Big Mantrap Lake Association


Thank you for your interest in the Big Mantrap Lake Loon Nesting Program. 

About half the nesting pairs on Big Mantrap are natural nesters and half use

the nesting rafts (also called platforms).  The nesting rafts are backups in the

event of high water or predation. 

There is no guarantee loons will use this raft design.

Researchers have discovered that territorial male and female loons are replaced

every 6 or 7 years. Male loons select the nest site. Loons may have nested

successfully on a raft for many years, then the new male may select a natural

nest site within the territory.


Big Mantrap Lake is 1556 acres in size, with more than 21 miles of irregular

shoreline, including five islands and many bays and coves.  Nineteen loon

nesting territories have been identified.  At this time 18-19 nesting pairs use

the lake.  Loon nesting rafts are set immediately the day the ice goes out and

removed three weeks after the chicks hatch. The rafts are removed so that

the natural beauty of the lake is not impaired.  Refurbishing the nests, setting

them out, and removing them, requires the efforts of a number of volunteers..


The Big Mantrap Lake Loon Nesting Program began in 1990 with rafts

based on the Minnesota DNR WOODWORKING FOR WILDLIFE model.

Our raft fabrication materials have shifted from wood to plastic and now

aluminum.  Light weight aluminum nesting rafts best suit the needs of our lake,

because of the number of rafts needed and the seven mile length of the lake. 

Two rafts with anchors and buoys can be hauled in and out of a 14 foot boat.  



Photo No. 1, 16 ft. Jon boat, 2 rafts, buoy, anchors & 3 crew 


Big Mantrap Raft Design Features:

Strong welded integral construction           Removable canopy frame and screen

Easy access ramp for adults and chicks     Nest ring

Light weight                                              Resistance to corrosion

Dry natural vegetation for nest                   Resting area

Seaworthy in rough water




Photo No. 2, Raft, unrigged, canopy open



Photo No. 3, Raft, canopy locked


Photo No. 4. Raft w/ 3/8" plywood





Photo No. 5, Loon nesting

Raft Fabricators

Two fabricators make Big Mantrap Lake loon nesting rafts. Both fabricators remodel rafts of earlier designs.

Duane Petterson, a retired St. Cloud Technical College instructor, is

fabricating the nesting rafts in his shop.  Duane is a major contributor to

the raft design. Address:  405 Hazeltine Pl NE Owatonna MN 55060 

E-mail:   Phone:  507.676.0022


Izzy’s Machine & Welding Shop, 607 N. Central Avenue, Park

Rapids, MN 56470

Phone:  218.732.9390


Access Ramp  

The access ramp is contained within the raft to make the raft compact for

easy handling. Some loon families have used the rafts for three weeks after

hatching.  Loons usually do not return to natural shoreline nests after the

chicks have hatch because of potential  predation, as well as the difficulty

for chicks to climb back on a shore nest.


Platform and Ramp Material

3/8" marine plywood is preferred for the platform and ramp; however, if it is

unavailable exterior plywood can be substituted.  Green treated plywood can

be toxic.  The plywood is fastened to the raft frame with stainless steel

1/4"-20 x 1" hex head cap screws with washers and nylon locknuts.


Texturing the ramp plywood will help the chicks return to the nest and warm

up. The ramp can be textured with coarse abrasives or by shallow parallel

saw (kerf) cuts about 1" apart.


In an experiment to give the rafts a more "natural" appearance, several raft ramps

have been covered with bulrushes. See photos No. 24 & No. 25. At this time,

there is no evidence of success.



Photo No. 6, Raft ramp w/kerf cuts


Nesting Material

Dry natural vegetation is warmer than living sedge grass mat at spring lake

temperatures.  The dry vegetation may contain fewer parasites than living

sedge grass mat.  Two to three inches of a combination of cattails

(Typha latifolia) and/or hardstem bulrush (Scirpus acutus) are spread over

the nesting area of the platform (McIntyre p. 23).  Sedge grass (Carex spp.)

is used to line the interior of the nest ring.  The natural vegetation is cut with a

snow shovel after the lake is frozen and before the snow is too deep.  A DNR

permit is required before harvesting vegetation.  Big Mantrap now uses

bulrushes instead of cattails because it is easier to form on the raft platform. 

The harvested bulrushes must not dry out or they become brittle and break

easily.  Store over winter on the ground with a cover tarp and wet in the spring

if necessary.



Photo No. 7, Cutting bulrushes w/snow shovel



Photo No. 8, Bulrush storage




 Photo No. 9, Bulrush storage w/tarp



Nest Ring  

The function of the nest ring is twofold; first the ring prevents the eggs from

rolling off the raft, and second, the ring keeps the natural vegetation from

blowing off the platform.  The nesting ring is made up of a 4 ft. length of

garden hose, inside foam pipe insulation (1" I.D. x 1 3/4" O.D.).  The interior

diameter of the nest ring is 12" to 13" (McIntyre, p. 24).  The hose ends are

joined with a 5/8" wood dowel about 2" long forced into the hose ends.  

Small screws can be used to fasten the hose to the dowel if the joint is too

loose.  The foam pipe insulation joint is covered with duct tape.



Photo No. 10, Nest Ring



Photo No. 11, Nest ring, hose exposed


Attaching Nest Ring

The nest ring is placed on top of the natural vegetation and secured with 18”

plastic cable ties (-41 degrees grade) through four eye screws in the plywood

platform.  Lesser grade cable ties will break in freezing temperatures.  We use

6", 12", and 18" length cable ties to attach the nesting ring and canopy screen. 

Place the nesting ring deep inside the raft.


Photo No. 12, Arlis McGinnis w/canopy open


Photo No.13, Nest circle, 16 1/2" dia. w/eye screws



Photo No. 14, 18" Cable ties through eye screws



Photo No. 15, Cable ties secured only at ends


Photo No. 16, Nest ring elevated for bulrush insertion


Photo No. 17, Bulrushes under nest ring (1)


Photo No. 18, Bulrushes under nest ring (2)


Photo No. 19, Bulrushes under nest ring (3)


Photo No. 20, Sedge grass under nest ring


Photo No. 21, Sedge grass completed


Photo No. 22, Drawing down nest ring


Photo No. 23, Excess trimmed, sharp ends rotated below bulrushes 


Photo No. 24, Raft ramp, ties and stick (experimental)



In an experiment to give the rafts a more "natural" appearance, several raft

ramps have been covered with bulrushes. See photos No. 24 and No. 25.

At this time, there is no evidence of success.


Photo No. 25, secured bulrushes (experimental)


Photo No. 26, Raft make ready completed



Loons prefer to enter and exit the nest undetected,

(McIntyre, Nests, p. 20-28).  The raft canopy provides a screen to reduce

detection and to give a sense of security.  Too many human intruders can be

detrimental as the incubating loon is turned into a "flusher" loon, which may

abandon the nest. 


The shape of the canopy is high in the bow and lower in the stern (ramp end). 

Thirty inches of space above the nest area is provided for loon copulation

(McIntyre Plate No. 1).  The low canopy at the stern reduces possible

detection by shore predators while giving the loon good visibility, and aids the

loon in slipping off the raft undetected.  At this time there has been no predation

on the Big Mantrap Lake rafts.


Canopy Frame and Screen

The exposed rods of the canopy frame provide protection from large aerial



The plastic screen is a partial barrier when viewing the raft from a distance,

while providing 360 degree visibility for the loon sitting close to the screen. 

In addition the screen is a windbreak, partial shade for the dark colored

incubating loon, and possibly a solar reservoir to keep the eggs warm when

the loon briefly leaves the nest.  The Big Mantrap Lake Association purchases

the screen in large rolls and will sell screen to other lake associations.  The

screen is attached to the canopy frame with plastic cable ties.


Loons encountering a nesting raft with a fully enclosed plastic canopy screen

may consider the raft to be a trap and thus avoid the raft. To condition loons

to the plastic canopy covering, the screen is added in two phases.  The first

year screen is 10"-12" high on three sides of the canopy base.  This is sufficient

for the loon to remain undetected in their head down hangover posture.  Loons

returning to nest in the following year have readily accepted a completely

covered canopy.                                                              



Photo No. 27, First year screen phase


Photo No. 28, Raft w/full screen cover w/reflectors


Loon Raft Location

Loons prefer to nest on islands or areas out of the wind (McIntyre, pp 20-28). 

Emergent vegetation is desirable for the chick nursery.  Deep water nearby

can help loons escape predators, as well as providing a margin of safety against

fluctuating water levels.  The bow or closed end of the raft is anchored facing

open water, onshore waves and curious boaters.  The stern or ramp end of the

raft is anchored facing shore. The raft distance from shore varies with the site,

but far enough away from shore to avoid discovery by shoreline predators. 

On large bulrush beds the raft can be located inside the outer edge of the bed.



Large (200 oz., 1 1/2 gal.) detergent bottles filled with concrete serve as

anchors for the nest sites out of wind.  Before the concrete sets up a length

of large chain is suspended in the concrete with one end exposed to attach

the rope snaps.  These anchors are compact, have a smooth exterior, and a

handle.  The wind prone nest sites on Big Mantrap Lake require heavy naval

type anchors with hinged flukes.  Generally 28 lb. anchors are used on the bow

toward open water and 20 lb. anchors on the stern toward shore.



Photo No. 29, Cast anchor, 25 lb.



 Photo No. 30, Anchor w/hinged flukes



 Anchor Lines

Anchor lines are 3/8" nylon rope with the largest size brass rope snaps

(251B-3) tied to each end.  Rope snaps are quite adequate for general use. 

For rough water sites a quick link or carabiner (3/8”), used in sports requiring

rope work can be used.  Anchor lines are 15-20 ft. long.



Photo No. 31, Rope snap 


Buoys and Territory Markers

Curious human intruders and occasional insensitive fishermen are potential

problems for nesting loons.  One LOON NESTING regulatory buoy in

combination with yellow fishing markers is used to define the loon's nesting

territory.  This system has been mostly successful in alerting potential intruders

and giving the loons a secure space. Rolyan Buoys, Inc. makes an excellent

regulatory buoy, with a silhouette of a loon, and the words CAUTION, LOON



Photo No. 32, Roylan buoy


Yellow Lindy-Little Joe fishing markers are used to form an arc to define

the perimeter of the nest territory.  The regulatory buoy is placed in the

center apex of the arc about 30 ft. from the nest.  The fishing markers are

restrung with 1/8" nylon rope, because the line issued with the marker is

not durable.  The length of the nylon ropes must be sufficient to

accommodate the water depth as well as potential wave height.  See the




Photo No. 33, Lindy, territory marker


Photo No. 34, Buoy with territory markers



Photo No. 35, Buoy with territory markers


Photo No. 36, Buoy with loon


Register Rafts with the County Sheriff’s Office

Notify the Sheriff Department of intent to place rafts on your lake.   Register

rafts with the County Sheriff’s Office and attach registration numbers to the

rafts.  The nesting rafts will require reflectors.



Bolts (cap screws), nuts, and washers should be stainless steel as other

metals in contact with aluminum will degrade through corrosion.  Lock nuts

with nylon inserts work best with cap screws.  


Loon Watcher Program

Record your loon observations with the Minnesota Loon Watcher Program.

For information contact:  Pam Perry, Minnesota Department of Natural

Resources, Regional Supervisor, Ecological and Water Resources, Nongame

Wildlife Specialist and Minnesota Loon Watcher

coordinator.  Phone:  218. 833.8728 



 Common Loon Research


University of Minnesota Press, 1988, ISBN0-8166-1651-5 with its reference

data has been an essential guide during development of our nesting raft.  


The May/June 2011, American Scientist article, "Marking Loons, Making Progress"

by Walter Piper, Jay Mager and Charles Walcot contains 18 years of shared

common loon research. Their research pioneers significant new insights into loon

behavior. These loon references will be of major importance in explaining loon

behavior witnessed on your lake.


Woodworking for Wildlife

WOODWORKING FOR WILDLIFE, by Carrol Henderson, published in

2009, by the Minnesota Department of Natural Resources notes the Big

Mantrap Lake Association loon nesting raft.



DNR Nongame Tax Check Off

Please remember the DNR Nongame Tax Check Off when you are filing

your Minnesota tax form.  When renewing your vehicle license plates, a

Critical Habitat donation will provide you with a special loon or other species

plate. If you reside in a state other than Minnesota, perhaps your state has

opportunities similar to those listed above.


Nest Buoys

Rolyan Buoys, Inc.

Regulatory buoy, measures 9" dia. x 61" high.

Silhouette of a loon, with LOON NESTING AREA, CAUTION  Phone:  888.269.2869


Canopy screen

Windbreak No. X05300-002, 4 feet x 50 feet roll

Order sample: Conwed Plastics 1.800.426.0149  

To purchase: 

Geo Synthetics Inc.

2401 Pewaukee Road, Waukesha WI, 53188

Phone:  800.444.5523


Retired Loon Nesting Rafts Available

Loon nesting raft design is an ongoing project.  Recently the changes have

been minor.  As new rafts are added to the collection, we retire rafts of

earlier designs.  These successfully used rafts are available to lakes wanting

to start a loon program.


 Ongoing Development

The development of this raft is due to the work and observations of numbers

of Big Mantrap Lake residents and fabricators.  Experimenting on hunches

and learning from errors in judgment has been our design process.  Resident's

donations and memorials pay for the fabrication of new rafts and supplies. 

Each year we think that the evolution of the nesting raft is complete only to

find that there are still other aspects needing attention.  We welcome your

questions and suggestions for continuing raft improvement.  You are also

welcome to visit our nesting raft "marina" on Big Mantrap Lake.  We wish

you success with your loon propagation.


Lyle Laske

28292 Junco Drive, Nevis, MN 56467

Phone (218) 652-2449




Create a Free Website