Species

Aechmophorus occidentalis is identifiable by its long, thin neck, which is entirely white on the sides and front, and the long, daggerlike yellow to greenish bill. The head is strongly bicolored black and white in adult plumages and the eyes are a brilliant carmine. Males on the average are larger than females (972 grams vs 822 grams), otherwise there are no measurable differences except for the bill length and depth (Johnsgard, 1987). In juveniles, the crown and hindneck are dark gray or dusky, the borders of the dark areas are not sharply defined, and the back feathers are edged with grayish white (Johnsgard, 1987).

Nesting and Status in Estuarine and Coastal Areas

This species is a winter migrant to estuaries. It is a colonial bird with hundreds, even thousands, of pairs at some lakes. Its nests are closely spaced (Palmer, 1962).  Lindvall and Low (1982) reported that 95% of nearly 400 observed nests were in colonies of 5 to 88 nests, with nest spacing about 30 meters for small colonies and 15 meters or less for colonies greater than 10 pairs (Johnsgard, 1987). A mating pair builds a floating nest of wet or decaying vegetation anchored to submerged plants and incubates 2 – 4 pale bluish white eggs for about 24 days (Fix and Bezener, 2000). Young are brooded on their parents’ backs for the first few days after hatching. Adults have been observed carrying chicks overland (Johnsgard, 1987).  Both parents brood; the male tends to carry newly-hatched young more frequently than the female. The non-brooding parent brings food for the young (Storer and Nuechterlein, 1992).

Abundance and Range

No thorough survey is available. The largest number reported by the Audubon count (U.S. and Canada) in the last 12 years is 118,000 birds. This count includes about 775 Clark’s grebes and 38,500 unidentified birds (Storer and Nuechterlein, 1992). The western grebe winters on coastal waters from S.E. Alaska to W. central Mexico, and inland from Central California and Nevada southward. This species breeds on lakes from S. British Colombia, N. Alberta, and Minnesota south to Colorado and N.E. and central E. California.  Irregularly spaced populations exist into central W. California and S. California (Cogswell, 1977).

Site Fidelity

The western grebe is a resident on some lakes from Central California, south to N. Baja California and on the Mexican Plateau (Storer and Nuechterlein, 1992). Western grebes have persisted as common winter residents in Puget Sound, Washington (late September – early October through April), with some non-breeders remaining in the summer (Larrison and Sonnenberg 1968; Angell and Balcomb, 1982).

Ease of Census

Simple

Feeding Habits

The diet of the western grebe appears to consist mainly of fish. G.E. Lawrence (1950) found grebe stomachs contained 81% fish, 17% insects, and 2% aquatic plants (Palmer, 1962).  Grebes may spend up to a minute or more below the surface in pursuit of fish (Cogswell, 1977). This species feeds in scattered singles with at least 200 ft. of open water between individuals, then joins in groups when resting on the water. The morning feeding begins when there is enough light to allow for good underwater visibility (Palmer, 1962).

Western Grebe Contaminant Exposure Data

  I.

Organochlorine Contaminants

A.

Concentrations in adults

 1.

Composite samples of visceral and subcutaneous fat from 2 “sick” western grebes collected at Clear Lake, California in January 1958 were analyzed and found to have unusually high concentrations of DDD (1600 mg/g) and no infectious disease (Hunt and Bischoff, 1960).  Subsequently, composite samples of the visceral and subcutaneous fat from 7 grebes collected October 1958 at the same site and analyzed for DDD had a mean of 723 mg/g.

 2.

3.

Fat samples from 41 western grebes collected from Clear Lake, California from 1959 to 1963 were analyzed for DDD (Linn and Stanley 1969). There was no well defined trend in residue concentrations from year to year. Following is a list of the yearly means: 1959 (n=5) 1,465 mg/g; 1960 (n=13) 679.3 mg/g; 1961 (n=6) 321.1 mg/g; 1962 (n=6) 2,033 mg/g, and 1963 (n=11) 790.9 mg/g.

4.

Tissues from western grebes found dead and collected between May 22 and June 2, 1960 at the Tule Lake and Lower Klamath Refuges (California) were analyzed for organochlorine residues (Keith, 1966). 12 grebes were among a total of 307 birds of 8 different species found dead.  Subsequently, 3 of 80 w. grebes found dead in 1962 in the same refuge were also analyzed.  DDT was present in all samples collected each year and was consistently among the highest residues found [For w. grebes in 1960, 75.5 mg/g average (n=6) in carcass and 459.5 mg/g average (n=2) in adipose; and in 1962 16.6 mg/g average (n=2) in heart-liver-kidney-muscle (HLKM) and 14.5 mg/g in Brain (n=1)].  Toxaphene was found in tissues from most birds’ whole carcasses in amounts ranging from 0.3 to 15.0 mg/g.  In 1960, w. grebes carcasses (n=6) contained an average of 0.3 mg/g and in adipose  (n=2) an average of 31.5 mg/g toxaphene. No toxaphene was detected in 1962 grebe samples. Dieldrin was present in all samples of w. grebes  [0.2 mg/g average  (n=2) for HLKM and trace for brain] collected in 1962 but was not detected in any other samples.

5.

Western grebes collected at Clear Lake, California from 1967 to 1968 were analyzed for various organochlorine pesticides (Herman et al, 1969). 10 different tissues were used in the analysis and included brain (B), leg muscle (LM), liver (L), breast muscle (BM), uropygial glands (UG), subcutaneous fat (SF), thigh fat (TF), visceral fat (VF), testes (T) and ovaries (O). DDD was the dominant residue found in 187 samples derived from tissues of 62 adult grebes (In mg/g ww: LM=4.56, L=12.21, BM=14.58, OV=48.92, UG=108.92, SF=499.55, TF=561.08, VF=570.25, O and T not recorded).  DDMU (a metabolite of DDD) was second most abundant and DDE was third (values not reported). DDT was hardly detectable and DDMS were found only in small quantity.

6.

Breast muscle (BM, n=24), visceral fat (VF, n=18) , blood (B, n=16), and whole eggs (E, n=40) of western grebes collected in 1973 and 1974 at the Bear River Migratory Bird Refuge, UT were examined for organochlorine compounds (Lindvall and Low 1979). DDE was the predominant contaminant found [In mg/g ww: BM=12.8 (513 in lipid); VF=61.5; B=0.55, E=6.6 (76.5 in lipid)]. PCB1260 and PCB1254 were found in lower concentrations than DDE but higher concentrations than DDD [In mg/g ww: BM (1260=3.8, 1254=3.5); VF(1260=22.4, 1254=16.7); B(1260 and 1254 were trace); E(1260 and 1254 were trace)]. DDD concentrations were lowest [In mg/g ww: BM=0.8 (29 in lipid); VF=5.2; B=0.07; E=1.3 (14.9 in lipid)]. An additional comparison was made showing birds with sparse visceral fat have greater average DDE (n=5, 1.14 mg/g) than birds with abundant visceral fat (n=4, 0.63 mg/g).

7.

Brain and liver samples from 8 western grebes found dead at Lake Berryessa, California in April 1982 were examined for organochlorine residues and found to have non-lethal concentrations of DDE:  22 mg/g ww in brains and 37 mg/g ww  in liver (Littrell 1991). 

8.

Plucked carcasses of western grebes collected on October 17, 1985 (early, n=20) and on February 6, 1986 (late, n=20)from the same population in Commencement Bay, Puget Sound, Washington were analyzed for lipophilic organochlorine pesticides (Henny et al, 1990).  There was a significant increase in lipid content from the early to the late collection period. Of the 20 grebes collected on October 17, 4 males and 1 female were in remige moult or replacement and were flightless. It is noteworthy that these five contained the five highest PCB residues and 5 of the 8 highest DDE residues. DDE increased significantly from the early (0.45 mg/g ww) to the late (1.8 mg/g ww) collecting period and the moulters contained even higher (7.0 mg/g ww) concentrations. DDD increased (0.12 mg/g ww to 0.24 mg/g ww) but not significantly and no DDT was detected. When moulters were excluded, chlordanes increased significantly from early (0.10 mg/g ww) to late (0.21 mg/g ww). trans-nonachlor was the form most frequently encountered, followed by cis-nonachlor, cis-chlordane, and oxychlordane. HCB was detected (0.12 mg/g ww) in one female from the early collection (a moulter) and in 2 males and 2 females in the late collection (0.10, 0.12, 0.16, and 0.16 mg/g).  PCB concentrations paralleled DDE and showed a significant increase from the early (1.9 mg/g) to the late (6.4 mg/g) collection when the molters were excluded.  Dieldrin was detected in 2 grebes (non-molters) in the early collection and none in the late collection. Heptachlor epoxide, endrin, and toxaphene were not detected during the study.

9.

Livers and/or breast muscles from western grebes collected during late winter at industrial and reference sites along coastal British Columbia, Canada from 1988 to 1993 were analyzed for PCDD, PCDF, PCBs, organochlorine pesticides, and chlorophenol-related compounds and were compared with analyses of other grebe and seaduck species collected concurrently (Elliott and Martin, 1998). Piscivorous species like western grebes had the highest contaminant concentrations. For example, the highest PCB concentration (2300 ng/g ww) was found in breast muscle of western grebes collected at Port Alberni in 1992. Of PCDDs and PCDFs, typically only 2,3,7,8-TCDD and –TCDF were present at substantial concentrations. W. grebes collected adjacent to pulp mills had highest concentration of 2,3,7,8-TCDF at 230 pg/g ww.  Contaminants in w. grebes collected at Port Alberni in 1989 had declined substantially by 1992: 2,3,7,8-TCDD dropped from 117 to 36 pg/g whereas (1,2,3,7,8-PnCDD, 1,2,3,6,7,8-HxCDD, and TCDF values were 36, 72 and 60 % of 1989 levels respectively (1,2,3,7,8-PnCDD went from 385 to 66 pg/g, 1,2,3,6,7,8-HxCDD from 249 to 64 pg/g, and TCDF from 217 to 69 pg/g). At Howe Sound, between 1989-90 and 1993, concentrations of PCDDs dropped substantially (2,3,7,8-TCDD went from 46 to 1.7 pg/g, 1,2,3,7,8-PnCDD went from 29 to 9.1 pg/g, and 1,2,3,6,7,8-HxCDD went from 77 to 8.2 pg/g) and 2,3,7,8-TCDF concentrations decreased by at least 50% in w. grebes (from 109 to 44 pg/g).  At the reference site (Alert Bay, 1992, n=2) the concentrations were all substantially lower with 2,3,7,8-TCDD, 1,2,3,7,8-PnCDD, 1,2,3,6,7,8-HxCDD, and TCDF only in trace amounts.   Breast muscle from pooled grebe samples collected at Nanaimo in 1992 and analyzed for 35 chlorophenol-related compounds (including chlorophenols, catechols and guaiacols) were found to have the following: pentachlorophenol=0.6 ng/g ww, 3,4,5,6-tetrachloroguaiacol was trace, 5-chloroguaiacol=6.3 ng/g, and 4,5-dichloroguaiacol was trace. Concentrations of DDE (breast muscle and liver) in western grebe livers varied from 100 ng/g (collected at Powell River 1992, n=5) to 210 ng/g (collected at Nanaimo 1992, n=3) and were detected at 47 ng/g at the Alert Bay reference site. DDT varied from Not Detected (Nanaimo) to 2.6 ng/g at Port Alberni.  Other organochlorine compounds detected were in lowest concentrations (ng/g ww ) at Nanaimo (dieldrin=1.3, heptachlor epoxide=2, oxychlordane=trace, and trans-nonachlor=9.4) while the highest levels were at Powell River (dieldrin=2.6, heptachlor epoxide=3.2, oxychlordane=Not Detected, trans-nonachlor=16).   PCB concentrations (breast muscle and liver) varied from 24 ng/g at the Alert Bay reference site to 2300 ng/g at Port Alberni in 1992. Cogeners 138 and 153 were the most dominant in the distribution of PCB cogeners.

10.

Livers from 5 western grebes collected downstream from the Port Alberni pulp and paper mill in Port Alberni, British Columbia, Canada in April 1989 were analyzed for PCDDs and PCDFs (Vermeer et al, 1993). The grebes were among 8 estuarine bird species collected concurrently for analysis. All birds contained PCDD and PCDF residues; the highest concentrations were found in grebes.  The following approximate quantities of PCDDs were found in western grebes (values are pg/g ww): 2,3,7,8-TCDD=115, 1,2,3,7,8-PnCDD=390, 1,2,3,6,7,8-HxCDD=250.  The PCDF, 2,3,7,8-T4CDF was found at approximately of 220 pg/g average, which was the highest concentration of all bird species.

B.

Concentrations in juveniles

1.

Composite samples of western grebe eggs collected from three sites within the Canadian prairie provinces (Cold Lake n=10, Jackfish Lake n=10, and Kawinaw Lake n=10) in 1968 (concurrently with 13 other bird species) were analyzed for DDE and dieldrin (Vermeer and Reynolds, 1970). The eggs of larids and fish-eating birds, such as western grebe, contained the highest DDE concentrations: Cold Lake =7.76 mg/g ww, Jackfish Lake = 3.94 mg/g and Kawinaw Lake = 3.46 mg/g. dieldrin was not detected in western grebe eggs from either Cold Lake or Jackfish Lake, but grebe eggs at Kawinaw Lake were found to have 0.128 mg/g dieldrin.

2.

Western grebe eggs (n=12) collected in 1981 at Tule Lake NWR (California) were analyzed for organochlorine residues and compared with white pelican (Pelecanus erythrorhynchos) eggs collected concurrently (Boellstorff et al, 1985). DDE residues occurred in all 12 western grebe eggs (ranging 0.84 – 2.3 mg/g ww). PCBs occurred in 11 (ranging from Not Detected to 11.0 mg/g), and DDT/ DDD occurred in 9 eggs (ranging from Not Detected to 1.5 mg/g ).  Dieldrin and endrin were not detected in w. grebe eggs. cis and trans-nonachlor were detected along with cis-chlordane in two grebe samples.  Concentration ranges (mg/g ww) in the grebe eggs were as follows: cis-chlordane, Not Detected-0.10; trans-nonachlor, Not Detected-0.25; cis-nonachlor, Not Detected-0.16.

3.

Eggs from western grebes collected in 1986 from Manitoba, Canada were analyzed for organochlorine residues and compared to eggs of other grebe species sampled from various locations in Canada from 1982 to 1987 (Forsyth et al 1994).  Samples were taken from 2 sites at each location with a 1 month interval between site collections. Western grebes had the highest concentrations of DDD [Duck Bay: 0.29 mg/g ww (n=10, site 1), 0.58 mg/g (n=4, site 2); Ninette: 0.47 mg/g (n=10, site 1), 0.66 mg/g (n=10, site 2)]. Significant DDE and PCB residues were detected in all samples [Duck Bay: DDE=0.70 mg/g (site 1) and 0.84 mg/g (site 2) ; PCB=2.55 mg/g (site 1) and 2.08 mg/g (site 2)]; [Ninette: DDE=2.60 mg/g (site 1) and 3.37 mg/g (site 2); PCB=4.22 mg/g (site 1) and 4.67 mg/g (site 2)]. Dieldrin and mirex were below detection limits in western grebes.

II.

Cholinesterase-Inhibiting Pesticides

No direct exposure data available

III.

Trace Elements, Metals, and Metalloids

 1.

Livers and kidneys of western grebes collected on October 17, 1985 (early, n=20) and on February 6, 1986 (late, n=20) from the same population in Commencement Bay, Puget Sound (Washington) were analyzed for trace elements (Henny et al, 1990).  Of the 20 grebes collected on 17 October, 4 males and 1 female were in remige molt or replacement and were flightless. These contained above average Hg concentrations and all contained above average concentrations of Se.  No significant change (with or without the molters) in Se concentrations was detected from the early (9.3 or 7.6 mg/g dw) to the late (7.9 mg/g) collection period. Concentrations of Hg increased significantly between the early (1.5 mg/g) and the late (2.5 mg/g) collection periods when molters were excluded. Significant increases in As concentrations from the early (0.96 or 1.1 mg/g) to the late (2.7 mg/g) collection period were found with or without molters. Mean Cu concentrations decreased significantly from the early (16.3 or 16.7 mg/g) to the late (13.2 mg/g) collection period with or without molters.  Kidney concentrations of Cd increased but not significantly from the early (0.70 or 0.38 mg/g) to the late (0.85 mg/g) collection period with or without molters. Grebes containing Pb included 1 of the 5 molters (1.5 mg/g), 2 of 15 early birds (0.42 and 2.2 mg/g) and 1 of 20 late birds (0.77 mg/g).

2.

Livers from western grebes collected at 3 locations in British Columbia, Canada were analyzed for the Butyltin compounds: MBT, DBT, TBT (Kannan et al., 1998).  Mean concentrations in ng/g ww were: Howe Sound, collected April 1990 (n=10), MBT=171, DBT=142, and TBT=9.9; Skidegate, collected November 1990 (n=4), MBT=16.1, DBT=10.6, and TBT=6.3; Prince Rupert Sound, collected February 1991 (n=11), MBT=40, DBT=40, TBT=4.

3.

Tissue from 23 western grebes (liver, kidney, breast muscle, and brain) collected July and August 1992 at three different lake sites in Northern California were analyzed for total Hg  (Elbert and Anderson, 1998). Although Hg concentration in liver were statistically indistinguishable between lakes (Clear Lake, n=13, 2.74 ± 0.89 mg/g ww; Eagle Lake, n=5, 4.35 ± 5.71 mg/g; and Tule Lake, n=5, 1.22 ± 0.08 mg/g). The average brain Hg wet weight concentrations found were 0.28 mg/g for Clear Lake, 0.13 mg/g for Eagle Lake, and 0.16 mg/g with for Tule Lake. Kidney, breast muscle, and brain Hg levels were significantly correlated to each other with the best correlation between breast muscle and brain.

4.

Flight feathers from 12 adult western grebes collected at Clear Lake, California in 1997 were analyzed for 15 different elements and compared to an identical analysis of feathers taken concurrently from 5 other bird species at Clear Lake (Cahill et al, 1998). The birds in the Clear Lake ecosystem show elevated mean Hg concentrations (9.75 mg/g in the w. grebes) with respect to comparison sites. The mean concentrations of other contaminants like Pb (trace), Se (1.38 mg/g ), and As (1.02 mg/g ) were low. Sulfur was present in high concentrations (2.9 to 3.4 % of the feather weight, 33,449 mg/g ), and its levels were very consistent between different species.  Other mean elemental concentrations (mg/g)  include: Ca=757, Ti=12.3, V=Not Detected, Cr=Not Detected, Fe=66.4,  Ni=trace, Zn=164, Br=42.6, Rb=trace, Sr=4.50.

IV.

Petroleum

1.

Two tankers collided in the mouth of San Francisco Bay, California on January 18, 1971 spilling 840,000 gallons of bunker C fuel oil (Smail et al., 1972). This oil spread over 17 miles out to sea and along the coast from Drake’s Bay south to Pt. Ano Nuevo during the following days.  An estimate of 6,000 oiled birds passed through cleaning stations, while an estimated minimum mortality of 20,000 birds may have resulted. Birds were censused at four cleaning stations along the coast of California. The following are numbers of oiled western grebes delivered to the stations: Bolinas 797, Farallon Island 1, Tiburon 555, Pacifica 702.  

2. 

On 19 March 1984 the tanker Mobiloil ran aground spilling 170,000 to 230,000 gallons of heavy residual oil, No. 6 fuel oil, and an industrial fuel oil into the Columbia River near St. Helens, Oregon (Speich and Thompson, 1987). Of the 450 live oiled birds retrieved from the vicinity of the spill, 227, or 50% of the total were oiled western grebes. Oiled birds retrieved during 23 March to 23 April 1984 were cleaned at a treatment center and 284 birds were released. Species identities of released birds were not recorded.

3.

On 21 December 1984 an unidentified vessel released around 5000 gallons of No. 6 fuel oil into Puget Sound near Whidby Island, Washington (Speich and Thompson, 1987).  Over 400 dead oiled birds were removed from beaches near the spill, of which 360 were unidentified species.  Of the identified birds 2 were western grebes.  Additionally, 15 western grebes were found oiled and free roaming and one was taken to the cleaning station. An unknown mix of western and red neck grebes (n=95) were also taken to the cleaning station.  

Western Grebe Contaminant Response Data

I.

Organochlorine Contaminants

1.

Western grebes (n=2) with a mean DDD concentration of 1600 mg/g  and 7 western grebes with a mean DDD concentration of 723 mg/g were collected at Clear Lake, California in January and October 1958 respectively (Hunt and Bischoff 1960). The following strong circumstantial evidence indicates grebe losses occurring after DDD treatments were caused by chronic poisoning from DDD at Clear Lake: 1. The decline in grebe population corresponded with the period in which pesticide applications were made (After the 1954 and 1957 applications of DDD to Clear Lake 100 grebes and 75 grebes respectively were found dead). 2. The absence of any known infectious diseases in autopsied grebes picked up after the chemical treatments. 3. Clinical symptoms common to poison victims were exhibited by some grebes from the lake. 4. An abnormally high concentration of DDD was found in fatty tissue of dead grebes.

2.

Western grebe eggs (n=93) collected between 1973 and 1974 from the Bear River Migratory Bird Refuge (MBR), UT were examined for organochlorine pesticide residues and PCB (Lindvall and Low, 1980).  Contamination was correlated to eggshell thinning and thickness.  DDE was the predominate contaminant detected, averaging 6.6 mg/g ww. DDD averaged 1.3 mg/g. Only trace PCBs were found.  Average eggshell thickness index of these eggs (1.898 mm) was significantly smaller than the same figure for pre-1940 eggs (n=389) measured in museums (1.989 mm).  Direct eggshell thickness measurements for the 1973 and 1974 eggs was 0.38 mm, which is greater than the average eggshell thickness of eggs collected at Clear Lake, California (0.33 mm) after DDD application to the lake.  Direct measurement of pre-1940 eggs revealed an average thickness of 0.389 mm, or 3.1% greater than 1973 and 1974 Bear River eggs. DDE was the only contaminant which was both correlated with and could explain variability in eggshell thickness and eggshell thickness index.

3.

Eggshell thickness was determined for 12 western grebe eggs collected in 1981  at Tule Lake NWR, California and compared to samples taken in 1972, 1952-1960 and pre-1947. (Boellstorf et al., 1985). Mean thickness of grebe eggshells collected at Tule Lake NWR in 1972 (n=24, .390 mm ) and 1981 (n=29, 0.383 mm) and from Northern California during 1952-1960 (n=11, 0.355 mm) were not significantly different from each other and were not thinner than eggs collected before 1947(n=24, 0.385 mm). No correlation was made between eggshell thinning and organochlorine concentrations detected (see entry IB2, organochlorine concentrations in juveniles).

II.

Cholinesterase-Inhibiting Pesticides

No response data available

III.

Trace Elements, Metals, and Metalloids

1.

Liver samples examined from 8 western grebes found dead at Lake Berryessa, California in April 1982 were found to have Hg concentrations at deleterious concentrations (20.2 mg/g ww) in kidneys, which may have contributed to their deaths (Litrell, 1991). Livers and kidneys of 2 western grebes found dead at Lake Berryessa in March 1986 were analyzed for Hg and one had a deleterious level (23.3 mg/g while the other bird had 2.7 mg/g). Kidney Hg concentrations were 2.1 and 6.5 mg/g.  Mercury concentrations in kidney and liver control samples of western grebes collected at Lake Berryessa in March 1983 (n=12, 1.1 to 9.0 mg/g in kidneys and 2.7 to 11.8 mg/g in livers) and at Clear Lake in March 1984 (n=20, 3.7 to 9.8 mg/g in livers) were below lethal values. 

2. 

Western grebes (n=23) collected July and August 1992 at three different lake sites in Northern California and analyzed for total Hg were compared using productivity rates measured as young to adult ratios from 1992 to 1994 (Elbert and Anderson, 1998). The grebes at Eagle Lake (kidney 0.95 mg/g ww Hg), and Tule Lake (kidney 0.72 mg/g Hg) were found to be reproducing at comparable rates (young/adult ratio = 0.47 and 0.34 respectively for 1994) to that reported elsewhere (Gould et al 1974, Koplin 1971 and Lindvall and Low 1982). Clear Lake (kidney 2.06 mg/g Hg) is clearly exhibiting lower reproductive success (0.06 for 1994).

IV.

Petroleum

No response data available

References for Western Grebe

Angell, T., K.C. Balcomb III. 1982. Marine birds and mammals of Puget Sound. University of Washington Press, Seattle. 145 pp.

Boellstorf, D.E., H.M. Ohlendorf, D.W. Anderson, E.J. O’Niell, J.O. Keith, R.M. routy. 1985. Organochlorine chemical residues in white pelicans (Pelecanus erythrorhynchos) and western grebes (aechmophorus occidentalis) from the Klamath Basin, California (USA). Arch. Environ. Contam. Toxicol. 14:485-494.

Cahill, T.M., D.W. Anderson, R.A. Elbert, B.P. Perley, D.R. Johnson. 1998. Elemental profiles in feather samples from a mercury-contaminated lake in Central California, Arch. Environ. Contam. Toxicol. 35:75-81.

Cogswell, H.L.  1977.  Water Birds of California. University of California Press, Berkeley. 399 pp.

Elbert, R.A., D.W. Anderson. 1998.  Mercury levels, production, and hematology in western grebes from three California lakes, USA.  Environ. Toxicol. Chem. 17:210-213. 

Elliott, J.E., P.A. Martin. 1998. Chlorinated hydrocarbon contaminants in grebes and seaducks wintering on the coast of British Columbia, Canada: 1988-1993.  Environ. Mon. Assess. 53:337 –362.

Finley, M.T., W. H. Stickel, R.E. Christensen.  1979.  Mercury residues in tissues of dead and surviving birds fed methylmercury. Bull. Environ. Contam. Toxicol. 21:105 – 110.

Fix, D, A.Bezener. 2000.  Birds of Northern California.  Lone Pine Publishing, Renton, Wa. 384 pp.

Forsyth, D.J., P.A. Martin, K.D. DeSmet, M.E. Riske. 1994.  Organochlorine contaminants and eggshell thinning in grebes from prairie Canada.  Environ. Pollut. 85:51 – 58.

Henny, C.J., L.J. Blus, R.A. Grove. 1990.  Western grebe, Aechmophorus occidentalis, wintering biology and contaminant accumulation in Commencement Bay, Puget Sound, Washington [USA]. Can. Field. Nat. 104:460-472.

Herman, S.G., R.L. Garrett, R.L. Rudd.  1969.  Pesticides and the western grebe.  In Chemical Fallout/ Current research on persistent pesticides. Thomas, Springfield, Ill. 531 pp.

Hunt, E.G., A.I. Bischoff. 1960. Inimical effects on wildlife of periodic DDD applications to Clear Lake.  Calif. Fish Game, 46(1):91–105.

Kannan, K., K. Senthilkumar, J.E. Elliott, L.A. Feyk, J.P. Giesy. 1998. Occurrence of butyltin compounds in tissues of water birds and seaducks from the United States and Canada.  Archiv. Environ. Contam. Toxicol. 35:64–69.

Keith, J.O. 1966. Insecticide contaminations in wetland habitats and their effects on fish- eating birds.  J. Appl. Ecol. 3(supp):71-85.

Koonz, W.H, P.W. Rakowski. 1985. Status of colonial waterbirds nesting in southern Manitoba. Can. Field Nat. 99:19-29.

Larrison, E.J., K.G. Sonnenberg. 1968.  Washington birds, their location and identification. The Seattle Audobon Society, Seattle, Washington. 258 pp.

Lindvall, M., J.B. Low. 1979. Organochlorine pesticide and PCB residues in western grebes from Bear River migratory bird refuge, Utah. Bull. Environ. Contam. Toxicol. 22(6):754–760.

Lindvall, M., J.B. Low. 1980.  Effects of DDE, TDE, and PCBs on shell thickness of western grebe eggs, Bear River migratory bird refuge, Utah 1973-74. Pest. Mon. J. 14: 108-111.

Linn, J.D., R.L. Stanley. 1969. TDE residues in Clear Lake animals. Calif. Fish and Game 55(3):164-178.

Littrell, E.E. 1991. Mercury in western grebes at Lake Berryessa and Clear Lake, California. California Fish and Game. 77:142–144.

Ohlendorf, H.M., D.M. Swineford, L.N. Locke. 1981. Organochlorine residues and mortality of herons. Pest. Mon. J. 14:125–135.

Johnsgard, P.A. 1987.  Diving Birds of North America. University of Nebraska Press, Lincoln. 292 pp.

Palmer, R.S. 1962. Handbook of North American Birds, Volume 1. Yale University Press, New Haven. 565 pp.

Smail, J., D.G. Ainley, H. Strong. 1972. Notes on birds killed in the 1971 San Francisco oil spill. California Birds 3(2):25-32.

Speich, S.M., S.P. Thompson. 1987. Impacts on waterbirds from the 1984 Columbia River and Whidby Island, Washington, oil spills. Western Birds 18:109-116.

Vermeer, K., W.J. Cretney, J.E. Elliott, R.J. Norstrom, P. Whitehead. 1993.  Elevated polychlorinated dibenzodioxin and dibenzofuran concentrations in grebes, ducks, and their prey near Port Alberni, British Columbia, Canada.  Marine Pollut. Bull. 26:431-435.

Vermeer, K., L.M. Reynolds. 1970. Organochlorine residues in Aquatic Birds in the Canadian prarie provinces. Can. Field Nat. Vol. 84:117-130.