Photo © Roger Eriksson

Cerulean Warbler Breeding Cerulean Warbler Breeding Habitat CharacteristicsHabitat Characteristics

Paul B. HamelPaul B. HamelUS Forest Service

Stoneville, MS

phamel@fs.fed.us

Regional Variation on Common Themes

• Tract Size / Area Sensitivity – Varies regionally

• Bimodal Site Types • Variety of Tree Species Regionally,

– May be more restricted locally • Big Trees• Tall Trees• Heterogeneous canopy structure

Habitat Associations of Cerulean Warblers

Rangewide

Regional

Landscape

Stand

Home range/microsite

Scale Descriptionregional,

physiographicforest type,

topographic, edaphic,

successional stage, stocking

tree species and size, nest vicinity, and

nest microsite

Data of Jennifer Baldy, Univ. of Memphis Thesis, 2005

Breeding Distribution is Dynamic within the Range

At least 1 year

Every year

Occurrence at High Significance1966-2003

Range from Dunnand Garrett 1997

Forest Managers in the Central Hardwoods are the Primary Stewards of

Cerulean WarblerBreeding Habitat

Landscape-scale Relationships

• Largely forested landscapes– eg. Cumberland Mountains, TN- 85% forested

and/or

• Large forest patch size– 700 ha- MD (Robbins et al 1992)– 1600 ha- Miss. Alluvial Valley (Hamel)

• Regional variation in sensitivity

Tract Size Utilization

Tract Size, ha

Num

ber o

f Site

s

0

25

50

75

100

10 30 61 142 304 607 1417 3036

R3 sites

R4 sites

R5 sitesNortheast

Southeast

Midwest

% Forest Cover

Forest Cover in Landscape(Bosworth 2003)

R² = 0.52, P = 0.05

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

50 60 70 80 90 100

CER

W A

bund

ance

00.5

11.5

22.5

33.5

44.5

Landscape

Mean density per 10 ha

Forested

Next to cut

Bakermans and Rodewald, in progress

(Check back in the summer)

0.94

0.95

0.96

0.97

0.98

0.99

Daily Survival Rate

Forested

Next to cut

Preliminary data from 2004-05 suggest that density and nest survival rates may be lower in forests adjacent to recent clearcut compared to more forested landscapes.

Habitat Relationships: Landscapes

• Area sensitivity– 1,780 ac (Robbins et al 1992)

– 4,000 ac in MAV (Hamel)

• Regional variation in sensitivity

• Edge avoidance varies

Forest type• Eyre (1980) lists 49 Eastern forest cover types

• Cerulean Warblers have been confirmed to nest in nominate tree species of 33

• Forest cover type use is selective within a locality

• Forest cover type use varies across localities

Tree species use

Percent of States0 25 50 75 100

Oaks

Maples

Hickories

Sycamore

Yellow-poplar

Cottonwood

Ash

Elm

Black Locust

Black Walnut

American Beech

Basswood

**

Cerulean Warbler on Desha Site Tree Availability vs Use

00.10.20.30.40.50.6

ACNE CELA FRPE LIST PLOC PODE ULAM

Tree Species

Prop

ortio

n of

Ste

ms

UsedAvailable

Topographic situations

0

50

100

150

200

250

300

350

400

450

Dry Slopes andRidgetops

Other Uplands Mesic Uplandsand Coves

BottomlandSites

Swamps andLake Margins

Site Type

Num

ber o

f Site

s

R3 sitesR4 sitesR5 sites

MidwestSoutheastNortheast

Elevation and aspect

0

15

30N

NE

E

SE

S

SW

W

NW Random PointsTerritoriesNest Sites

Important Cerulean Warbler Areas

0

5

10

15

20

0 300 600 900 1200

Elevation midpoint, m

Num

ber o

f Sta

tes

Elevations

Cumberland Mountains,Tennessee Site

Slope position(Weakland, Wood, Bosworth)

00.5

11.5

22.5

33.5

44.5

Territory density Abundance

Mea

n #

CER

W

bottommid-sloperidge

A

BABB

B

A

Edge Effects?

• Reduced density (Wood et al.) and possibly reduced productivity in areas adjacent to hard edges.

• Effective distance unknown– Needs to be documented for different forest

management types

• Importance of canopy gaps?

– Canopy heterogeneity vs. canopy gaps

Use of edge types

01020304050

Naturalgap

Partlyopen-

canopyroad

Open-canopyroad

Mine

Perc

en

Use Available

(Weakland and Wood 2005)

Edge vs. Gaps• Territories included canopy gaps / trails• did not appear to avoid open-canopy edges•• did not use did not use powerlinepowerline edgesedges

Successional stage

• Cerulean Warblers occur in areas dominated by sawtimber sized trees

• Dominant trees may be – Shade Intolerant, pioneer species – Shade Tolerant, later successional species

• But they are always big trees

Stand Stocking

• Relates tree number and tree size to available light and growing space in a predictable way

• Foresters understand this concept implicitly

• Ornithologists generally do not

• Conservationists often miss the point that tree growth means that habitats are in continuous change

0

20

40

60

80

100

120

140

160

0 50 100 150 200 250 300 350 400 450

Trees per acre

Bas

al a

rea

per a

cre

(sq.

ft./a

cre)

A-line

B-line

C-line

100%

90%

80%

70%

60%

50%

40%

30%

20%

110%

Percent Stocking

Quadratic Mean Diameter

78

910

1214

1618

2022

Cerulean WarblerPresentAbsent

Stocking of Cerulean Warbler Study Sites in Allegheny Hardwoods, Pennsylvania

0

20

40

60

80

100

120

140

160

0 50 100 150 200 250 300 350 400 450

Trees per acre

Bas

al a

rea

per a

cre

(sq.

ft./a

cre)

A-line

B-line

C-line

100%

90%

80%

70%

60%

50%

40%

30%

20%

110%

Percent Stocking

Quadratic Mean Diameter

78

910

1214

1618

2022

Cerulean Warbler Density> 2 / 25 acres< 2 / 25 acres

Stocking of Cerulean Warbler Study Sites in Southern Ohio

Absent

Spatial distribution within stands

Meeman Shelby Forest SP & WMA, TN

From Barg et al., Journal of Animal Ecology 2005 74:139–149,Fig. 1

Ontario

Tree size

0

0.2

0.4

0.6

0.8

5 25 45 65 85 105 125 145

Diameter, cm

Prop

ortio

n of

Tre

es >

3 c

m

AvailableMale UseFemale Use

Cerulean Warbler use of trees in Mississippi Alluvial Valley sites, N=3690 used, >200,000 available

Boxelder in the MAV, from SOFIA, 2002

0

10

20

30

40

50

0 50 100 150

DBH, cm

HT, m

toptop25Mean htCrown basebottom25bottomCERWnest

Habitat Relationships: Forest stand structure

0

5

10

15

20

25

30

35

0 0.2 0.4 0.6 0.8 1

Proportion of Space

0

5

10

15

20

25

30

35

0 0.2 0.4 0.6 0.8 1

Proportion of space

0

5

10

15

20

25

30

35

0 0.2 0.4 0.6 0.8 1

Proportion of Space

Hei

ght,

m

Queen’s University Biological Station, Ontario, Canada, 1999

Frozen Head State NaturalArea, Tennessee, USA, 1999

Chickasaw National WildlifeRefuge, Tennessee, USA, 2001

Proportion of Space

*

**

* Nest sites

Vertical Vegetation Structure at Nests varies with Location

Photo by Heinz Meng

Nest site

24.3 m

40.8 cm dbh

11.8 m

16.2 m

2.7 m3.4 m

102o

Figure 2: Mean nest site characteristics of 49 Cerulean Warbler nests, CumberlandMountains, Tennessee, 1996-1998.

Nest Tree Characteristics

Chickasaw Desha Meeman Total

Nests 19 19 28 66

Tree Species 8 4 9 14

Tree Height, m 29 +/- 1.7 28 +/- 2 31 +/- 1.4 30 +/- 1

Nest Height, m 18 +/- 1.2 17 +/- 1.2 20 +/- 1.3 19 +/- 0.74

Tree DBH, cm 58 +/- 6 55 +/- 5 46 +/- 3 52 +/- 2.6

Nest from Bole, m 6.2+/-0.8 3.5+/-0.5 3.4+/-0.3 4.2+/-0.35

Crown Radius Test Open grown No data Open grown

Cerulean Warbler Nest Trees in the LMAV

Cerulean Warbler Nest Trees, Mississippi Alluvial Valley 1992-1998

0

50

100

150

200

0 30 60 90 120Tree Diameter, cm

Rela

tive

Ht, %

MedianMedian25 %ile

75 %ile

Roost Trees of Cerulean Warblers in LMAV

0

50

100

150

200

0 30 60 90 120 150

Tree Diameter, cm

Rel

ativ

e H

t, m Bottomlands

UplandsNo DataMedianQ25Q75

Broadcast Arena may be common denominator in male habitat selection

General Habitat Relationships

• Large tracts of mature deciduous forest

• Ridge tops, floodplain and mesic cove forests.

• Common denominator = emergent, structurally diverse canopy

Suggestions

• Common features of habitats reflect the birds’ biology

• Regional variations reflect external limiting factors, e.g., parasitism and predation

• Preliminary Finding, Cerulean Warblers in the LMAV occur in very productive sites

• Effect of climate change should not be overlooked

Generalizations are difficult because so much is context dependent…

More on habitats during migration and nonbreeding residency periods later

0

50

100

150

200

250

300

350

0 500 1000

Trees per acre

Bas

al A

rea

ft2 p

er a

cre

20100120CHKDESMEECHK meanDES MeanMEE MeanLog. (120)Log. (100)Log. (20)

Stocking of Study GridsMississippi Alluvial ValleyBottomland Hardwoods

% Stocking

Study Site

0

50

100

150

200

250

300

350

0 100 200 300 400

Trees per acre

Basa

l Are

a ft

2 per

acr

e

20100120CHKDESMEECHK MeanDES MeanMEE Mean12010020

Stocking at Cerulean WarblerNest Sites

Same Study Sites In Mississippi Alluvial ValleyBottomland Hardwoods

% Stocking

Study Site

Stocking of Cerulean Warbler Study Sites in Mississippi Alluvial Valley

0

20

40

60

80

100

120

140

160

180

0 50 100 150 200 250 300 350 400

Trees per acre

Bas

al A

rea

ft2 per

acr

e

20%

40%

60%

80%

120%

100%

Stocking percent

Quadratic Mean Diameter

81012131416

16CHKMEEDESCHK nestsDES NestsMEE Nests

“B”-line

0

20

40

60

80

100

120

140

160

0 50 100 150 200 250 300 350 400 450Trees per acre

Bas

al a

rea

per a

cre

(sq.

ft./a

cre)

A-line

B-line

C-line

100%

90%

80%

70%

60%

50%

40%

30%

20%

110%

Percent Stocking

Quadratic Mean Diameter

78

910

1214

1618

2022

Cerulean WarblerPresentRandom points

Stocking of Cerulean Warbler Study Sites in Southern Indiana

Pairs

Stocking of Cerulean Warbler Study Sites in Eastern Tennessee

Study SiteRoyal Blue WMASundquist WMA

0

20

40

60

80

100

120

140

160

0 50 100 150 200 250 300 350 400 450

Trees per acre

Basa

l are

a pe

r acr

e (s

q. ft

./a

A-line

B-line

C-line

100%

90%

80%

70%

60%

50%

40%

30%

20%

110%

Percent Stocking

Quadratic Mean Diameter

78

910

1214

1618

2022

Cerulean Warblers in Southern Ohio, 2004-2005

Terr

itorie

s/25

acr

es

0

1

2

3

4

5

6

7

8

0 10 20 30 40 50 60 70 80 90 100

Stocking Percent