Demography and Populations

Age At First Breeding; Intervals Between Breeding

First breeding by males and females occurs at ≥ 2 yr of age, although many individuals breed for the first time at later ages. Of 22 females of known age (banded as ducklings) in British Columbia, 8 females (36%) were first recorded breeding (incubated a clutch) at 2 yr of age, 7 females (32%) at 3 yr of age, 5 females (22%) at 4 yr of age, and 1 female each at 5 and 6 yr of age (mean age 3.09 yr, SE 0.24; JME). These estimates do not correct for failed nest attempts and may be confounded by the fact that some breeding females lay eggs only as brood parasites (i.e., do not establish a nest of their own) or that not all nests were found.

Most individuals breed every year, although “skips” in breeding years occur; 10 of 140 females in British Columbia (7.1%) skipped ≥ 1 yr (JME). Skips were often associated with changes of nest site in subsequent breeding years, and may represent cases of nest failure or competition for nest sites.

Clutch Size

Average clutch sizes ranges from 7.4 to 10.3 eggs (Appendix 3). The smallest clutch that was incubated in British Columbia was 4 eggs (JME) (in Ontario 5 eggs; Mallory et al. 1994); the largest incubated clutch in British Columbia contained 20 eggs (JME). In Minnesota, average clutch size ranges from 8.4 to 12.3 eggs among study lakes (M. C. Zicus pers. comm.). Clutch size estimates in the literature are confounded by frequent intraspecific brood parasitism. In British Columbia, clutches of > 13 eggs are invariably the result of ≥ 2 females. Mallory et al. (1994) found that all clutches with ≥ 11 eggs were parasitized intraspecifically. Using criteria based on egg morphology, counts of postovulatory follicles, timing of egg-laying, and DNA fingerprinting, Eadie (1989, unpubl. data) found that single females never lay >12 eggs. Clutch size in all nests averaged 9.77 eggs (SE 0.24, range 1–28, 237 nests), but when parasitized nests were excluded, clutch size averaged 7.13 eggs (0.26, 1–11, 100 nests). In parasitized nests, clutch sizes averaged 11.69 eggs (0.28, 3–28, 137 nests). Rajala and Ormio (1970) excluded parasitized clutches, and their estimate of 8.1 eggs is comparable to our value for nonparasitized nests. Mallory et al. (1994) excluded clutches of >10 eggs and found that mean clutch size ranged between 7.9 and 8.6 eggs (some parasitized clutches probably went undetected; MLM). True clutch size of Common Goldeneyes is probably between 6 and 9 eggs.

Clutch size in British Columbia and Ontario was negatively correlated with nest initiation date (British Columbia, r²= 0.24, n = 102, P<0.0001, JME; n. Ontario, r²= 0.29, n = 71, P<0.01, HGL; n. Ontario, r²= 0.19, n = 46, P<0.01, MLM); in British Columbia, it was positively correlated with the age of female (r²= 0.21, n = 33, P = 0.007; JME).

Only 1 brood/year. Females may initiate a new clutch if a nest is destroyed during early egg-laying, but they will not renest if a nest is lost after clutch is complete. Only 1 confirmed instance of renesting has been reported (Zicus 1990). Females that lose a nest during egg-laying are also unlikely to lay eggs parasitically (Eadie et al. 1987).

Annual And Lifetime Reproductive Success

Nest success (percentage of nests where at least 1 egg hatched) of 223 nests in British Columbia: 64.1% (1984–1992; JME). Most nests that failed were deserted by female during egg-laying (51.2% of 80 failed nests) or during incubation (33.8% of failed nests). Nest desertion is the single largest cause of breeding failure in British Columbia; nest loss due to predation or other causes was relatively low (11.7% of failed nests). Of nests that were successfully incubated, hatching success (proportion of eggs that hatched) was high: 84.0% (SE 1.6, range 11.1–100, 143 nests; JME). Nest desertion is also the primary cause of nest loss in ne. Ontario (MLM), and tends to be higher for nests on lakes situated close to each other. Mallory (1991) concluded that nest loss in these situations may be higher because of increased disturbance at the nest from other females. Of nests that were successfully incubated, hatching success ranged from 77. 6 to 88.9% and was not influenced by habitat type (Mallory 1991).

In British Columbia, survival of young after leaving the nest (percentage of hatched young that survive to independence) averaged 36.5% (SE 3.8, 86 broods; JME). Average number of young/nesting female reared to independence in a single year (annual reproductive success) was 1.30 (SE 0.18, 145 females; JME).

Lifetime reproductive success for 108 females in British Columbia, followed from their first breeding year to the end of their lifespan, averaged 2.25 (SE 0.32; JME) independent offspring. Lifetime reproductive success is highly skewed; most females produce no fledged offspring, and a few produce large numbers (Fig. 6). Of the 243 fledged offspring produced during 1984–1992, 185 (76.1%) were produced by only 25 (23.2%) of breeding females. These estimates should be viewed as conservative because some females may have left the study area rather than died or may have had nests that were not found.

Little information available for males. Annual survival of breeding females is 61.2% (SE 6.5 ; 95% CI 45.4–77.0), based on 9 years of capture-recapture data (1984–1992) for 85 breeding females in the Cariboo Parkland of British Columbia using a Jolly-Seber open population model (JME). These estimates are only for females banded and recaptured on nest boxes. An earlier analysis based on return rates for a small sample of females in British Columbia yielded an estimate of 62.3% (Savard and Eadie 1989). Similar values reported elsewhere; Minnesota 63% (Moyle et al. 1964), Saskatchewan 58% (Du Wors et al. 1984), Sweden 74% (Dow and Fredga 1984) and 63% (Nilsson 1971).

In British Columbia, average breeding lifespan is 1.58 yr (SE 0.09, range 1–7, 140 banded females, includes only females that were recorded breeding at least once; JME). Given an average age of first breeding of 3.09 yr (above), we estimate the average total lifespan of females in British Columbia as 3.67 yr (2.09 yr prebreeding and 1.58 yr breeding). This estimate should be viewed with caution given the small sample sizes and the lack of information on the survival of parasitic females. In Sweden, Nilsson (1971) calculated an expectation of adult life of 6 yr. Previous breeding experience did not influence return rates of females in British Columbia (Savard and Eadie 1989), but survival in Sweden was reduced if females produced a large clutch in the first year (Dow and Fredga 1984).

Canadian Wildlife Service banding records (for Common Goldeneyes banded in Canada) indicate that maximum male age is 11 yr and maximum female age 12 yr (measured as the maximum number of hunting seasons survived). There are records of a 14- and a 15-yr-old, but sex was not recorded for either. Mean number of hunting seasons survived was 2.17 yr (SE 0.10, n = 365 recoveries of birds banded across Canada). Age of the oldest known breeding female in British Columbia is 10 yr (JME).

Diseases

Include botulism (Clostridium botulinum), avian cholera (Pasteurella multocida), and duck viral enteritis (Fay 1969, Botzier 1991).

Body Parasites

Include Protozoa: Leucocytozoon anatis (Nelson and Gashwiler 1941), Haemoproteus and Plasmodium sp. (Grenier et al. 1975), Eimeria sp. (Gayadhar et al. 1983); Trematoda: Prosthogonimus ridolphii, Amphimerus elongatus, Maritrema nettae, Microphallus (= Spelotrema) pygmaeum, Stephanoprora spinosa, Cotylurus flabelliformis (Gower 1938); Cestoda: Dicranotaenia coronula, Retinimetra macracauthos, Fimbriaria fasciolaris, Anomotaenia ciliata (McLaughlin and Burt 1979); Digenea: Echinostoma revolutum, Echinoparyphium recurvatum, Apatemon gracilis, Prosthogonimus cureatus (McLaughlin and Burt 1979); Nematoda: Amidostomum anseris, Epomidiostomum orispinum, Contracaecum micropapillatum, Contracaecum speculigerum (Gower 1939), Capillaria anatinis (Mawson 1956), Tetrameres crami (Swales 1936). The list of parasites of Common Goldeneyes in Eurasia is longer (see Gower 1939, Lapage 1961).

Poorly known; hunting, predation, and disease are principal causes. Predation occurs predominantly on incubating females and broods (see Behavior: predation). Females observed misjudging entrance to nest cavity and may occasionally die as a result (M. C. Zicus pers. comm., MLM). Lead poisoning and other trace metal or organochlorine contaminants do not appear to cause significant mortality (Friend 1987, Scheuhammer 1991) but may have chronic, sublethal effects. Cold, wet weather can lead to high mortality of newly hatched ducklings (see Breeding: young birds).

Initial Dispersal From Natal Site

Although data are limited, natal philopatry is evident in females but apparently absent in males. In British Columbia, recruitment of ducklings is low; only 22 of 1,249 ducklings that were web-tagged as 1-d-old ducklings were recruited into the breeding population (JME). However, all of these were females. Fourteen (64%) of these females nested on their natal lake (1 female used her natal nest box, 10 others nested <300 m from their natal nest site), whereas the remaining 8 females nested on nearby lakes (within 2 km of their natal lake). Of 17 females that returned to their natal area to breed in Sweden, 94% nested within the immediate vicinity of their natal nest site (Dow and Fredga 1983).

Fidelity To Breeding Site And Winter Home Range

Breeding philopatry is marked in females; 63.0% of 81 females that bred ≥ 2 yr in British Columbia returned to their previous nest site, 32.1% moved to a new site located on the same lake (usually within 200–300 m), and only 4.9% moved to a nest site on a different lake (JME). Females that were unsuccessful were significantly more likely to change nest sites in subsequent years (Eadie 1989, M. C. Zicus pers. comm.). Breeding philopatry of males is not known, although 67% of male Barrow’s Goldeneyes return to their previous breeding area in subsequent years (Savard and Eadie 1989).

Dispersal From Breeding Site Or Colony

Of 66 birds banded as flightless young in Minnesota, 59% were shot within an 80-km radius of the banding location, 19% elsewhere in Minnesota, 12% in other states near the Great Lakes and along the Mississippi River, and 10% in Manitoba and Ontario (Moyle et al. 1964). Band recoveries of 69 adult males, presumably molt migrants, banded in the Fort McMurray area of Alberta indicate a dispersal to winter south to the interior of British Columbia, Washington, Oregon, California, Idaho, and w. Montana (56%); to Wyoming, Nebraska, and Colorado (16%); and across the Great Lakes and to the Atlantic coast (23%). The remaining 5% were recovered on their migration route through Alberta and Manitoba. Band recoveries from central Ontario of adult females and juveniles indicate a dispersal south and southeast; 59 of 64 recoveries were within Ontario (HGL).

Home Range

No information; see above, Behavior: spacing.

Estimates Or Counts Of Density

Breeding densities vary substantially by region. Bellrose (1980) reports densities ranging from approximately 8 Common Goldeneyes/100 km2 in the prairie parklands and open boreal forest in Saskatchewan, Alberta, and British Columbia to 770/100 km2 on the Athabasca River Delta in the Northwest Territories. In e. Canada, breeding densities range from 2 breeding pairs/100 km2 in New Brunswick (Cartar 1958) to 1–17 breeding pairs/100 km2 in Ontario (McNicol et al. 1987a). Recent data (1990–1993) collected on study plots as part of the Black Duck Joint Venture (North American Waterfowl Management Plan) indicate densities of approximately 8 birds/100 km2 in Maine, 3/100 km2 in New Brunswick, 18/100 km2 in Newfoundland, 2/100 km2 in Nova Scotia, 19/100 km2 in Ontario, and 15/100 km2 in Quebec (K. Dickson unpubl. data).

Population Numbers And Trends

Population size for Common Goldeneyes in North America was estimated at 1.25 million birds by Bellrose (1980). Data from U.S. Fish and Wildlife Service’s (USFWS) May Aerial Waterfowl Population Survey suggest a population of roughly 500,000 birds, but USFWS acknowledges that this is substantially low because of insufficient coverage in prime breeding areas (n. and e. Canada). Target population for combined continental population of Barrow’s and Common goldeneyes is 1.5 million birds, based on estimate of numbers of these species between 1970 and 1979.

Most information on Common Goldeneyes suggests that populations are presently stable. Breeding Bird Surveys (BBSs; 1966–1992), Christmas Bird Counts (CBCs; 1959–1988), and USFWS May Aerial Waterfowl Population Surveys (1955–1993) all suggest no overall significant trend in population size. Data on birds shot by hunters in e. Canada and ne. U.S. suggest a decline in kill-per-thousand-successful-hunters between 1976 and 1991, but this may be related to factors other than a declining population (preliminary analysis, H. Boyd pers. comm.). Numbers of Common Goldeneye pairs on 6 n.-central Minnesota lakes have also declined by about 50% between 1959 and 1988 (M. C. Zicus unpubl. data). Observations of migrating Common Goldeneyes at Long Point Bird Observatory in Ontario show that numbers of Common Goldeneyes have fluctuated with no consistent pattern between 1974 and 1993 (R. Knapton pers. comm.). Nonetheless, in e. North America, concern over the loss of unaltered, natural environments (e.g., Great Lakes-St. Lawrence lowlands and the boreal forest) and the effect of habitat alteration on Common Goldeneye populations is being expressed (Can. Wildl. Serv. 1994). The abundance of breeding Common Goldeneyes in the Cariboo Parklands of British Columbia has increased since the mid-1980s (JME), perhaps indicating that this species is moving into areas where it has not previously been known to breed (see Munro 1939).

Most important factor limiting populations is probably nest-cavity availability, particularly in recently or historically logged regions. Nest-box programs and subsequent local population increases support this hypothesis (Coulter 1979). The role of hunting in population regulation is unknown, largely due to poor population estimates. Most data indicate that populations are presently stable (see Population Status, above), but numbers of Common Goldeneyes shot are declining (H. Boyd pers. comm.), suggesting that the effect of hunting may be small.

Changes in breeding or wintering habitat quality may be important in regulating regional populations. In areas of e. Canada affected by acid rain, Common Goldeneyes exploit acidified, fishless habitats where acid-tolerant aquatic invertebrates thrive, but the birds avoid moderately acidic habitats where acid-tolerant, competitor fish (e.g., yellow perch) persist (Eadie and Keast 1982, McNicol et al. 1987a, 1995, Mallory et al. 1994). At the local population level, intra- and interspecific territoriality may play a role in limiting the density of breeding individuals. High frequencies of intraspecific brood parasitism can reduce breeding success and may influence local population dynamics (Eadie and Fryxell 1992).