Double-Crested Cormorant Conflict Management and Research on Leech Lake 2007 Annual Report

Double-Crested Cormorant Conflict Management And Research On Leech Lake 2007 Annual Report

Prepared by Fish, Wildlife, and Plant Resources Program Division of Resources Management Leech Lake Band of Ojibwe

This report has been prepared to provide an update on the cormorant conflict management issues and diet study, as well as other colonial waterbird management efforts on Leech Lake that are being conducted by the Leech Lake Band of Ojibwe. The overall goal of this project is to determine if cormorants played a role in the decline of walleye in the early 2000’s and if they did, at what population level they can be managed without having a significant negative effect on gamefish and on other species of colonial waterbirds that nest alongside cormorants on Little Pelican Island. Most aspects of this past field season went very well and we are well on the way towards resolving cormorant conflict issues.

Fish Population Recovery Fish population monitoring, conducted mainly by the Minnesota Department of Natural Resources (MN DNR), has found that walleye and yellow perch populations that seemed to have been experiencing higher than expected mortality are well on their way to recovery. They have also had good growth rates in recent years. Fishing has also been very good for most anglers on the lake over the past couple of years. The MN DNR has compiled data on Leech Lake’s fish populations and this information is available from them.

Cormorant Conflict Management Cormorant control was conducted again this past summer with 2754 birds killed. Of these, 305 adults were saved for diet sampling. An additional 30 cormorant eggs were removed from the tern nesting site for a total of 2784 cormorants removed from Leech Lake. Like past years, all control occurred on tribal lands on Little and Big Pelican Islands. The Band contracted this work out to USDA Wildlife Services with part of the funding for this effort coming from the MN DNR. Suppressed .22 caliber rifles were used early in the season at the colony site in addition to pass shooting using shotguns on an adjacent island to collect birds. Cormorants are becoming more wary and it is anticipated that control will become more difficult and costly in the years to come.

Under the Environmental Assessment prepared for this project and the Decision Notice signed by the Band, our goal was to try to reduce the number of cormorant nests on the lake to 500. This represents 500 adult pairs and these pairs would be allowed to naturally reproduce. It was anticipated that it might take two to three years to reach this goal. This level will be maintained until results of the diet study allow us to make a better assessment of whether or not cormorants were the cause of low walleye populations, and if so, how many cormorants the lake could support without having a significant negative effect on gamefish populations. In 2007, we were able to get down to 563 nests, which is just a little above our target population goal. The graph in Figure 1 shows the numbers of cormorants on the lake from 2005-2007. Count numbers are based on a number of factors, including the aerial photo counts over the summer, ground nest counts, colony site counts, as well as the number of birds removed through control efforts.

Spring and fall migrants were not seen in great abundance this year and migrants did not stage on Leech Lake for any length of time. We did observe some cormorants foraging on Traders Bay this year and a small migrant flock on Walker Bay late in the fall.

Cormorant Population Trends on Leech Lake 2005, 2006, and 2007

8000 Control starts 7000 (2005, 2006, 2007)

6000 Migration starts

5000 2005

4000

3000 Young birds start fledging 2006 Target Level 2000 2007

Total NumberTotal Cormorants of on Lake 1000 Ice out 0

8 7/ 8/5 9/2 4/15 4/29 5/13 5/27 6/10 6/24 7/22 8/19 9/16 9/30 10/14 Month and Day 2005 2006 2007 Fall Target Population Level

Figure 1. Total numbers of cormorant on Leech Lake in recent years. (Data from LL Res. DRM)

Cormorant Diet Study The diet study that was initiated in 2005, using a grant from the US Fish and Wildlife Service to the Leech Lake Band, continued this past summer. A whole host of agencies and individuals have been involved in or support this study. They include the University of Minnesota, MN DNR, USDA Wildlife Services, US Fish and Wildlife Service, Leech Lake Association, as well as some private individuals. Adult birds were collected in 2004, 2005, 2006, and 2007 and regurgitated samples from juvenile birds were collected in 2005, 2006, 2007. Samples from 2007 will be examined this winter, but a preliminary look at them indicates they will have similarities to previous years, with fewer walleyes.

Cormorants have been noted in many studies to feed primarily on fish species that are very abundant and easy to catch. Small yellow perch continue to be the most common component of the diet, as would be expected, due to their abundance in the lake. Shiners have been found to make up second most common food item in the diet samples. The third most common species found was trout perch, a species that is fairly abundant in Leech Lake but is probably unfamiliar to most people. This species has also been found to be a common diet item in other cormorant diet studies. All other species made up less than 5% of the diet. Figures 2 lists all the species of fish found in the samples collected on Leech Lake, and Figures 3 and 4 show a percentage breakdown for various species. The differences in the diet between 2005 and 2006 were that shiner and trout perch were more prevalent in 2006 and that lake herring (tullibee or cisco) showed up in larger numbers in 2006. This was probably due to the hot weather that often results in lake herring being thermally stressed and more vulnerable to capture.

Lake herring (tullibee) Golden shiner Trout perch Log Perch Lake whitefish Emerald shiner Burbot Johnny darter Central mudminnow Bigmouth shiner Rock bass Iowa darter Northern pike Spottail shiner Bluegill Yellow Perch Bluntnose minnow White sucker Pumpkinseed Walleye Common shiner Greater redhorse Largemouth bass Sculpin Mimic shiner Black bullhead Black crappie Sand shiner Yellow bullhead Brook Stickleback Fathead minnow Tadpole madtom Ninespine stickleback Figure 2. List of fish species found in cormorant diet samples from Leech Lake.

Yellow Perch

Shiners

Herring Other

Trout Perch

Walleye

Figure 3. Breakdown of fish found in cormorant stomachs on Leech Lake by numbers in 2005.

Yellow Perch Shiners

Herring Other

Trout Perch Walleye

Figure 4. Breakdown of fish found in cormorant stomachs on Leech Lake by numbers in 2006.

Walleyes make up less than one percent (0.38%) of the diet and they are almost all young-of-the- year. This is a much smaller figure than anyone expected and would seem to indicate that direct cormorant predation on walleyes might not a big factor. In addition, an excellent walleye fingerling growth rate over the past couple of years seems to preclude cormorant predation on forage species as the cause of recent poor walleye recruitment. However, we caution everyone to not draw premature conclusions about whether or not this predation is a significant factor on walleyes in the lake and to what level the cormorant population should be managed by the band. These questions cannot be answered until the fish/cormorant population modeling efforts are completed.

Although is may seem intuitively simple that if cormorants eat large numbers of small fish they have a negative effect on the fish population. Unfortunately the natural world is a complex place and it is not that simple. It all comes down to whether or not cormorant consumption is compensatory or additive in nature. The vast majority of small fish of all species in our lakes are lost from the population every year. They can be lost due to bad weather during early life stages, disease, or eaten by invertebrates, to name a few causes of loss, but the vast majority of fish are eaten by larger fish. In the big picture it doesn’t make a great deal of difference how these fish die, as they just end up being recycled thought the food web in different ways. Since cormorants feed mostly on small fish, their predation ends up being highly compensatory in nature (eating fish that would have died anyhow). On average, cormorants on Leech Lake are consuming fish near the small end (2-4 inches) of their size preference range. Other studies have found the size preference range to be 2-6 inches.

It is only when and if cormorant predation or other losses of fish exceeds the compensatory levels or if cormorants were to consume larger size fish that you would expect to see changes in the fish population. These are called additive losses and are nothing more than losses to a population that are in excess of levels that would have naturally occurred anyway. The most obvious example of additive loss is human harvest of fish. Because humans typically harvest fish that have survived most of the compensatory losses that are predominant when fish are small, much of our harvest is additive. For this reason, we have seasons, limits, and special regulations in an effort to prevent humans from over-harvesting many species. Only by conducting extensive modeling efforts, will be able to answer questions about if and how cormorants are affecting fish populations on Leech Lake.

The other factor to consider in fish population dynamics is that in order for a large year class of almost any species to occur, there needs to be abundant habitat and food available for it to exploit. In the case of Leech, the years of low numbers of small walleyes set the stage for this to happen. Although there is a desire by many people to have high numbers of certain fish each year, in the natural world this is a rare event and it is typically not sustainable. Once a system is saturated and the available habitat and food utilized it is very difficult, if not impossible, to get another large year class. In all likelihood this is the reason the numbers of 2007 walleye young- of-the year were lower than the past couple of years. It is only when another void is created that a large year class of fish will be possible.

The unexpected results of the study are complicating the justification for culling large numbers of cormorants, so the Band, along with our partners, resubmitted the grant application to the US Fish and Wildlife Service to conduct a time-budget analysis, and radio telemetry work. This information is needed to refine the modeling efforts.

Plans For 2008 It appears that walleye and perch numbers and growth rates are very good in Leech Lake and the recovery of these populations in well in excess of what was predicted in the Environmental Assessment (EA) that we prepared for the project. Under the EA it was projected that the walleye population would not recover unless cormorant numbers were reduced down to about 500 reproducing pairs. We have been very close to attaining this level the past few years in the fall of the year, but cormorant numbers are higher in the first part of the summer. Figures 1 and 5 are graphic examples of cormorant numbers on Leech Lake.

Even though we have removed about 9000 cormorants from the lake over the past three years, on average we have been in excess of cormorant numbers that should have allowed for recovery to occur, yet it has occurred. This leads us to believe that there are other factors at play beside cormorant predation in Leech Lake. Results of the modeling efforts from the first two years should be available by early 2008 and the Band will consider this information in deciding at what level cormorants we will manage for on our lands and waters in future years.

Total number of cormorants on Leech Lake

11000

10000

9000 8000

7000

6000 5000 4000 No. Cormorants No. Cormorants 3000

2000 1000 0 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 Year

Spring or pre cull cormorant numbers Fall or post cull numbers

Figure 5. Spring or (Pre-cull) and fall or (post-cull) cormorant numbers on Leech Lake. Line at 2000 is the fall population goal. (500 nests x 2 adults + 2 offspring per nest) (Data from LL Res. DRM)

Cormorant Nest Material Removal Like a number of years in the past, we again collected cormorant nests on Little Pelican Island and burned them. This effort reduces the amount of nesting material on the island, and over time should help to reduce the attractiveness of the site to cormorants for nesting. A special thanks to Jerry McCauley for assisting us in this effort.

Trespass Into Closed Areas Over the past several years, we have observed increasing numbers of individuals trespassing into the closed area around the islands. This area is closed for the protection of boaters and to prevent interference with culling operations and the diet study. Trespassing not only puts these individuals at risk, but also makes these operations more difficult and is increasing the wariness of the birds. It also puts the whole operation at risk because under the Federal Depredation Order, there is no allowance for the disturbance of other species to the point that their reproduction is reduced. Under the Environmental Assessment, we also have to maintain the 500 pairs of cormorants. The closed area extends approximately one quarter mile out from Little Pelican, Gull and portions of Big Pelican Island where operations are taking place. We stepped up enforcement of the closure area this past summer to prevent people from jeopardizing the future of this project. We ask that the public honor the closed areas and encourage anyone who observes violations to report them the Cass County Sheriffs Department or Tribal or State Conservation Officers. Figure 6 outlines the areas around the lake that are closed and Figure 7 shows an example of surveillance photos that are being used for enforcement purposes.

Figure 6. Closure zones Figure 7. Example of surveillance photo of boat inside closure zone

Disease Outbreak While conducting some routine surveillance for bird diseases on the Gull and Pelican Island Complex late this fall, an unusual number of dead birds were observed. Most of the dead birds were young gulls, but there were also 74 cormorants, two terns and a white pelican. Samples of these birds were collected and sent to the National Wildlife Health Lab as well as several other laboratories for testing. Results of this testing found that most of the birds died of avian cholera, but the some of the cormorants were found to also have a non-virulent strain of Newcastle Disease.

Avian cholera is bacterial disease is usually associated with large concentrations of waterfowl, particularly snow geese, and outbreaks in wild birds usually occur during migration periods. The status of the disease in Minnesota is listed as frequent in occurrence and usually results in the death of moderate to small numbers of birds. This disease is thought to have first arrived in Minnesota about 10-15 years ago and over this time a number of outbreaks have occurred, usually at waterfowl refuges around the state.

Newcastle disease is a viral infection that can be found in a wide variety of bird species, but it has been noted to kill cormorants in a number of locations. Outbreaks have been documented in the Great Lakes, Canadian Provinces, the Dakotas, as well as Minnesota. Since neither of these diseases were present during the summer; they were probably brought into the area by migrating

7 waterfowl and spread to the other birds on the islands. Neither of these diseases is believed to survive our winters. To further reduce this possibility the dead birds were picked up and incinerated. These diseases do not pose a risk to human health.

Colonial Waterbird Paper Over this past year we prepared and submitted for publication a paper that outlines the changes in colonial waterbirds on Leech Lake. We anticipate it will be published in late 2007 or early 2008.

Lawsuit Update The lawsuit challenging the Federal Cormorant Depredation order is on appeal and is scheduled to be heard in Federal court in November. This suit challenges the decision and the rational for the decision made by the US Fish and Wildlife Service to allow for the reduction of cormorants under some circumstances. It is unknown what the outcome of this suite is likely to be and the implications it might have for the work we are doing on Leech Lake.

Predator Control As in recent years, predator control on the Pelican Island complex was contracted to USDA Wildlife Services. Mink are the predator of most concern, since they have been known to kill large numbers of common terns and gulls. No predators were captured on the island this year and no loss of birds due to predators was noted.

Nesting Activities of Other Colonial Waterbirds

Common Terns Common terns nested in good numbers on Leech Lake with 323 nests counted. Reproduction was not good however, with only 134 young fledgling. Low reproduction was due to several factors. In an effort to get all the terns to move to the new nest site, we did not place a grid over the old nest site or remove gull nests and eggs from this area as in past years.. As a consequence, reproduction was low from this section of the island. The second factor was poor reproduction from the terns that nested on the south beach of the island. In most years these nests are wiped out by high waves that can come from this direction during storms. This occurred this year. Terns that nested in the new nest site did quite well. It is our desire to get most if not all of them to move to this location. Competition with other colonial waterbirds, mainly ring-billed gulls for nest space continues to be an issue for common terns and we don’t see this situation changing anytime soon. Without significant management effort, terns would not be able to successfully nest on Leech Lake.

Caspian Terns One of the most notable events that occurred on the island this past summer was the successful nesting of Caspian terns on Little Pelican Island. Although this species may have nested on Leech Lake prior to construction of the dam, it has only been documented to have attempted nesting on two occasions in Minnesota. The first occurred in 1969 when two pair tried to nest on Gull Island. The second occurred in 2004 when a pair attempted to nest on Hennepin Island in Mille Lacs Lake. Neither of these attempts was successful. The nesting of this species on Leech Lake is the first documented successful nesting of the species in Minnesota. This year on Leech Lake, 28 Caspian terns established 13 nests, and hatched 15 young of which 11 fledged. Figure 8 is a picture of two adult Caspian terns and four fledglings.

The Caspian tern is the largest tern species in the world and is about the size of a medium gull. They feed almost entirely on fish and forage by flying over the water and dropping down to

catch prey that is at, or very near the waters surface. The most common fish we see them catch are shiners. Because of their feeding behavior, they pose little threat to any gamefish on Leech Lake. We look forward to continued nesting of the species on the Lake.

Figure 8. Caspian tern young and adults. This is the first documented successful nesting of this species in Minnesota.

Elegant Tern Another unusual surprise on Leech Lake was the presence of what was believed to be an elegant tern on the Little Pelican Island. The closest nesting colony of this species is near San Diego California and it is rarely seen away from costal habitat. If this record is accepted, this will be the first time this species has ever been observed in Minnesota and the upper Midwest. Figure 9 is a photo of the bird in question. The Gull and Pelican Island Complex has always been somewhat of an ornithological wonder due to the diversity and abundance of birds that use it. It continues to uphold its reputation.

Figure 9. Photo of what is believed to be an elegant tern that was observed on Little Pelican Island. This is the first time this species has ever been documented in Minnesota.

Ring-billed Gulls Ring-billed gulls nested in high numbers on Little Pelican Island and in fewer numbers on Gull Island. Using the same photographs we used to enumerate cormorants, we obtained accurate counts of gulls again this year. A total of 3712 nests were counted on Little Pelican Island and 47 on Gull Island. These nests fledged approximately 1700 ring-billed chicks this year.

Herring Gulls All herring gull nesting activity occurred on Gull Island with the exception of two nests that were located on Little Pelican Island. This year, 15 nests were counted and 10 chicks fledged.

White Pelicans Varying numbers of white pelicans were counted over the summer. The highest count in a single day was 240 birds. Pelicans are known to travel long distances on a daily basis to forage for food. A total of 6 nests were initiated on Little Pelican Island this year, but none of the eggs hatched. This species is not very tolerant of disturbance and this may explain why they did not fledge any young Leech Lake again this year.

If you have further questions on the diet study or control activities please contact Steve Mortensen, or John Ringle at the Leech Lake DRM, 218/335-7400.

Acknowledgements We would like to thank the following individuals and organizations for their participation or support of all or portions this project.

Leech Lake Band, Division of Resources Management Richard Robinson, Jr., John Ringle, Steve Mortensen, Frank Bowstring, Jamie Mitchell, Richard Tanner, Jon Finn, Gary White, Martin Robinson, Dr. Rebecca Knowles, Tyler Godin

MN, Department of Natural Resources Lee Pfannmuller, Dr. Don Pereria, Ron Payer, Henry Drewes, Harlan Fierstine, Doug Schult , Jeff Lawrence, Dave Rave, Jim Berdeen, Gary Sommers Mille Lacs WMA

USDA, Wildlife Services Bill Paul, Kim Wagner, Jeff Grabarkewitz, Pete Sahr, Abraham Wolf, Paul Wolf, John Hart, Shawn McDowell

US, Fish and Wildlife Service Dr. Steve Lewis, Shauna Hanisch, John Leonard, Sheila Oconnor, Pat Lund

US Geological Survey National Wildlife Health Center Dr. Mark D Jankowski

University of Minnesota Dr. Andrew Simons, Dr. Francie Cuthbert, Linda Wires, Peter Hundt, Ozge Goktepe

Cass Co. Sheriff’s Department Tim Bergland, Bob Landreville, Aaron Ammerman, Travis Collette

Pro-West and Associates Inc. Lee Westfield

Leech Lake Association Jerry McCauley Others Leech Lake Tribal Council: (George Gogglerye, Jr. Arthur “Archie” Larose, Lyman Losh, Donald “Mick” Finn, Robbie Howe State Representative Larry Howes State Senator Mary Olson State Senator John Marty State Representative Frank Moe Leech Lake Band of Ojibwe Natural Resources Advisor Committee Mick and Miles Lord Family Chippewa Lodge, Jim Springsteele, Owner Huddle’s Resort, Roy Huddle, Owner