21 April 2015Charles McColeB.S. Wildlife and Fisheries SciencesPennsylvania State UniversityUniversity Park, PA, USAEmail: cvm5196@psu.edu

RH: McCole et al. Ruffed Grouse Populations in Scotia Barrens

Proposed Reversal of the Steady Decline in Ruffed Grouse Populations in the Scotia

Barrens Region of Pennsylvania

CHARLES MCCOLE¹, Department of Ecosystem Science and Management, Pennsylvania State

University, 416 Forest Resources Building, University Park, PA, USA

MARK CHRONISTER², Department of Ecosystem Science and Management, Pennsylvania

State University, 416 Forest Resources Building, University Park, PA, USA

SHARA HERMAN³, Department of Ecosystem Science and Management, Pennsylvania State

University, 416 Forest Resources Building, University Park, PA, USA

Corresponding author: cvm5196@psu.edu

Present address: 416 Forest Resources Building, University Park, PA, USA

ABSTRACT

Ruffed grouse (Bonasa umbellus) are a species of concern for the state of Pennsylvania.

Historical records compared to current population densities are revealing a sharp decline across

the state at a rate of ~15% per year. Conservation efforts are needed to reverse the trend enabling

the reestablishment of growing populations across the state. The Centre County population

located on Pennsylvania Game Land #176, commonly called Scotia Barrens, is the basis for our

study. We used an age-structured Leslie matrix model for our population projections. Models

were ran which simulate the management actions that were considered: do nothing, increase

suitable grouse habitat, and implement an open season on avian predators. Population data was

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obtained from a previous long-term study done in the Scotia Barrens form 1976 to 1998 (Storm

2003). Data for the effects of habitat management and avian predator reduction on ruffed grouse

populations was also obtained from the study. The current growth rate (λ) of the grouse

population that we studied is 0.84, which indicates a declining population. Our goal for the study

was to determine if implementing the proposed management action could increase the λ-value

greater than 1.0. After running the models, it was determined that our habitat management action

would increase the λ by 0.19, which would result in a λ of 1.03. We also ran a model for our

management action of reducing the avian predator population by opening a hunting season,

removing a quarter of the predators. Our results showed that λ only increased by 0.05, up to 0.89,

much lower than our target value. Although it is commonly known that ruffed grouse

populations operate in a 10 year cycle, it is clear from our results that habitat plays a very large

role in their success and managing habitat has the greatest effect on their numbers.

Key Words: Ruffed Grouse, Bonasa Umbellus, Scotia, Habitat, Avian, Predation

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The Ruffed grouse (Bonasa umbellus) is the state bird of Pennsylvania. It has become a

commonly hunted game species throughout the state. Ruffed grouse have a maximum lifespan in

the wild of about 8 years. The females mate every year and on average lay 10 eggs per season.

However, 63% of the first nesting events are unsuccessful, meaning that no eggs are hatched

from the nest. In those cases, there is a 100% re-nesting rate, although only 33% of second nests

are successful. Grouse chicks are precocial and will begin to walk on their own and forage upon

hatching. In a week they are able to fly. Grouse mature at age 1 and have a constant fecundity

rate once maturity is reached. Male grouse are territorial although grouse are not monogamous

and both males and females can mate with multiple grouse. They thrive in early successional

habitat which is growing scarce throughout the state of Pennsylvania, resulting in their declining

numbers (Rusch 2000).

Pennsylvania’s population of grouse is rapidly decreasing and if current rates of decline

continue the population will be essentially extinct in 35 years.  Specifically, in Scotia Barrens,

abundance has declined 10-15% per year. Though the trend is thought to be primarily a result

from habitat destruction, predation may also be a cause for concern. To reverse the decline of

grouse, habitat must be analyzed to determine if a change in the landscape will contribute to the

reversal in population trajectories (Storm 2003.).

The objective of our study is to increase the current rate of population growth (λ) by a

minimum 0.19, thereby increasing it to 1.03 and promote population increase. Current research

indicated that grouse populations in PA are declining at a rate of 16% a year (λ=0.84). (Table 2,

3). To determine the success at meeting this objective, we looked at population abundance using

flush counts and nest counts. Counting nests can give you the female population abundance as

well as nest productivity numbers. Three actions were chosen and modeled to determine which

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management practices would help us to achieve our objective. They are: do nothing, increase

suitable grouse habitat, and implement an open season on avian predators.

MANAGEMENT ACTIONS

The first action that we are proposing is to do nothing. This is the easiest and most cost efficient

action, as no extra effort will have to be made. For this action, no changes will be made to any of

the current management plans concerning ruffed grouse and the populations will continue to be

observed until quasi-extinction is reached.

Our second action is to increase the suitable habitat of the ruffed grouse in the study area

by at least 50%. Suitable habitat is thought to be one of the biggest contributors to survivability

of ruffed grouse. Grouse thrive in a very narrow age class of vegetation which makes it difficult

to maintain suitable habitat for long periods of time. The constant creation of new habitat

involves clear-cutting tracts of land to enable proper vegetation to grow. However, this process

has the potential of being very costly if done over large tracts of land.

Our third action is to remove a specified number of avian predators from the study area.

Avian predators account for 80% of the mortality of ruffed grouse. Northern goshawk, northern

harriers, great horned owl, and barred owls are the top predators of grouse chicks. By reducing

the number of predators in grouse habitat this would allow a higher rate of chicks to survive to

maturity and a breeding age. By having more breeding adults in a population the abundance

should increase dramatically over time.

To meet the objectives, full cooperation is required from all stakeholders that have an

interest in the success of the species. Hunters provide a valuable source of income that aids in all

management objectives implemented. A compromise needs to be made if the decline of a

popular game species is to be averted. Both alternatives can be met with adjustments to the

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regular hunting season and suspension of the birds of prey protection clause covered in the

Migratory Bird Treaty Act. Allowing for the harvest of a species like the Red Tailed Hawk

would provide a substitute to the temporary removal of Grouse as a game species. Additionally,

the action would increase the survival of ruffed grouse by eliminating a direct prey species. This

two-step solution has the ability to remove the additive effects of harvest and predation and

could return the population to lambda levels greater than 1.0.

STUDY AREA

The Pennsylvania Game Commission maintains about 1.5 million acres of land across the state

of Pennsylvania (PGC 2015). This land is open to the public and maintained by funds generated

through license and firearms sales. Many sites are managed and manipulated to research various

species of game animals to better the experience for hunters. Specific to this grouse project State

Game Land (SGL) 176, also named Scotia Barrens, has been managed to improve and better

understand the habits of ruffed grouse. SGL 176 characteristics are mixed hardwoods common

to the Pennsylvania landscape. One major difference to the area is in the name. The barrens of

the area are derived from the abundance of jack, pitch, and white pines growing in the acidic

soils that are found at SGL176. Elevations ranged from 360 m to 450 m. Temperatures in the

area range from -3.4° C to 21.9° C (National Oceanic and Atmospheric Administration 1985).

1,120 ha of land with in SGL 176 (2500ha total) were used to establish a controlled area. This

area has been selectively managed by the PGC since 1975 to establish ideal habitat for ruffed

grouse and other various game species to prosper (Storm 2003).

METHODS

In our original population model, we used population abundance data obtained from a study done

from 1976-1998 at our study site. Survival and fecundity rates were obtained from a grouse

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demography report put out by the USGS as well as a breeding bird survey. An age-based Leslie

matrix was used to estimate population abundance into the future, based on the current

population, fecundity, and survivability numbers. The model showing the original data and

population projection was used as our do nothing model.

In order to change the current population projection two methods of management were

chosen; increasing favorable habitat and decreasing avian predation. The best grouse habitat is a

mosaic of different age structures. They need early successional patches to nest, hide from

predators, and soft mast crops. Mature growth habitat is needed for hard mast that will feed them

through the winter.

In order to achieve this mosaic patchwork the Barrens were put on a clear-cut rotation.

Every 10 years a 1-ha plot will be systematically chosen to be clear-cut and allowed to

regenerate. Any harvestable trees will be sold while undesired trees will be cleared out of pocket.

In particularly dense blocks an understory burn will take place before the cut in order to recycle

nutrients back into the soil and open up the understory for easier navigation. Hard mast

producing trees will be left in place to ensure that the regeneration is of the appropriate species.

Based on the previous Scotia Barrens grouse study, grouse chick survivability increased

proportionally with an increase in suitable grouse habitat, which is reflected in our tables and

graphs (Storm 2003).

In order to decrease avian predation, there will be a reduction of avian predators in our

study area. Over the entire study site, 2500 Ha, we determined that there were about 20 total

individuals representing the four species that we targeted. The removal of 20% of all avian

predators from the study area, a total of about five individuals over the site, is proposed. A

temporary open season on avian predators will be enacted to allow for hunters to harvest the

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allotted amount to achieve our management action. All falcons are protected under the birds of

prey protection clause in the Migratory Bird Treaty Act. We chose 20% because many avian

predators prey on other nuisance species as well. The changes in survivability and population

abundance is shown in our tables and graphs.

RESULTS

Our do nothing model resulted in a grouse population declining at 16% per year, a λ of 0.84. λ

was reached at the 7 year mark. At that rate, the ruffed grouse population at our study site would

go extinct at the 35 year mark.

It was found that when suitable grouse habitat is increased by 50%, first year survival

will increase by at least 50%. This will ensure that the chicks have a higher rate of survival

during the first year which would bolster the upper age classes in the following years. This

practice increased the lambda to 1.03 within 7 years, an increase of 0.19.

The removal of 20% of avian predators was not found to be as successful. At this rate the

lambda only increased to .89, an increase of 0.05. In order to increase this rate by removal alone

many more birds would need to be harvested which is not feasible.

MANAGEMENT IMPLICATIONS

At the current rate, the grouse population in Scotia Barrens of Pennsylvania will be extirpated

within 35 years. Predation accounts for over 80% of all mortality. Avian predators account for

most of the predation deaths. Management action is drastically needed to protect this vital game

species. A couple management practices have been discussed in this paper such as increased

habitat and an open season on avian predators.

Habitat has shown to be one of the most important determining factors in a successful

ruffed grouse population. Habitat provides adequate cover and the proper food source for all age

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classes. The data for our study was taken from a ruffed grouse study done at the Scotia Barrens

in north central Pennsylvania. The study found that increasing suitable grouse habitat by fifty

percent increases first year survival by at least 50%. For our study we manipulated the habitat

cover to increase abundance. The result was that the lambda increased by 0.19. The resulting

lambda was 1.03 which indicates an increasing population. If that data is accurate, this

management practice would solve the current population decline problems. Additionally, it

shows that even more habitat management could result in higher lambda values. This action has

the potential to create more hunting opportunities and increase hunter satisfaction which would

be a secondary benefit.

The second action that was researched was opening up a season on avian predators,

mainly red-tailed hawks, northern harriers, great horned owls, and barred owls. The main goal

was to increase the lambda above 1.0. After the removal of the allotted predators our lambda

only increased by 0.05, from 0.84 to 0.89 which is far below the goal. However, this directive

will extend the time before the population becomes extirpated from the region. An increase in

predator harvest was considered but avian predators play other important roles in the

environment and nearly all would need to be removed to have a dramatic impact on the growth

rate. Overall, this action did not prove to be a viable option for our goals. For one, the likelihood

that a season would be opened is very slim, as all of these species are protected under federal

law. The second reason is that it isn’t feasible to remove the number of individuals that are

required to increase lambda by our desired amount.

It was found that it is possible to increase the growth rate of the ruffed grouse population

in the region and to prevent future extirpation. The most ideal situation is to indirectly affect the

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population by improving desirable habitat. The alterations to the environment have the

possibility of benefitting other game species and increasing overall hunter satisfaction.

REFERENCES

Fearer, Todd M.; Stauffer, Dean F. 2004. Relationship of ruffed grouse Bonasa umbellus to

landscape characteristics in southwest Virginia, USA. Wildlife Biology. 10(2): 81-89.

Hewitt, David G.; Keppie, Daniel M.; Stauffer, Dean F. 2001. Predation effects on forest grouse

recruitment. Wildlife Society Bulletin. 29(1): 16-23.

Rusch, Donald H.; Destefano, Stephen; Reynolds, Michael C.; Lauten, David. 2000. Ruffed

grouse--Bonasa umbellus. In: Poole, A.; Gill, F., eds. The birds of North America. No.

515. Philadelphia, PA: Birds of North America. 28 p.

Sauer, J. R., J. E. Hines, J. E. Fallon, K. L. Pardieck, D. J. Ziolkowski, Jr., and W. A. Link. 2014.

The North American Breeding Bird Survey, Results and Analysis 1966 - 2012. Version

02.19.2014 USGS Patuxent Wildlife Research Center, Laurel, MD

Storm, G. L., W. L. Palmer, and D. R. Diefenbach. 2003. Ruffed grouse responses to

management of mixed oak and aspen communities in central Pennsylvania. Grouse

Research Bulletin No. 1, Pennsylvania Game Commission, Harrisburg, Pennsylvania,

USA

National Oceanic and Atmospheric Administration. 1985. Climates of the states. II. Gale

Research Company, Detroit, MI. 1572pp.

PGC, Pennsylvania Game Commission, 2015. Pennsylvania State Game Lands. April 24, 2015.

http://www.portal.state.pa.us/portal/server.pt/community/state_game_lands/11363

(accessed April 24, 2015).

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Table 1. Survival and fecundity, presented in a Leslie matrix, for Ruffed Grouse in the Scotia

Barren region of Pennsylvania adjusted for each of our actions. Survival rates were obtained

from a USGS report on Ruffed Grouse. Fecundity rates and the initial population values were

obtained from USGS Patuxent Wildlife Research Center, Laurel, MD North American Breeding

Bird Survey. Fecundity rates reflect an initial nesting event and a secondary nesting event that

occurs in the case of a failed first nest.

Do Nothing 0 1 2 3 4+

0.4447 2.5997 2.3497 1.8497 1.34970.069 0 0 0 0

0 0.5 0 0 00 0 0.45 0 00 0 0 0.35 0.25         

Predator Removal0 1 2 3 4+

0.4447 2.5997 2.3497 1.8497 1.34970.0828 0 0 0 0

0 0.5 0 0 00 0 0.45 0 00 0 0 0.35 0.25         

Habitat Increase0 1 2 3 4+

0.4447 2.5997 2.3497 1.8497 1.34970.139 0 0 0 0

0 0.5 0 0 00 0 0.45 0 00 0 0 0.35 0.25

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Table 2. The proportion of the total population that is occupied in each age class at any given

year once the asymptotic lambda is reached. All three management actions are represented in the

table. Asymptotic lambda is reached in the 7th year of our projection.

Proportion of individuals in age class (Do Nothing)

0 1 2 3 4+ YearAsym

Lambda0.853082666 0.069959518 0.041565822 0.02221529 0.013176703 7 0.841399663             

Proportion of individuals in age class (Predator Decrease)

0 1 2 3 4+ YearAsym

Lambda0.841194106 0.078858414 0.044637943 0.022729369 0.012580168 7 0.883262454             

Proportion of individuals in age class (Habitat Increase)

0 1 2 3 4+ YearAsym

Lambda0.803787567 0.109050549 0.053233548 0.023361108 0.010567228 7 1.024524577

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Figures

Figure 1. Semi-log graph showing the population size projections for all age classes as well as

the total population, predicted 35 years into the future for the do nothing action. Age classes 1

through 4+ reach extinction between years 12 and 23. Age class 0, as well as the total population,

reaches extinction around year 35. The consistent population decline correlates with the

asymptotic lambda, 0.84.

Figure 2. Semi-log graph showing the population size projections for all age classes as well as

the total population, predicted 35 years into the future for the habitat increase action. An

asymptotic lambda of 1.024 is reached at year 7. Populations continue to increase throughout the

35 year projection.

Figure 3. Semi-log graph showing the population size projections for all age classes as well as

the total population, predicted 35 years into the future for the avian predator removal action.

Lambda was 0.89, which pushed extinction back 20 years.

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Figure 1.

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Figure 2.

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Figure 3.

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