Effects of Acid Mine Drainage (AMD) on Nesting Tree Swallows.

Effects of Acid Mine Drainage (AMD) on

Nesting Tree Swallows

Acid Mine Drainage (AMD)

Streams contaminated with AMD cause ecological and biological stresses by

• Low pH

• High metal concentrations

• Deposition of metal oxides

Ecological Effects of AMD

• Effects at all levels of food chain from periphyton and fungal communities upwards

• Effects on invertebrates include– Reduced abundance and biomass– Reduced species diversity– Shift in species composition from metal-

intolerant taxa to metal-tolerant taxa (mayflies shown to be more susceptible)

Effects of AMD (cont’d)

Tree Swallows• Readily use nestboxes

• Feed near their nestboxes (< 400m)

• Primarily eat emergent aquatic insects

Study Objectives

• Evaluate the relationships among metal concentrations detected in the water, benthic invertebrates and nesting tree swallows

• Evaluate the effect of streams contaminated with heavy metals on the nesting success of tree swallows

Study Area

• Central Colorado near Keystone Ski Resort

• 9 sites selected along Snake River and two tributaries (St John’s Creek and Deer Creek)

• 10-30 nestboxes erected at sites May 2003

Upper Snake River• Low pH• High metal concentrations

Deer Creek• Near neutral pH• Low metal concentrations

St John’s Creek• Near neutral pH• Low metal concentrations

Methods

Samples collected at each site included:

• Water samples

• Benthic invertebrates

• Aerial invertebrates

• Tree swallow livers and diets

Methods - Water Samples

• Collected in triplicates in 250ml Nalgene bottles on weekly basis during summer 2004

• Sampling dates are 6/17, 6/21, 6/28, 7/8, 7/15, 7/22, and 7/29

• Chemical analysis by USGS, Denver

- metal concentrations

- pH and conductivity

Methods – Benthic Invertebrates

• Surber and Ekman grabs used

• Samples collected on 6/24, 7/1, 7/8, 7/15, 7/22 and 8/1 during 2004

• Number of samples varied from site to site

• Metal concentration analysis by USGS, Denver

Methods – Aerial Invertebrates

• Assess food availability at each site

• Used aerial tow-nets that rotate in the wind

Methods – Tree Swallow Monitoring/Sampling

• Part of a larger study conducted by Christine Custer (USGS, La Crosse, WI) to analyze effects of trace metals on tree swallows

• Nestboxes monitored on weekly basis from 1st week of June to last week in July (2003 and 2004)

• Progress of nest construction, number of eggs/young recorded

• Nestling liver and diet samples collected• Metal analysis done by USGS, Denver

Tree Swallow Nests

Statistical Analysis

• Regressions between metal concentrations detected in the water, benthic invertebrates, nestling diets and livers

• Principal Component Analysis (PCA) was also used to analyze metal concentrations in the water, benthic invertebrates, nestling diets and livers

Water Quality Results

• pH lowest at MS

• Conductivity highest at MS

• MS had the highest Al, Zn, Pb and Cd concentrations for most days

• US water chemistry more similar to those along Deer Creek than MS

Water Results - pH

Water Results – Conductivity

Al Concentrations

Zn Concentrations

Benthic Invertebrates Results

• Highest number of taxa caught along Deer Creek sites

Number of taxa of invertebrates caught at each site by sampling day. No insects were caught at MS on 7/1/04.

  24-Jun 1-Jul 8-Jul 15-Jul 22-Jul 1-Aug

# of taxa

# of sam.

# of taxa

# of sam.

# of taxa

# of sam.

# of taxa

# of sam.

# of taxa

# of sam.

# of taxa

# of sam.

Upper Deer 4 2 3 3 4 2 8 2 4 2 6 2

Middle Deer 6 1 7 2 11 1 7 1 5 1 8 2

Lower Deer 3 1 7 2 9 1 9 1 5 1 5 2

St John 4 1 6 4 6 2 6 3 7 3 8 5

Upper Snake 2 6 2 5 5 5 1 4 3 5 2 5

Middle Snake 3 5 NA NA 2 5 3 5 2 5 2 6

Montezuma 2 2 2 3 2 3 1 5 3 5 4 12

Denver Water 1 2 3 7 2 7 4 6 3 8 5 11

Keystone 2 5 6 7 2 8 2 7 3 7 4 8

Number of individual invertebrates caught at each site by sampling day.

  24-Jun 1-Jul 8-Jul 15-Jul 22-Jul 1-Aug

# of ind.

# of sam.

# of ind.

# of sam.

# of ind.

# of sam.

# of ind.

# of sam.

# of ind.

# of sam.

# of ind.

# of sam.

Upper Deer 5 2 13 3 23 2 27 2 56 2 23 2

Middle Deer 8 1 17 2 41 1 44 1 37 1 49 2

Lower Deer 13 1 41 2 39 1 46 1 56 1 26 2

St John 9 1 15 4 23 2 26 3 38 3 53 5Upper Snake 23 6 2 5 35 5 77 4 87 5 94 5Middle Snake 3 5 NA NA 49 5 79 5 80 5 67 6

Montezuma 20 2 11 3 25 3 25 5 20 5 14 12Denver Water 1 2 3 7 20 7 31 6 18 8 25 11

Keystone 2 5 16 7 3 8 11 7 30 7 27 8

Metal Concentrations in BenthicInvertebrates

• For benthic invertebrates, most of the highest metal concentrations were detected at MD and MS

• Highest average Al, Co, Mn, Ni, and Pb, concentrations at MD

• Highest average Cd, Cr, Zn concentrations at MS

• Highest average Fe concentration at US• Huge contrast to water samples.

Fe Concentrations in Invertebrates

Al, Mn, Zn concentrations

Cu and Pb Concentrations

Cd, Co, Cr and Ni concentrations

Aerial Invertebrate Results

• Based on number of individuals caught, no significant difference among the sites

• Over 60% of invertebrates belonged to the Order Diptera

• Most invertebrates between 3-8mm; few Lepidoptera and Trichoptera

• Invertebrates with larger biomass such as Odonota, Plecoptera and Ephemeroptera were not caught at any sites

• Does not seem to be any difference in food availability for the tree swallows

Nest Occupancy Rates

# of nests

available

2003 2004

Total Occupied

TS

MC

VG

MB

Percent Occupied

Total Occupied

TS

MC

VG

MB

Percent Occupied

Upper Deer 10 1 1 0 0 0 10 3 1 0 1 1 30

Middle Deer 7 0 0 0 0 0 0 0 0 0 0 0 0

Lower Deer 9 0 0 0 0 0 0 3 1 2 0 0 33

St John 13 1 1 0 0 0 8 4 1 3 0 0 31

Upper Snake 25 0 0 0 0 0 0 2 2 0 0 0 8

Middle Snake 10 0 0 0 0 0 0 1 0 1 0 0 10

Montezuma 18 4 3 1 0 0 22 8 3 4 1 0 44

Denver Water 14 2 2 0 0 0 14 1 1 0 0 0 7

Keystone 20 7 7 0 0 0 35 10 7 3 0 0 50

Overall 126 15 10 30 21

Interaction between Water Quality, Benthic Invertebrates, and Tree

Swallows

• PCA of metal concentrations in water quality, invertebrates, and tree swallow livers

• Correlation between metal concentrations in water quality, invertebrates, tree swallow diets and nestlings

Correlation Between Metals in Water and Bird Samples

Water and Liver Water and Diet

r2 values P-values r2 values P-values

Cd 0.46 0.07 0.05 0.60

Co 0.06 0.55 0.01 0.87

Cu 0.19 0.28 0.04 0.63

Fe 0.81 0.0022 0.00 0.92

Mn 0.47 0.06 0.13 0.14

Pb 0.19 0.29 0.07 0.52

Zn 0.28 0.17 0.20 0.26

Correlation in Metals Between Water and Benthic Invertebrate

Samples

r2 values P-values

Al 0.04 0.61

Cd 0.10 0.40

Co 0.00 0.87

Fe 0.30 0.13

Mn 0.09 0.43

Pb 0.09 0.45

Zn 0.17 0.26

Correlation Between Metals in Nestling Diets, Livers and Invertebrates

Diet and Liver (n=17)

Diet and Invertebrates (n=8)

r2 p-values r2 P-values

Al NA NA 0.00 0.98

Cd 0.00 1.00 0.08 0.49

Co 0.62 0.02 0.07 0.53

Cr 0.38 0.11 0.12 0.40

Cu 0.64 0.02 0.05 0.61

Fe 0.10 0.45 0.04 0.64

Mn 0.23 0.23 0.00 0.98

Pb 0.35 0.12 0.02 0.71

Zn 0.20 0.26 0.25 0.20

Correlation in Metals Between Benthic Invertebrate and Liver

Samples

r2 P-values

Cd 0.77 0.004

Co 0.04 0.64

Cr 0.70 0.010

Cu 0.09 0.48

Fe 0.12 0.41

Pb 0.46 0.07

Zn 0.76 0.005

Principal Component Analysis (PCA)

• Principal Component Analysis was used to analyze metal concentrations in the water, macroinvertebrate samples, nestling diets and livers.

• PCA reduces the dimensionality of a large set of data by transforming a number of correlated variables into a smaller number of uncorrelated variables (principal components)

• Takes metal concentrations (correlated variables) in samples and transforms them into principal components

PCA – Metal Concentrations in Water Samples

  PC1 PC2

Al 0.3565 -0.15

Cd 0.3503 -0.0836

Co 0.3712 -0.1742

Cu 0.3729 -0.1645

Fe 0.3247 -0.0774

Mn 0.3601 0.0931

Ni 0.3717 -0.1849

Pb 0.162 0.7578

Zn 0.2718 0.5386

PCA – Metal Concentrations in Benthic Invertebrates

  PC1 PC2

Al -0.3355 0.3471

Cr -0.3055 -0.3009

Mn -0.3343 0.0574

Fe -0.1281 -0.4951

Co -0.3487 0.2092

Ni -0.3881 -0.0195

Cu -0.0695 0.6491

Zn -0.3463 -0.1579

Cd -0.3605 -0.2014

Pb -0.3727 0.0979

PCA – Metal Concentrations in Nestling Diets

  PC1 PC2

Al -0.1539 -0.6128

Cr -0.3271 0.1865

Mn -0.3685 -0.2803

Fe -0.3504 -0.2803

Co -0.3462 -0.1807

Ni -0.2741 -0.2577

Cu -0.2697 0.5051

Zn -0.3838 0.1091

Cd -0.3345 0.3353

Pb -0.2896 -0.1691

PCA – Invertebrate Composition

Subscripts 1,2,3,4,5, and 6 denotes sampling days 6/24, 7/1, 7/8, 7/15, 7/22 and 8/1 respectively

Discussion – Water Samples

• Water samples are important for understanding overall water quality

• Poor indicator of nest occupancy rates• Poor correlation between metals in water

and in benthic invertebrates• Significant correlation between Fe

concentrations in water and nestling diet• Poor correlation between all metal

concentrations in water and nestling livers

Discussion – Metal Concentrations in Benthic Invertebrates

• Metal concentrations in benthic invertebrates are good predictors of nest occupancy rates for a site

• Significant correlation between Cd, Cr and Zn concentrations between benthic invertebrates and nestling livers

Discussion

• Correlation may be affected by averaging metal concentrations in nestling livers, diets and invertebrates

• Unclear why metal concentrations in benthic invertebrates at MD is so high; sediment and *aufwuchs samples should be included in future studies

*aufwuchs - biotic and abiotic material accumulating on submerged surfaces

ConclusionAMD does have an effect on nesting

tree swallows:• tree swallows seem to be avoiding sites

where metal concentrations in benthic invertebrates are high

• high correlation between Cd, Cr and Zn concentrations between benthic invertebrates and nestling livers