings. We did not conduct avian point counts or arthropod population estimates. We will use Breeding Bird

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Survey data collected in Moose, WY to track avian population trends. We have no current methods in place to estimate arthropod population trends.

We also began an effort to look at nest site selection, specifically focused on Red-tailed Hawks and Common Ravens. At each documented 2014 nest site, we took a host of measurements at the actual nest site as well as a nearby random site. With this information, we will be able to assess nest site selection at multiple spatial scales (nest site and territory level) to assess differences in nest site selection between the two species.

Results We detected 12 raptor species as well as Common Ravens and American Crows in the study area during the 2014 nesting season (Table 1). We confirmed incubation at 33 nests from 10 species (Table 1). In addition to the 33 initiated nests, we located an additional 12 territories where raptors were present over repeated visits but we either did not locate their nests, their nests failed before we were able to find them or the birds did not nest but defended their nesting territory. There were 2 owl species that we did not attempt to find nests due to the difficulty associated with locating nests for those species (Table 1). Of the 33 initiated nests, 21 were successful in producing 47 young (Table 1).

Table 1. Total number of territories, initiated nests, successful nests and young produced during the 2014 nesting season in the Blacktail Butte study area. Initiated nests are confirmed, initiated nests. Total Initiated # Young Territories Nests Successful Produced American Crow 6 6 4 10 American Kestrel 16 7 6 12 Boreal Owl1 1 Unk Common Raven 8 8 4 13 Great Gray Owl 1 1 1 2 Great Horned Owl 2 2 1 3 Northern Harrier 1 1 0 Northern Saw-whet Owl1 4 Unk Osprey 1 1 0 Peregrine Falcon 1 0 0 Red-tailed Hawk 3 3 2 2 Sharp-shinned Hawk 4 2 2 4 Cooper's Hawk 1 0 0 Swainson's Hawk 2 2 1 1 1We did not attempt to determine whether these species initiated a nest but they were detected during broadcast surveys.

From the 8 small mammal grids, we had 100 total captures over 600 unadjusted trap nights or 16.7 captures per 100 unadjusted trap nights. Eight of the total captures were recaptures. We captured individuals from 4 different species but the most common species was the deer mouse

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(Peromyscus maniculatus, Table 2). We have not yet analyzed these data to assess estimated abundances of small mammals in the study area. We completed 9 Uinta Ground Squirrel transects and counted 203 burrows. We completed 20 vegetation plots (10 used and 10 random) to assess nest site selection by Common Ravens and Red-tailed Hawks. Both the small mammal trapping data and vegetation data will be fully analyzed after the 2015 nesting season.

Table 2. Summary of small mammal captures by habitat type. Riparian Grassland Sagebrush Coniferous Deer Mouse 19 23 21 27 Masked Shrew 0 0 2 0 Montane Vole 0 0 1 1 Western Jumping Mouse 6 0 0 0

For historic comparison, we detected 14 species this year compared to an average of 8.8 per year (SD = 2.1; Table 3). The total number of confirmed nesting pairs, 33, was lower than the historic average of 39.1 (SD = 6.6) but the overall territory density was similar. Most notably, in 2014 we found the first Peregrine Falcon eyrie on Blacktail Butte in an unknown number of years. The pair was unsuccessful and we are unsure if the pair did lay eggs but they were seen copulating and defending the territory throughout the nesting season. Also of interest, we documented a substantial decrease in the number of Red-tailed Hawks since the 1940’s and a substantial increase in the number of Common Ravens. This trend was also true when the study area was surveyed in the early 2000’s.

Future Plans We plan on an additional year of data collection in 2015 to support the data collected in 2014. After the 2015 field season, we will analyze the data collected from all years the study has been done to assess which factors explain the changes in the raptor community in the Blacktail Butte study area over the last 70 years.

Literature Cited Anderson, D.E. Survey Techniques. P. 89-100 In D.M. Bird and K.L. Bildstein (eds.), Raptor research and management techniques. Hancock House Publishers, Blaine, Washington, USA. Chalfoun, A., D. Craighead, and R. Smith. 2000. The distribution and abundance of Uinta ground squirrels, Spermophilus armatus, in GTNP, Wyoming. Unpublished report, Beringia South. Crozier, M.L., M.E. Seamans, and R.J. Gutierrez. 2003. Forest Owls Detected in the Central Sierra Nevada. Western Birds 34: 149-156. Rosenfield, R. N., J. Bielefeldt, and R.K. Anderson. 1988. Effectiveness of broadcast calls for detecting breeding Cooper's hawks. Wildlife Society Bulletin 16:210-212. Steenhof, K. and I. Newton. 2007. Assessing nesting success and productivity. P. 181-192 In D.M. Bird and K.L. Bildstein (eds.), Raptor research and management techniques. Hancock House Publishers, Blaine, Washington, USA.

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