BIOLOGICAL REPORT 82(10.86)

APRIL 1985

Library

Nation 1Wetlands Res rch Center

U. S. Fish and 'lldllfe Service

700 Cajundome Boulevard

I::l!fa,elle. bll' 70§QG

HABITAT SUITABILITY INDEX MODELS:

RUFFED GROUSE

j

..t.

F:i$b and Wildlife Service,

~~1 tepartment of the Interior . U54

no.82-

10 .86
This is one of the first reports to be published in the new "Biological

Repor-t" series. This technical report series, published by the Research

and Deve 1opment branch of the U. S. Fi sh and Wil dl He Servi ce, replaces

the "FWS/OBS" series published from 1976 to September 1984. The Biological Report series is designed for the rapid publication of reports with

an application orientation, and it continues the focus of the FWS/OBS

series on resource management issues and fish and wildlife needs.
MODEL EVALUATION FORM

Habitat models are designed for a wide variety of planning applications where habitat information is an important consideration in the

decision process. However, it is impossible to develop a model that

performs equally well in all situations. Assistance from users and

researchers is an important part of the model improvement process. Each

model is published individually to facilitate updating and reprinting as

new information becomes avai lable. User feedback on model performance

will assist in improving habitat models for future applications. Please

complete this form following apo l i ce t i on or review of the model. Feel

free to include additional information that may be of use to either a

model developer or model user. We also would appreciate information on

model testing, modification, and application, as well as copies of modified

models or test results. Please return this form to:

Habitat Evaluation Procedures Group

U.S. Fish and Wildlife Service

2627 Redwing Road, Creekside One

Fort Collins, CO 80526-2899

Thank you for your assistance.

Species

Habitat or Cover Type(s)

Geographic

Location

Type of Application: Impact Analysis Management Action Analysis __

Baseline Other -------------------------

Variables Measured or Evaluated

Was the species information useful and accurate? Yes No

If not, what corrections or improvements are needed?----------
Were the variables and curves clearly defined and useful? Yes No

If not, how were or could they be improved?

Were the techniques suggested for collection of field data:

Appropriate? Yes No

Clearly defined? Yes No

Easily applied? Yes No

If not, what other data collection techniques are needed?

Were the model equations logical? Yes No

Appropriate? Yes No

How were or could they be improved?

Other suggestions for modification or improvement (attach curves,

equations, graphs, or other appropriate information)

Additional references or information that should be included in the model:

Model Evaluater or Reviewer Date ------------ -------

Agency ~_

Address

Telephone Number Comm:----------- FTS _
Biological Report 82(10.86)

April 1985

HABITAT SUITABILITY INDEX MODELS: RUFFED GROUSE

by

Brian S. Cade

Colorado Cooperative Wildlife Research Unit

Colorado State University

Fort Collins, CO 80523

and

Patrick J. Sousa

Habitat Evaluation Procedures Group

Western Energy and Land Use Team

U.S. Fish and Wildlife Service

Drake Creekside Building One

2627 Redwing Road

Fort Collins, CO 80526-2899

Western Energy and Land Use Team

Division of Biological Services

Research and Development

Fish and Wildlife Service

U.S. Department of the Interior

Washington, DC 20240
This report should be cited as:

Cade, B. S., and P. J. Sousa. 1985. Habitat suitability index models:

Ruffed grouse. U.S. Fish Wi1d1. Servo Bio1. Rep. 82(10.86). 31 pp.
PREFACE

This document is part of the Habitat Suitability Index (HSI) Model Series

[Biol. Rep. 82 (formerly FWS/OBS-82/l0)], which provides habitat information

useful for impact assessment and habitat management. Several types of habitat

information are provided. The Habitat Use Information Section is largely

constrained to those data that can be used to derive quantitative relationships

between key environmental variables and habitat suitability. The habitat use

information provides the foundation for HSI models that follow. In addition,

this same information may be useful in the development of other models more

appropriate to specific assessment or evaluation needs.

The HSI Model Section documents a habitat model and information pertinent

to its application. The model synthesizes the habitat use information into a

framework appropriate for field application and is scaled to produce an index

value between 0.0 (unsuitable habitat) and 1.0 (optimum habitat). The application information includes descriptions of the geographic ranges and seasonal

application of the model, its current verification status, and a listing of

model variables with recommended measurement techniques for each variable.

In essence, the model presented herein is a hypothesis of species-habitat

relationships and not a statement of proven cause and effect relationships.

Results of model performance tests, when avail ab1e, are referenced. However,

models that have demonstrated reliability in specific situations may prove

unreliable in others. For this reason, feedback is encouraged from users of

this model concerning improvements and other suggestions that may increase the

utility and effectiveness of this habitat-based approach to fish and wildlife

planning. Please send suggestions to:

Habitat Evaluation Procedures Group

Western Energy and Land Use Team

U.S. Fish and Wildlife Service

2627 Redwing Road

Ft. Collins, CO 80526-2899

iii
iv
CONTENTS

PREFACE iii

ACKNOWLEDGMENTS vi

HABITAT USE INFORMATION 1

Genera 1 1

Food 1

Water 2

Cover/Reproduction 3

Interspersion and Composition 9

Special Considerations........................................... 10

HABITAT SUITABILITY INDEX (HSI) MODEL 11

Model Applicability.......... 11

Model Description................................................ 12

Appl ication of the Model 20

SOURCES OF OTHER MODELS 25

REFERENCES 25

v
ACKNOWLEDGMENTS

We gratefully acknowledge Gordon W. Gullion for reviewing and assisting in

development of this model, providing habitat use and ruffed grouse population

data from the Cloquet Forestry Center, and ai di ng in i nterpretati on of the

data. Gretchen Mehme 1 and Peter Sanda measured characteri sti cs of ruffed

grouse habitat at Cloquet. Janet Schreur tabulated habitat data provided by

Gullion and mapped cover types sampled at Cloquet.

We also thank David A. Boag, Robert E. Chambers, Ralph W. Dimmick,

Daniel M. Keppie, John F. Kubisiak, Keith R. McCaffery, and Robert J. Stoll,

Jr. for their critical reviews of this habitat model. The cover of this

document was illustrated by Jennifer Shoemaker. Word processing was done by

Carolyn Gulzow and Dora Ibarra.

vi
RUFFED GROUSE (Bonasa umbellus)

HABITAT USE INFORMATION

General

The ruffed grouse (Bonasa umbellus) is the most widely distributed species

of the Tetraoni nae in North Ameri ca, occurri ng in forested habitats from

central Alaska to northern California; through the central Rocky Mountains of

Idaho, Montana, western Wyomi ng, and north-central Utah; i so1ated in western

South Dakota; from British Columbia east across Canada to southern Labrador;

and from Minnesota, Michigan, Wisconsin, northeastern Iowa, Illinois, Missouri,

and northern Arkansas east through Indiana, Ohio, New York, New England, and

the southern Appalachian Mountains from Pennsylvania to northern Georgia

(Aldrich 1963). Ruffed grouse have been successfully introduced outside their

original range into Newfoundland and northeastern Nevada (Johnsgard 1973). It

is the most widely hunted grouse in North America, providing recreational

sport hunting in 43 States and Provinces.

Food

Ruffed grouse feed on a variety of plant foods, with regional and seasonal

variations occurring in their diet (Korschgen 1966). Animal foods, primarily

insects, are consumed in small quantities (4 to 5% of diet) by adults during

summer (Edminster 1954) and in large quantities (50 to 75%) by chicks during

their first few weeks of life (Bump et al. 1947; Edminster 1954). Insects

decrease in importance in the diet of chicks throughout summer, and by August

their diet is similar to adults, consisting primarily of plant foods (Stewart

1956). Kimmel and Samuel (1984) studied the foraging behavior of ruffed

grouse chicks imprinted on humans. The diet of chicks up to 3 weeks of age

was> 90% invertebrates; plant parts were not predominant until chicks were 8

weeks old.

In regions where snow cover is continuous throughout winter (e.g.,

northern New England and New York, Great Lakes States, Canada, Alaska, and the

Rocky Mountains), the winter diet of ruffed grouse is comprised of buds and

catkins of hardwood shrubs and trees (Bump et al. 1947; Gullion and Svoboda

1972; Johnsgard 1973). The staminate flower buds of aspens (Populus spp.),

especially quaking aspen (P. tremuloides), are the critical winter food

resource in Minnesota (Svoboda and Gullion 1972). A single mature male quaking

aspen in Minnesota provides 8 to 9 days of food for one grouse. Aspens are an

important wi nter food throughout much of the range of ruffed grouse (Brown

1946; Phillips 1967; Schemnitz 1970; Doerr et al. 1974; Gullion 1977, 1981;

Kubisiak et al. 1980; Stoll et al. 1980; Schulz et al. 1983).

1
Other hardwood species also are used, especially when aspens are not

predominant. Willow (Salix spp.) and aspen were 29 and 35%, respectively, of

the total winter food----vofume consumed by ruffed grouse in Alberta (Doerr

et a 1. 1974). Wi 11 ow buds and twi gs were 34% and aspen buds and twi gs were

55% of the dry weight of food in crops of ruffed grouse collected in interior

Alaska during winter (McGowan 1973). Ruffed grouse in central New York

preferred buds of black cherry (Prunus serotina) and apple (Malus pumila) to

those of aspen (Woehr and Chambers 1975). Winter foods of ruffed grouse in

northeastern Ohio included buds of black cherry, hawthorn (Crataegus spp.),

and hophornbeam (Ostrya virginiana), as well as aspen (Stoll et al. 1980).

Buds and catkins of trees continue to provide food for ruffed grouse into the

spring breeding season (Edminster 1954; Gullion and Svoboda 1972).

In regions where snow cover during winter is minimal or of short duration

(e.g., Pacific coast, southern Ohio, Indiana, Illinois, southern Appalachians),

the winter diet of ruffed grouse is more variable, including buds, fruits, and

leaves from a variety of understory shrubs and herbaceous plants, as well as

buds and fruits from trees (Korschgen 1966; Johnsgard 1973). Ruffed grouse in

western Washington fed on buds and catkins of black cottonwoods (Populus

trichocarpa) and leaves of buttercups (Ranunculus spp.) during winter (Brewer

1980). Acorns (Quercus spp.) and hophornbeam catkins were pri nci pa 1 wi nter

foods of ruffed grouse in Mi ssouri (Korschgen 1966). Frui ts of sumac (Rhus

spp.), bittersweet (Celastrus scandens), poison ivy (Toxicodendron radica~

greenbrier (Smilax spp.), and dogwood (Cornus spp.), in addition to buds of

hawthorn, aspen, and hophornbeam, were used by ruffed grouse in central and

southern Ohio (Stoll et al. 1980). Gilfillan and Bezdek (1944) also noted the

importance of understory species as winter food for ruffed grouse in Ohio.

Greenbrier, mountain laurel (Kalmia latifolia), Christmas fern (Polystichum

acrostichoides), Japanese honeysuckle (Lonicera japonica), and dogwood were

important wi nter food items in eastern Tennessee and western North Carol ina

(Stafford and Dimmick 1975). Soft and hard fruits from a variety of shrubs

and trees were eaten by ruffed grouse in southwestern Virginia (Norman and

Kirkpatrick 1984).

Summer foods include numerous fruits, berries, green vegetation, and

insects (Bump et al. 1947; Edminster 1954; Korschgen 1966). Ruffed grouse

feed on a great variety of berries, herbaceous vegetation, and leaves, buds,

and fruits of hardwood trees and shrubs during fall when potential food items

are most abundant (Gullion 1966). Hungerford (1957) reported extensive use of

insects and limited use of western redcedar (Thuja plicata) leaves during fall

in northern Idaho.

Water

Most grouse foods contain considerable moisture (Johnsgard 1973), and it

is unlikely that ruffed grouse require free water for drinking. When grouse

are found near water, it is because they prefer the food or cover associ ated

with mesic habitats and not because of a dependence on free water (Edminster

1954).

2
Cover/Reproduction

Cover sui tab1e for drummi ng grouse duri ng spri ng is sui tab1e fall and

winter cover (Berner and Gysel 1969; Gullion 1977), and suitable fall to

spring cover for males also is suitable for females (Gullion 1967, cited by

Moulton 1968). Females with broods prefer habitats similar to those preferred

by drumming males (Berner and Gysel 1969; Porath and Vohs 1972; Kubisiak

1978).

The seasonal requirements of ruffed grouse are met by a combination of

different cover types or age classes of forest (Bump et al. 1947; Gullion and

Svoboda 1972; Gullion 1977). Ruffed grouse are associated principally with

deciduous hardwood forests (Bump et al. 1947; Edminster 1954; Johnsgard 1973),

especially those with aspen as a dominant species (Gullion and Svoboda 1972).

However, hardwood trees are absent from some regions inhabited by ruffed

grouse, e.g., northern Idaho (Hungerford 1951), and conifers are used for

winter and escape cover in many regions (Bump et al. 1947; Edminster 1947;

Lewis et al. 1968; Woehr 1974; Stoll et al. 1977).

Although the relationship between ruffed grouse and the distribution of

aspens is not obligatory, ruffed grouse achieve their greatest abundance in

northern regions where aspens, especially quaking aspen, are a dominant component of the forest (Gullion and Svoboda 1972; Gullion 1977, 1984a). Optimal

aspen cover supports 20 to 40 drumming males/100 ha during peak populations.

Maximum densities are usually lower, ranging from 2 to 8 males/100 ha, in the

peripheral range of ruffed grouse, where aspen often is unavailable (Table 1).

Ruffed grouse males typically drum from a fallen log although other

objects also are used (Bump et al. 1947; Sousa 1978). An acceptable drumming

log provides sufficient height to allow a view of the surroundings and a

relatively level stage (Boag and Sumanik 1969). Throughout their range,

ruffed grouse prefer drumming sites that are surrounded by a moderate density

of woody stems (Table 2), especially in the tall shrub or sapling layers

(Pa 1mer 1963; Boag and Suman i k 1969; Gull ion 1970; Woehr 1974; Ti tus 1976;

Salo 1978; Kelly and Major 1979, cited by Backs 1984; Stoll et al. 1979;

Brewer 1980; Kubisiak et al. 1980; Stauffer 1983; Hunyadi 1984). The

importance of stem density to habitat suitabil ity for drumming grouse was

confirmed by an experimental removal of woody stems < 5 cm dbh from a 0.005-ha

circle surrounding each of 32 primary drumming logs in southwestern Al be r t a

(Boag 1976a). Occupancy rates and recruitment of males were lower at treatment

sites than at 32 control logs, and occupancy of secondary drumming logs was

greater in activity centers associated with treatment than with control logs.

No preference for high stem densities was observed in northern Georgia (Hale

et al. 1982) and Vermont (Sousa 1978), however, and ruffed grouse in central

Alberta preferred drumming sites with lower densities of stems < 10.2 cm dbh

and greater densities of stems> 10.2 cm dbh (Rusch and Keith 1971).

Suitabl e drummi ng cover at the Cloquet Forestry Center in Mi nnesota

occurs when 8 to 12-year old aspen stands have thinned to < 19,800 stems/ha

(Gullion and Svoboda 1972). Cover suitability increases with natural thinning

3
Table 1. Densities of breeding male ruffed grouse throughout their range (values converted to males/IOO ha).

Breeding

males/lOO ha a

Max Min Loca t i on Per i od General habitatb Reference

..:::.

41.7

35.7

22.2

15.8

14.7

14.0

10.4

10.1

10.1

7.8

7.2

6.9

20.5

10.7

12.3

5.6

5.7

2.5

1.0

2.7

4.6

0.0

2.7

Minnesota: Cloquet Forestry Center

Wisconsin: Sandhil I Wi Idl ife Area

Central Alberta

New York: Connecticut Hi I I

Ontario: Algonquin Park

Minnesota: Cloquet Forestry Center

Michigan: Rifle River Area

Wisconsin: Sandhill Wildlife Area

Southwestern Alberta

Minnesota: Cloquet Forestry Center

Indiana: Maumee Grouse Study Area

Northeastern Iowa

1959-77

1968-77

1966-68

1930-42

1971-82

1959-82

1950-58

1968-77

1965-75

1959-82

1969-73,

1975-83

1967

10-25 yea r aspen

Aspen-alder

Aspen

AI Iegheny and

no rthe rn ha rdwoods with

con ifers

Mixed coniferaspen, sugar maple-hemlock

Aspen, no rthe rn ha r-dwoods , with

some con ife rs

Mixed conifer,

no rthe rn ha rdwoods, aspen, alder

Aspen and oak

Aspen, ba I sam

poplar, white

spruce

Pine, spruce-fir, with some aspen

Oak

Maple-basswood, oak-hickory,

aspen

Gull ion (1977)

Kubi s ia k e t a I. (1980)

Rusc~ and Keith (1971)

Bump et a l . (1947)

Theberge and Gauthier

(1982)

Gull ion and Aim (1983)

Palmer and Bennett (1963)

Kubisiak et a l , (1980)

Boag (1 976a )

Gu I I i on a nd AI m (1983)

Backs (1984)

Porath and Vohs (1972)
Breed i ng

rna les/l00 ha a

Max Mi n

Table 1.

Location

(concluded).

Pe r i od General habitatb Reference

6.2

6.2

6.1

4.6

(Jl

4.4

3.9

2.6

2.6

5.5

2.8

3.2

1.8

1.2

1.8

Western Washington

Southeastern Ohio

New York: Adirondack area

Missouri: Ashland Area and Daniel

Boone Forest

Wisconsin: Stone Lake Experimental Area

Southeastern Idaho: Wasatch Mountains

Northern Georg ia

Vermont: Grafton

1977-79

5 yea rs

1932-38

1963-83

1968-77

1979-82

1976-79

1975

Black cottonwood,

red alder,

western hemlock

Oak-hickory, beech-maple,

pine

Mixed conifers,

northern hardwoods

Oak-hickory,

sugar maple, hopho rnbeam

Balsam fir, aspen

Aspen, mixed

con ife r

Oak-hickory, yellow poplar, pine

Maple, beech,

yellow birch,

mixed conifers

Brewe r (1980)

Stoll e t a l , (1973)

Bump et a I. (1947)

Hunyad i (1984)

Kub i s ia k et a I. (1980)

Stauffer (1983)

Hale et al. (1982)

Sousa (1978)

aAI I estimates based on counts of drumming males except Stauffer (1983) which was a subjective estimate.

bcommon and scientific names of plants not mentioned in text: balsam poplar (Populus balsamifera); basswood (~ americana); beech (Fagus grandifol ia); hemlock (Tsuga canadensis); hickory (Carya spp.); red alder (Alnus rubra);

sugar maple (Acer saccharum); western hemlock (Tsuga heterophylla); yel low birch (Betula al leghaniensis); and

yel low poplar (Liriodendron tul ipifera).
Table 2. Stem densities at ruffed grouse drumming sites (values

converted to stems/ha).

Location Size category Stems/ha Comments Reference

Minnesota: Cloquet Aspen > 0.6 m ta 11 4,900-14,800 Optimal 13-25 Gullion (1970, 1977)

Forestry Center year aspen

Wisconsin: Sandhi11 > 1. 8 m ta 11 4,400-14,800 Optimal 6-25 Kubisiak (pers. comm.)

Wil dl ife Area year aspen

Central Alberta Shrubs> 0.9 m tall

Trees < 10.2 cm dbh

Trees> 10.2 cm dbh

8,545ns

3,815a***

b*** 850

Means for 67 Rusch and Keith (1971)

drumming sites

compared with

163 random

stations

New York: Tug Hill < 30 cm tall a*** 975

Plateau > 30 cm tall to 1. 25 cm dbh 17,575ns

2.5 cm dbh 7,712b***

5.0 cm dbh 912ns

7.5 cm dbh 350a**

> 10.0 cm dbh 480ns

Ontario: Algonquin < 10 cm dbh 2,872 and

Park 3,980ns

Means for

drummi nq sites

compared with

avail ab1e

habitat

Means for 2

areas with

different grouse

densities

Woehr (1974)

Theberge and Gauthier

(1982)

Michigan: Rifle

River Area

< 0.6 m tall

O.6-1. 5 m ta 11

1. 5- 2. 4 m ta 11

> 2. 4 m ta 11 to

7.6 cm dbh

7.6-15.2 cm dbh

15.2-22.9 cm dbh

> 22.9 cm dbh

31,849a**

13,289ns

4,776ns

8,401b***

1, 181 b**

138b**

109

Means for Palmer (1963)

habitat within

10.1 m

radius of 40

drumming logs

compared with

habitat 10.1 to

20.1 m distant

Southwestern Alberta < 1.0 m tall

> 1.0 m tall to 5 em dbh

5-10 cm dbh

10-20 cm dbh

> 20 cm dbh

2,120b

4, nob

2, nob

620a

140b

Means for 80 Boag and Sumanik (1969)

drumming logs

compared with

98 unused logs

Indiana < 13 cm dbh 35,000b***

6

Means for 64

drumming logs

compared with

unused logs

Kelly and Major (1979,

cited by Backs 1984)
Table 2. (concluded).

Location Size category Stems/ha Comments Reference

Western Washington > 0.2 m tall 21,592b** ~~eans for 25 Brewer (1980)

drumming logs

compared with

26 unused logs

Southeastern Ohio < 1. 0 m ta 11 80,060ns Means for 30 Stolletal. (1979)

> 1.0 m tall to 2.5 em dbh 16,803b*** perennial logs

2.6-5.1 em dbh 1,977b*** compared with

5.2-10.2 em dbh 988ns 27 transient

centers

Missouri: Monkey Mt. > 1.0 m tall 15,296b ~·1eans for Hunyadi (1984)

and Anderson 13,412b drumming logs

Wi 1dl ife Areas, 11,760b at 3 areas

Boone Forest compared with

available

habitat

Southeastern Idaho < 7 em dbh 8,509b* ~~eans for 19 Stauffer (1983)

7-15 em dbh 494ns drumming logs

15-23 em dbh 174ns compared with

> 23 em dbh lOOns 19 unused logs

Northern Georgia < 0.5 m tall 120,000ns Means for 14 Hale et al. (1982)

> 0.5 m tall to 10 em dbh 14,000ns drumming logs

> 10 em dbh 556ns compared with

14 unused logs

Vermont: Grafton < 2.5 em dbh 941-5,651ns Densities for Sousa (1978)

2.5-12.7 em dbh 2,063-6,098ns 5 drumming logs

> 12.7 em dbh 494-941ns compared with

available habitat in stands

aMean less than mean for available habitat or unused logs.

bMean greater than mean for available habitat or unused log.

nsp > 0.10

*p < 0.10

**p < 0.05

***p < 0.01

7
and increasing height of stems associated with maturation of a stand (Gullion

and Svoboda 1972; Gullion 1977). Optimal drumming cover occurs in 13 to

25-year old aspen stands with a stem density of 4,900 to 14,800/ha (Gull ion

1970:Fig.3) and a closed canopy about 10 m overhead (Gullion and Svoboda

1972; Gull ion 1977). The habi tat has "qone-by" and rather abruptly ceases to

support drumming grouse when stem densities decrease to < 4,900/ha (Gullion

and Svoboda 1972; Gullion 1977). Aspen in central Wisconsin initially are

occupied when stands are < 5 years of age and have maximum stem densities of

19,800/ha (Kubisiak et al. 1980; Kubisiak 1985; Kubisiak pers. comm.). Optimal

drumming cover is provided by 6 to 25 year old aspen stands having densities

of woody stems> 1.8 m tall from 4,400 to 14,800/ha and a canopy height 4.6 m

(Kubisiak pers. comm.).

The age when a tree stand initially provides suitable habitat for ruffed

grouse and length of time that it remains suitable habitat will be affected by

growth rates of plants providing cover, and this varies among species and

growing site environments (Gullion 1984b). Mature hardwood tree stands that

have thinned below suitable tree densities continue to provide suitable cover

if there is sufficient density and height of woody shrubs in the understory

(Kubisiak et al. 1980; Gullion 1984a). Shrubs> 0.9 m in height provide

suitable cover when there are 80 to 200 stems within a 3.0 to 3.7 m radius of

the drumming stage (Gullion 1972, cited by Boag 1976a), equivalent to densities

of 19,000 to 68,700/ha. However, shrubs need to be > 1.5 m tall to provide

suitable overhead cover (Kubisiak 1985; Gullion pers. comm.). Forty-three of

112 drumming sites located by Salo (1978) in western Washington were in dense

thickets (300,000 stems> 2.5 m tall/ha) of salmonberry (Rubus spectabilis) in

the understory of mature, open canopy forests.

Optimal drumming habitat provides cover for ruffed grouse and even stem

spac i ng which allows them to rna i nta in effective survei 11 ance for predators

(Gullion and Svoboda 1972; Gullion 1977). This is referred to as vertical

cover. Preferred habitats provide optimal cover across the major portion of

an acti vi ty center and not just immedi ate ly surroundi ng the drummi ng log

(Gullion and Marshall 1968; Gullion 1984b). Grouse territories that include

several suitable alternate drumming sites are more likely to be occupied for

extended peri ods (perenn i a1 use) than territori es without sui tab1e alternate

drumming sites (Boag 1976b). Mid-seral aspen stands provide optimal vertical

cover during fall through spring and suitable snow conditions for snow-burrow

roosting during winter (Gullion and Svoboda 1972).

Conifers can be detrimental to survival of ruffed grouse in drumming

habitats (Gullion and Marshall 1968; Gullion 1970; Rusch and Keith 1971),

because low-growing conifers provide concealment for mammalian predators, and

the "h i qh pi ne" conifers provide concealment and excellent opportunities for

raptors to ambush grouse. Gullion and Marshall (1968) attributed 86% of

ruffed grouse kills at Cloquet, Minnesota to raptor predation. Maximum grouse

densities during peak populations at Cloquet (Table 1) were twice as high in a

predominantly hardwood tract compared to a predominantly coniferous tract of

forest (Gullion and Alm 1983). Mean longevity and survival of ruffed grouse

also were greater in the predominantly hardwood forest tract. Maximum

densities of drumming males (7.5/100 ha) in balsam fir (Abies balsamea)

8
habitats at Stone Lake, Wisconsin were only 20% of maximum densities

(35.7/100 ha) in optimal aspen-alder (Alnus spp.) habitat at Sandhill,

Wisconsin (Kubisiak et al. 1980). The presence of conifers around drumming

sites in central Ontario was not considered detrimental to ruffed grouse

populations because avian predators were scarce (Theberge and Gauthier 1982).

Conifers provi de the only sui tab1e drummi ng or winter cover in some

regions, but densities of ruffed grouse are lower in these habitats than in

optimal aspen habitats (Table 1). Young white spruce (Picea glauca) < 10 cm

dbh provided drumming cover in mixed deciduous/coniferous forests in southwestern Alberta (Boag and Sumanik 1969), and young balsam fir in the understory

of mature aspen forests provided cover for drummi ng grouse at Stone Lake,

Wisconsin (Kubisiak et al. 1980). Conifers were considered important winter

cover in New York (Bump et al. 1947; Edminster 1947; Woehr 1974), Ohio (Stoll

et al. 1977), Indiana (Muehrcke and Kirkpatrick 1969), Missouri (Lewis et al.

1968), and Idaho (Hungerford 1951). Ruffed grouse in north-central Minnesota

preferred jack pine (Pinus banksiana) forests for cover during winter, a

habitat type also used~spruce grouse (Dendragapus canadensis) (Pietz and

Tester 1982). Ruffed grouse inhabiting the boreal forest region of New

Brunswick used spruce-fir and jack pine forests throughout the year (Keppie

pers. comm.). Conifers, especially fir and spruce with branches growing low

to the ground, provide important thermal cover for grouse in regions where

snow depths or snow conditions during winter limit snow-burrow roosting (Woehr

1974; Chambers pers. comm.; Keppie pers. comm.). More than 90% of winter

roosts in central New York were located in conifers duri ng two winters when

snow-burrow roosting was prohibited by wet or crusted snow on all but five

nights (Woehr 1974).

Ruffed grouse nests typically are located at the base of trees in open

hardwood stands although other sites are used, such as the base of stumps,

under slash, bushes, or brush piles (Bump et al. 1947; Edminster 1947). Aspen

stands in Minnesota with stem densities < 4,900/ha provide preferred nesting

cover (Gullion 1977), and nesting females feed extensively on emerging aspen

leaves and prefer to locate their nests close to mature aspens (Gull ion and

Svoboda 1972; Gullion 1977; Maxson 1978). Nearby undergrowth is usually

sparse (Bump et al. 1947; Gullion 1977).

Brood cover occurs in transition zones between lowland and upland forests

or forest edges and openings with a well-developed herbaceous and shrub understory (Bump et al. 1947; Edminster 1947; Sharp 1963; Porath and Vohs 1972;

Stauffer 1983). Optimal brood habitat in Minnesota occurs in regenerating

aspen stands with 12,400 to 29,000+ stems/ha (Gullion 1970, 1977). Most

upland aspen stands in Wisconsin can provide suitable brood habitat, but

optimal habitat occurs in 6 to 25 year old stands or where alder or other

equivalent cover exists (Kubisiak 1978).

Interspersion and Composition

Ruffed grouse are not migratory, but they will move short distances among

different seasonal habitats (Johnsgard 1973). Optimal interspersion of cover

types occurs when all seasonal habitat requirements are contained within 4 ha

9
(Gullion and Svoboda 1972). In Minnesota, these seasonal requirements are met

by an interspersion of seedling (l to 12 years old), sapling (13 to 25 years

old), and mature (> 25 years old) aspen stands (Gull ion and Svoboda 1972).

Mature male aspen within 91 m of adequate fall to spring cover provide the

essential winter food source (Gullion 1977). Kubisiak et al. (1980) found 98%

of drumming sites in Wisconsin within 40 m of a mature aspen food source.

However, only 53% of drumming logs in southern Ohio were within 100 m of

mature aspen (Stoll et al. 1979).

Male ruffed grouse in Minnesota occupied an average of 8.9 ha from March

to June but occupi ed a reduced area of 6.7 ha duri ng the drummi ng season

(Archibald 1975). Females occupied areas of 16.5 ha, moving from lowlandupland edge in early spring to upland sites for nesting. Females gradually

reduce their movements from prelaying through incubation (Maxson 1978).

Occupied areas averaged 12.1 ha during prelaying, 8.4 ha during laying, and

0.9 ha during incubation. Females can move their broods up to 5.8 km to

suitable cover (Schladweiler 1965). The cruising radius of most broods,

however, is < 0.4 km (Chambers and Sharp 1958). Juveniles are more mobile

than adults during fall (Hale and Dorney 1963), and juvenile females disperse

farther than males (Godfrey and Marshall 1969).

Special Considerations

Ruffed grouse are associated with di sturbed forest habitats (Gull ion

1977). However, elimination of forest cover over an area> 4 ha results in

reduced breeding densities (Gullion 1970). Extensive areas of a single cover

type are not as valuable to ruffed grouse as the close interspersion of several

smaller cover types. Aspen regeneration 1 to 12 years old provides optimal

brood cover in Minnesota, aspen saplings 13 to 25 years old provide optimal

fall to spring (drumming) cover, and aspens> 25 years old provide an essential

winter food source and nesting habitat (Gullion and Svoboda 1972; Gul li on

1977). .

Small clearcuts (Edminster 1947; Stauffer 1983; Gullion 1984a) and burning

(Sharp 1970) can improve grouse habitat by maintaining an interspersion of

young through mature successional stages of forest. Grazing by 1ivestock can

adversely affect brood habitat (Robertson 1976; Stauffer 1983), extensive

timber harvesting reduces breeding densities, and lack of timber management

results in large tracts of mature forest that are unsuitable for ruffed grouse

(Gullion 1977).

Ruffed grouse occur sympatrically with spruce and/or blue grouse

(Dendragapus obscurus) throughout portions of their range (Aldrich 1963).

Ruffed and spruce grouse use the same winter habitats in north-central

Minnesota (Pietz and Tester 1982), and these two species use similar habitats

throughout much of the boreal forest (Keppie pers. comm.). Ruffed and blue

grouse in Idaho rarely use the same habitats even though they occupy the same

areas (Marshall 1946; Stauffer 1983); ruffed grouse occur in more mesic sites

with greater canopy cover. There is no evidence of competition between ruffed

and blue or spruce grouse (Pietz and Tester 1982; Stauffer 1983).

10
HABITAT SUITABILITY INDEX (HSI) MODEL

Model Applicability

Geographical area. This model is intended for application within the

region where aspen is a predominant component of the forest ecosystem. With

modifications, discussed under Application of the Model, it may be applicable

throughout the range of ruffed grouse.

Season. This model was developed to evaluate the year-round habitat of

the ruffed grouse.

Cover types. This model was developed to evaluate habitat suitability in

Deciduous and Evergreen Forest (OF, EF), Tree Savanna (DTS, ETS), and Shrubland

(OS, ES) cover types (U.S. Fish and Wildlife Service 1981). Further subdivision of these cover types is possible and is discussed on page 20 under

Application of the Model.

Minimum habitat area. Minimum habitat area is defined as the minimum

amount of contiguous sui tabl e habi tat that is requi red before an area will be

occupied by a particular species. This information was not found in the

literature for ruffed grouse. An activity center for an individual drumming

male can be as small as 2.4 ha (Gullion 1977), but a pair of grouse/4 ha is

about the highest density grouse population that can be expected under most

conditions (Gullion and Svoboda 1972). Therefore, this model should not be

applied on an area < 4 ha. Both Stoll (pers. comm.) and Chambers (pers.

comm.) recommended a minimum habitat area of 20 ha for isolated blocks of

forest surrounded by unsuitable grouse habitat, e.g., a farm woodlot surrounded

by cropland.

Verification level. This model was developed with the assistance of

Gordon W. Gullion, Project Leader of the University of Minnesota's Forest

Wildlife Project at the Cloquet Forestry Center, near Cloquet, Minnesota. The

variables in this model are based on Mr. Gullion's experience and long-term

data collected on the Cloquet Forest. In 1981, the U.S. Fish and Wildlife

Service contracted Mr. Gullion to provide habitat and grouse use data from 20

drumming logs, 20 4-ha activity centers surrounding the logs, and five blocks

of forested habitat ranging from 18.1 to 27.5 ha. These data (Cade 1984) were

used to refine variable relationships and suitability levels from earlier

drafts of the model.

Previous drafts of this model were also reviewed by:

David A. Boag, Professor, Department of Zoology, University of Alberta,

Edmonton, Alberta

Robert E. Chambers, Professor, Department of Env i ronmenta 1 and Forest

Biology, State University of New York, Syracuse, NY

Ralph W. Dimmick, Professor, Department of Forestry, Wildlife, and

Fisheries, University of Tennessee, Knoxville, TN

11
Daniel M. Keppie, Professor, Department of Forest Resources, University

of New Brunswick, Fredericton, New Brunswick

John F. Kubisiak, Project Leader, Forest Wildlife Research Group,

Wisconsin Department of Natural Resources, Babcock, WI

Keith R. McCaffery, Project Leader, Forest Wildlife Research Group,

Wisconsin Department of Natural Resources, Rhinelander, WI

Robert J. Stoll, Jr., Wildlife Biologist, Ohio Department of Natural

Resources, New Marshfield, OH

Specific comments from each reviewer were incorporated into the current model.

Boag (pers. comm.), Chambers (pers. comm.), Dimmick (pers. comm.), and Stoll

(pers. comm.) questioned whether it was possible to develop a single habitat

suitabil i ty model that woul d be app 1i cab1e throughout the range of ruffed

grouse. Modifications of this model that may increase its usefulness in

various regions are discussed under Application of the Model.

Model Description

Overview. Optimal habitat for ruffed grouse is provided by the interspersion of several forest age classes. The ruffed grouse is considered in

this model to be a multicover type species, using different age classes of

forests. Winter Food and Fall to Spring Cover are the life requisites considered in this model and are assumed to be the same for both male and female

grouse. It is assumed that water is not a limiting factor for ruffed grouse

populations. Nesting and brood-rearing habitat are assumed to never be more

limiting than winter food and fall to spring cover requirements.

The following sections identify important habitat variables used in the

model, describe suitability levels of the variables, and describe the relationships among variables.

Winter food component. Optimal winter food for ruffed grouse is provided

by the flower buds of mature male aspens (Svoboda and Gullion 1972; Gullion

1984a). Other plants also provide a winter food source, but they will be of

lower value and support fewer grouse than will mature male aspen. Svoboda and

Gullion (1972) estimated that one average mature male aspen would provide a

grouse with 8 to 9 days of food. Based on a 180 day winter (November-April),

one grouse would require 20 mature male aspen during winter (KUbisiak et al.

1980). Suitability of winter food will be determined by the interspersion of

mature male aspen and fall to spring cover. Optimal winter food is assumed to

exist when 20 mature male aspen are within 91 m of fall to spring cover

(Gull ion 1977). Suitabil ity of winter food is assumed to decrease as the

distance between 20 mature male aspen and fall to spring cover increases from

91 to 183 m. If there are < 20 mature male aspen within 183 m of fall to

spring cover, it is assumed that other deciduous shrubs and trees will provide

winter food but at a lower level of suitability. Because mature male aspens

can be clustered in clones or scattered throughout a stand, winter food suitability is measured as the average radius of circles encompassing 20 mature

12
male aspen (Fig. 1), i.e., the distance to the 20th mature male aspen from a

sampling point. This distance relationship is used whether suitable

wi nter food and fall to spri ng cover occur in the same or di fferent cover

types (stands).

1.0 ......

:>

.....

V) 0.8

x

OJ

-0 0.6 t:

.....

>,

+J 0.4 ......

......

..0

ttl 0.2 +J

......

:::l

V) 0.0

e 61 122 183 244 + m

0 200 400 600 800 +ft

Average radius of circles

encompassing 20 mature male

aspens

Figure 1. The relationship between the average radius of circles

encompassing 20 mature male aspen and suitability indices for winter

food.

Fa11 to spri ng cover component. Fall to spri ng cover is a function of

the degree of obstruction provided by woody vegetation and is dependent upon

density, height, and growth form of woody stems. Dense hardwood stems (trees

or shrubs) provide physical obstruction to predators as well as a high level

of visibility for the grouse (vertical cover). Coniferous stems also provide

physical obstruction to predators but may restrict visibility for ruffed

grouse. Overhead cover is provi ded by sui tab1e dens i ty and hei ght of plant

growth forms providing vertical cover.

Vert i ca 1 cover may be provi ded by deci duous shrubs, deci duous trees,

coniferous trees, or by a mixture of these forms. Trees are defined in this

model as woody plants having a single, erect stem originating from a single

base at the ground, and shrubs are defined as woody plants having multiple,

erect stems originating from a single base at the ground. The difference

13
between deciduous trees and deciduous shrubs is even spacing versus clumping

of erect stems. Thi s differs from the practice of using stem hei ght to

differentiate trees and shrubs, as defined by the U.S. Fish and Wildlife

Service (1981) for other HSI models. It is assumed that a certain amount of

physical obstruction (vertical cover) is necessary to provide optimal fall to

spring cover for ruffed grouse. Cover provided by deciduous trees (especially

aspens) has been most thoroughly studied and forms the basis for comparing

cover provided by woody vegetation of various growth forms.

Stem densities of deciduous trees ranging from 4,900 to 14,800 stems/ha

are considered to be optimum (Gullion 1970). Stem densities of deciduous

trees 5 4,400 stems/ha are considered too sparse to provide vertical cover,

and densities 21,000 stems/ha are considered too dense to provide suitable

verti ca 1 cover because mobil ity and vi sibil ity for ruffed grouse will be

restricted. Because the growth form of deciduous trees differs considerably

from that of deciduous shrubs and conifers, it is necessary to convert shrub

and conifer stem densities to an equivalent stem density value in order to

compare various growth forms. Equivalent stem density is defined as the

number of stems of deciduous shrubs or conifers that will provide the

equivalent amount of cover provided by one deciduous tree.

The typical growth form of deciduous shrubs [e.g., beaked hazel (Corylus

cornuta)] is that of a woody plant with multiple, clumped, narrow stems

« 2.5 cm dbh). It is assumed in this model that, on the average, four typical

deciduous shrub stems 0.9 m in height will occupy the space and provide

equivalent density of vertical cover as one deciduous tree (Gullion pers.

comm.). The equivalent stem density coefficient for deciduous shrubs 0.9 m

in height, therefore, is 0.25. Shrubs < 0.9 m in height are assumed to be too

short to provide any vertical cover.

The growth form of conifers is that of a woody plant with a dense, wide

crown. Because of this growth form, it is assumed that one typical conifer

with a low crown hei ght (hei ght to the lowest 1ive branch) between 0.0 and

0.9 m above ground provides the same amount of vertical cover (i .e., physical

obstruction) as provided by four deciduous trees. As the low crown height of

conifers increases from 0.9 to 4.6 m, the equivalent cover provided by conifers

decreases from four times the cover provided by one deciduous tree to a value

equal to the cover provided by one deciduous tree. Vertical cover will be

provided only by the trunk and not the branches of conifers when lowest branch

heights are 4.6 m. This relationship is shown in Figure 2a.

14
Ul Fig. 2a Fig. 2b +-'

e

QJ

...... 4.0 1.0 U M

:::- '+- ...... '+- (/') 0.8

QJ

0'--"

UN X :::- 3.0 QJ

Em -0 0.6

QJ- e +-' ...... l/ll/ls; >,

+-'QJ +-' 0.4

e'+-

QJ ...... 2.0 r-r- e ro 0 ..0 > U ro 0.2 +-' s, c:ro

W'+- 1.0 (/') 0.0

0 1.5 3.0 4.6 + m 0.0 4.9 9.9 14.8 19.8 24.7 / ha

0 5.0 10.0 15.0 + ft 0.0 2.0 4.0 6.0 8.0 10.0 / acre

Average lowest-branch height Total equivalent stem density of conifers in thousands of stems

Figure 2. The relationship between lowest-branch height of conifers and

equivalent stem density coefficients for conifers (2a) and between total

equivalent stem density and suitability indices for vertical cover (2b).

Total equivalent stem density can be determined by Equation 1:

Total equivalent stem density =d + 0.25s + ~V2c (1)

where d = number of deciduous trees/ha

s = number of deciduous shrub stems/ha

c = number of coniferous trees/ha

~V2 = equivalent stem density coefficient for conifers

15
The relationship between habitat suitability and total equivalent stem density

is the same as that previously described for deciduous trees and is depicted

in Figure 2b.

The suitabi 1i ty of vert i ca1 cover for ruffed grouse is determi ned by

total equivalent stem density and height of woody stems providing cover.

Woody stems 4.6 m in height provide optimal suitability for overhead cover

(Kubisiak pers. comm.). Suitability decreases when woody stems are < 4.6 m in

height, and woody stems s 1.5 m in height do not provide suitable overhead

cover (Gullion pers. comm.; Kubisiak pers. comm.) (Fig. 3). The relationship

between stem height and suitability is assumed to be the same for all three

woody growth forms that may provide vertical cover.

1.0

<;;j-

>-

.......

(/) 0.8

x

(])

"0 0.6 I::

.......

0.4

......

..c

co 0.2

+>

......

::::l

(/) 0.0

0.0 1.5 3.0 4.6 6.1 + m

0.0 5.0 10.0 15.0 20.0 + ft

Average height of woody stems

Figure 3. The relationship between woody stem heights and

suitability indices for height of vertical cover.

During secondary succession of deciduous forests, suitability of vertical

cover for ruffed grouse will increase as total equivalent stem density

decreases from 21,000 to 14,800 stems/ha and stem heights increase to 4.6 m.

Most aspen stems will have grown to optimal heights (~4.6 m) when an aspen

stand has matured and thinned to optimal total equivalent stem densities

(4,900 to 14,800 stems/ha) (Kubisiak pers. comm.). As an aspen stand continues

to mature and thi ns to s 4,400 tree stems/ha, habi tat suitabil ity wi 11 also

depend upon the density and height of understory woody shrubs or conifers

(Kubisiak et al. 1980; Gullion 1984a).

16
SUitability of vertical cover height is assumed to be optimum if there

are a minimum of 4,900 equivalent stems/ha at optimal heights (i.e., 4.6 m).

When this minimum height/density relationship is met, additional stems at

either suboptimal or optimal heights will not alter the suitability of vertical

cover height. Therefore, suitability of vertical cover height is evaluated

for the 4,900 equivalent stems/ha having highest suitability for stem height

(SIV4) and may include any single or combination of woody growth forms. If

total equivalent stem density is > 4,900/ha, then a weighted SIV4 is determined

by considering equivalent stems by growth form beginning with the most suitable

growth form (i. e., havi ng hi ghest SIV4) and conti nui ng until exactly 4,900

equivalent stems/ha are included in Equation 2:

3

Weighted SIV4 =i:1 [SIV4i x

(equivalent stems/ha)i]

4,900/ha (2)

where = 1, 2, and 3 are different woody growth forms (i .e., deciduous

shrubs, deciduous trees, or coniferous trees) such that

3

SIV4 1 SIV4 2 SIV4], and L (equivalent stems/ha)i = 4,900/ha

i=1

If the growth form with the highest SIV4 (SIV41 ) has> 4,900 equivalent

stems/ha, then the weighted SIV4 equals SIV4 1 • If growth form 1 has < 4,900

equivalent stems/ha, then the maximum number of equivalent stems/ha that can

be entered for growth form 2 equals 4,900 minus the number of stems for growth

form 1. If the sum of equivalent stems/ha for growth forms 1 and 2 is < 4,900

stems/ha, then the maximum number of equivalent stems/ha that can be entered

for growth form 3 equals 4,900 minus the sum of equivalent stems/ha for growth

forms 1 and 2. For example: A cover type has 800 deciduous trees/ha with an

average height of 10.0 m (SIV4 = 1.0), 20,000 deciduous shrubs/ha with an

average height of 2.4 m (SIV4 = 0.3), and 200 conifers/ha with an average

height of 3.0 m (SIV4 = 0.5) and average low-branch height of 0.5 m (~V2 = 4.0). There are 800 equivalent stems of deciduous trees, 5,000 equivalent stems of deciduous shrubs, and 800 equivalent stems for conifers.

Therefore, the weighted SIV4 = [(1.0 x 800) + (0.5 x 800) + (0.3 x 3,300))/

4,900 = 0.447. Note that 3,300, rather than 5,000, equivalent shrub stems are

entered in the weighted SIV4 making the sum of the equi va1ent stems (800 +

800 + 3,300) equal to 4,900/ha.

If total equivalent stem density is 4,900 stems/ha, the weighted SIV4

can be determined using equation 2, but without any restrictions on the order

that growth forms are entered or that their equivalent stem densities sum to

4,900/ha.

17
Tall conifers provide concealment for raptors which prey upon ruffed

grouse, and coni fers wi th low branches provi de concealment for mammal ian

predators. Maximum densities and survival of ruffed grouse are lower in

forests where conifers are the predominant trees (Gullion and Marshall 1968;

Kubisiak et al. 1980; Gullion and Alm 1983). An area that provides optimal

equivalent stem density and height of vertical cover for ruffed grouse but has

only conifers in the tree strata is assumed to provide only 25% of the optimal

fall to spring cover value. Similarly, the presence of any conifers in an

otherwise suitable habitat will reduce suitability of fall to spring cover

because of the additional concealment for predators provided by conifers. The

recommended relationship is presented in Equation 3:

conifer penalty =[~x c d)+ 1]-1 (3)

where c =number of coniferous trees/ha

d = number of deciduous trees/ha

This equation represents a curvilinear relationship (Ft q . 4) that reduces

suitability at a more rapid rate with a low percentage of conifers and at a

less rapid rate with higher percentages of conifers. Cover suitability is

assumed to decline quickly with a small percentage of conifers which can

conceal raptors. However, cover suitability decreases at a lower rate with

increasing percentage of conifers, because it is unlikely that there will be a

proportional increase in predation opportunities with increasing percentage of

conifers.

LO

:>

......

(/) 0.8

x

OJ

"'0 0.6 s::

......

>,

.....

+-' 0.4

0""

..0

rt:l 0.2

+-'

:::::l

(/) 0.0

0 20 40 60 80 100

Percent coni fers

Figure 4. The relationship between percent coniferous trees and

the suitability index for the conifer penalty.

18
Fall to spring cover can be summarized as follows:

1. Vertical cover can be provided by deciduous trees, coniferous trees,

deciduous shrubs, or any combination of these growth forms.

2. A certain amount of physical obstruction (stem density) is necessary

to provide suitable vertical cover. The equivalent of one deciduous

tree is assumed to be four deci duous shrub stems and 0.25 to one

coniferous tree, depending on the low crown height. Total equivalent

stem density is determined based on these assumed relationships.

3. Suitability of vertical cover also depends upon the height of woody

stems providing vertical cover density. However, not all stems need

to have suitable heights for vertical cover height to be optimum.

4. As the percentage of cover provided by coniferous trees increases,

the suitabi 1ity of the habitat for ruffed grouse decreases due to

increased concealment for predators. If conifers provide the only

tree cover, then the maximum value for fall to spring cover will be

0.25, or 25% of the potential of sites with only deciduous trees.

Fall to spring cover value is a function of the suitability of total

equivalent stem density (S1V3, Fig. 2b) modified by the weighted suitability

of the heights of woody stems (Fig. 3, Equation 2), and further modified by

the suitability of the percentage of trees that are conifers (S1V5, Fig. 4).

This model evaluates cover for ruffed grouse based on vertical cover suitability modified by predator concealment suitability. Equation 4 is recommended

for determining the suitability of Fall to Spring Cover (FSCOV):

FSCOV = S1V3 x Weighted S1V4 x S1V5 (4)

This equation allows either unsuitable (S1 = 0.0) total equivalent stem

density or unsuitable height of woody stems to produce unsuitable Fall to

Spring Cover. Because none of the variables are considered compensatory and

each directly modifies the suitability of the others, suboptimal suitabilities

for two or three variables yield a suitability index for Fall to Spring Cover

that is lower than the lowest individual suitability index for the variables.

HSl determinations. Calculation of an HS1 for a multicover type species

involves consideration of both the suitability and the interspersion of life

requisites. However, the interspersion of life requisites is incorporated in

the Winter Food variable (S1V1, Fig. 1) in this model. Several steps and

calculations are necessary to determine an overall HS1 for a study area:

1. Compute life requisite values for each cover type by collecting

field data for each variable, entering this data into the proper

equat ion, coeffi ci ent curve, or sui tabi 1i ty curve, and using the

resulting index values in the appropriate life requisite equations.

19
2. The HSI for a cover type equals the lower of the values for Fall to

Spring Cover and Winter Food.

3. Determine the weighted HSI score for each cover type by multiplying

the area of each cover type by its corresponding HSI value (from 2

above) .

4. The overall HSI for a study area is equal to the sum of the weighted

HSI scores (from 3 above) divided by the total area of all cover

types potentially used by ruffed grouse in the study area.

Application of the Model

Summary of model variables. Seven habitat variables must be sampled to

evaluate Fall to Spring Cover for ruffed grouse; one habitat variable is used

to evaluate Winter Food (Fig. 5). Definitions of habitat variables and

suggested field measurement techniques (Hays et al. 1981) are provided in

Figure 6. In order to obtain an HSI for the ruffed grouse using this model,

field data for habitat conditions (existing or future) must be measured or

estimated and mean habitat characteristics entered into the appropriate equations or suitability curves.

Fall to Spring Cover and Winter Food variables should be measured at the

same samp1i ng poi nts. Samp1i ng poi nts shoul d be stra t ifi ed by cover types or

individual timber stands. Stratifying samples by the most homogeneous units

possible will provide the greatest accuracy and precision for habitat and HSI

estimates. Individual timber stands are likely to be more homogeneous than

broad cover types, such as defined by the U.S. Fish and Wildlife Service

(1981). If U.S. Fish and Wildlife Service (1981) cover types are used, Forest

and Tree Savanna cover types can be subdivided into seedling (stems 2.5 cm

dbh), sapling (stems> 2.5 cm to 15.2 cm db~), and pole/mature (stems> 15.2 cm

dbh) classes to create more homogeneous groups. Failure to stratify samples

may result in a suitable Fall to Spring Cover rating for unsuitable grouse

habitat if structural characteristics of early and late successional forest

stands (both unsuitable Fall to Spring Cover) are averaged together, falsely

indicating the presence of suitable mid-seral conditions. This can occur

because the SI curve for total equivalent stem density (SIV3) is a non-linear

response function.

Model assumptions and modifications. The major assumptions in this model

are:

1. Winter food and fall to spring cover are the limiting requirements

for ruffed grouse populations.

2. Optimal winter food for ruffed grouse is provided by mature male

aspens.

3. Vertical cover for ruffed grouse is dependent on growth form, density

and height of woody stems.

20
Habitat variable Derived va ria b Ie Life requisite Cover type

Average radius of

circles encompassing Winter Food (SIV1)

20 mature male aspen

Average low-branch height of

conifers ( V2)

N

>-'

Stem density of deciduous

shrubs

Stem density of deciduous

trees

Stem density of coniferous

trees

Average height of deciduous

sh rubs

Average height of deciduous

trees

Average height of coniferous

trees

I Total equivalent

stem density (vert ica I cover

density - SIV3)

I Weighted height of ta Ilest 4,900

equivalent stems

( ve rt ica I cove r height-weighted

SIV4)

Fal I to Spring Cover

(SIV3 x weighted SIV4 x SIV5)

Deciduous

Eve rg reen

Deciduous

Savanna

Eve rg reen

Savanna

Deciduous

Evergreen

Forest} Fa rest

Tree

HSI

Tree

Shrub land

Shrub land

Stem density

trees

Stem density

trees

of deCidUOUS]------ Percent can ifers

(conifer penaltySIV5) of can ire rou s

Figure 5. Relationships of habitat variables, derived variables, life requisites,

and cover types to the habitat suitability index (HSI) for the ruffed grouse.
Variable (definition)

The average radius of circles

encompassing 20 mature male

aspen [staminate flower producing aspen (Gullion 1984a),

typically 25 years of age

and 15.2 cm (6 inches) dbh].

Density of deciduous shrub

stems [number/ha (2.471 acres)

of deciduous woody stems 0.9 m

(3.0 ft) tall growing with multiple,

clumped, erect stems emanating

from a common base at the ground].

Density of deciduous trees

[number/ha (2.471 acres) of

deciduous woody stems 0.9 m

(3.0 ft) tall growing with a

single, erect stem from the

ground].

Density of coniferous trees

[number/ha (2.471 acres) of

coniferous woody stems 0.9 m

(3.0 ft) tall growing with a

single, erect stem from the

ground].

Average lowest-branch height

above ground (measured to

lowest point on bottom of

branch) of conifers.

Average height of woody stems

(the average vertical distance

from the grounq to the top of

woody stems, measured separately

for deciduous shrubs, deciduous

trees, and conifers).

Cover types

DF,EF,DTS,

ETS,DS,ES

DF,EF,DTS,

ETS,DS,ES

DF,EF,DTS,

ETS,DS,ES

DF,EF,DTS,

ETS,DS,ES

DF,EF,DTS,

ETS,DS,ES

DF,EF,DTS,

ETS,DS,ES

Suggested techniques

Tape measure, optical

range finder, pacing

Quadrat count [variable

sized plots depending

upon the relative

density 0 f p1ant

r---growth forms (e.g.,

0.004 ha for abundant

growth forms and

0.04 ha for scarce

growth forms)]

Graduated rod

Graduated rod,

trigonometric

hypsometry

Figure 6. Definitions of habitat variables and suggested

measuring techniques.

22
4. Conifers provide vertical cover for ruffed grouse, but because they

also provide cover for predators that prey upon grouse, the net

effect of having conifers in ruffed grouse habitats is a reduction

in habitat suitability.

The primary model assumption identifies winter and the spring and fall

drummi ng peri ods as the 1imi t i ng seasons for ruffed grouse. A coro 11 ary to

thi s assumption is that nesting and brood reari ng requi rements wi 11 never be

more limiting than fall to spring requirements. This assumption might be

incorrect for ruffed grouse at the southern extreme of their range. Based on

observed low juvenile to adult ratios (1:1) during fall, Dimmick (pers. comm.)

suggests that nesting or brood rearing requirements limit fall populations of

ruffed grouse in Tennessee. This hypothesis has not been substantiated, but

users applying this model in the southern Appalachians should proceed with

caution. Boag (pers. comm.) suggests that 1i mit i ng factors change wi th the

abundance of ruffed grouse, and density of the birds during the breeding

season, through lack of space per se, is limiting for high density populations

of ruffed grouse. It is important to recognize that use of this model for

habitat assessment is inappropriate if conditions in the potential application

area differ from those assumed limiting in this model.

If a user feels that the primary assumption is valid for an identified

application, then the other three major assumptions must be addressed.

Modifications of these assumptions and specific assumptions described under

each component can be made if the user bel i eves that such modi fi cati on wi 11

better approximate conditions in the intended area of application. Users

should be aware that output from modified models will not be directly comparable with other applications employing this model in its unmodified form.

However, this has little consequence when a user desires to rank habitat

suitability according to availability of habitats within a limited geographical

area rather than according to availability on a continent-wide basis.

The second major assumption identifies mature male aspens as optimal

wi nter food for ruffed grouse. The importance of aspens as wi nter food for

ruffed grouse decreases in regions where winter snow cover is nonexistent or

of short duration (Gullion and Svoboda 1972). Aspens often are unavailable to

ruffed grouse in these regions. Other food items such as sumac, bittersweet,

poi son ivy, greenbri er, dogwood, and hophornbeam may need to be inc 1uded in

Variable 1 (Fig. 1) for model applications in Ohio, Indiana, and Illinois

(Stoll et al. 1980; Stoll pers. comm.). Likewise, mountain laurel, Christmas

fern, and honeysuckle may need to be included in Variable 1 for model applications in the southern Appalachian Mountains (Stafford and Dimmick 1979).

However, the amount of these food items required to support grouse over winter

has not been determined, and users will have to exercise their own discretion

when incorporating other food items in the Winter Food variable. Winter food

requirements of ruffed grouse in regions where winter-long snow cover does not

occur are sufficiently broad that winter food may not be limiting (Gullion

1984b), and Variable 1 can appropriately be deleted from the model for some

applications.

23
The third major assumption identifies density and height of woody stems

as important components of vertical cover for ruffed grouse. However, in some

ruffed grouse habitats in the southeastern states, vertical cover is provided

by an understory of Japanese honeysuckle vines or a branching, evergreen

canopy of mountain laurel and/or rhododendron (Rhododendron spp.) (Dimmick

pers. comm.). Actual stem densities are low in pole sized timber stands and

SIV3, consequently, would indicate unsuitable vertical cover. A vegetation

profile board (Hays et al. 1981) may provide a better measure of cover density

than stem density in habitats where vines are providing significant vertical

cover. Actual calibration of the suitability curve for Variable 3 to reflect

percent cover as measured by a vegetation profile board will have to be

determined by individual users.

The fourth major assumption identifies conifers as having an overall

negative impact on habitat suitability for ruffed grouse, because they provide

concealment for predators, especially raptors. Predation on ruffed grouse is

not always a significant decimating factor associated with coniferous habitats

(Theberge and Gauthier 1982; Chambers pers. comm.; Dimmick pers. comm.; Keppie

pers. comm.; Stoll pers. comm.). Furthermore, conifers with low-growing

branches (e. g., spruce and fi rs) may have greater cover value for ruffed

grouse than concealment value for raptors and should not be considered as

detrimental as "high pine" conifers (Gullion and Marshall 1968; Boag pers.

comm.; Chambers pers. comm.). Several modifications of the conifer penalty

(SIV5, Fig. 4) are possible to reflect these different assumptions. A user

can choose to eliminate the conifer penalty (SIV5) from the HSI equation for

Fall to Spring Cover, modify the conifer penalty (Equation 3) to include only

certain conifer species or growth forms (e.g., long-needled "high pines"), or

modify the conifer penalty to differentially weight the detrimental impacts of

conifer species or growth forms (e.g., weight spruce and fir as having 25% of

the negative impact of pines).

Conifers provide important thermal cover for ruffed grouse inhabiting

regions where winter snow cover is absent [e.g., Missouri (Lewis et al. 1968)]

or unsuitable for snow-burrow roosting [e.g., central New York (Woehr 1974)].

Snow-burrow roosting may represent the optimal solution for thermal regulation

by ruffed grouse, but wet or crusted snow condi t ions wi 11 prevent snow-burrow

roosting (Woehr 1974), increasing winter mortality of grouse (Dorney and Kabat

1960). Roosting in conifers may be the best alternative available to ruffed

grouse when snow-burrow roosting is impossible (Woehr 1974). Thus, conifers

may actually have an overall positive impact on habitat suitability for ruffed

grouse in regions where snow-burrow roosting is limited for extended periods,

even though predation losses also are high (Chambers pers. comm.; Keppie pers.

comm.). Chambers (pers. comm.) suggested that 15 to 30% conifer cover

represents optimal suitability for winter cover in northeastern habitats, with

sui tabil ity decreasi ng at ei ther lower or hi gher percentages of conifers.

Several clumps (0.1 to 0.2 ha in size) of conifers provide better cover than

either scattered or large, contiguous stands of conifers.

24
SOURCES OF OTHER MODELS

A dynamic linear model developed by Steinke (1975) attempts to maXlmlze

ruffed grouse numbers per unit area by simulating optimal production of the

winter food source, i.e., buds of mature male aspens. Maximum theoretical

grouse populations were achieved after 40 years by clearcutting and burning

hardwood forests to maintain mid-seral stages. Although cover and the

interspersion of cover and food were recognized as important factors for

ruffed grouse populations, they were not incorporated into St.e i nkel s (1975)

model, precluding evaluation of year-round habitat suitability for ruffed

grouse.

A pattern recognition (PATREC) model developed for ruffed grouse in

southeastern Idaho (Wi 1son 1983) uses condi tiona 1 probabi 1iti es wi th BayesI

Theorum to relate habitat patterns to a potential for having high (7.7 grouse/

100 hal and low (0.4 grouse/l00 hal density grouse populations. Probabilities

can be converted to indicate the relative number of grouse that a tract of

land can potentially support. No explanation was provided as to why the

selected variables might be related to habitat suitability and, thus, able to

differentiate between habitats supporting high and low density grouse populations. The lack of information relating model variables to habitat requirements of the ruffed grouse will make it difficult to adapt this model for

application outside of southeastern Idaho.

REFERENCES

Aldrich, J. W. 1963. Geographic orientation of American Tetraonidae. J.

Wildl. Manage. 27(4):529-545.

Archibald, H. L. 1975. Temporal patterns of spring space use by ruffed grouse.

J. Wildl. Manage. 39(3):472-481.

Backs, S. E. 1984. Ruffed grouse restoration in Indiana. Pages 37-58 in

W. L. Robinson, ed. Ruffed grouse management: state of the art in the

early 1980' s. North Central Sect., The Wildl. Soc. 181 pp.

Berner, A., and L. W. Gysel. 1969. Habitat analysis and management considerations for ruffed grouse for a multiple use area in Michigan. J. Wildl.

Manage. 33(4):769-778.

Boag, D. A. 1976a. The effect of shrub removal on occupancy of ruffed grouse

drumming sites. J. Wildl. Manage. 40(1):105-110.

1976b. Influence of changing grouse density and forest attributes

on the occupancy of a seri es of potentia 1 territori es by rna 1e- ruffed

grouse. Can. J. Zool. 54:1727-1736.

Personal communication (letters dated 30 October 1984 and 13 March

1985). Dept. Zool., Univ. Alberta, Edmonton, Alberta T6G 2E9.

25
Boag, D. A., and K. M. Sumanik. 1969. Characteristics of drumming sites

selected by ruffed grouse in Alberta. J. Wildl. Manage. 33(4):621-628.

Brewer, L. W. 1980. The ruffed grouse in western Washington. Washington

State Dept. Game, Biol. Bull .16. 102 pp.

Brown, C. P. 1946. Food of Maine ruffed grouse by seasons and cover types.

J. Wildl. Manage. 10(1):17-28.

Bump, G., R. W. Darrow, F. C. Edminster, and W. F. Crissey. 1947. The ruffed

grouse: life history, propagation, management. New York State Conserv.

Dept. 915 pp.

Cade, B. S. 1984. Results of a field test of an HSI model for ruffed grouse.

U.S. Fish Wildl. Serv., Western Energy and Land Use Team, Ft. Collins,

CO. Unpubl. rep. 46 pp.

Chambers, R. E. Personal communication (letter and comments on draft dated

20 December 1984, and letter dated 12 March 1985). Dept. Environ. For.

Biol., State Univ. New York, Syracuse, NY 13210.

Chambers, R. E., and W. M. Sharp. 1958. Movement and dispersal within a

population of ruffed grouse. J. Wildl. Manage. 22(3):231-239.

Dimmick, R. W. Personal communication (letters dated 7 December 1984 and

8 March 1985). Dept. of Forestry, Wildlife and Fisheries, Univ.

Tennessee, P.O. Box 1071, Knoxville, TN 37901-1071.

Doerr, P. D., L. B. Keith, D. H. Rusch, and C. A. Fisher. 1974. Characteristics of winter feeding aggregations of ruffed grouse in Alberta. J.

Wildl. Manage. 38(4):601-615.

Dorney, R. S., and C. Kabat. 1960. Relation of weather, parasitic disease

and hunting to Wisconsin ruffed grouse populations. Wisconsin Conserv.

Dept. Tech. Bull. 20. 64 pp.

Edminster, F. C. 1947. The ruffed grouse: its life story, ecology, and

management. Macmillan, NY. 385 pp.

1954. American game birds of field and forest. Charles

Scribner's Sons, NY. 490 pp.

Gilfillan, M. C., and H. Bezdek. 1944. Winter foods of the ruffed grouse in

Ohio. J. Wildl. Manage. 8(3):208-210.

Godfrey, G. A., and W. H. Marshall. 1969. Brood breakup and dispersal of

ruffed grouse. J. Wildl. Manage. 33(3):609-620.

Gullion, G. W. 1966. A viewpoint concerning the significance of studies of

game bird food habits. Condor 68(4):372-376.

26
1967. The ruffed grouse in northern Minnesota. Univ. of

Minnesota. Forest Wildlife Relations Proj. 20 pp. Cited by Moulton

1968.

1970. Factors influencing ruffed grouse populations. Trans.

N. Am. Wildl. Nat. Resour. Conf. 35:93-105.

1972.

Minnesota Agric.

1976a.

Improving your forested lands for ruffed grouse.

Exp. Stn. Misc. Publ. 1439. 34 pp. Cited by Boag

1977. Forest manipulation for ruffed grouse. Trans. N. Am.

Wildl. Nat. Resour. Conf. 42:449-458.

1981. Rejuvenation and maintenance of forest habitats for the

American ruffed grouse. Paper presented at the World Pheasant Assoc.

Grouse Symp., Edinburgh, Scotland, March 16-20, 1981.

1984a. Managing northern forests for wildlife. The Ruffed

Grouse Soc., Coraopolis, PA. 72 pp.

1984b. Ruffed grouse management.

eighties? Pages 169-181 in W. L. Robinson, ed.

state of the art in the-early 1980's. North

Soc. 181 pp.

Where do we stand in the

Ruffed grouse management:

Central Sect., The Wildl.

Personal communication (letters, phone conversations, and

meetings from 29 May 1980 - 12 March 1985). Project Leader, University

of Minnesota, Forest Wildlife Project, Cloquet Forestry Center, MN

55720.

Gullion, G. W., and A. A. Alm. 1983. Forest management and ruffed grouse

populations in a Minnesota coniferous forest. J. For. 81(8):529-532,

536.

Gull ion, G. W., and W. H. Marshall. 1968. Survival of ruffed grouse in a

boreal forest. The Living Bird 7:117-167.

Gullion, G. W., and F. J. Svoboda. 1972. The basic habitat resource for

ruffed grouse. Proc. Aspen Symp., U.S. For. Servo Gen. Tech. Rep.

NC-1: 113-119.

Hale, J. B., and R. S. Dorney. 1963. Seasonal movements of ruffed grouse in

Wisconsin. J. Wildl. Manage. 27(4):648-656.

Hale, P. E., A. S. Johnson, and J. L. Landers. 1982. Characteristics of

ruffed grouse drumming sites in Georgia. J. Wildl. Manage. 46(1):115-123.

Hays, R. L., C. Summers, and W. Seitz. 1981. Estimating wildlife habitat

variables. U.S. Fish Wildl. Servo FWS/OBS-81/47. III pp.

27
Hungerford, K. E. 1951. Ruffed grouse populations and cover use in northern

Idaho. Trans. N. Am. Wildl. Conf. 16:216-224.

1957. Evaluating ruffed grouse foods for habitat improvement.

Trans. N. Am. Wildl. Conf. 22:380-394.

Hunyadi, B. W. 1984. Ruffed grouse restoration in Missouri. Pages 21-35 in

W. L. Robinson, ed. Ruffed grouse management: state of the art in the

early 1980' s. North Central Sect., The \'Jildl. Soc. 181 pp.

Johnsgard, P. A. 1973. Grouse and qua il s of North America. Univ . Nebraska

Press, Lincoln. 553 pp.

Kelly, S. T., and P. D. Major.

drumming sites in Indiana.

11 pp. Cited by Backs 1984.

1979. Characteristics of

Indiana Dept. Nat. Resour.

ruffed grouse

Unpubl. Rep.

Keppie, D. M. Personal communication (letter and comments on draft dated

14 March 1985). Dept. For. Resour., Univ. New Brunswick, Fredericton,

New Brunswick E3B 6C2.

Kimmel, R. 0., and D. E. Samuel. 1984. Implications of ruffed grouse brood

habitat studies in West Virginia. Pages 89-108 in W. L. Robinson, ed.

Ruffed grouse management: state of the art in the early 1980' s. North

Central Sect., The Wildl. Soc. 181 pp.

Korschgen, L. J. 1966. Foods and nutri t i on of ruffed grouse in Mi ssouri. J.

Wildl. Manage. 30(1):86-100.

Kubisiak, J. F. 1978. Brood characteristics and summer habitats of ruffed

grouse in central Wisconsin. Wisconsin Dept. Nat. Resour. Tech. Bull.

108. 12 pp.

1985. Ruffed grouse habitat relationships in aspen and oak

forests of central Wisconsin. Wisconsin Dept. Nat. Resour. Tech. Bull.

151. In press.

Personal communication (letters and comments on draft dated

8 November 1984 and 19 March 1985). Project Leader, Sandhill Wildl.

Area, Wisconsin Dept. Nat. Resour., Babcock, WI 54413.

Kubisiak, J. F., J. C. Moulton, and K. R. McCaffery.

density and habitat relationships in Wisconsin.

Resour. Tech. Bull. 118. 15 pp.

1980. Ruffed grouse

Wi scon sin Dept. Na t.

Lewis, J. B., J. D. McGowan, and T. S. Baskett. 1968. Evaluating ruffed

grouse reintroduction in Missouri. J. Wildl. Manage. 32(1):17-28.

Marsha 11, W. H. 1946. Cover preferences, seasonal movements and food habits

of Richardson's grouse and ruffed grouse in southern Idaho. Wilson Bull.

58(1):42-52.

28
Maxson, S. J. 1978. Spring home range and habitat use by female ruffed

grouse. J. Wildl. Manage. 42(1):61-71.

McGowan, J. D. 1973. Fall and winter foods of ruffed grouse in i nteri or

Alaska. Auk 90(3):636-640.

Moulton, J. C. 1968. Ruffed grouse habi tat requi rements and management

opportunities. Wisconsin Dept. Nat. Resour. Rep. 36. 32 pp.

Muehrcke, J. P., and C. M. Kirkpatrick. 1969. Observations on ecology and

behavior of Indiana ruffed grouse. Proc. Indiana Acad. Sci. 79:177-186.

Norman, G. W., and R. L. Kirkpatrick. 1984.

of ruffed grouse in southwestern

48(1):183-187.

Foods, nutrition, and condition

Virginia. J. Wildl. Manage.

Palmer, W. L. 1963. Ruffed grouse drumming sites in northern Michigan. J.

Wildl. Manage. 27(4):656-663.

Palmer, W. L., and C. L. Bennett, Jr. 1963. Relation of season length to

harvest of ruffed grouse. J. Wildl. Manage. 27(4):634-639.

Phillips, R. L. 1967. Fall and winter food habits of ruffed grouse in

northern Utah. J. Wildl. Manage. 31(4):827-829.

Pietz, P. J., and J. R. Tester. 1982. Habitat se 1ect i on by sympatri c spruce

and ruffed grouse in north central Minnesota. J. Wildl. Manage.

46(2):391-403.

Porath, W. R., and P. A. Vohs, Jr. 1972. Population ecology of ruffed grouse

in northeastern Iowa. J. Wildl. Manage. 36(2):793-802.

Robertson, R. L. 1976. Ruffed grouse habitat preferences and effects of

livestock grazing on habitat utilization. M.S. Thesis, Utah State Univ.,

Logan. 71 pp.

Rusch, D. H., and L. B. Keith. 1971. Ruffed grouse - vegetation relationships

in central Alberta. J. Wildl. Manage. 35(3):417-429.

Salo, L. J. 1978. Characteristics of ruffed grouse drumming sites in western

Wa shi ngton and thei r relevance to management. Ann. Zoo1. Fenn.

15:261-278.

Schemnitz, S. D. 1970. Fall and winter feeding activities and behavior of

ruffed grouse in Maine. Trans. Northeast Fish Wildl. Conf. 27:127-140.

Schladweiler, P. 1965. Movements and activities of ruffed grouse (Bonasa

umbellus (L.)) during the summer period. M.S. Thesis, Univ. Minnesota,

St. Paul. 107 pp.

29
Schulz, J. W., A. Aufforth, and J. Woods. 1983. Fall foods of ruffed grouse.

N.D. Outdoors 46(4):12-15.

Sharp, W. M. 1963. The effects of habitat manipulation and forest succession

on ruffed grouse. J. Wildl. Manage. 27(4):664-671.

1970. The role of fi re in ruffed grouse habitat management.

Proc. Annu. Tall Timbers Fire Ecol. Conf. 10:47-61.

Sousa, P. J. 1978. Characteristics of drumming habitat of ruffed grouse

(Bonasa umbellus) in Grafton, Vermont. M.S. Thesis, Univ. Vermont,

Burlington. 134 pp.

Stafford, S. K., and R. W. Dimmick. 1979. Autumn and winter foods of ruffed

grouse in the southern Appalachians. J. Wildl. Manage. 43(1):121-127.

Stauffer, D. F. 1983. Seasonal habitat relationships of ruffed and blue

grouse in southeastern Idaho. Ph.D. Diss., Univ. Idaho, Moscow. 108 pp.

Steinke, T. S. 1975. Ruffed grouse habitat management through dynamic linear

programming. M.S. Thesis, Univ. Massachusetts, Amherst. 128 pp.

Stewart, R. E. 1956. Ecological study of ruffed grouse broods in Virginia.

Auk 73(1):33-41.

Stoll ,R. J., Jr. Personal communication (letters and comments on draft dated

6 November 1984 and 22 February 1985). Ohio Dept. Nat. Resour., Div.

Wildl. New Marshfield, OH 45766.

Stoll, R. J., Jr., M. W. McClain, and G. C. Hart. 1977. Ruffed grouse fall

and winter cover preferences. Ohio Dept. Nat. Resour., Div. Wildl.,

Wildl. In-Service Note 370. 8 pp.

Stoll, R. J., Jr., M. W. McClain, R. L. Boston, and G. P. Honchul. 1979.

Ruffed grouse drumming site characteristics in Ohio. J. Wildl. Manage.

43(2):324-333.

Stoll, R. J., Jr., M. W. McClain, C. M. Nixon, and D. M. Worley. 1980. Foods

of ruffed grouse in Ohio. Ohio Dept. Nat. Resour., Div. Wildl., Fish

Wildl. Rep. 7. 17 pp.

Stoll, R. J., Jr., C. M. Nixon, M. W. McClain, and D. M. Worley. 1973. Fall

and winter foods of Ohio ruffed grouse. Ohio Dept. Nat. Resour., Div.

Wildl., Wildl. In-Service Note 221. 32 pp.

Svoboda, F. J., and G. W. Gullion. 1972. Preferential use of aspen by ruffed

grouse in northern Minnesota. J. Wildl. Manage. 36(4):1166-1180.

Theberge, J. B., and D. A. Gauthier. 1982. Factors influencing densities of

territorial male ruffed grouse, Algonquin Park, Ontario. J. Wildl.

Manage. 46(1):263-268.

30
Titus, R. R. 1976. Habitat utilization by ruffed grouse in the Missouri

Ozarks. M.S. Thesis, Univ. Missouri, Columbia. 118 pp.

U.S. Fish and Wildlife Service. 1981. Standards for the development of

Habitat Suitability Index models. 103 ESM. U.S. Fish Wildl. Serv., Div.

Ecol. Servo n.p.

Wilson, J. A. J.

southeastern

104 pp.

1983. Pattern recognition habitat evaluation models for

Idaho. M.S. Thesis, Colorado State Univ., Fort Collins.

Woehr, J. R. 1974. Winter and spring shelter and food selection by ruffed

grouse in central New York. M.S. Thesis, State Univ. New York, Coll.

Environ. Sci. For., Syracuse. 129 pp.

Woehr, J. R., and R. E. Chambers. 1975. Winter and spring food preference of

ruffed grouse in central New York. Trans. Northeast Fi sh Wildl. Conf.

32:95-110.

31
50272 -101

REPORT DOCUMENTATION Il'13R~P01RT toto. 1 R t 82(10 86) 1

2

• PAGE 10 og1ca epor .

3. Recipient's Accession No.

4. Title and SubtItle

Habitat Suitability Index models: Ruffed grouse

5. Report Date

April 1985

6.

7. Author(s)

Brian S. Cade and Patrick J. Sousa

8. Performing Organization Rept. No.

(G)

10. Project/Task/Work Unit No.

Colorado Cooperative Wildlife Research Unit, Colorado State Univ , Fort Colli ns , CO 80523; and Western Energy and Land Use Team, Ir1-<-1·-.-C-on-tr-a-ct-(C-)-o-r·G-r-a-nt-(G-)-N-o-.----I

U.S. Fish and Wildlife Service, 2627 Redwing Road, Fort Collins, (C)

CO 80526-2899.

9. Performing Organization Name and Address

12. Sponsoring Organization Name and Address Western Energy and Land Use Team 13. Type of Report & Period Covered

Division of Biological Services I

Research and Development Fish and Wildl ife Service r-14~.--------------

f-- ---=-D...::..e.!.-pa.~r_t::..:..:m:...::.e_.:...:n...::.. t 0f the Interi or, Wa shi ngton __D_C_2_02_4_0 ______1

15. Supplementary Notes The Biological Report series was initiated in October 1984 to replace the

FWS/OBS series published since 1976. The report number assigned to this model follows consecutively from the Habitat Sui~~bilit:y Index models published as FWS/OBS-82/l0. , now

numbered as Bioloaical Reoort 82l10. J. -

-16. Abstract (Limit: 200 words)

A review and synthesis of existing information were used to develop a Habitat

Suitability Index (HSI) model for the ruffed grouse (Bonasa umbellus). The model

consolidates habitat use information into a framework appropriate for field

application, and is scaled to produce an index value between 0.0 (unsuitable

habitat) and 1.0 (optimum habitat). HSI models are designed to be used with

Habitat Evaluation Procedures previously developed by the U.S. Fish and Wildlife

Service.

t------------------------.------------------------------.J

17. Document Analysis a. Descriptors

Birds

Wildlife

Habitability

Mathematical models

b. Identlfiers/Open·Ended Terms

Ruffed grouse

Bonasa umbellus

Habitat suitability

c. COSATI Field/Group

18. Availability Statement

Release unlimited

I 19. Security Class (This Report)

I Unclassified

1

20. Security Class (Thi~ Page) Unclass1f1ed

21. No. of Pages

31

22. Price

(See ANSI-Z39.18) See Instructions on Reverse

-I:< U.S. GOVERNMENT PRINTING OFFICE: 198~79·231/25226 REGION NO.8

OPTIONAL FORM 272 (4-77)

(Formerly NTIS-35)

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.. ....,-. .. ..

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services. Wasn,ngton. DC

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Leerown. WV

* Naloonal Coastal Ecosystems Team

Slide ll LA

• Western Energy aM LaM Use Team

FI ccu.ns. CO

• Locat ions of RegIonal Ollices

UGION 1

Rqiunlll Director

O.S. Fish lind Wildlife Service

Uoyd Five Hundred Building, Suite 1692

500N.E. Multnomah Street

Portland, Oregon 97232

REGION 4

Regional Director

U.S. Fish and Wildlife Service

Richard B. Russell Building

75 Spring Street, S.W.

Atlanta, Georgia 30303

,

,

I __r----

6!

,----- L, J_

1

, : ,--- I ,

I

REGION 2

Regional Director

U.S. Fish and Wildlife Service

P.O. Box 1306

Albuquerque, New Mexico 87103

REGION S

Regional Director

U.S. Fish and Wildlife Service

One Gateway Center

Newton Comer, Massachusetts 02158

REGION 7

Regional Director

U.S. Fish and Wildlife Service

10II E. Tudor Road

Anchorage, Alaska 99503

,."

REGION 3

Regional Director

U.S. Fish and Wildlife Service

Federal Building, Fort Snelling

Twin Cities, Minnesota 5SIII

REGION 6

Regional Director

U.S. Fish and Wildlife Service

P.O. Box 25486

Denver Federal Center

Denver, Colorado 80225
DEPARTMENT OF THE INTERIOR

u.s. FISH AND WILDLIFE SERVICE

As the Nation's principal conservation asency, the Department of the Interior has responsibility for most of our .nationally owned public lands and natural resources. This includes

fosterins the wisest use of our land and water resources, protecting our fish and wildlife,

preserving th.environmental and cultural'values of our national parks and historical places,

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