Northern Prairie Wildlife Research Center

Relationships of Habitat Patch Size to Predator Community and Survival of Duck Nests

Tables

**Table 1.** Characteristics of small or large habitat patches^a studied in the Prairie Pothole Region of North Dakota, South Dakota, and Minnesota, 1993-95.
	1993	1994	1995
Perennial cover (ha)	36	6-101	578	107-1,789	48	5-101	593	106-2,342	48	4-101	588	106-2,342
% CRP	86		49		82		46		84		48
% hayland	2		5		4		4		4		4
% grassland	10		41		12		47		11		45
% woodland	2		5		2		3		2		3
Wetland^b (ha)	7	0-105	155	1-596	12	0-118	121	4-468	11	0-118	118	4-468
Area past perimeter^c (ha)	32		131	2-311	35	26-42	117	11-287	33	26-40	117	7-287
^a Patch was composed of all adjoining tracts of Perennial Cover (grassland, hayland, planted cover, woodland, and land enrolled in the Conservation Reserve Program) that shared a common side, and temporary and seasonal wetlands located within the Perennial Cover. Patch size based on area of Perennial Cover: small patch = ≤105 ha, large patch >105 ha. ^b Includes only seasonal and temporary basins within Perennial Cover. ^c Study area was 41.4 km². Area of Perennial Cover contiguous with patches that abutted the perimeter of a study area was estimated to a distance of 0.8 km from perimeter. Number of patches beyond perimeter for small and large patches respectively, was 1 and 24 in 1993, 4 and 28 in 1994, and 3 and 30 in 1995.

Table 1. Characteristics of small or large habitat patches^a studied in the Prairie Pothole Region of North Dakota, South Dakota, and Minnesota, 1993-95.

1993

1994

1995

Small
n = 32

Large
n = 35

Small
n = 36

Large
n = 35

Small
n = 37

Large
n = 37

Range

Perennial cover (ha)

6-101

578

107-1,789

5-101

593

106-2,342

4-101

588

106-2,342

% CRP

% hayland

% grassland

% woodland

Wetland^b (ha)

0-105

155

1-596

0-118

121

4-468

0-118

118

4-468

Area past perimeter^c (ha)

131

2-311

26-42

117

11-287

26-40

117

7-287

^a Patch was composed of all adjoining tracts of Perennial Cover (grassland, hayland, planted cover, woodland, and land enrolled in the Conservation Reserve Program) that shared a common side, and temporary and seasonal wetlands located within the Perennial Cover. Patch size based on area of Perennial Cover: small patch = ≤105 ha, large patch >105 ha.
^b Includes only seasonal and temporary basins within Perennial Cover.
^c Study area was 41.4 km². Area of Perennial Cover contiguous with patches that abutted the perimeter of a study area was estimated to a distance of 0.8 km from perimeter. Number of patches beyond perimeter for small and large patches respectively, was 1 and 24 in 1993, 4 and 28 in 1994, and 3 and 30 in 1995.

**Table 2.** Results of analysis of variance on daily survival rates of upland duck nests in the Prairie Pothole Region of Minnesota, North Dakota, and South Dakota in relation to patch size^a, location (northwest or southeast of 46°8'N and 97°43'W), nest initiation date^b (early or late), and year (1993, 1994, or 1995).
Source	df	F	P
Patch size	1,80	4.46	0.038
Location	1,80	0.39	0.536
Patch size × location	1,80	3.02	0.086
Initiation date	1,100	5.22	0.024
Initiation date × location	1,100	1.52	0.221
Initiation date × patch size	1,100	0.14	0.714
Initiation date × patch size × location	1,100	0.02	0.902
Yr	2,80	2.01	0.140
Yr × patch size	2,80	0.07	0.936
Yr × location	2,80	0.45	0.639
Yr × patch size × location	2,80	0.59	0.556
Yr × initiation date	2,58	3.79	0.028
Yr × initiation date × patch size	2,58	3.37	0.041
Yr × initiation date × location	2,58	1.03	0.362
Yr × initiation date × patch size × location	2,58	1.22	0.302
^a Patch defined as in Table 1. ^b Early and late nests were partitioned by median nest initiation date each year. Early nests were initiated on or before 1 June in 1993, and 7 June in 1994 and 1995; late nests were initiated after those dates.

Table 2. Results of analysis of variance on daily survival rates of upland duck nests in the Prairie Pothole Region of Minnesota, North Dakota, and South Dakota in relation to patch size^a, location (northwest or southeast of 46°8'N and 97°43'W), nest initiation date^b (early or late), and year (1993, 1994, or 1995).

Source

Patch size

1,80

4.46

0.038

Location

1,80

0.39

0.536

Patch size × location

1,80

3.02

0.086

Initiation date

1,100

5.22

0.024

Initiation date × location

1,100

1.52

0.221

Initiation date × patch size

1,100

0.14

0.714

Initiation date × patch size × location

1,100

0.02

0.902

2,80

2.01

0.140

Yr × patch size

2,80

0.07

0.936

Yr × location

2,80

0.45

0.639

Yr × patch size × location

2,80

0.59

0.556

Yr × initiation date

2,58

3.79

0.028

Yr × initiation date × patch size

2,58

3.37

0.041

Yr × initiation date × location

2,58

1.03

0.362

Yr × initiation date × patch size × location

2,58

1.22

0.302

^a Patch defined as in Table 1.
^b Early and late nests were partitioned by median nest initiation date each year. Early nests were initiated on or before 1 June in 1993, and 7 June in 1994 and 1995; late nests were initiated after those dates.

**Table 3.** Numbers of nests, exposure days, and least-squares means estimates of daily survival rate of upland duck nests in the Prairie Pothole Region of Minnesota, North Dakota, and South Dakota relative to year × nest initiation date^a (early or late) × patch size^b interaction (F_2,49 = 5.86, P < 0.01). Within categories early or late for each year, statistical differences (*) between patch sizes are based on Fisher's protected LSD procedure (P ≤ 0.05).
Yr	Patch size	Number of nests	Exposure days	Daily survival rate
1993	Small	79	116	849	1,444	0.924	0.014	0.943	0.010
Large	294	248	3,515	3,181	0.937	0.008	0.950	0.007
1994	Small	174	151	2,162	3,467	0.930	0.007	0.949	0.007
Large	289	280	2,051	3,468	0.944	0.006	0.954	0.006
1995	Small	231	231	3,028	5,080	0.950	0.006	0.937*	0.006
Large	400	380	2,554	4,920	0.952	0.006	0.962*	0.006
^a Early and late nest initiation dates defined as in Table 2. ^b Patch defined as in Table 1.

Table 3. Numbers of nests, exposure days, and least-squares means estimates of daily survival rate of upland duck nests in the Prairie Pothole Region of Minnesota, North Dakota, and South Dakota relative to year × nest initiation date^a (early or late) × patch size^b interaction (F_2,49 = 5.86, P < 0.01). Within categories early or late for each year, statistical differences (*) between patch sizes are based on Fisher's protected LSD procedure (P ≤ 0.05).

Patch
size

Number of nests

Exposure days

Daily survival rate

Early

Late

Early

Late

Early

Late

Estimate

1993

Small

116

849

1,444

0.924

0.014

0.943

0.010

Large

294

248

3,515

3,181

0.937

0.008

0.950

0.007

1994

Small

174

151

2,162

3,467

0.930

0.007

0.949

0.007

Large

289

280

2,051

3,468

0.944

0.006

0.954

0.006

1995

Small

231

3,028

5,080

0.950

0.006

0.937*

0.006

Large

400

380

2,554

4,920

0.952

0.006

0.962*

0.006

^a Early and late nest initiation dates defined as in Table 2.
^b Patch defined as in Table 1.

**Table 4.** Results of analysis of variance on predator activity indices in the Prairie Pothole Region in Minnesota, North Dakota, and South Dakota in relation to patch size^a, location (northwest or southeast of 46°8'N and 97°43'W), and year (1993, 1994, 1995).
Source	df	Red fox	Coyote	Striped skunk	American badger	Franklin's ground squirrel
F	P	F	P	F	P	F	P	F	P
Patch size	1,117	4.11	0.045	1.88	0.173	0.49	0.485	0.01	0.909	0.02	0.886
Location	1,117	0.01	0.906	4.49	0.036	1.09	0.300	1.48	0.226	14.78	<0.001
Patch size × location	1,117	0.52	0.470	0.03	0.862	0.34	0.560	0.46	0.500	0.30	0.587
Yr	2,81	2.24	0.113	4.93	0.010	17.38	<0.001	6.44	0.003	2.82	0.066
Yr × patch size	2,81	2.05	0.135	0.20	0.817	0.16	0.853	0.67	0.693	0.65	0.527
Yr × location	2,81	5.33	0.007	0.12	0.891	0.36	0.701	0.78	0.463	0.07	0.929
Yr × patch size × location	2,81	0.37	0.691	4.07	0.021	1.31	0.276	1.49	0.232	0.85	0.431
^a Patch defined as in Table 1.

Table 4. Results of analysis of variance on predator activity indices in the Prairie Pothole Region in Minnesota, North Dakota, and South Dakota in relation to patch size^a, location (northwest or southeast of 46°8'N and 97°43'W), and year (1993, 1994, 1995).

Source

Red fox

Coyote

Striped skunk

American badger

Franklin's ground squirrel

Patch size

1,117

4.11

0.045

1.88

0.173

0.49

0.485

0.01

0.909

0.02

0.886

Location

1,117

0.01

0.906

4.49

0.036

1.09

0.300

1.48

0.226

14.78

<0.001

Patch size × location

1,117

0.52

0.470

0.03

0.862

0.34

0.560

0.46

0.500

0.30

0.587

2,81

2.24

0.113

4.93

0.010

17.38

<0.001

6.44

0.003

2.82

0.066

Yr × patch size

2,81

2.05

0.135

0.20

0.817

0.16

0.853

0.67

0.693

0.65

0.527

Yr × location

2,81

5.33

0.007

0.12

0.891

0.36

0.701

0.78

0.463

0.07

0.929

Yr × patch size × location

2,81

0.37

0.691

4.07

0.021

1.31

0.276

1.49

0.232

0.85

0.431

^a Patch defined as in Table 1.

**Table 5.** Correlation coefficients between daily survival rates^a (DSR) of upland duck nests in the Prairie Pothole Region of Minnesota, North Dakota, and South Dakota, and between explanatory variables, 1993-95.
	n^b	DSR (late)^c	Patch location^d	Patch size^e	Activity index^f
DSR (early)	184	0.03	0.05	0.15	−0.06	0.21	0.02	−0.06	−0.01
DSR (late)	182		0.02	0.19	−0.16	0.05	0.07	−0.07	−0.04
Patch location	212			0.13	−0.02	0.14	0.02	−0.12	−0.30
Patch size	212				−0.22	0.12	−0.07	−0.03	−0.01
Red fox	212					−0.15	0.29	0.16	−0.03
Coyote	212						0.21	0.08	0.12
Striped skunk	212							0.06	−0.01
American badger	212								0.18
^a Estimated by Mayfield method, as modified by Johnson (1979). ^b Number of patch × year combinations; n = 154 for correlation of DSR (early) × DSR (late). ^c Early and late nest initiation dates defined as in Table 2. ^d Patch defined as in Table 1. ^e Patch size = ln (ha). ^f Mean proportion of plots around study fields that contained carnivore tracks during 3 annual surveys, or number of unique Franklin's ground squirrels captured per trap day in 4 24-hr periods (Sargeant et al. 1993, Sovada et al. 1995).

Table 5. Correlation coefficients between daily survival rates^a (DSR) of upland duck nests in the Prairie Pothole Region of Minnesota, North Dakota, and South Dakota, and between explanatory variables, 1993-95.

n^b

DSR
(late)^c

Patch
location^d

Patch
size^e

Activity index^f

Red fox

Coyote

Striped
skunk

American
badger

Franklin's
ground squirrel

DSR (early)

184

0.03

0.05

0.15

−0.06

0.21

0.02

−0.06

−0.01

DSR (late)

182

0.02

0.19

−0.16

0.05

0.07

−0.07

−0.04

Patch location

212

0.13

−0.02

0.14

0.02

−0.12

−0.30

Patch size

212

−0.22

0.12

−0.07

−0.03

−0.01

Red fox

212

−0.15

0.29

0.16

−0.03

Coyote

212

0.21

0.08

0.12

Striped skunk

212

0.06

−0.01

American badger

212

0.18

^a Estimated by Mayfield method, as modified by Johnson (1979).
^b Number of patch × year combinations; n = 154 for correlation of DSR (early) × DSR (late).
^c Early and late nest initiation dates defined as in Table 2.
^d Patch defined as in Table 1.
^e Patch size = ln (ha).
^f Mean proportion of plots around study fields that contained carnivore tracks during 3 annual surveys, or number of unique Franklin's ground squirrels captured per trap day in 4 24-hr periods (Sargeant et al. 1993, Sovada et al. 1995).

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