Double-crested Conflict Management And Research On Leech Lake 2005 Annual Report

Prepared by

Leech Lake Band of Ojibwe Division of Resources Management

Minnesota Department of Natural Resources

US Department of Agriculture Wildlife Services

Photo by Steve Mortensen

This report summarizes cormorant conflict management and research that occurred on Leech Lake during 2005. The overall goal of this project is to determine at what level cormorant numbers can be managed for on the lake without having a significant negative effect on gamefish and on other species of colonial waterbirds that nest alongside on Little Pelican Island. Work conducted this summer went much better than anticipated and we are well on the way towards resolving cormorant conflict issues on Leech Lake.

Cormorant Management Environmental Assessment An environmental assessment (EA) was prepared that gathered and evaluated information on cormorants and their effects on fish and other resources. We compiled, considered, and incorporated input from all parties that have an interest or concern about the proposed controlling of cormorants on Leech Lake.

This document could have been written specifically so the Leech Lake Band could address the Leech Lake cormorant colony, but it was decided to prepare it as a joint effort between LLBO Division of Resources Management (DRM) and USDA Wildlife Services (WS), MN Department of Natural Resources (MN DNR), and US Fish and Wildlife Service (FWS). WS served as lead agency in this effort. By preparing it in this manner, it could be utilized by other agencies elsewhere in Minnesota if resource damage was documented.

The EA proposed to reduce the Leech Lake colony more than 10% so, under provisions of the Federal Depredation Order, the Leech Lake Band submitted a request to the US Fish and Wildlife Service to go to a higher population reduction limit (reduction to 500 nests). This was done with the understanding that a diet study will be completed that will help to determine what level cormorant numbers can be maintained without having significant negative effects on walleye populations. Decision notices were signed and published by the DRM, FWS and WS outlining the work to be done over the next few years at this colony.

Cormorant Diet Study Grant Increasing numbers of cormorants on Leech Lake and concerns about predation on walleye and perch populations prompted LLBO to submit a grant proposal to the FWS Tribal Wildlife Grant Program. Partners and cooperators in this project include the MN DNR, WS, FWS, University of Minnesota (UM), and several local organizations and individuals. This grant has been combined with other funds and in-kind support to conduct a two-year study.

Walleye Stocking The MN DNR stocked 7.56 million walleye fry into Leech Lake this past spring (2005). The fish were marked with oxytetracycline, a chemical that allows biologists to identify a fish as stocked. Stocking marked walleye fry provides an opportunity to evaluate the success of natural reproduction in Leech Lake by analyzing the ratio of marked (stocked) to unmarked (natural) fingerlings. This ratio can be tracked over time and may prove useful in the cormorant diet study. Catch rates for standard trawling efforts this year were nearly twice the long-term average and are indicative of a strong walleye year- class (Figure 1). Marked fish accounted for 39% of the fingerlings sampled this year. Oxytetracycline marked otolith (Photo from MNDNR)

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Y 200 No. Walleye YOY sampled No. Walleye

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0 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Year

Y OY w alleye Long term average

Figure 1. Long term walleye young-of-the year trend on Leech Lake . (Trawling data from MN DNR)

Cormorant Efforts to cull cormorants were initiated on May 4, 2005, at the nesting site on Little Pelican Island. LLBO contracted this work to WS, with the MN DNR providing over 50% of the funding. A total of 2993 birds were shot and removed from the lake for the culling and diet sampling projects. This reduced the number of cormorant nests to about 700, down from 2524 nests in 2004 (Figure 2). To reduce the disturbance to other colonial waterbirds on the island and to 500 cormorant nests that were to be conserved, culling was conducted early in the nesting season, 1-2 times per week. Carcasses were collected each day of culling and transported to shore where they were frozen. The frozen carcasses that were not retained for the diet study were transported to the Mille Lacs Area for disposal by incineration.

All culling efforts at the nest sites were conducted from elevated blinds using precharged, .22 caliber air rifles. Birds were collected for the diet study off of the eastern end of Big Pelican Island using shotguns. Contrary to news reports, silencer-equipped firearms were not used. Legislation to permit their use was not passed in time and, as of the date of this report, we are still trying to determine whether the wording of the new law will permit use of silencer-equipped firearms on tribal lands or whether this legislation will need to be amended.

Cormorant nest on Little Pelican Island (Photo from LL DRM) 3

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2000 No. nests and fledglings and nests No.

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0 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Year

Es timated Number Of Nes ts W ithout Culling Nests Number Fledged

Figure 2. Numbers of cormorant nests and fledglings on Leech Lake in recent years. (Data from LL DRM)

Bird Counts We contracted with MN DNR pilots to conduct flights over Leech Lake in an effort to estimate cormorant numbers and to identify locations where they frequently forage. In addition, we contracted with Pro-West and Associates for high-resolution aerial photographs of Gull and Pelican Islands. These images were used to get accurate counts of birds and nests on the island. In general bird numbers were down this year from last year with many resident cormorants leaving the lake early this year.

Example of high-resolution aerial photos that are used for bird counts (Pro-West and Associates)

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Diet Study Sampling To determine what cormorants are consuming on Leech Lake, stomach contents were collected from foraging adults as well as juvenile birds. We collected adult birds by shooting them (with shotguns) on their return flights. This operation was conducted approximately weekly off tribal land on the eastern end of Big Pelican Island to minimize disturbance to the nesting colony and to bald eagles that nest on the island complex We sampled juvenile birds by approaching them on their nests and then collecting the material they regurgitate when disturbed. Juveniles were sampled about two weeks after hatching and then up until they began leaving their nests and moving about the colony. We preserved all samples with formalin and shipped them to University of Minnesota where a graduate student is examining the collections and quantifying the stomach contents. Diet samples collected from adults as well as from juvenile birds this summer have found that the vast majority of the fish they consume are small perch with the second most common species being shiners. As of the date of this report several hundred cormorants have been examined and only ten walleyes have been found. Diet studies on cormorants have consistently found that diets vary considerably from lake to lake and it appears that Leech Lake will be no exception. Combining this lake-to-lake variation with compensatory loses (the vast majority of small fish die or are eaten anyway) of young fish and you can see why it is so difficult to determine what is going on with a fish population in a lake. Peter Hundt collecting juvenile diet samples. (Photo from LL DRM)

Fish Population Sampling The MN DNR collects a large amount of fish data annually from Leech Lake as part of their Large Lake sampling program. This includes shoreline seining, trawling, electrofishing and gill netting. These data document changes in fish populations over time. The MN DNR also collected diet data for yellow perch, walleye, and northern pike. We will use these data to assist computer modeling cormorant impacts on Leech Lake. Figures 3 and 4 show some of the fish population trends in Leech Lake.

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4 Pounds Of Walleye Sampled Per Net Per Sampled Walleye Of Pounds

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0 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Year

Walleye Main Lake Walleye Deep Figure 3. Pounds of walleye sampled by gill net in the main and deep water bays of Leech Lake, 1983-2005 (Data from MN DNR, 2005)

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Number per set 15

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0 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Year

Deep Water Main Lake

Figure 4. Numbers of yellow perch sampled by gill net in the main and deep-water bays of Leech Lake, 1987-2005. (Data from MN DNR, 2005)

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Walleye fingerlings sampled by trawling on Leech Lake in 2005 (Photo from MN DNR)

Pat and Ozge shoreline seining for young-of-the year walleye (Photo from LL DRM)

Fish Population Modeling When sufficient information has been collected from diet sampling, Large Lake sampling, and other sources, we will use a computer program to model the effects of cormorant predation on yellow perch and walleye. In addition, we will try to assess crayfish predation, cannibalism, and other fish mortality factors. They will be using Ecopath and Ecosim models to do this analysis. Ozge Goktepe, another UM graduate student, along with Dr. Don Pereria from the MN DNR are working on this part of the project. This past summer they also completed a Ricker stock recruitment analysis for the walleye population in Leech Lake.

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Predator Control As in recent years, predator control on the Pelican Island complex was contracted to WS. Mink are the predator of most concern, as they have been known to kill large numbers of common terns and gulls. No mink or other small predators were caught early in the nesting season this year. We did have coyotes late in the nesting season and they did kill cormorant chicks, but all five coyotes were killed within a short time of their detection. This is the reason for the lower than anticipated cormorant reproduction this year. We expected about 1000-1250 chicks from the 500 cormorant nests that were protected, but only 212 cormorant chicks fledged this year

Cormorant Nesting Habitat Reduction This is the third year we have reduced cormorant nesting habitat on Little Pelican Island. These efforts aim to reduce the amount of available nesting material thus reducing the island’s attractiveness to cormorants. This project may reduce the need for the culling methods described above, which are very unpopular with some people. This year, with assistance from three volunteers from the Leech Lake Association, we piled and burned most of the remaining nesting material on the island.

Nest material removal by Larry Anderson, Jerry Demars, Jerry McCauley (Photo from LL DRM)

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Nesting Activities of Other Colonial Waterbirds Common Terns Common terns successfully reproduced this year, but ring-billed gulls that were displaced by cormorants intensely competed for nesting space and probably reduced tern success.

The nest site was totally dominated by ring-billed gulls this year, and only through regular removal of gull eggs were we able to provide nesting for the terns. As a result, we had 213 tern nests on the traditional nest site and an additional 44 nests on the south shore of Little Pelican Island (257 nests total). All of the nests on the south shore were washed out by wave action. The terns on the main nest site fledged 125 young.

Although reducing the number of cormorants on Little Pelican Island will provide extra space for nesting gulls, the gulls have become so well established on the north side of the island that we decided to build a new nest site for terns this fall. . This site is in the middle of the island and should give the terns additional space and safer nesting in future years.

Common tern nest area overrun by ring-billed gulls and new tern nesting area (Photos from LL DRM) 9

Ring-billed Gulls Ring-billed gulls nested in high numbers on Little Pelican Island but in fewer numbers on Gull Island. Using the same photographs we used to enumerate cormorants, we obtained accurate counts of gulls for the first time in many years. We counted 497 nests on Gull Island and 3116 nests on Little Pelican Island (3613 nests total). These nests fledged an estimated 900 ring- billed chicks this year.

Herring Gulls All herring gull nesting activity occurred on Gull Island with the exception of one nest. This year, 22 nests were counted and an estimated 25 chicks fledged.

White Pelicans Varying numbers of white pelicans were counted over the summer but no nesting activity was observed. The highest count in a single day was 302 birds. This species does not seem highly tolerant of disturbance, and this may explain the absence of nesting on Leech Lake this year.

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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, JamieMitchell, Richard Tanner, Jon Finn, Martin Robinson, Dr. Rebecca Knowles, Tyler Godin

MN, Department of Natural Resources Lee Pfannmuller, Dr. Don Pereria, Ron Payer, Henry Drewes, Harlan Fierstine, Pat Rivers, Erika Rivers, Jeff Lawrence, Gary Sommers Tom Pfingsten, Don Murray, John Heineman, 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, Jeff Gosse, Rachel Levin, John Leonard, Sheila Oconnor, Pat Lund

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 Watershed Project John Steward

Leech Lake Association Jerry McCauley, Jerry Demars, Larry Anderson

Others Leech Lake Tribal Council: (George Gogglerye, Jr. Arthur Larose, Lyman Losh, Donald “Mick” Finn, Burton “Luke” Wilson Representative Larry Howes Senator Carrie Ruud Senator John Marty Representative Frank Moe

Mick and Miles Lord Family Chippewa Lodge, Jim Springsteele Huddle’s Resort, Roy Huddle 11