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) 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 1 st 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/ Jun1-Jul8-Jul15-Jul22-Jul1-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 Middle Deer Lower Deer St John Upper Snake Middle Snake 35NA Montezuma Denver Water Keystone

Number of individual invertebrates caught at each site by sampling day. 24-Jun1-Jul8-Jul15-Jul22-Jul1-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 Middle Deer Lower Deer St John Upper Snake Middle Snake 35NA Montezuma Denver Water Keystone

Metal Concentrations in Benthic Invertebrates 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 Total Occupied TSTS MCMC VGVG MBMB Percent Occupied Total Occupied TSTS MCMC VGVG MBMB Percent Occupied Upper Deer Middle Deer Lower Deer St John Upper Snake Middle Snake Montezuma Denver Water Keystone Overall

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 LiverWater and Diet r 2 valuesP-valuesr 2 valuesP-values Cd Co Cu Fe Mn Pb Zn

Correlation in Metals Between Water and Benthic Invertebrate Samples r 2 valuesP-values Al Cd Co Fe Mn Pb Zn

Correlation Between Metals in Nestling Diets, Livers and Invertebrates Diet and Liver (n=17) Diet and Invertebrates (n=8) r2r2 p-valuesr2P-values AlNA Cd Co Cr Cu Fe Mn Pb Zn

Correlation in Metals Between Benthic Invertebrate and Liver Samples r2r2 P-values Cd Co Cr Cu Fe Pb Zn

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 PC1PC2 Al Cd Co Cu Fe Mn Ni Pb Zn

PCA – Metal Concentrations in Benthic Invertebrates PC1PC2 Al Cr Mn Fe Co Ni Cu Zn Cd Pb

PCA – Metal Concentrations in Nestling Diets PC1PC2 Al Cr Mn Fe Co Ni Cu Zn Cd Pb

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

Conclusion AMD 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