California Clapper Rail (Rallus longirostris obsoletus) Population monitoring: 2005-2008 Leonard Liu, Julian Wood, Nadav Nur, Diana Stralberg, and Mark Herzog prbo conservation Science




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Table 2. Five monitoring scenarios used in the power analysis. Sites contain an average of 5.7 listening stations. Scenarios 1, 2, and 3 represent Estuary-wide monitoring scenarios. Scenarios 4 and 5 represent reduced survey efforts.

Scenario 1- current effort and design (90 sites)

Density

Sites

Surveys/yr




Zero to very low

30

3




Med-low

15

3




Medium

15

3




Med-high

15

3




High

15

3




Scenario 2- current effort, re-allocated (90 sites)

Density

Sites

Surveys/yr




Zero- very low

10/yr Rotated

2




Med-low and medium

30

3




Med-high and high

30

5




Scenario 3- effort reduced to 50% of current design (45 sites)

Density

Sites

Surveys/yr




Zero to very low

15

3




Med-low

6

3




Medium

7

3




Med-high

6

3




High

7

3




Scenario 4- effort reduced by 66% (30 sites)

Density

Sites

Surveys/yr




Zero to very low

10

3




Med-low

5

3




Medium

5

3




Med-high

5

3




High

5

3




Scenario 5- effort reduced by 93% (6 sites)

Density

Sites

Surveys/yr




Zero to very low

2

3




Med-low

1

3




Medium

1

3




Med-high

1

3




High

1

3




Table 3. DISTANCE vs. Observer-derived estimates of total number of California Clapper Rails, average 2005-08.

Bay

Number of Individuals (DISTANCE)

Number of Individuals (Observer)

Central San Francisco Bay

121

108

San Pablo Bay

442

521

South San Francisco Bay

878

761

Suisun Bay

7

13

Total

1,448

1,403


Table 4. Analysis of inter-annual change and trends in Clapper Rail abundance for San Pablo, South San Francisco, and Central San Francisco Bays, combined and separate.

Region

Time period

% change

SE

P value

Regression coefficient

SE reg. coeff.

All

2005-08

-20.6%

3.8%

<0.0001

-0.231

0.048

All

2005-06

19.3%

17.7%

0.23

0.177

0.148

All

2006-07

-14.6%

11.3%

0.23

-0.157

0.132

All

2007-08

-46.0%

6.8%

<0.0001

-0.616

0.125

San Pablo Bay

2005-08

-22.2%

6.7%

0.004

-0.252

0.087

San Pablo Bay

2005-06

13.0%

19.7%

>0.4

0.122

0.174

San Pablo Bay

2006-07

-25.3%

23.1%

>0.3

-0.291

0.308

San Pablo Bay

2007-08

-23.6%

23.2%

>0.3

-0.270

0.302

South SF Bay

2005-08

-22.0%

4.7%

<0.0001

-0.249

0.060

South SF Bay

2005-06

22.2%

27.2%

>0.3

0.200

0.222

South SF Bay

2006-07

-3.5%

13.1%

>0.7

-0.035

0.135

South SF Bay

2007-08

-57.4%

5.0%

<0.0001

-0.853

0.117

Central SF Bay

2005-08

-5.0%

19.2%

>0.8

-0.051

0.202

Central SF Bay

2005-06

Insufficient data

Central SF Bay

2006-07

Insufficient data

Central SF Bay

2007-08

-25.4%

33.5%

>0.5

-0.293

0.446

Table 5. Effect of marsh area (natural log-transformed) on Clapper Rail density (natural log-transformed), controlling for annual trend and for Bay Region (San Pablo Bay vs. South San Francisco Bay) including marshes surveyed in 2 or more years where density >0 in 1 or more years, 2005 to 2008.

Density (ln)

Coefficient

SE

P value

95% CI Low

95% CI High

Annual trend

-0.227

0.052

< 0.001

-0.329

-0.124

Marsh area (ln)

0.106

0.098

> 0.281

-0.087

0.299

Bay region

-0.090

0.316

> 0.776

-0.710

0.529

Table 6. Power analysis results from program MONITOR. Power level represents percent chance to detect the stated positive or negative annual and cumulative change. Refer to methods for scenario design details.

Scenario

Power Level

Minimum Positive Annual Change

10-year Positive Change

Minimum Negative Annual Change

10-year Negative Change

1- current effort and design

(90 sites)



80%

1.4%

14.9%

-1.5%

-13.8%

90%

1.6%

17.2%

-1.7%

-16.1%

2- current effort, re-allocated

(90 sites)



80%

1.3%

13.5%

-1.4%

-12.9%

90%

1.5%

16.1%

-1.6%

-14.9%

3- effort reduced 50% (45 sites)

80%

2.0%

21.9%

-2.2%

-19.9%

90%

2.3%

26.0%

-2.6%

-23.0%

4- effort reduced 66% (30 sites)

80%

2.5%

28.4%

-2.8%

-25.0%

90%

3.0%

33.9%

-3.4%

-29.2%

5- effort reduced 93% (6 sites)

80%

10.0%

170%

N/A

N/A

90%

N/A

N/A

N/A

N/A

40%

N/A

N/A

-10.6%

-67.4%

50%

N/A

N/A

-15.0%

-80.3%

Figures

Figure 1. Map of sites surveyed in San Pablo and Central San Francisco Bays between 2005 and 2008 by PRBO and partners. Sites color-coded by observer-derived density estimate averaged over 2005 to 2008. Site numbers correspond to sites in Table 1 and Appendix 2.



Figure 2. Map of sites surveyed in South San Francisco Bay between 2005 and 2008 by PRBO and partners. Sites color-coded by observer-derived density estimate averaged over 2005 to 2008. Site numbers correspond to sites in Table 1 and Appendix 2.



Figure 3. Map of sites surveyed in Suisun Bay between 2005 and 2008 by PRBO and partners. Sites color-coded by observer-derived density estimate averaged over 2005 to 2008. Site numbers correspond to sites in Table 1 and Appendix 2.

Figure 4. Bay-wide Clapper Rail densities (all sites in San Pablo, Central and South San Francisco Bays), 2005-08. The fitted line assumes a constant percent change per year and is derived from the site by site analysis. The plotted values are shown for illustration and represent pooled mean densities. Error bars represent 1 Standard Error.





Figure 5. San Pablo Bay Region Clapper Rail densities, 2005-08. The fitted line assumes a constant percent change per year and is derived from the site by site analysis. The plotted values are shown for illustration and represent pooled mean densities. Error bars represent 1 Standard Error.



Figure 6. South San Francisco Bay Region Clapper Rail densities, 2005-08. The fitted line assumes a constant percent change per year and is derived from the site by site analysis. The plotted values are shown for illustration and represent pooled mean densities. Error bars represent 1 Standard Error.



Figure 7. Central San Francisco Bay Region Clapper Rail densities, 2005-08. The fitted line assumes a constant percent change per year and is derived from the site by site analysis. The plotted values are shown for illustration and represent pooled mean densities. Error bars represent 1 Standard Error.

Figure 8. Predicted California Clapper Rail probability of occurrence based on Maxent model.





Figure 9. Maxent-modeled relationship between California Clapper Rail presence and landscape variables (proportion within 1-km radius, except salinity): (a) high-intensity development; (b) low-intensity development proportion; (c) salinity; (d) agriculture; (e) estuarine wetlands; (f) palustrine and estuarine wetlands combined; and (g) elevation.

a



b



c




d




e



f


Figure 9 continued



g






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