Annual Reports

2019

David Wolfson, Minnesota Cooperative Fish and Wildlife Research Unit, Department of Fisheries, Wildlife, and Conservation Biology, University of Minnesota, St. Paul, Minnesota, USA.

David E. Andersen, U.S. Geological Survey, Minnesota Cooperative Fish and Wildlife Research Unit, 200 Hodson Hall, 1980 Folwell Ave, St. Paul, Minnesota, USA.

John Fieberg, Department of Fisheries, Wildlife, and Conservation Biology, University of Minnesota, St. Paul, Minnesota, USA.


Abstract: The Interior Population (IP) of trumpeter swans (Cygnus buccinator) was established through extensive re-introductions beginning in the late 1960s throughout the Upper Midwest. To date, the primary conservation objective for IP trumpeter swans has been to re-establish breeding populations across their historical distribution. Since those early restoration efforts, the IP has far exceeded original population objectives and numbered 27,055 in the latest (2015) North American Swan Survey. Annual population growth rate estimates since 2000 (based on the number of swans observed on annual waterfowl surveys in Minnesota) are ~1.20. Across much of their current breeding distribution, IP trumpeter swans have transitioned from a rare to a common component of the regional waterfowl community. However, unlike many other waterfowl species, very little is known about the ecology of IP trumpeter swans, including movement ecology and habitat use at multiple spatial scales. Beginning in 2019, we began addressing some of these information needs through a collaborative project to deploy GPS/GSM transmitters on trumpeter swans distributed across the IP. In 2019, we deployed 19 transmitters on IP trumpeter swans (7 in Minnesota and 12 in Michigan) and have since monitored their movements remotely.

Introduction

Interior Population (IP) trumpeter swans have high intrinsic and economic value as a protected wildlife species. For example, Minnesota citizens enthusiastically invested in the restoration of trumpeter swans through the check off donation and other funding sources to the Minnesota Department of Natural Resources (MNDNR) Nongame Program since the mid-1980s. The Interior Population of trumpeter swans has increased dramatically since they were re-established beginning in the 1960s and 1970s and both population size and distribution have expanded significantly. Trumpeter swans in Minnesota are an example of such increases, with an original reintroduction goal of 15 breeding pairs and a revised interim goal of 500 individuals by 2001 (Fig 1). The Minnesota population was estimated at > 17,000 in the most recent North American survey in 2015 (Groves 2017), and estimates of population growth rate based on trumpeter swans observed on annual Minnesota waterfowl surveys is ~1.20 since 2000 (Minnesota Department of Natural Resources, unpublished data).

Trumpeter swans currently breed throughout most of the western Great Lakes region, including in Minnesota, Wisconsin, Michigan, Iowa, Manitoba, Ontario, and Ohio. However, beyond estimates of population size and trend and distribution, there is relatively little recent information about their ecology, hindering conservation decision-making. To address current information needs, we initiated a project in 2019 to mark a sample of Interior Population trumpeter swans with GPS/GSM transmitters. These transmitters record high-resolution, high frequency location and related data and transmit those data through cellular phone networks, and will allow us to:

  1. Evaluate year-round swan movements, including determining the locations where swans spend the winter, and the timing and duration of their movements.
  2. Determine whether and where trumpeter swans make molt migrations.
  3. Evaluate year-round habitat use and selection patterns of trumpeter swans.
  4. Estimate annual survival rates of trumpeter swans, if sample sizes are adequate and fates (i.e., mortality events) can be determined.

Results of this study will inform current and future IP trumpeter swan conservation by providing basic information about migration, year-round movements, mortality risks, and use of agricultural and other landscapes. As part of this project, location data will be archived and made available to the public via a website (https://trumpeterswan.netlify.com/locations.html) (Fig 2) that summarizes trumpeter swan movements and habitat use. Thus, the project will also offer the opportunity to actively engage and inform the general public about how their past investment in conservation made a positive difference to the region’s natural heritage today.

Study Area

Our study area is defined by the current distribution of IP trumpeter swans (Groves 2017). In 2019, we trapped and deployed transmitters on IP trumpeter swans in Minnesota and project collaborators captured swans in Michigan. Capture locations in Minnesota ranged from as far south as the west metropolitan area of the Twin Cities (45.0° N, 93.6° W) to as far north as Thief Lake (48.5° N, 95.9° W). Capture locations in Michigan spanned from southwestern Michigan (42.3° N, 85.3° W) to Seney National Wildlife Refuge in the Upper Peninsula (46.3° N, 85.9° W). Capture locations in Minnesota occurred in a mix of Laurentian Mixed Forest and Eastern Broadleaf Forest, and Aspen Parklands in the most northern portion of the study area (Cleland et al. 1997). Capture locations in Michigan occurred in Laurentian Mixed Forest.

Methods

Swan capture: We captured swans during the Definitive Prebasic Molt period when adults are flightless. In Minnesota during 2019, we used a variety of watercraft to evaluate the efficacy of different capture methods; these included airboats, jon-boats, and square-stern canoes with either an outboard or long-tail mud motor. We hand-captured swans using a shepherd’s crook pole. Collaborators captured swans in Michigan using a step deck transom boat with a surface drive motor and a shoulder-mounted netlauncher (CODA Enterprises, Mesa, Arizona, USA). All capture and handling methods were approved by the University of Minnesota Institutional Animal Care and Use Committee (Protocol #1905-37072A)

We marked swans in Minnesota with 55-g neck collars with GPS/GSM transmitter incorporated into the collar housing (Model OrniTrack-N62 3G, Ornitela, Vilnius, Lithuania; see Fig 3). Collaborators marked swans in Michigan with 140-g GPS transmitters (Model CTT-ES400, Cellular Tracking Technologies, Rio Grande, New Jersey, USA) that were adhered to 64-mm neck collars (Haggie Engraving, Crumpton, Maryland, USA; see Fig 4). All swans marked in 2020 will be fitted with Ornitela collars. Neck collars for all swans in this study also had a unique 2-character, alpha-numeric code (black characters on a white background). We took feather samples from all captured swans in 2019 for potential genetic and/or isotopic analyses.

Data: Transmitters are programmed to collect GPS locations at 15-min intervals throughout the 24-hr daily period. Locations are stored on-board in internal transmitter memory. Once a day, the transmitters attempt to upload the entire batch of locations to the Ornitela back-end database via a cellular network using a General Packet Radio Service (GPRS) connection if available, or a Global System for Mobile Communication (GSM) connection if GPRS is not available. GPRS is a more efficient and upgraded transmission option than GSM. Cellular Tracking Technologies (CTT) transmitters attempt to upload once a day to the CTT back-end database using a GSM connection. All new locations from both companies’ databases are uploaded daily to a data repository at Movebank for archiving and future processing.

Results

We deployed 19 transmitters in Minnesota (n = 7) and Michigan (n = 12) during the summer of 2019. One marked swan in Michigan died as a result of a powerline strike but we recovered the transmitter and plan to re-deploy it in summer 2020.

Swans marked during summer 2019 stayed near their breeding territories between the date of capture (July-September) and October. Once temperatures dropped in November, most marked swans in Minnesota left their territories and flew south, although there was considerable variation in the timing of these departures. The earliest longer-distance movements from capture locations (> 100 km) were by swans in the most northern section of the study area. Some swans exhibited a direct flight path to where they settled for the winter whereas others moved shorter distances and lingered in what appear to be stop-over areas for several weeks. Most swans (5 of 7) captured in Minnesota traveled > 100 km from their capture site but only 2 swans in Michigan made movements > 100 km and most are still in the vicinity of their summer territory. Swans appear to be predominantly overwintering on major rivers, likely related to the presence of open (i.e., not frozen) water during the winter.

Project outreach: From August 2019-February 2020, we presented project overviews to a variety of stakeholders at the Mississippi Flyway Council Technical Meeting in Duluth, Minnesota; the 25th Trumpeter Swan Society Meeting in Alton, Illinois; the 80th Midwest Fish and Wildlife Conference in Springfield, Illinois; the Northwest Minnesota, Minnesota Department of Natural Resources Managers Meeting in Norris Camp, Minnesota; and the Annual Meeting of the Minnesota Chapter of The Wildlife Society in Willmar, Minnesota. To facilitate public engagement with project objectives and ongoing results we created a project website (https://trumpeterswan.netlify.com). During the fall and winter of 2019, we added 3 state natural resources agencies (Iowa, Wisconsin, and Ohio), 1 provincial Canadian government agency (Manitoba/Canadian Wildlife Service), and 1 tribal agency (Great Lakes Indian Fish and Wildlife Commission) as collaborators to increase the geographical scope of our project. As the project develops, we will continue to reach out to individuals that can provide relevant expertise and who may be in a position to further expand the scope of our project (see Appendix I for a list of project collaborators).

Future Plans

Swan capture will take place in 2020 once adult swans begin Prebasic Molt on their breeding territories. We plan to deploy ~75 additional transmitters spread throughout the IP breeding range during the summer of 2020. Approximately 30 transmitters will be deployed in Minnesota and the remainder will be distributed among the other states and province. We are also working with the Trumpeter Swan Society to deploy transmitters on wintering trumpeter swans in Arkansas during winter 2020-2021.

We anticipate that data from deployed collars will continue to be received until the end of the project in 2023. Starting in 2020 we plan to also collect blood samples for potential genetic and ecotoxicology analyses.

Literature Cited

Cleland, D. T., P. E. Avers, W. H. McNab, M. E. Jensen, R. G. Bailey, T. King, and W. E. Russell. 1997. National hierarchical framework of ecological units. Pages 181-200 in Boyce, M. S. and A. Haney, editors. Ecological management application for sustainable forest and wildlife resources. Yale University Press, New Haven, Connecticut, USA.

Groves, D. J. 2017. The 2015 North American Trumpeter Swan Survey. Unpublished report, U. S. Fish and Wildlife Service, Division of Migratory Bird Management, Juneau, Alaska, USA.


Figure 1. Minnesota trumpeter swan population size estimated from waterfowl surveys conducted over approximately 39% of the area of the state (MN DNR, unpublished data). The trumpeter swan population in Minnesota has increased substantially, dramatically exceeding original and interim population goals, and is currently growing at an annual rate of ~1.20.



Figure 2 Locations of all marked swans are regularly uploaded to a project website that allows users to interactively visualize swan movements. Capture and end locations are represented by colored points. Lines connecting these points show individual movement trajectories observed thus far.



Figure 3 An example of the Ornitela OrniTrack-N62 collars with GPS/GSM transmitter incorporated into the internal housing that were deployed in Minnesota during 2019. All new deployments in 2020 will be this design.



Figure 4 An example of the Cellular Tracking Technology CTT-ES400 model transmitters affixed to neck collars that were deployed on trumpeter swans in Michigan during 2019.

2020

David Wolfson, Minnesota Cooperative Fish and Wildlife Research Unit, Department of Fisheries, Wildlife, and Conservation Biology, University of Minnesota, St. Paul, Minnesota, USA.

David E. Andersen, U.S. Geological Survey, Minnesota Cooperative Fish and Wildlife Research Unit, 200 Hodson Hall, 1980 Folwell Ave, St. Paul, Minnesota, USA.

John Fieberg, Department of Fisheries, Wildlife, and Conservation Biology, University of Minnesota, St. Paul, Minnesota, USA.


Abstract: The Interior Population (IP) of trumpeter swans (Cygnus buccinator) was established through extensive re-introductions beginning in the late 1960s throughout the Upper Midwest. Across much of their current breeding distribution, IP trumpeter swans have transitioned from a rare to a common component of the regional waterfowl community. However, unlike many other waterfowl species, very little is known about the ecology of IP trumpeter swans, including movement ecology and habitat use at multiple spatial scales. Beginning in 2019, we began addressing some of these information needs through a collaborative project to deploy GPS/GSM transmitters on trumpeter swans distributed across the IP. In 2019, we deployed 19 transmitters on IP trumpeter swans (7 in Minnesota and 12 in Michigan). In 2020, we deployed an additional 77 transmitters on IP trumpeter swans (10 in Manitoba, 40 in Minnesota, 9 in Iowa, 5 in Wisconsin, 1 in Michigan, 12 in Ohio). Movements of marked swans have been highly variable across the IP breeding range, with swans that breed at higher latitudes more likely to migrate and travel longer distances during the winter.

Introduction

Interior Population (IP) trumpeter swans have high intrinsic and economic value as a protected wildlife species. For example, Minnesota citizens enthusiastically invested in the restoration of trumpeter swans through the check off donation program and other funding sources supporting the Minnesota Department of Natural Resources (MNDNR) Nongame Program since the mid-1980s. Since they were re-established beginning in the 1960s and 1970s, IP trumpeter swans have increased dramatically in population size and expanded their distribution significantly. Trumpeter swans in Minnesota are an example of such increases, with an original reintroduction goal of 15 breeding pairs and a revised interim goal of 500 individuals by 2001 (Fig. 1). The Minnesota population was estimated at > 17,000 individuals in the most recent North American survey in 2015 (Groves 2017). We estimated an annual finite population growth rate of ~1.20 using observations of trumpeter swans during annual Minnesota waterfowl surveys from 2000-2017 (Minnesota Department of Natural Resources, unpublished data).

Trumpeter swans currently breed throughout most of the western Great Lakes region, including in Minnesota, Wisconsin, Michigan, Iowa, Manitoba, Ontario, and Ohio. However, beyond estimates of population size and trend and breeding distribution, there is relatively little recent information about their ecology, therefore hindering conservation decision-making. To address current information needs, we initiated a project in 2019 to mark and follow a sample of IP trumpeter swans with GPS/GSM transmitters for multiple years. These transmitters record high-resolution, high frequency location and related data and transmit those data through cellular phone networks, and will allow us to:

  • Evaluate year-round swan movements, including determining the locations where swans spend the winter and the timing and duration of their movements.
  • Determine whether and where trumpeter swans make molt migrations.
  • Evaluate year-round habitat use and selection patterns of trumpeter swans.
  • Estimate annual survival rates of trumpeter swans, if sample sizes are adequate and fates (i.e., mortality events) can be determined.

Results of this study will inform current and future IP trumpeter swan conservation by providing basic information about migration, year-round movements, mortality risks, and use of agricultural and other landscapes. As part of this project, location data will be archived and made available to the public via a website (https://trumpeterswan.netlify.com/locations.html; Fig. 2) that summarizes trumpeter swan movements and habitat use. Thus, the project will also offer the opportunity to actively engage and inform the public about how their past investment in conservation made a positive difference to the region’s natural heritage today.

Since inception of the original project centered in Minnesota (where the bulk of IP trumpeter swans breed), additional funding and collaborations with additional project partners have allowed us to expand the scope of the project to include the following research objectives:

  • Quantify the extent of gene flow among IP trumpeter swans, their overall genetic diversity, and genetic differentiation from source populations.
  • Evaluate the association between migratory behavior and genetic divergence of different groups of trumpeter swans.
  • Quantify concentrations of lead in IP trumpeter swans and assess potential sub-lethal effects of lead exposure on migration and annual movements.

In addition to Minnesota, other states and provinces that are also marking trumpeter swans as part of the larger study include Michigan, Iowa, Wisconsin, Ohio, and Manitoba. State biologists from the Nebraska Game and Parks Commission are also contributing blood samples from the High Plains flock of IP trumpeter swans to include in the genetic analyses.

Study Area

Our study area is defined by the current distribution of IP trumpeter swans (Groves 2017). We deployed transmitters on IP trumpeter swans as far north and west as southern Manitoba (51.1° N, 99.7° W) and as far south and east as central Ohio (40.6° N, 82.7° W). Capture locations occurred in a mix of Laurentian Mixed Forest, Prairie Parkland, Eastern Broadleaf Forest, and Aspen Parklands (Cleland et al. 1997).

Methods

Swan capture: We captured swans during the definitive prebasic molt period when adults are flightless. In Minnesota during 2019, we used a variety of watercraft to evaluate the efficacy of different capture methods; these included airboats, kayaks, and square-stern canoes with either an outboard or long-tail mud motor. We hand-captured swans using a shepherd’s crook pole. Collaborators captured swans in Michigan using a step deck transom boat with a surface drive motor and a shoulder-mounted netlauncher (CODA Enterprises, Mesa, Arizona, USA).

In Minnesota during 2020, we partnered with staff from the Minnesota DNR and Three Rivers Park District to locate and capture trumpeter swans throughout Minnesota using a flat-bottom jon boat with a lightweight 6.5 horsepower mud motor (Powell Performance Fab, Hutchinson, Minnesota, USA). We implemented COVID-19 safety protocols throughout the summer, which necessitated single-occupancy vehicles, reduced numbers of field staff, social distancing, and use of personal protective equipment. COVID-19 safety protocols also limited our ability to work in close physical proximity with project collaborators, and we therefore captured most swans with a 2-person field crew.

Protocols for capturing and marking trumpeter swans in U.S. states have been approved by the University of Minnesota Animal Care and Use Committee (protocol no. 1905-37072A), the Minnesota Department of Natural Resources (Special Permit no. 19017), the Michigan Department of Natural Resources (Threatened and Endangered Species Permit TE 175), the U.S. Fish and Wildlife Service (Research & Monitoring Special Use Permit no. K-10-001), and the U.S. Geological Survey Bird Banding Laboratory (Federal Bird Banding Permit no. 21631). All capture and marking of trumpeters swans in Manitoba was conducted under Federal Scientific Permit to Capture and Band Migratory Birds (no. 10271), Federal Animal Care Committee approval (project 20FB02), Provincial Species at Risk Permit (no. SAR20012), and Provincial Park Permit (no. PP-PHQ-20-016).

We marked swans in Minnesota with 55-g neck collars with GPS/GSM transmitter incorporated into the collar housing (Model OrniTrack-N62 3G, Ornitela, Vilnius, Lithuania; see Fig. 3). Collaborators marked swans in Michigan with 140-g GPS transmitters (Model CTT-ES400, Cellular Tracking Technologies, Rio Grande, New Jersey, USA) that were adhered to 64-mm neck collars (Haggie Engraving, Crumpton, Maryland, USA; see Fig. 4). All swans marked in 2020 (except a transmitter redeployed in Michigan recovered from a mortality in 2019, see below) were fitted with Ornitela collars. Neck collars for all swans in this study also had a unique 2-character, alpha-numeric code (black characters on a white background). We took feather samples from all captured swans in 2019 and blood samples from all captured swans in 2020 for genetic analyses and testing for lead concentrations. We clipped the calamus from collected feathers and stored them in 2mL cryotubes with 95% ethanol solution. We used a 23-gauge, 1 inch needle and a 3mL syringe to extract 2mL of blood. Approximately 0.1mL of blood was deposited on a Whatman FTA card (Sigma-Aldrich, St. Louis, Missouri, USA). We collected the rest of the blood sample in a 2mL tube containing ethylenediaminetetraacetic acid (EDTA) and refrigerated all tubes until they were received at the diagnostic lab.

During the winter of 2019⁠—⁠2020, 8 of the deployed GPS-GSM collars failed due to extreme temperatures and/or water penetration. To address this issue, we worked with the manufacturer during the off-season to amend the collar design for the next generation of collars we deployed in 2020. We replaced the lightweight foam insulation within the collar housing with a high-density epoxy that is more weather-resistant and have had no more apparent failures due to weather conditions at the time of this report.

Data: Transmitters are programmed to collect GPS locations at 15-min intervals throughout the 24-hr daily period. Locations are stored on-board in internal transmitter memory. Once per day, the transmitters attempt to upload the entire batch of stored locations to the Ornitela back-end database via a cellular network using a General Packet Radio Service (GPRS) connection if available, or a Global System for Mobile Communication (GSM) connection if GPRS is not available. GPRS is a more efficient and upgraded transmission option than GSM. Cellular Tracking Technologies (CTT) transmitters attempt to upload once a day to the CTT back-end database using a GSM connection. If an upload attempt fails, location data are stored on-board the transmitter until a successful connection can be made. All new locations from both companies’ databases are uploaded daily to a data repository at Movebank for archiving and future processing.

Analysis of lead concentrations: We analyzed blood lead concentrations using inductively coupled plasma mass spectrometry at the Veterinary Diagnostic Laboratory of Iowa State University. We measured the concentration of lead in parts per billion (ppb) from whole blood samples preserved with EDTA.

To explore the sub-lethal effects of lead, we used quantile regression to test the relationship between swan blood lead concentration and distance traveled from the capture site to the furthest point south during the winter. We used quantile regression to estimate the conditional median of the response variable as opposed to least squares estimation because it relaxes the assumption of equal variance among residuals and is more appropriate for skewed distributions (Cade and Noon 2003).

Results

We deployed 19 transmitters in Minnesota (n = 7) and Michigan (n = 12) during July-August 2019. One marked swan in Michigan died as a result of a powerline strike but we recovered the transmitter and re-deployed it in summer 2020. We deployed 40 GPS-GSM transmitters on trumpeter swans in Minnesota during June-September 2020. During the summer 2020 field season (June-September), partnering agencies captured and collared 38 trumpeter swans in Manitoba (n=10), Iowa (n=9), Wisconsin (n=5), Michigan (n=1) and Ohio (n=12).

Swans marked during summer 2019 stayed near their breeding territories between the date of capture (July-September) and October. Once temperatures dropped in November, most marked swans in Minnesota left their territories and flew south, although there was considerable variation in the timing of these departures. The earliest longer-distance movements from capture locations (> 100 km) were by swans in the most northern section of the study area. Some swans exhibited a direct flight path to where they settled for the winter whereas others moved shorter distances and lingered in what appear to be stop-over areas for several weeks. Most swans (5 of 7) captured in Minnesota traveled > 100 km from their capture site but only 2 swans in Michigan made movements > 100 km and most remained in the vicinity of their summer territory. Swans predominantly overwintered on major rivers, likely related to the presence of open (i.e., not frozen) water during the winter.

We have observed a large amount of variability this fall (2020) in the prevalence of long-distance migration (Fig. 5). Swans that bred at latitudes ≥ 48° N (n=13) all migrated long distances (\(\bar{x}\)= 767 km, s= 364 km, range = 262—1,330 km). Swans that bred in the middle latitudes of our study area, between 43° and 48° N (n=55), showed a variety of migration strategies, with some traveling over 1,250 km while others stayed within 5 km of their breeding territory (\(\bar{x}\)= 293 km, s= 349 km, range = 5—1,287 km). Swans that bred or were captured during the breeding season at southern latitudes, below 43° N (n = 15), all stayed within 22 km of their breeding territories (\(\bar{x}\)= 8 km, s= 6 km, range = 1—21 km).

Most swans overwintering north of 41° N latitude settled on major rivers, although 13 swans used either lakes with aerators or gravel quarries because they provide water bodies not completely covered with ice during winter (Fig. 6). Most swans that overwintered south of 41° N latitude used a variety of wetlands, lakes, and reservoirs that we presume are ice-free (Fig. 7).

There are currently 84 trumpeter swans with active GPS-GSM collars marked as part of this collaborative project, which upload ~7,000 locations each day to the back-end database. We have compiled ~1.5 million locations on the Movebank data repository.

We detected the presence of lead in all marked swans, though concentrations were low for almost all swans (\(\bar{x}\)=81 ppb, s=136 ppb, range = 4.3—1,076 ppb). We did not find a significant effect of blood lead concentrations on the distance traveled during autumn 2020 (Table 1).

Project outreach: From August 2019—February 2020, we presented project overviews to a variety of stakeholders at the Mississippi Flyway Council Technical Meeting in Duluth, Minnesota; the 25th Trumpeter Swan Society Meeting in Alton, Illinois; the 80th Midwest Fish and Wildlife Conference in Springfield, Illinois; the Northwest Minnesota, Minnesota Department of Natural Resources Managers Meeting in Norris Camp, Minnesota; and the Annual Meeting of the Minnesota Chapter of The Wildlife Society in Willmar, Minnesota. To facilitate public engagement with project objectives and ongoing results we created a project website (https://trumpeterswan.netlify.com).

From March 2020—February 2021, we gave project presentations at the 27th Annual Wildlife Society Conference (virtual), the 81th Midwest Fish and Wildlife Conference (virtual), and the Mississippi Flyway Council (virtual). The project was featured in 4 local television news segments, 7 newspaper articles, and the press releases of 4 state natural resource agencies. We also were interviewed in 3 different podcast series. Since adding an analytics-tracking feature to the project website on 10 September 2020, we tracked ~5,000 visitation sessions from ~3,000 unique users in 20 different countries.

Discussion

Our preliminary results suggest that IP trumpeter swans exhibit a variety of migration strategies. Individuals that breed in the northern part of the current distribution all made relatively long-distance autumn migrations. Autumn migration distances of swans breeding at mid-latitudes were variable, with some swans moving considerable distances, and some swans remaining near their breeding locations. Swans breeding at lower latitudes all remained relatively near their breeding locations. Monitoring swans for additional years will allow us to evaluate consistency of migration between years for individual swans, and whether variation in annual conditions (e.g., winter severity, access to open water during winter, etc.) are related to migration behavior. We are also starting genetic analyses to help determine whether genetic lineage is related to migration distance.

Although we detected lead in all swans we sampled, lead concentrations did not appear to be related to autumn migration distance. Most swans we sampled had blood lead concentrations below those considered to result in lethal or sub-lethal effects. The very high blood concentration we observed in a single swan is perplexing, and the fate of that swan will be of particular interest to monitor.

Future Plans

Partners plan to deploy 14 additional collars during summer 2021 and 3 collars in Arkansas during winter 2021—2022.

We are continuing to host a project website showing the full summary of movement data and other project information. We have started the process of annotating the location data with remote sensing environmental variables, to facilitate future movement and habitat-selection analyses.

We have secured funding for genetic analyses, and are working with Dr. Sushma Reddy and the University of Minnesota Genomics Center to conduct these analyses. Processing genetic samples will begin in early 2021.
Literature Cited

Cade, B. S., and B. R. Noon. 2003. A gentle introduction to quantile regression for ecologists. Frontiers in Ecology and the Environment, 1(8): 412-420.

Cleland, D. T., P. E. Avers, W. H. McNab, M. E. Jensen, R. G. Bailey, T. King, and W. E. Russell. 1997. National hierarchical framework of ecological units. Pages 181-200 in Boyce, M. S. and A. Haney, editors. Ecological management application for sustainable forest and wildlife resources. Yale University Press, New Haven, Connecticut, USA.

Groves, D. J. 2017. The 2015 North American Trumpeter Swan Survey. Unpublished report, U. S. Fish and Wildlife Service, Division of Migratory Bird Management, Juneau, Alaska, USA.


Figure 1. Minnesota trumpeter swan population size estimated from waterfowl surveys conducted over approximately 39% of the area of the state (MN DNR, unpublished data). The trumpeter swan population in Minnesota has increased substantially, dramatically exceeding original and interim population goals, and is currently growing at an annual rate of ~1.20. The current (2020) spring population estimate is near 30,000.



Figure 2. Locations of all marked swans are regularly uploaded to a project website that allows users to interactively visualize swan movements. Capture and end locations are represented by colored points. Lines connecting these points show individual movement trajectories observed thus far. This figure represents swan captures in Minnesota and Michigan in 2019.



Figure 3. An example of the Ornitela OrniTrack-N62 collars with GPS/GSM transmitter incorporated into the internal housing that were deployed in Minnesota during 2019. All new deployments in 2020 were this design, with a modification to minimize failures experienced in 2019 that were likely the result of water entering the transmitter housing.



Figure 4. An example of the Cellular Tracking Technology CTT-ES400 model transmitters affixed to neck collars that were deployed on trumpeter swans in Michigan during 2019.



Figure 5. Distances traveled by marked swans from capture location to the farthest point south during 2020.



Figure 6. Overwintering locations of marked swans (through Dec 2020) and whether they settled on rivers, artificial open water (lakes with aerators, quarries, or gravel ponds), or naturally open water (wetlands and lakes without ice).



Figure 7 Flowchart showing the proportions of marked swans from each capture state that moved to each state to overwinter (through Dec 2020) and whether they settled on rivers, artificial open water (lakes with aerators, quarries, or gravel ponds), or naturally open water (wetlands and lakes without ice).



Table 1 Model coefficients, 95% confidence intervals (CI) around coefficients, and t- and _P-_values for the relationship of swan blood lead concentration (in parts per billion) to distance moved from capture location to the farthest point south during autumn migration in 2020.

Est. 2.5% 97.5% t val. p
(Intercept) 131.05 -12.88 274.97 1.82 0.07
lead_ppb 0.35 -0.56 1.26 0.77 0.44

Manitoba 2020