DEPARTMENT OF THE INTERIOR

U.S. FISH AND WILDLIFE SERVICE

REGION 8

Toxic Thresholds of Selenium in Mallard Eggs: Data Report

FINAL REPORT

USFWS ID # 200310005.2

USEPA Interagency Agreement # DW-14-92253201-3

Prepared by:

Kevin M. Aceituno

Environmental Contaminants Specialist

and

Thomas C. Maurer

Environmental Contaminants Specialist

Chief, Investigations and Prevention Branch

U.S. Fish and Wildlife Service

Environmental Contaminants Division

Sacramento Field Office
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

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August, 2011

BLANK PAGE
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

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INTRODUCTION

As part of the Department of the Interior’s irrigation drainwater research program of the mid1980's to mid-1990's several experimental feeding studies were conducted with game-farm 

mallards (Anas platyrhynchos) to determine toxic threshold concentrations of selenium in avian 

eggs (summarized in Heinz, 1996). Coordinated field studies of shorebirds, primarily blacknecked stilts (Himantopus mexicanus) and American avocets (Recurvirostra americana), were 

also conducted in an attempt to document toxic threshold concentrations of selenium in avian 

eggs (summarized in Skorupa, 1998). Results of these efforts indicated that the selenium toxic 

threshold point, based on reduced egg viability, occurs somewhere in the region of 6-10 μg/g

(dry weight basis or dwb). Based on well documented bioaccumulation factors for selenium, 

only 2-4 ug/L of selenium in water can lead to 6-10 μg/g selenium (dwb) in avian eggs (Skorupa,

1998). These results are one of the core scientific foundations for the U.S. Fish and Wildlife 

Service’s (Service) recommendation that the U.S. Environmental Protection Agency (EPA)

revise the national chronic water quality criterion for selenium downward from 5 ug/L to 2 ug/L 

(USFWS, 2000: California Toxics Rule Biological Opinion).

A debate in the professional literature (Fairbrother et al., 1999; Skorupa, 1999; Fairbrother et al.,

2000; CH2M HILL, 2000) and at professional meetings (Adams et al., 2000) has taken place

regarding the Service’s data interpretations. Fairbrother et al. (1999) and Adams et al. (2000) reexamined the Service’s experimental feeding studies with game-farm mallards. Based on new 

statistical analyses of existing data, Fairbrother et al. (1999) and Adams et al. (2000) argued that 

the data from laboratory studies of mallard ducks support a critical threshold value of 16-20 μg/g

selenium (dwb) in avian eggs. The authors’ analysis forms one of the core scientific foundations 

for the Regulated Community’s recommendation that EPA should either retain the current water 

quality criteria for selenium, or revise it upward. Skorupa (1999) responded to those 

recommendations by identifying additional data points not considered by Fairbrother et al. 

(1999) and Adams et al. (2000), and by showing that the authors’ statistical methods, when 

applied to the complete data set, yield a critical threshold value of 7.9 μg/g (dwb); a number 

consistent with the Service’s recommendation. A third, and independent, analysis of the 

Service’s laboratory data for mallards was conducted by CH2M HILL (2000) under contract to

Chevron Oil Company. This analysis identified additional data points not included in any of the 

earlier analyses and this larger data set yielded an estimated threshold value of 8.4 μg/g (dwb); 

also a number consistent with the Service’s recommendation.

Since the Service’s original laboratory feeding experiments were based on relatively small 

sample sizes, typically 10-15 ducks per treatment group, and because there is a fair amount of 

individual variation in sensitivity to selenium poisoning among mallard ducks, all of the various 

analyses of the data have fairly wide statistical confidence boundaries. For example, CH2M 

HILL’s analysis estimated the threshold point at 8.4 μg/g, but with 95% confidence intervals that 
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

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extended from 1.0 μg/g to 13.7 μg/g. Thus, currently existing data, while supporting the Service 

position more than it supports other interpretations, does not conclusively eliminate either 

position statistically speaking. This lack of statistical power associated with small sample sizes 

has led to scientific uncertainty. 

The Service had a uniquely inexpensive opportunity to conduct a large-sample field study wellsuited to conclusively resolving the debate over the precise location of the selenium toxicity 

threshold point for mallard eggs. The City of Davis, California (City), a community 15 miles 

west of Sacramento, routinely disposes of treated sewage water by irrigating upland fields. The 

treated sewage water contains a slightly elevated concentration of selenium (approximately 4 

ug/L). To maximize evaporative transpiration of the applied sewage water, the fields are 

periodically mowed to promote new growth. The fields have consistently attracted large 

numbers of nesting mallards, and as a conservation measure City personnel search for duck nests 

before they mow a field. They salvage the eggs from all nests found and turn them over to the 

North Delta Conservancy where the eggs are artificially incubated, and the hatched ducklings are 

raised until they are old enough to be re-introduced into the wild. Because the water has slightly 

elevated selenium levels, the duck eggs contain slightly elevated selenium levels as well. Past 

monitoring of mallard eggs conducted by the City of Davis (Mike Conners, City of Davis, pers. 

comm.) has revealed egg selenium concentrations as high as about 20 μg/g (dwb) and as low as 

normal background of about 1-3 μg/g (Skorupa and Ohlendorf, 1991). This range of exposure is 

ideal for a large sample size determination of the critical threshold point for toxicity. Typically 

the City of Davis sends anywhere from 300 to 800 mallard eggs per nesting season to the North 

Delta Conservancy. This report summarizes the methods and data generated by an investigation 

designed to provide statistical resolution of the selenium toxicity threshold point for mallard eggs 

with enough precision to distinguish between two alternative interpretations of laboratory 

toxicity testing results: (1) a lower threshold estimated by Service of 6-10 μg/g (dwb) versus (2) 

a higher threshold of 16-20 μg/g estimated by the Regulated Community.

METHODS

Egg Collection

Egg collection was done in coordination with City personnel, and took place during the 2000 to 

2005 nesting seasons (April through July). During this time the Overland Flow site of the Davis 

Wastewater Treatment Facility (Figures 1 & 2) was monitored and searched for nests once every 

ten days. Although mallards were the primary target species, gadwall (Anas strepera) and 

cinnamon teal (Anas cyanoptera) nests were also located and collected. Nest searches were 

conducted using a chain dragged between two ATVs. This method is commonly used to locate 

nests of cryptic species as discussed in Higgins et al. (1969). When a duck was observed flying 

off a nest a spotter identified the species while others continued to move to the sighting. Upon 

location of the nest, clutch size was recorded and one egg was randomly selected for dissection 

and chemical analysis. Random selection was done by using a random number table to generate 
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

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a number zero through nine. One person would hold a finger over the egg closest to the 

approach and begin scanning over the clutch, while another person would observe the second 

indicator on a digital clock and indicate when to stop scanning (when seconds match the 

randomly generated number). The randomly selected egg was designated as the “A” egg, placed 

inside an egg carton inside of a cooler, and taken back to the Sacramento Fish and Wildlife 

Office (SFWO) for processing. The remainder of the clutch was collected and stored in an egg 

carton at ambient temperature with the air cell facing upward, and transported to the artificial 

incubation facility within the same day. When a large clutch (i.e., 8-12 eggs) was located, the 

“A” egg was collected as well as three additional eggs (also randomly selected using the methods 

described above). All four eggs were collected for chemical analysis to ensure that an individual 

egg from each clutch would provide an appropriate representation of clutch-wide selenium 

exposure. To assess the variability of selenium among eggs within a single clutch we calculated 

the coefficient of variation for each large clutch sampled using the following formula:

Artificial Egg Incubation

Collected eggs were sent to the North Delta Conservancy (Conservancy) in Walnut Grove, 

California for artificial incubation and hatching. Eggs were incubated in a GQF Model 1202 

incubator (GQF Manufacturing Company, Savannah, GA) at 99.5o F and 56% relative humidity 

until hatching, or sufficiently past term to indicate failure to hatch. The Conservancy’s artificial 

incubation (hatchability) rate for mallard clutches was 92% (i.e. 92% equals the site-specific 

control hatchability), this was based on observing hatching rates of clutches collected from other 

areas of the region that were delivered to the Conservancy for artificial incubation. The fate of 

each egg was monitored to determine hatching success for each clutch. Hatching success was 

measured by determining the percent of eggs we delivered to the Conservancy that hatched. 

Failed-to-hatch eggs were returned to the SFWO where they were dissected according to the 

protocol outlined above and the fate of each embryo was determined. 
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

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Figure 1.

City of Davis Wastewater Treatment Facility

Figure 2.

The Davis Wastewater Treatment Facility Overland Flow Site. 

Woodland

Sacramento

Davis
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

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Egg Processing

Eggs collected for inspection and chemical analysis were held at ambient temperature and 

processed within six hours of collection. Egg length and breadth were measured to the nearest 

0.01 millimeter using digital calipers, and whole egg mass was measured to the nearest 0.01 

gram using a digital scale. A small hole was then cut in the blunt end of the egg over the air sac 

using stainless steel scissors and the egg shell bisected so the contents could be inspected and 

removed. To ensure no cross contamination between eggs occurred, scissors were rinsed with 

dilute nitric acid and deionized water between samples. Egg stage and condition were 

determined through direct observation of egg contents using the methods outlined in Caldwell 

and Snart (1974). Egg contents were stored in certified clean I-Chem® 200 series glass jars with 

Teflon-lined caps and immediately frozen at - 20o C.

Chemical Analysis

Samples selected for selenium analysis were sent to the Laboratory and Environmental Testing, 

Inc. (LET) facility in Columbia, Missouri and analyzed using hydride generation atomic 

absorption spectroscopy (HGAA). LET is a Service contract laboratory which utilizes 

Analytical Control Facility (ACF) approved analytical techniques and QA/QC procedures (SOPs 

used by LET are available upon request). 

In addition to selenium analysis a subset of eggs was randomly selected for full inorganic 

analysis including aluminum, arsenic, boron, barium, beryllium, cadmium, chromium, copper, 

iron, mercury, magnesium, manganese, molybdenum, nickel, lead, strontium, vanadium and 

zinc. These additional analyses were done to determine if any contaminants besides selenium 

were present and if they had the potential to influence hatchability. Eggs selected for full 

inorganic scan were processed in the same manner as eggs analyzed for selenium. Inorganic 

scans were also conducted by LET using either inductively-coupled plasma emission 

spectrometry (Al, B, Ba, Be, Cd, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Sr, V), graphite furnace atomic 

absorption spectrometry (Pb), or cold vapor atomic absorption spectrometry (Hg). All inorganic 

data presented in this report are in parts per million (μg/g) on a dry weight basis.

An additional subset of eggs was also selected for organic chemical analysis to ensure that 

organic contaminants were not influencing hatchability. Eggs selected for organic analysis were 

processed using the same methods as eggs selected for inorganic analysis except dissecting tools 

were rinsed with hexane between samples to avoid cross contamination. Samples were then sent 

to the California Department of Fish and Game’s Water Pollution Control Laboratory (WPCL) in 

Rancho Cordova, California. The organic analysis was done using gas chromatography-mass 

spectrometry and included organochlorine pesticides scan (e.g., DDT, chlordane, dieldrin), 

congener specific polychlorinated biphenyl (PCB) scan, congener specific polybrominated 

diphenyl ether (PBDE) scan, and phthalate scan. When randomly selecting eggs for organic 

analysis, only fresh and one day old eggs were considered to control for potential chemical 

breakdown. This also assisted in reporting results, as organic contaminants are presented as parts 

per million (μg/g) on a fresh wet weight basis. 

Following chemical analysis, selenium concentrations for sample eggs were matched to the 
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

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hatchery performance data of sibling eggs, providing a complete data set suitable for creating a 

statistically precise estimate of the toxicity threshold point for mallard eggs exposed to relatively 

low concentrations of selenium. Henny et al. (2000) found that hatching success in artificially 

incubated eggs depended on egg stage at the time of collection. They found that mallard eggs 

incubated naturally for less than three days hatched at a lower rate than eggs incubated for three 

or more days. To control for this confounding effect, we only analyzed clutches that had three or 

more days of natural incubation at the time of collection.

RESULTS

Selenium and Hatchability Analysis

Between 2000 and 2005 a total of 96 mallard clutches were found with 3 or more days of natural 

incubation. These clutches were used for selenium and hatching analysis. Selenium 

concentrations in the randomly collected “A” egg ranged from 1.7 to 14 μg/g (dry weight) with a 

mean of 4.2 μg/g (geometric mean). Hatching success of individual clutches ranged from 50 to 

100% with an overall mean of 91%. Annual breakdown of selenium and hatching data is shown 

in Table 1 (See Appendix A for complete data set).

Table 1. Selenium and hatching data for mallard clutches collected from the Davis Wastewater Treatment 

Facility. 

Intra-Clutch Selenium Variation

Clutches large enough to facilitate intra-clutch analysis were not found during the 2000 field 

season, but a total of 15 large clutches were found during the 2001 to 2005 seasons. Eleven

clutches were mallard, three were gadwall and one was cinnamon teal. The mean coefficient of 

variation was 18.1% and ranged from a minimum of 3.8% to a maximum of 74.3%. The clutch 

with 74.3% variation had one egg with a selenium concentration substantially more elevated than 

the other two (13 μg/g compared to 3.8 and 4.2 μg/g). When this clutch was omitted the mean 

coefficient of variation dropped to 14.1%. Complete variation data for all clutches are presented 

in Table 2 (See Appendix B for complete data set).

Table 2. Intra-clutch variation in selenium concentrations.

2000 2001 2002 2003 2004 2005 All Years

# Clutches 

Collected 23 17 13 4 28 11 96

Mean [Se]* 

(Range)

4.1 

(1.7 - 14)

3.4 

(2.4 - 5.2)

5.0 

(3.2 - 7.3)

4.1 

(2.1 - 5.7)

4.7 

(1.8 - 11)

3.6 

(1.9 - 12)

4.2 

(1.7 - 14.0)

Mean % 

Hatch 

(Range)

87% 

(50 - 100)

90% 

(66.67 - 100)

98% 

(83.33 - 100)

82% 

(40.00 - 100)

91% 

(50.00 - 100) 100% 91% (40.00 - 100)

* Geometric mean presented as μg/g dry weight.
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

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Complete Inorganic and Organic Contaminant Analysis

A subset of 31 eggs was randomly selected for an inorganic scan. Of the 18 elements included in 

the scan, 11 were detected in at least one egg; however, only barium, copper, iron, magnesium, 

manganese, strontium and zinc were detected in all 31 eggs. The results indicate extremely 

elevated concentrations of barium with a geometric mean of 27.61 μg/g (see discussion). A 

complete summary of detection frequency, range and means for each metal is presented in Table 

3.

An additional subset of 5 fresh eggs was selected for organic analysis. All five eggs contained 4, 

4’ dichlorodiphenyldichloroethylene (DDE), a metabolite of DDT, at concentrations ranging 

from 0.08 to 0.22 μg/g (fresh wet weight). Three phthalate esters were also detected: Di-n-butyl 

phthalate (DBP) ranged from 0.06 to 0.18 μg/g, Bis-2-ethyhexyl phthalate (DEHP) ranged from 

0.08 to 0.21 μg/g, and Diphenylphthalate (DPP) ranged from 0.07 to 0.11 μg/g. Four PBDE 

congeners were detected in all five eggs as well. BDE 47 ranged from 0.001 to 0.17 μg/g, BDE 

99 ranged from 0.003 μg/g to 0.23 μg/g, BDE 100 ranged from 0.003 μg/g to 0.10 μg/g, and 

BDE 155 ranged from 0.002 μg/g to 0.021 μg/g. The remaining organic contaminants were not 

consistently present in all eggs, were below detection limits, or were below quantifiable 

concentrations. A complete list of organic analytes and results is presented in Appendix C.

Table 3. Results summary of full metals scan. Concentrations are presented in μg/g on a dry 

weight basis.

Year Species # Eggs 

Collected

Mean [Se] ± SE 

(μg/g dry weight)

Range Coefficient of 

Variation (%)

Mallard 4 2.3 ± 0.1 2.1 - 2.4 4.3

Mallard 4 4.6 ± 0.2 4.3 - 4.9 6.5

Mallard 4 3.0 ± 0.2 2.6 - 3.4 10.0

Mallard 4 3.1 ± 0.2 2.9 - 3.5 9.7

Mallard 4 6.9 ± 0.6 6.0 - 8.4 15.9

Mallard 4 3.8 ± 0.1 3.7 - 4.0 2.6

Mallard 4 4.2 ± 0.3 3.7 - 5.0 14.3

Mallard 3 7.0 ± 3.0 3.8 - 13.0 74.3

Mallard 4 6.2 ± 0.2 5.9 - 6.5 4.8

Mallard 5 6.5 ± 0.3 5.5 - 7.4 10.8

Mallard 4 3.5 ± 0.7 2.4 - 5.3 37.1

Gadwall 4 4.5 ± 1.2 2.9 - 8.0 53.3

Cinnamon teal 3 5.3 ± 0.1 5.1 - 5.5 3.8

Gadwall 3 7.3 ± 0.6 6.6 - 8.4 13.7

Gadwall 6 8.6 ± 0.4 7.6 - 9.7 10.5

2001

2002

2004

2005
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

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DISCUSSION

A concern during this investigation was ensuring that observed decreases in hatchability were 

due to low level selenium exposure instead of exposure to additional contaminants known to 

impair avian reproduction. The National Irrigation Water Quality Program (NIWQP) identified 

several contaminants of concern on irrigated lands due to their potential adverse effects on 

wildlife. This includes seven inorganic contaminants: arsenic, boron, cadmium, copper, 

mercury, molybdenum and zinc (U.S. DOI, 1998; Seiler et al., 2003). For these seven elements 

we compared the data from our full scan to background concentrations, no observable effect 

levels (NOEL), and lowest observable effect levels (LOEL) compiled by NIWQP (Table 4). 

Cadmium and molybdenum were not detected in any of the Davis duck eggs, and copper was 

detected at concentrations below the established background level. Arsenic, boron and mercury 

were all detected at levels above background, but the mean concentration of all three were 

considerably lower than NOEL or LOEL concentrations. Zinc concentrations were above the 

established background level. However, it is unlikely that zinc was impairing hatchability since 

it is an essential element, and concentrations in the Davis duck eggs were not substantially higher 

than background. Additionally, birds are considered relatively tolerant to zinc and effects on 

avian offspring are only seen in laboratory experiments in which hens are fed extremely elevated 

doses of zinc (Eisler, 1993).

Table 4. Comparison of Davis Ducks data to metals identified by the National Irrigation Water 

Element Detection 

Frequency

Minimum Maximum Mean

Aluminum 0/31 - - -

Arsenic 3/31 non detect 0.6 0.36

Boron 11/31 non detect 3 2.32

Barium 31/31 8.2 77.4 27.61

Beryllium 0/31 - - -

Cadmium 0/31 - - -

Chromium 0/31 - - -

Copper 31/31 1.3 5.1 3.39

Iron 31/31 91 170 127.11

Mercury 19/31 non detect 1.1 0.20

Magnesium 31/31 318 950 449.06

Manganese 31/31 1 5 2.65

Molybdenum 0/31 - - -

Nickel 0/31 - - -

Lead 1/31 non detect 0.3 -

Strontium 31/31 6.7 47 16.48

Vanadium 0/31 - - -

Zinc 31/31 47 84 59.47
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

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Quality Program as a potential concern on irrigated lands (US DOI, 1998; Seiler et al., 2003). 

Concentrations are presented in μg/g dry weight.

The inorganic scan also revealed elevated concentrations of barium ranging from 8.2 to 77.4 

μg/g with a geometric mean of 27.6 μg/g. We were unable to find any barium toxicity 

thresholds for avian eggs, but barium concentrations were much higher compared to eggs from 

other studies. The highest barium concentrations found in mallard eggs came from a study done 

in the Cook Inlet in Alaska where concentrations ranged from 2.3 to 5.5 μg/g dry weight 

(USFWS, 1994). The highest barium concentrations found in California came from great blue 

heron (Ardea herodias) and great egret (Ardea alba) eggs from Stone Lakes National Wildlife 

Refuge (Thomas, 1999). Great blue heron egg concentrations ranged from 2.05 to 6.91 μg/g,

and great egret eggs ranged from 3.12 to 6.66 μg/g. In another study conducted in California, 

Schwarzbach et al (2006) documented barium concentrations in failed-to-hatch California 

clapper rail (Rallus longirostris obsoletus) eggs from San Francisco Bay. They found eggs with 

deformed embryos contained higher concentrations of barium (2.2 – 4.1 μg/g) than eggs without 

deformed embryos (0.20 – 0.59 μg/g). Although the difference in barium concentrations was 

significant, a similar trend was also found in strontium, aluminum and chromium concentrations 

and the authors were unable to definitively conclude that barium was responsible for the 

abnormal growth observed. 

The Davis mallard eggs contained barium concentration at least on order of magnitude higher 

than other eggs from throughout the United States. Due to this discrepancy, we ensured that the 

results were not the product of laboratory error. ACF conducts a complete QA/QC check on all 

data before results are considered final. Further, LET conducts matrix spikes and sample 

duplicates as a measure of analytical accuracy. We inspected the raw lab data and both matrix 

spike and duplicate results indicated that the elevated concentrations were not a result of 

laboratory error. Moreover, in an effort to determine the impacts of elevated barium, we 

examined the relationship between barium concentration in the egg and hatching success in the 

corresponding clutch, but found no correlation between barium concentration and hatching 

success (p = 0.95). Despite elevated barium levels, the overall hatching success of eggs collected 

for this study is considered high and it does not appear that barium was impairing hatchability.

In addition to inorganic contaminants, a number of organic chemicals were also detected in 

Davis Duck eggs. DDE is known to impair avian reproduction and was detected in mallard and 

gadwall eggs. The presence of DDE is not surprising given a long history of DDT use in 

California and its persistence in the environment. The impact of DDE on avian reproductive 

Element Background NOEL LOEL Detection 

Frequency

Mean

Arsenic 0.25 1.8 3.6 3/31 0.36

Boron 1 22 38 11/31 2.32

Cadmium 0.15 - - 0/31 -

Copper 5.5 - - 31/31 3.39

Mercury 0.1 - 2.86* 19/31 0.20

Molybdenum 0.25 23 33 0/31 -

Zinc 50 - - 31/31 59.47

*Heinz, 1979 (value converted from 0.86 μg/g fresh wet weight assuming 70% moisture)
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

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performance is highly dependent on species. In white ibis (Plegadis chihi), a fresh wet weight 

concentration as low as 0.25 μg/g in eggs was associated with 4.5% egg shell thinning (King et 

al., 1980). A 15.4 % decrease in thickness in common goldeneye (Bucephala clangula) egg 

shells occurred at egg concentrations of 0.52 μg/g (Zicus et al., 1988). The black duck (Anas 

rubripes), a close relative of the mallard, appears to be less sensitive to DDE exposure with 

eggshell thinning occurring at 46.3 μg/g (Longcore et al., 1971). DDE concentrations found in 

this investigation are below the lowest toxicity benchmarks, and are orders of magnitude lower 

than a toxicity benchmark for a closely related species. Therefore, DDE does not appear to be 

adversely impacting hatchability.

Three phthalate esters were also detected in this investigation. These chemicals have been 

largely used as plasticizers in a broad range of applications. We were unable to find 

toxicological effect thresholds for phthalate esters in avian eggs, or any studies characterizing 

phthalate concentrations in eggs. It has been recognized that phthalate esters have a low degree 

of acute and chronic toxicity to aquatic wildlife given their lack of water solubility and 

bioaccumulative potential (Autian, 1970; Parkerton and Staples, 2003) thus we do not think these 

chemicals impaired hatching in this study.

The presence of PBDE congeners found in this study likely reflects the widespread use of these 

chemicals as fire retardants. PBDE products are typically a mixture of different congeners and 

the leading commercial mixture, a pentaBDE product commonly referred to as DE-71, contains 

primarily BDEs 47, 99, 100 and 153 (EPA, 2006). These are the four congeners detected in this 

study, but determining the impact of these chemicals is difficult given a lack of toxicity 

thresholds for avian eggs. Many studies have investigated total PBDEs in eggs. Among the 

highest were peregrine falcon (Falco peregrinus) eggs with an average concentration of 6.6 μg/g 

(Chen et al., 2008). McKernan et al (2009) conducted a dosing study using DE-71, and found 

that injecting eggs with 10 and 20 μg/g DE-71 decreased pipping and hatching success in 

American kestrels (Falco sparverius), but had no effect on chickens (Gallus gallus) or mallards. 

The PBDE concentrations detected in this study are well below those found in other eggs, and 

are considerably lower than dosing concentrations that had no toxicological impact. Given these 

comparisons, we do not consider any decreases in hatchability to be caused by PBDEs.

Because the laying order of eggs within the clutches collected was not observed, we relied on 

random selection and analysis of one egg to provide a representation of selenium concentrations 

in all eggs. Many studies have shown that there is no relationship between selenium 

concentration and laying order in mallard eggs produced from selenium-dosed hens (Heinz et al., 

1987; Heinz et al., 1989; Stanley et al., 1994). Additionally, Bryan et al. (2003) found no intraclutch variation in selenium concentrations of common grackle (Quiscalus quiscala) eggs and 

Smith et al. (1988) also found no variation in black-crowned night-herons (Nycticorax 

nicticorax). Further, both of these studies documented similar coefficients of variation to what 

we found in our intra-clutch comparison (13.8% in common grackles, 16% in black-crowned 

night-herons). Our results and the findings of others indicate that the randomly selected “A” 

eggs provide a suitable representation of clutch-wide selenium exposure. 

This investigation was necessary because laboratory-based selenium toxicity testing is limited to 

small samples sizes, largely due to the expense of housing and caring for captive ducks. These 
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

13

studies have yielded results that are relatively imprecise and consequently open to alternative 

interpretations. Additionally, many field studies examining selenium toxicity are focused on 

already contaminated sites, thus egg concentrations from these studies tend to fall into the higher 

effect range. This still leaves the lower concentration range poorly populated with data, resulting 

in the lack of statistical power required to determine low level toxicity effects. We capitalized 

on a unique opportunity to generate data regarding the impact of selenium on reproductive 

performance in mallards. The goal of this investigation was to collect enough eggs from adult 

mallards exposed to slightly elevated levels of selenium to provide greater statistical resolution 

of low level effect concentrations. In total, nearly 100 clutches were sampled and the low level 

of selenium exposure is reflected in an average egg concentration of 4.2 μg/g. This is above the 

expected background concentration of selenium in eggs (1 to 3 μg/g; Skorupa and Ohlendorf, 

1991), but still well below egg concentrations ( > 60 μg/g) from areas considered highly 

impaired due to selenium contamination (Ohlendorf, 2003). 

RECOMMENDATIONS

The Service used an opportunity to collect data suitable for integration with existing toxicity 

studies. The next step in the process is to take the data generated in this investigation and 

incorporate it into larger data sets utilized by researchers to assess threshold selenium effect 

levels. The eventual result will be a statistically powerful, field-based data set with the ability to 

accurately define the toxicity threshold of selenium to reproductive performance in mallards. 

Selenium is a widespread and potent contaminant threat to trust resources and resolution of the 

uncertainty surrounding the toxic threshold point will have significant regulatory implications. 

The next step to take is to add these data to the master database maintained by the Service and 

perform the appropriate statistical analyses that will provide a refined selenium toxicity threshold 

for mallard eggs.

REFERENCES

Adams, W.J., Tear, L.M., Edwards, M., Fairbrother, A. and Brix, K.V. 2000. Re-analysis of 

field data used to derive selenium toxicity thresholds for birds. Abstract for Platform 

Presentation as 21st Annual Meeting of the Society of Environmental Toxicology and Chemistry. 

Pp. 43 in Abstract Book, SETAC 21st Annual Meeting, 12-16 November 2000, Nashville, 

Tennessee. SETAC, Pensacola, California.

Autian, J. 1973. Toxicity and Health Threats of Phthalate Esters: Review of the Literature. 

Environmental Health Perspectives 4:3-26.

Bryan, A.L., Hopkins, W.A., Baionno, J.A. and Jackson, P. 2003. Maternal Transfer of 

Contaminants to Eggs in Common Grackles (Quiscalus quiscala) Nesting on Coal Fly Ash 

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Caldwell, P.J. and Snart, A.E. 1974. A Photographic Index for Aging Mallard Embryos. 

Journal of Wildlife Management 38:298-301.

CH2M HILL. 2000. Relative Sensitivity of Avian Species to Selenium-Related Reproductive 

Effects. Report prepared on behalf of Chevron Oil Company for submission to the California 
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Regional Water Quality Control Board, San Francisco Bay Region. December, 2000. 13 pp.

Chen, D., LaGuardia, M.J., Harvey, E., Amaral, M., Wohlfort, K. and Hale, R.C. 2008. 

Polybrominated Diphenyl Ethers in Peregrine Falcon (Falco peregrinus) Eggs from the 

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Toxic Thresholds of Selenium in Mallard Eggs: Data Report

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Appendix A

Selenium and Hatching Data
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

17

Appendix A: Table 1. Selenium and hatching data from 2000. Samples highlighted in red were omitted from analysis due to lack of natural incubation or 

insufficient hatching data.

Egg Condition Key: LN=live, normal; LA=live, abnormal; LU=live, unknown; DN=dead, normal; DA=dead, abnormal; DU=dead, unknown; UU=unknown, unknown 

Sample ID Year Spp

Collection 

Date

Collection 

type Nest # Egg #

Egg 

Stage (d)

Egg 

Condition

Clutch 

Size

Eggs 

Collected

Failed 

to 

Hatch Hatch

% 

Hatching 

Success

Se (ppm 

dw)

00M002AR 2000 mallard 5/4/2000 Random 002 1 0 UU 8 1 3 4 57.14 4.5

00M003AR 2000 mallard 5/4/2000 Random 003 1 0 UU 4 1 3 0 0.00 2.6

00M004AR 2000 mallard 5/4/2000 Random 004 1 0 UU 8 1 3 4 57.14 4.5

00M006AR 2000 mallard 5/4/2000 Random 006 1 15 LN 5 1 0 4 100.00 3.9

00M011AR 2000 mallard 5/17/2000 Random 011 1 10 LN 7 1 3 3 50.00 4.6

00M013AR 2000 mallard 5/17/2000 Random 013 1 20 LN 4 1 0 3 100.00 4.1

00M015AR 2000 mallard 6/12/2000 Random 015 1 13 LN 6 1 3 2 40.00 2.9

00M016AR 2000 mallard 5/17/2000 Random 016 1 14 DN 6 1 0 5 100.00 4.6

00M019AR 2000 mallard 5/18/2000 Random 019 1 8 LN 6 1 1 3 75.00 7.7

00M020AR 2000 mallard 5/18/2000 Random 020 1 8 LN 10 1 2 4 66.67 2.3

00M021AR 2000 mallard 5/18/2000 Random 021 1 16 LN 10 1 0 9 100.00 12

00M031AR 2000 mallard 5/22/2000 Random 031 1 14 LN 8 1 0 7 100.00 4.2

00M032AR 2000 mallard 5/22/2000 Random 032 1 8 LN 8 1 0 7 100.00 4.6

00M035AR 2000 mallard 5/22/2000 Random 035 1 15 LN 5 1 1 3 75.00 14

00M036AR 2000 mallard 5/22/2000 Random 036 1 8 LN 5 1 1 3 75.00 4.8

00M037AR 2000 mallard 6/12/2000 Random 037 1 18 LN 9 1 0 8 100.00 2.8

00M038AR 2000 mallard 6/12/2000 Random 038 1 13 LN 9 1 0 8 100.00 2.5

00M053AR 2000 mallard 5/24/2000 Random 053 1 16 LN 5 1 1 3 75.00 3.7

00M063AR 2000 mallard 6/1/2000 Random 063 1 16 LN 7 1 0 6 100.00 3.1

00M067AR 2000 mallard 6/1/2000 Random 067 1 16 LN 8 1 0 7 100.00 3.1

00M071AR 2000 mallard 6/1/2000 Random 071 1 12 LN 5 1 1 3 75.00 4

00M075AR 2000 mallard 6/1/2000 Random 075 1 9 LN 4 1 0 3 100.00 4.9

00M079AR 2000 mallard 6/12/2000 Random 079 1 15 DA 4 1 2 1+ 5.5

00M082AR 2000 mallard 6/12/2000 Random 082 1 20 LN 8 1 1 6 85.71 4.8

00M086AR 2000 mallard 6/19/2000 Random 086 1 13 LN 8 1 0 4 100.00 1.7

00M088AR 2000 mallard 6/19/2000 Random 088 1 20 LN 6 1 1 4 80.00 3.7

00M089AR 2000 mallard 6/19/2000 Random 089 1 16 LN 4 1 0 3 100.00 2.6
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

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Appendix A: Table 2. Selenium and hatching data from 2001. Samples highlighted in red were omitted from analysis due to lack of natural incubation.

Egg Condition Key: LN=live, normal; LA=live, abnormal; LU=live, unknown; DN=dead, normal; DA=dead, abnormal; DU=dead, unknown; UU=unknown, unknown 

Sample ID Year Spp

Collection 

Date

Collection 

type Nest # Egg #

Egg 

Stage (d)

Egg 

Condition

Clutch 

Size

Eggs 

Collected FTH Hatch

% 

Hatching 

Success

Se (ppm 

dw)

01M008AR 2001 mallard 4/25/2001 Random 008 1 18 LN 10 1 0 9 100.00 4.4

01M011AR 2001 mallard 4/27/2001 Random 011 1 18 LN 8 1 0 7 100.00 5.2

01M012AR 2001 mallard 4/27/2001 Random 012 1 unk DU 10 1 1 8 88.89 4

01M013AR 2001 mallard 4/27/2001 Random 013 1 24 LN 9 4 2 5 71.43 2.4

01M018AR 2001 mallard 5/2/2001 Random 018 1 7 LN 10 1 2 7 77.78 4.5

01M019AR 2001 mallard 5/4/2001 Random 019 1 14 LN 9 1 0 8 100.00 3.1

01M021AR 2001 mallard 5/4/2001 Random 021 1 14 LN 12 4 1 8 88.89 4.3

01M022AR 2001 mallard 5/4/2001 Random 022 1 unk UU 8 1 0 7 100.00 3.7

01M024AR 2001 mallard 5/9/2001 Random 024 1 6 LN 10 1 0 9 100.00 3.6

01M025AR 2001 mallard 5/9/2001 Random 025 1 20 DA 8 1 1 2 66.67 4.2

01M030AR 2001 mallard 5/9/2001 Random 030 1 24 LN 6 1 0 5 100.00 4

01M033AR 2001 mallard 5/16/2001 Random 033 1 14 LN 5 1 0 4 100.00 2.5

01M040AR 2001 mallard 5/23/2001 Random 040 1 8 LN 9 4 0 5 100.00 3.1

01M044AR 2001 mallard 5/30/2001 Random 044 1 6 LU 9 1 2 6 75.00 2.5

01M046AR 2001 mallard 5/30/2001 Random 046 1 12 LN 6 1 1 4 80.00 3.2

01M048AR 2001 mallard 6/6/2001 Random 048 1 14 LN 9 4 1 4 80.00 3.5

01M049AR 2001 mallard 6/6/2001 Random 049 1 6 LU 9 1 1 7 87.50 2.8

01M050AR 2001 mallard 6/6/2001 Random 050 1 14 LN 5 1 0 4 100.00 2.5

01M053AR 2001 mallard 6/18/2001 Random 053 1 16 LN 5 1 0 4 100.00 3.1
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

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Appendix A: Table 3. Selenium and hatching data from 2002.

Egg Condition Key: LN=live, normal; LA=live, abnormal; LU=live, unknown; DN=dead, normal; DA=dead, abnormal; DU=dead, unknown; UU=unknown, unknown 

Appendix A: Table 4. Selenium and hatching data from 2003.

Egg Condition Key: LN=live, normal; LA=live, abnormal; LU=live, unknown; DN=dead, normal; DA=dead, abnormal; DU=dead, unknown; UU=unknown, unknown 

Sample ID Year Spp

Collection 

Date

Collection 

type Nest # Egg #

Egg 

Stage (d)

Egg 

Condition

Clutch 

Size

Eggs 

Collected FTH Hatch

% 

Hatching 

Success

Se (ppm 

dw)

02M007AR 2002 mallard 4/16/2002 Random 007 1 18 LN 8 1 0 7 100.00 5.1

02M012AR 2002 mallard 5/9/2002 Random 012 1 12 LN 8 1 0 7 100.00 7.3

02M017AR 2002 mallard 5/9/2002 Random 017 1 14 LN 10 4 0 6 100.00 6

02M019AR 2002 mallard 5/10/2002 Random 019 1 9 LN 7 1 0 6 100.00 6.7

02M023AR 2002 mallard 5/10/2002 Random 023 1 18 LN 7 1 0 6 100.00 4

02M026AR 2002 mallard 5/17/2002 Random 026 1 12 LN 6 1 0 5 100.00 4.9

02M027AR 2002 mallard 5/17/2002 Random 027 1 10 DU 5 1 0 4 100.00 6.9

02M028AR 2002 mallard 5/17/2002 Random 028 1 8 LN 7 1 0 6 100.00 5.1

02M032AR 2002 mallard 5/17/2002 Random 032 1 11 LN 8 1 1 6 85.71 6.7

02M037AR 2002 mallard 5/31/2002 Random 037 1 21 LN 10 4 1 5 83.33 3.8

02M041AR 2002 mallard 6/14/2002 Random 041 1 22 LN 9 4 0 5 100.00 4.1

02M043AR 2002 mallard 6/14/2002 Random 043 1 20 LN 8 1 0 7 100.00 3.2

02M044AR 2002 mallard 6/14/2002 Random 044 1 18 LN 7 1 0 6 100.00 3.2

Sample ID Year Spp

Collection 

Date

Collection 

type Nest # Egg #

Egg 

Stage (d)

Egg 

Condition

Clutch 

Size

Eggs 

Collected FTH Hatch

% 

Hatching 

Success

Se (ppm 

dw)

03M002AR 2003 mallard 5/16/2003 Random 002 1 12 LN 9 1 1 7 87.50 4.5

03M007AR 2003 mallard 6/2/2003 Random 007 1 9 LN 6 1 3 2 40.00 2.1

03M308AR 2003 mallard 6/2/2003 Random 308 1 18 LN 6 1 0 5 100.00 5

03M403AR 2003 mallard 6/2/2003 Random 403 1 9 LN 8 1 0 7 100.00 5.7
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

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Appendix A: Table 5. Selenium and hatching data from 2004. Samples highlighted in red were omitted from analysis due to lack of natural incubation.

Sample ID Year Spp

Collection 

Date

Collection 

type Nest # Egg #

Egg 

Stage (d)

Egg 

Condition

Clutch 

Size

Eggs 

Collected FTH Hatch

% 

Hatching 

Success

Se (ppm 

dw)

04M001AR 2004 mallard 4/23/2004 Random 001 1 addled unk 3 1 1 1 50.00 3.9

04M012AR 2004 mallard 5/2/2004 Random 012 1 0 UU 4 1 1 3 75.00 15

04M013AR 2004 mallard 5/2/2004 Random 013 1 14 LN 9 1 3 5 62.50 7.5

04M014AR 2004 mallard 5/2/2004 Random 014 1 23 LN 5 1 2 2 50.00 4.2

04M016AR 2004 mallard 5/2/2004 Random 016 1 6 LU 9 1 1 7 87.50 11

04M017AR 2004 mallard 5/2/2004 Random 017 1 3 LU 8 1 2 5 71.43 4.1

04M019AR 2004 mallard 5/2/2004 Random 019 1 0 UU 3 1 1 1 50.00 3.6

04M021AR 2004 mallard 5/2/2004 Random 021 1 5 LU 8 1 1 6 85.71 6.4

04M023AR 2004 mallard 5/2/2004 Random 023 1 24 LN 9 1 0 8 100.00 5.8

04M026AR 2004 mallard 5/9/2004 Random 026 1 7 LU 8 1 2 5 71.43 1.8

04M033AR 2004 mallard 5/9/2004 Random 033 1 2 LU 10 4 2 4 66.67 6.3

04M037AR 2004 mallard 5/17/2004 Random 037 1 21 LN 11 4 2 5 71.43 7.4

04M040AR 2004 mallard 5/17/2004 Random 040 1 24 LN 5 1 0 4 100.00 5.3

04M042AR 2004 mallard 5/17/2004 Random 042 1 14 LN 9 1 0 8 100.00 3.3

04M043AR 2004 mallard 5/24/2004 Random 043 1 10 LN 6 1 0 5 100.00 3

04M044A2R 2004 mallard 5/24/2004 Random 044 1 24 LN 2 1 0 1 100.00 5.7

04M045AR 2004 mallard 5/24/2004 Random 045 1 26 LN 11 1 2 8 80.00 8.5

04M047AR 2004 mallard 5/24/2004 Random 047 1 25 LN 7 1 0 6 100.00 11

04M049AR 2004 mallard 5/24/2004 Random 049 1 9 LU 9 1 0 8 100.00 8.9

04M051AR 2004 mallard 5/24/2004 Random 051 1 25 LN 9 1 0 8 100.00 7.9

04M058AR 2004 mallard 5/24/2004 Random 058 1 14 LN 6 1 0 5 100.00 4.7

04M059AR 2004 mallard 5/24/2004 Random 059 1 16 LN 5 1 0 4 100.00 2.7

04M061AR 2004 mallard 5/24/2004 Random 061 1 25 LN 9 1 0 8 100.00 3.5

04M062AR 2004 mallard 5/24/2004 Random 062 1 26 LN 8 1 0 7 100.00 6.9

04M082AR 2004 mallard 6/20/2004 Random 082 1 7 LU 10 4 0 6 100.00 3.5

04M083AR 2004 mallard 6/20/2004 Random 083 5 14 LN 8 1 0 7 100.00 8.2

04M086AR 2004 mallard 6/20/2004 Random 086 1 17 LN 8 1 0 7 100.00 2.3

04M087AR 2004 mallard 6/20/2004 Random 087 1 10 LN 8 1 1 6 85.71 1.8

04M091AR 2004 mallard 6/20/2004 Random 091 1 24 LN 9 1 0 8 100.00 3.4

04M100AR 2004 mallard 7/1/2004 Random 100 1 21 LN 8 1 0 7 100.00 2.5

04M101AR 2004 mallard 7/1/2004 Random 101 1 21 LN 8 1 1 6 85.71 4.1

04M102AR 2004 mallard 7/1/2004 Random 102 1 28 LN 7 1 0 6 100.00 4
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

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Egg Condition Key: LN=live, normal; LA=live, abnormal; LU=live, unknown; DN=dead, normal; DA=dead, abnormal; DU=dead, unknown; UU=unknown, unknown
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

21

Appendix A: Table 6. Selenium and hatching data from 2005.

Egg Condition Key: LN=live, normal; LA=live, abnormal; LU=live, unknown; DN=dead, normal; DA=dead, abnormal; DU=dead, unknown; UU=unknown, unknown 

Sample ID Year Spp

Collection 

Date

Collection 

type Nest # Egg #

Egg 

Stage (d)

Egg 

Condition

Clutch 

Size

Eggs 

Collected FTH Hatch

% 

Hatching 

Success

Se (ppm 

dw)

05M001AR 2005 mallard 4/19/2005 Random 001 1 24 LN 9 1 0 8 100.00 2.3

05M003AR 2005 mallard 5/16/2005 Random 003 1 8 LN 7 1 0 6 100.00 12

05M005AR 2005 mallard 5/16/2005 Random 005 1 13 LN 9 1 0 8 100.00 8.3

05M015AR 2005 mallard 5/16/2005 Random 015 1 20 LN 8 1 0 7 100.00 5

05M016AR 2005 mallard 5/16/2005 Random 016 1 14 LN 5 1 0 4 100.00 2.6

05M028AR 2005 mallard 6/16/2005 Random 028 1 16 LN 9 1 0 8 100.00 4.2

05M029AR 2005 mallard 6/16/2005 Random 029 1 14 LN 9 1 0 8 100.00 2.9

05M100AR 2005 mallard 6/20/2005 Random 100 1 26 LN 9 1 0 8 100.00 2.6

05M102AR 2005 mallard 6/20/2005 Random 102 1 25 LN 7 1 0 6 100.00 1.9

05M111AR 2005 mallard 6/27/2005 Random 111 1 24 LN 9 1 0 8 100.00 2.3

05M113AR 2005 mallard 6/27/2005 Random 113 1 25 LN 9 1 0 8 100.00 3.2
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

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Appendix B

Intra-Clutch Selenium Data
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

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Appendix B: Table 1. Intra-clutch Selenium Data. Concentrations presented as μg/g on a dry weight basis.

Sample ID Year Spp Site

Collection 

Date Nest # Egg #

Clutch 

Size

Eggs 

Collected Se (ppm dw)

01M013AR 2001 mallard Davis overland flow site 4/27/2001 013 1 9 4 2.4

01M013E 2001 mallard Davis overland flow site 4/27/2001 013 2 9 4 2.2

01M013G 2001 mallard Davis overland flow site 4/27/2001 013 3 9 4 2.3

01M013H 2001 mallard Davis overland flow site 4/27/2001 013 4 9 4 2.1

01M021AR 2001 mallard Davis overland flow site 5/4/2001 021 1 12 4 4.3

01M021B 2001 mallard Davis overland flow site 5/4/2001 021 2 12 4 4.5

01M021C 2001 mallard Davis overland flow site 5/4/2001 021 3 12 4 4.7

01M021D 2001 mallard Davis overland flow site 5/4/2001 021 4 12 4 4.9

01M040AR 2001 mallard Davis overland flow site 5/23/2001 040 1 9 4 3.1

01M040B 2001 mallard Davis overland flow site 5/23/2001 040 2 9 4 3.0

01M040C 2001 mallard Davis overland flow site 5/23/2001 040 3 9 4 2.6

01M040D 2001 mallard Davis overland flow site 5/23/2001 040 4 9 4 3.4

01M048AR 2001 mallard Davis overland flow site 6/6/2001 048 1 9 4 3.5

01M048B 2001 mallard Davis overland flow site 6/6/2001 048 2 9 4 3.1

01M048C 2001 mallard Davis overland flow site 6/6/2001 048 3 9 4 2.9

01M048D 2001 mallard Davis overland flow site 6/6/2001 048 4 9 4 3.0

02M017AR 2002 mallard Davis overland flow site 5/9/2002 017 1 10 4 6.0

02M017B 2002 mallard Davis overland flow site 5/9/2002 017 2 10 4 6.1

02M017C 2002 mallard Davis overland flow site 5/9/2002 017 3 10 4 7.2

02M017D 2002 mallard Davis overland flow site 5/9/2002 017 4 10 4 8.4

02M037AR 2002 mallard Davis overland flow site 5/31/2002 037 1 10 4 3.8

02M037B 2002 mallard Davis overland flow site 5/31/2002 037 2 10 4 3.8

02M037C 2002 mallard Davis overland flow site 5/31/2002 037 3 10 4 3.7

02M037D 2002 mallard Davis overland flow site 5/31/2002 037 4 10 4 4.0

02M041AR 2002 mallard Davis overland flow site 6/14/2002 041 1 9 4 4.1

02M041B 2002 mallard Davis overland flow site 6/14/2002 041 2 9 4 3.7

02M041C 2002 mallard Davis overland flow site 6/14/2002 041 3 9 4 5.0

02M041D 2002 mallard Davis overland flow site 6/14/2002 041 4 9 4 4.0

04M014AR 2004 mallard Davis overland flow site 5/2/2004 014 1 5 1 4.2

04M014D1FTH 2004 mallard Davis overland flow site 6/28/2004 014 2 5 1 3.8

04M014D2FTH 2004 mallard Davis overland flow site 6/28/2004 014 3 5 1 13.0

04M033AR 2004 mallard Davis overland flow site 5/9/2004 033 1 10 4 6.3

04M033BR 2004 mallard Davis overland flow site 5/9/2004 033 2 10 4 6.5

04M033CR 2004 mallard Davis overland flow site 5/9/2004 033 3 10 4 6.0

04M033DR 2004 mallard Davis overland flow site 5/9/2004 033 4 10 4 5.9

04M037AR 2004 mallard Davis overland flow site 5/17/2004 037 1 11 4 7.4

04M037F 2004 mallard Davis overland flow site 8/31/2004 037 2 11 4 6.5

04M037I1R 2004 mallard Davis overland flow site 5/17/2004 037 3 11 4 6.5

04M037I2R 2004 mallard Davis overland flow site 5/17/2004 037 4 11 4 5.5

04M037KR 2004 mallard Davis overland flow site 5/17/2004 037 5 11 4 6.6

04M082AR 2004 mallard Davis overland flow site 6/20/2004 082 1 10 4 3.5

04M082BR 2004 mallard Davis overland flow site 6/20/2004 082 2 10 4 2.4

04M082CR 2004 mallard Davis overland flow site 6/20/2004 082 3 10 4 2.7

04M082DR 2004 mallard Davis overland flow site 6/20/2004 082 4 10 4 5.3

04G001AR 2004 gadwall Davis overland flow site 4/23/2004 001 1 9 4 8.0

04G001BR 2004 gadwall Davis overland flow site 4/23/2004 001 2 9 4 3.4

04G001FR 2004 gadwall Davis overland flow site 4/23/2004 001 3 9 4 3.7

04G001GR 2004 gadwall Davis overland flow site 4/23/2004 001 4 9 4 2.9

05G001AR 2005 gadwall Davis overland flow site 5/16/2005 001 1 9 1 6.8

05G001BFTH 2005 gadwall Davis overland flow site 8/12/2005 001 2 9 1 8.4

05G001DFTH 2005 gadwall Davis overland flow site 8/12/2005 001 3 9 1 6.6

05G004AR 2005 gadwall Davis overland flow site 6/1/2005 004 1 10 1 7.6

05G004CFTH 2005 gadwall Davis overland flow site 8/12/2005 004 2 10 1 8.6

05G004FFTH 2005 gadwall Davis overland flow site 8/12/2005 004 3 10 1 9.4

05G004GFTH 2005 gadwall Davis overland flow site 8/12/2005 004 4 10 1 8.3

05G004HFTH 2005 gadwall Davis overland flow site 8/12/2005 004 5 10 1 7.7

05G004JFTH 2005 gadwall Davis overland flow site 8/12/2005 004 6 10 1 9.7

T008AR 2004 cinnimon teal Davis overland flow site 5/24/2004 008 1 8 1 5.5

T008FFTH 2004 cinnimon teal Davis overland flow site 6/30/2004 008 2 8 1 5.1

T008HFTH 2004 cinnimon teal Davis overland flow site 6/30/2004 008 3 8 1 5.2
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

26

Appendix C

Results of Inorganic and Organic Scans
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

25

Appendix C: Table 1. Results of inorganics scan. Concentrations are presented as μg/g on a dry weight basis. 

*Non-detects are reported as less than the method detection limit (in red). 

Sample ID Year Spp Al As B Ba Be Cd Cr Cu Fe Hg Mg Mn Mo Ni P b S e S r V Zn

01M008AR 2001 mallard < 2 < 0.2 < 2 25.00 < 0.1 < 0.1 < 0.5 4.2 160 0.3 442 2.4 < 2 < 0.5 < 0.2 4.4 11 < 0.5 65

01M013AR 2001 mallard < 2 < 0.2 3 38.00 < 0.1 < 0.1 < 0.5 2.4 140 0.66 569 4.8 < 2 < 0.5 < 0.2 2.4 37 < 0.5 55

01M013E 2001 mallard < 2 < 0.2 2 43.00 < 0.1 < 0.1 < 0.5 2.5 130 0.71 453 4.1 < 2 < 0.5 < 0.2 2.2 21 < 0.5 51

01M013H 2001 mallard < 2 < 0.2 2 50.00 < 0.1 < 0.1 < 0.5 3.2 150 1.1 416 5 < 2 < 0.5 < 0.2 2.1 19 < 0.5 55

01M021AR 2001 mallard < 2 < 0.2 < 2 16.00 < 0.1 < 0.1 < 0.5 3.9 110 0.1 318 1.6 < 2 < 0.5 < 0.2 4.3 10 < 0.5 48

01M021B 2001 mallard < 2 < 0.2 < 2 14.00 < 0.1 < 0.1 < 0.5 4 99 0.1 381 2.5 < 2 < 0.5 < 0.2 4.5 11 < 0.5 61

01M021C 2001 mallard < 2 < 0.2 < 2 25.00 < 0.1 < 0.1 < 0.5 3.4 120 < 0.1 372 3.2 < 2 < 0.5 < 0.2 4.7 11 < 0.5 61

01M021D 2001 mallard < 2 < 0.2 < 2 25.00 < 0.1 < 0.1 < 0.5 2.6 170 < 0.1 359 3.4 < 2 < 0.5 < 0.2 4.9 13 < 0.5 76

01M022AR 2001 mallard < 2 < 0.2 < 2 8.20 < 0.1 < 0.1 < 0.5 3.9 120 < 0.1 358 2.8 < 2 < 0.5 < 0.2 3.7 6.7 < 0.5 59

01M025AR 2001 mallard < 2 < 0.2 < 2 20.00 < 0.1 < 0.1 < 0.5 4 120 0.1 471 2 < 2 < 0.5 < 0.2 4.2 23 < 0.5 62

01M048AR 2001 mallard < 2 < 0.2 < 2 34.00 < 0.1 < 0.1 < 0.5 3.2 130 0.1 410 3.9 < 2 < 0.5 < 0.2 3.5 16 < 0.5 61

04M014AR 2004 mallard < 2 < 0.2 < 2 20 < 0.1 < 0.1 < 0.5 3.1 120 0.1 434 1 < 2 < 0.5 0.3 4.2 16 < 0.5 50.1

04M023AR 2004 mallard < 2 < 0.2 < 2 22.2 < 0.1 < 0.1 < 0.5 1.3 91 < 0.1 448 1.9 < 2 < 0.5 < 0.2 5.8 14 < 0.5 62.5

04M026AR 2004 mallard < 2 < 0.2 < 2 11 < 0.1 < 0.1 < 0.5 3.6 95 0.3 348 1 < 2 < 0.5 < 0.2 1.8 6.7 < 0.5 58.7

04M037AR 2004 mallard < 2 < 0.2 2 23.5 < 0.1 < 0.1 < 0.5 4 120 < 0.1 391 3 < 2 < 0.5 < 0.2 7.4 10 < 0.5 63.6

04M040AR 2004 mallard < 2 < 0.2 < 2 23.7 < 0.1 < 0.1 < 0.5 1.5 120 < 0.1 451 2.1 < 2 < 0.5 < 0.2 5.3 13 < 0.5 53

04M043AR 2004 mallard < 2 < 0.2 < 2 25 < 0.1 < 0.1 < 0.5 4.2 130 < 0.1 397 2.5 < 2 < 0.5 < 0.2 3 10 < 0.5 57

04M045AR 2004 mallard < 2 < 0.2 2 35.2 < 0.1 < 0.1 < 0.5 4.6 130 < 0.1 595 4.1 < 2 < 0.5 < 0.2 8.5 32.3 < 0.5 72.8

04M047AR 2004 mallard < 2 < 0.2 < 2 24.8 < 0.1 < 0.1 < 0.5 4.3 120 < 0.1 470 2.7 < 2 < 0.5 < 0.2 11 23.5 < 0.5 65.1

04M051AR 2004 mallard < 2 < 0.2 3 30.3 < 0.1 < 0.1 < 0.5 3.8 140 < 0.1 578 2.6 < 2 < 0.5 < 0.2 7.9 25 < 0.5 68.5

04M059AR 2004 mallard < 2 < 0.2 < 2 20 < 0.1 < 0.1 < 0.5 4.3 120 0.3 371 2.4 < 2 < 0.5 < 0.2 2.7 16 < 0.5 50

04M061AR 2004 mallard < 2 < 0.2 < 2 33.8 < 0.1 < 0.1 < 0.5 3.7 120 0.2 622 1.5 < 2 < 0.5 < 0.2 3.5 20.4 < 0.5 70.2

04M062AR 2004 mallard < 2 < 0.2 3 39.3 < 0.1 < 0.1 < 0.5 2.5 130 0.2 950 1.9 < 2 < 0.5 < 0.2 6.9 27.7 < 0.5 65.7

04M082AR 2004 mallard < 2 0.6 < 2 39.7 < 0.1 < 0.1 < 0.5 3.6 110 0.2 390 4 < 2 < 0.5 < 0.2 3.5 12 < 0.5 53.3

04M083AR 2004 mallard < 2 < 0.2 < 2 29.3 < 0.1 < 0.1 < 0.5 3 140 < 0.1 375 2.6 < 2 < 0.5 < 0.2 8.2 15 < 0.5 50

04M086AR 2004 mallard < 2 < 0.2 < 2 14 < 0.1 < 0.1 < 0.5 3.5 130 < 0.1 408 2.6 < 2 < 0.5 < 0.2 2.3 13 < 0.5 47

04M087AR 2004 mallard < 2 < 0.2 3 58.7 < 0.1 < 0.1 < 0.5 4.1 150 0.2 385 3.1 < 2 < 0.5 < 0.2 1.8 19 < 0.5 57.5

04M091AR 2004 mallard < 2 < 0.2 < 2 41 < 0.1 < 0.1 < 0.5 4.6 120 0.1 529 3.7 < 2 < 0.5 < 0.2 3.4 22.7 < 0.5 51.5

04M100AR 2004 mallard < 2 < 0.2 2 54.4 < 0.1 < 0.1 < 0.5 3.1 120 0.36 488 2.4 < 2 < 0.5 < 0.2 2.5 21.9 < 0.5 61.4

04M101AR 2004 mallard < 2 0.4 2 77.4 < 0.1 < 0.1 < 0.5 3.9 160 0.1 504 4.7 < 2 < 0.5 < 0.2 4.1 24.5 < 0.5 65.5

04M102AR 2004 mallard < 2 0.2 2 37.5 < 0.1 < 0.1 < 0.5 5.1 170 0.1 626 2.8 < 2 < 0.5 < 0.2 4 47 < 0.5 84
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

28

Appendix C: Table 1. Results of organochlorine scan. Concentrations presented as ng/g wet weight.

Sample ID G020AR M024A M025A M026AR M050AR

Species Gadwall Mallard Mallard Mallard Mallard

Collection Date 7/5/2005 6/1/2005 6/1/2005 6/1/2005 7/5/2005

Egg Stage (d) Fresh Fresh Fresh 1 Fresh

aldrin <0.259 <0.259 <0.259 <0.257 <0.257

chlordane, cis <0.713 <0.714 <0.714 <0.709 <0.707

chlordane, trans <0.4025 <0.403 <0.403 <0.400 <0.399

chlordene, alpha <0.275 <0.275 <0.275 <0.273 <0.273

chlordene, gamma <0.255 <0.255 <0.255 <0.253 <0.253

chlorpyrifos <0.833 <0.834 <0.834 <0.828 <0.826

dacthal <0.6295 <0.63 <0.63 <0.626 <0.624

DDD, o,p' <0.765 <0.766 <0.766 <0.76 <0.758

DDD, p,p' <0.897 1.13 DNQ <0.898 <0.891 <0.889

DDE, o,p' <0.6695 0.67 <0.67 <0.665 <0.664

DDE, p,p' 78.65 221.00 107.00 179.00 165.00

DDMU, p,p' <1.20 <1.20 <1.20 <1.19 <1.19

DDT, o,p' <1.01 <1.01 <1.01 <1.01 <1.00

DDT, p,p' <2.465 <2.47 <2.47 <2.45 <2.44

diazinon <6.735 <6.74 <6.74 <6.69 <6.68

dieldrin 13.75 29.80 15.10 13.90 9.39

endosulfan I <1.075 <1.08 <1.08 <1.07 <1.07

endosulfan II <3.985 <3.99 <3.99 <3.96 <3.95

endosulfan sulfate <3.985 <3.99 <3.99 <3.96 <3.95

endrin <0.9365 1.17 DNQ 1.12 DNQ 1.2 DNQ 1.75 DNQ

HCH, alpha <0.4745 <0.475 <0.475 <0.471 <0.47

HCH, beta <0.6135 <0.614 <0.614 <0.61 <0.608

HCH, delta <0.3585 <0.359 <0.359 <0.356 <0.356

HCH, gamma <0.3385 <0.339 <0.339 <0.337 <0.336

heptachlor <0.514 <0.515 <0.515 <0.511 <0.51

heptachlor epoxide 0.62 1.1 DNQ <0.503 1.14 DNQ 0.50

hexachlorobenzene 1.62 1.36 0.378 DNQ 1.15 0.78

methoxychlor <1.475 <1.48 <1.48 <1.47 <1.46

mirex <0.9405 <0.942 <0.942 <0.935 <0.932

nonachlor, cis <0.9765 <0.978 <0.978 <0.97 <0.968

nonachlor, trans 3.39 5.43 1.49 DNQ 7.52 1.58 DNQ

oxadiazon <0.9325 <0.934 <0.934 <0.927 <0.924

oxychlordane 2.92 6.82 1.52 DNQ 4.22 1.44 DNQ

parathion, ethyl <0.837 <0.838 <0.838 <0.832 <0.83

parathion, methyl <1.515 <1.52 <1.52 <1.50 <1.50

tedion <0.733 <0.734 <0.734 <0.729 <0.727

*Non-detect reported as less than method detection limit (in red), DNQ = detected not quantified

ORGANOCHLORINES
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

29

Appendix C: Table 2. Congener specific PCB scan. Results presented as ng/g wet weight.

Sample ID G020AR M024A M025A M026AR M050AR

Species Gadwall Mallard Mallard Mallard Mallard

Collection Date 7/5/2005 6/1/2005 6/1/2005 6/1/2005 7/5/2005

Egg Stage (d) Fresh Fresh Fresh 1 Fresh

8 <0.1 <0.1 <0.1 <0.099 <0.099

18 <0.1 <0.1 <0.1 <0.099 <0.099

27 <0.1 <0.1 <0.1 <0.099 <0.099

28 0.1925 0.425 0.1 0.555 0.12 DNQ

29 <0.1 <0.1 <0.1 <0.099 <0.099

31 <0.1 <0.1 <0.1 <0.099 <0.099

33 <0.1 <0.1 <0.1 <0.099 <0.099

44 <0.1 <0.1 <0.1 <0.099 <0.099

49 0.103 <0.1 <0.1 <0.099 <0.099

52 0.1885 0.152 DNQ 0.1 DNQ 0.112 DNQ 0.116 DNQ

56 <0.1 <0.1 <0.1 <0.099 <0.099

60 <0.1 0.201 DNQ <0.1 0.186 DNQ <0.099

66 0.2495 0.462 <0.1 0.599 <0.099

70 0.17 0.179 DNQ <0.1 0.109 DNQ 0.115 DNQ

74 0.409 0.779 <0.1 0.578 0.135 DNQ

87 <0.1 <0.1 <0.1 <0.099 <0.099

95 0.1525 0.147 DNQ 0.138 DNQ 0.17 DNQ 0.15 DNQ

97 <0.1 <0.1 <0.1 <0.099 <0.099

99 0.647 0.962 0.186 DNQ 0.92 0.225 DNQ

101 0.429 0.281 DNQ 0.122 DNQ 0.193 DNQ 0.127 DNQ

105 0.559 1.05 0.197 DNQ 0.648 0.241 DNQ

110 0.201 0.246 DNQ 0.135 DNQ 0.148 DNQ 0.127 DNQ

114 <0.1 <0.1 <0.1 <0.099 <0.099

118 1.495 2.43 0.467 1.68 0.564

128 0.319 0.482 0.119 DNQ 0.284 DNQ 0.119 DNQ

137 <0.1 <0.1 <0.1 <0.099 <0.099

138 1.65 2.24 0.432 1.63 0.439

141 <0.1 <0.1 <0.1 <0.099 <0.099

149 0.1825 0.245 DNQ 0.141 DNQ 0.23 DNQ 0.099

151 <0.1 <0.1 <0.1 <0.099 <0.099

153 2.93 3.54 1.04 2.43 0.97

156 0.2055 0.294 DNQ 0.1 0.202 DNQ 0.099

157 <0.1 <0.1 <0.1 <0.099 <0.099

158 0.134 0.179 DNQ <0.1 0.147 DNQ <0.099

170 0.386 0.462 0.165 DNQ 0.328 DNQ 0.14 DNQ

174 <0.1 <0.1 <0.1 <0.099 <0.099

177 0.133 0.209 DNQ <0.1 0.151 DNQ <0.099

180 0.665 1.31 0.395 DNQ 1.00 0.212 DNQ

183 0.3385 0.366 DNQ <0.1 0.287 DNQ <0.099

187 1.0075 1.47 0.688 0.792 0.544

189 <0.1 <0.1 <0.1 <0.099 <0.099

194 0.2195 0.219 DNQ 0.107 DNQ 0.141 DNQ 0.165 DNQ

195 <0.1 <0.1 <0.1 <0.099 <0.099

200 <0.1 <0.1 <0.1 <0.099 <0.099

201 0.317 0.471 0.485 0.36 DNQ 0.347 DNQ

203 0.2485 0.252 DNQ 0.164 DNQ 0.227 DNQ 0.212 DNQ

206 0.135 0.197 DNQ 0.218 DNQ 0.116 DNQ 0.235 DNQ

209 <0.1 <0.1 0.118 DNQ <0.099 0.103 DNQ

PCB 1248 <9.965 <9.98 <9.98 <9.9 <9.88

PCB 1254 20 29 4 DNQ 21 5 DNQ

PCB 1260 10 11 DNQ 8 DNQ 9 DNQ 8 DNQ

*Non-detect reported as less than method detection limit (in red), DNQ = detected not quantified

PCB's
Toxic Thresholds of Selenium in Mallard Eggs: Data Report

30

Appendix C: Table 3. Congener specific PBDE scan. Results presented as ng/g wet weight.

Appendix C: Table 4. Phthalate esters scan. Results presented as ng/g wet weight.

Sample ID G020AR M024A M025A M026AR M050AR

Species Gadwall Mallard Mallard Mallard Mallard

Collection Date 7/5/2005 6/1/2005 6/1/2005 6/1/2005 7/5/2005

Egg Stage (d) Fresh Fresh Fresh 1 Fresh

BDE 17 <0.277 <0.277 <0.277 <0.275 <0.275

BDE 28 <0.295 <0.295 <0.295 <0.293 <0.292

BDE 47 129.5 171 1.21 DNQ 112 2.20

BDE 66 0.268 <0.268 0.352 DNQ 0.38 DNQ 0.351 DNQ

BDE 100 98.95 100 2.64 164 2.80

BDE 99 116.5 178 4.52 237 3.08

BDE 85 1.235 1.16 DNQ <0.353 2.77 <0.35

BDE 154 11.3 10.4 1.13 DNQ 14.8 1.65

BDE 153 21.35 19.6 1.91 17.6 5.71

BDE 138 1.76 1.45 DNQ <0.399 1.31 DNQ <0.395

BDE 183 0.8845 0.859 DNQ <0.593 0.923 DNQ <0.587

BDE 190 <0.87 <0.871 <0.871 <0.865 <0.863

*Non-detect reported as less than method detection limit (in red), DNQ = detected not quantified

PBDE's

Sample ID G020AR M024A M025A M026AR M050AR

Species Gadwall Mallard Mallard Mallard Mallard

Collection Date 7/5/2005 6/1/2005 6/1/2005 6/1/2005 7/5/2005

Egg Stage (d) Fresh Fresh Fresh 1 Fresh

Butyl benzyl phthalate (BbzP) <5.0 <5.0 <5.0 <5.0 <5.0

Di-n-butyl phthalate (DBP) 66.4 57.2 143 177.5 195

Bis(2-ethylhexyl)phthalate (DEHP) 81.0 106 215 203 89.6

Diphenylphthalate (DPP) 103 72.4 90.4 96.6 111

Phthalate Esters by LC/MS

*Non-detect reported as less than method detection limit (in red), DNQ = detected not quantified