Duckling Survival Research Articles

Interactive effects of arsenate, selenium, and dietary protein on survival, growth, and physiology in mallard ducklings.

High concentrations of arsenic (As) and selenium (Se) have been found in aquatic food chains associated with irrigation drainwater. Total biomass of invertebrates, a major source of protein for wild ducklings, may vary in environments that are contaminated with selenium. Day-old mallard (Anas platyrhynchos) ducklings received an untreated diet (controls) containing 22% protein or diets containing 15 ppm Se (as selenomethionine), 60 ppm Se, 200 ppm As (as sodium arsenate), 15 ppm Se with 200 ppm As, or 60 ppm Se with 200 ppm As. In a concurrent experiment, the same sequence was repeated with a protein-restricted (7%) but isocaloric diet. After 4 weeks, blood and tissue samples were collected for biochemical and histological examination. With 22% protein and 60 ppm Se in the diet, duckling survival and growth was reduced and livers had histopathological lesions. Arsenic alone caused some reduction in growth. Antagonistic interactive effects occurred between As and Se, including complete to partial alleviation of the following Se effects: mortality, impaired growth, hepatic lesions and lipid peroxidation, and altered glutathione and thiol status. With 7% protein, survival and growth of controls was less than that with 22% protein, Se (60 ppm) caused 100% mortality, and As (200 ppm) caused mortality, decreased growth, and liver histopathology. These findings suggest the potential for antagonistic effects of Se and As on duckling survival, growth, and physiology with adequate dietary protein but more severe toxicological effects when dietary protein is diminished.

Effects of Saline Water on Growth and Survival of Mottled Duck Ducklings in Louisiana

We studied the effects of saline drinking water on the growth and survival of penned mottled duck (Anas fulvigula) ducklings at Rockefeller Wildlife Refuge in southwestern Louisiana in 1989. Duckling mortality at different salinities was 100% at 18 ppt, 90% at 15 ppt, and 10% at 12 ppt. No ducklings died within treatments of <12 ppt, but the growth rate of ducklings in the 12-ppt treatment was lower (P _ 0.05) than all lower salinity treatments. When ducklings were given 12-ppt salinity water and exercised, mortality would have exceeded 70%. Initial lethargy shown by ducklings in the 9-ppt treatment, combined with potentially high mortality of ducklings given 12-ppt salinity water and exercised, suggested that the upper salinity threshold tolerated by wild mottled duck broods lies within this range. We advocate creation and management of semi-impoundments in coastal Louisiana and Texas to prevent deterioration and/or loss of marshes of <9-ppt salinity to provide quality habitat for mottled duck broods and other species of flora and fauna dependent on these marshes. J. WILDL. MANAGE. 55(3):471-476 The mottled duck is a nonmigratory species occupying a restricted range in North and Central America. Isolated populations occur in Florida, central Mexico, and the coastal marshes from Mississippi westward to northern Veracruz, Mexico (Bellrose 1980). However, the greatest number (98%) of mottled ducks occurs in coastal marshes of Louisiana and Texas where there is an estimated breeding population of 110,000 (Stutzenbaker 1988). There is concern about the mottled duck because annual surveys conducted in Louisiana have indicated a 44% decline from 1971 to 1983 (Stutzenbaker 1988). Stutzenbaker (1988) hypothesized that the loss and deterioration of remaining habitat in both Texas and Louisiana might be responsible. Saltwater intrusion, in particular, has caused significant habitat changes in Louisiana marshes. From 1968 to 1978, for example, freshwater marsh vegetation decreased and saline vegetation increased, especially in areas transected by large canals (Chabreck and Linscombe 1982). Furthermore, saline drinking water may affect the condition of both adult and juvenile waterfowl (Windingstad et al. 1987, Tiejte and Teer 1988). Ducklings are even less tolerant of salt water than adult birds because their salt glands are poorly developed, especially at <6 days of age (Ellis et al. 1963, Schmidt-Nielsen and Kim 1964, Riggert 1977). Mallard ducklings, for instance, suffered mortality, reduced growth, and a variety of sublethal physiological abnormalities when exposed to high concentrations of sodium sulfate, magnesium sulfate, and saline water occurring in natural wetlands in Saskatchewan (Mitcham and Wobeser 1988a,b). In North Dakota, wild ducklings concentrated and fed around freshwater seepages on saline lakes (Swanson et al. 1984). Female mottled ducks often bypass less productive areas of marsh close to the nest while leading ducklings to more productive broodrearing areas (Baker 1983). Therefore, ducklings traveling through, or remaining in, marshes affected by saltwater intrusion could suffer decreased survivorship. Our study determined the effects of saline water on the growth and survival of mottled duck ducklings. We hypothesized that survivorship, growth rates, and levels of body mass and carcass components would decrease as salinity levels increased. Financial support was provided by private corporations and landowners concerned with wetland management in the Louisiana coastal zone. We are extremely grateful to R. G. Vincent, Jr., from the Miami Corp., B. N. Kirkpatrick from the J. G. Gray Estate, W. P. Hardeman from the Amoco Production Co., J. P. Donohue from the Vermilion Corp., T. Wright from the Sweetlake Land and Oil Co., and J. Woddard from the FINA Oil and Chemical Co. J. T. Joanen and W. G. Perry provided assistance and ideas throughout the study. W. M. Shields and L. W. VanDruff reviewed the manuscript, and

Interactive effects of boron, selenium, and dietary protein on survival, growth, and physiology in mallard ducklings

High concentrations of boron (B) and selenium (Se) have been found in aquatic food chains associated with irrigation drainwater. Total biomass of invertebrates, a major source of protein for wild ducklings, is sometimes diminished in agricultural drainwater ponds contaminated with Se and B. Day-old mallard (Anas platyrhynchos) ducklings received an untreated diet (controls) containing 22% protein or diets containing 15 ppm (microgram/g) Se (as selenomethionine), 60 ppm Se, 1,000 ppm B (as boric acid), 15 ppm Se with 1,000 ppm B, or 60 ppm Se with 1,000 ppm B. In a concurrent experiment, the above sequence was repeated with a protein-restricted (7%) but isocaloric diet. After four weeks, blood and tissue samples were collected for biochemical and histological examination. With 22% protein and 60 ppm Se in the diet, duckling survival and growth was reduced and histopathological lesions of the liver occurred. Boron alone caused some reduction in growth. Several interactive effects occurred between B and Se, including further reduction in growth, and increases in plasma glutathione reductase activity, hematocrit, hemoglobin and plasma protein concentrations. With 7% protein, the growth of controls was less than that with 22% protein, 60 ppm Se caused 100% mortality, and growth effects of 15 ppm Se and 1,000 ppm B alone were more pronounced than with 22% protein. Selenium accumulation increased in the liver with 7% protein. Interactive effects were greater for Se and B with 7% protein than with 22% protein and included significant mortality and enhanced accumulation of Se in the liver. These findings suggest the potential for more severe toxicological effects of Se and B independently and interactively on duckling survival and development when dietary protein is diminished.

Survival of Mallard Broods on Benton Lake National Wildlife Refuge in Northcentral Montana

We estimated duckling survival in broods of 31 radio-marked female mallards (Anas platyrhynchos) on Benton Lake National Wildlife Refuge (NWR) in northcentral Montana in 1985 and 1986. Overall survival for the 60-day prefledging period was 0.3951, and 87% of all duckling losses occurred within the first 18 days. Survival through the Class I interval (0.4664) was lower (P 0.05) between marked and unmarked adult females. J. WILDL. MANAGE. 54(1):62-66 Low recruitment by mallards and other dabbling ducks over major portions of their breeding range is cause for concern (Greenwood et al. 1987, Hochbaum et al. 1987, Klett et al. 1988). Major determinants of recruitment include nest success, renesting rate, and duckling survival; the latter is perhaps the least understood component (Cowardin et al. 1985:28). However, obtaining precise counts of ducklings is difficult in the dense habitat often used by mallard broods (Talent et al. 1982, 1983; Cowardin et al. 1985). Ringelman and Longcore (1982) encountered similar problems studying black ducks (Anas rubripes). Our objective was to estimate survival rates of mallard ducklings relative to age classes, seasonal chronology of hatch, and body mass of the adult female. We thank N. E. Hall and B. P. Rogers for field assistance, R. J. Everett for manuscript review, and the entire staff of Benton Lake National Wildlife Refuge for encouragement and logistic support. Financial support was provided by the Refuge Division, Region 6, U.S. Fish and Wildlife Service.

The adaptive significance of crèching behaviour in the white-winged scoter (Melanitta fusca deglandi)

I tested several hypotheses regarding the adaptive significance of crèching behaviour using white-winged scoters (Melanitta fusca delgnadi) at Redberry Lake, Saskatchewan. Scoter crèches consist of a single female tending the young of one or more conspecifics. There was no relationship between a female's weight at the end of incubation and whether she stayed with ducklings. Therefore, there is no evidence that females in poor condition abandon their young more frequently than other females. No relationship was found between a female's age and her association with ducklings. Therefore, crèching does not appear to be related to female age or experience. Observations of color-marked ducklings in 1985 showed that 7 out of 10 females tended crèches that were composed entirely of fostered young. The survival of ducklings from large groups was greater than that from small groups, so crèching does not appear to be a strategy that enhances individual fitness of crèche-tending females. However, because of the high degree of philopatry displayed by female scoters, crèching could enhance inclusive fitness if crèches contain the young of related individuals. This hypothesis could not be tested.

The Effect of Drought on Duckling Survival of Maned Ducks

Regular brood surveys on a population of maned ducks, Chenonetta jubata, in south-eastern Australia provided information on the timing of breeding, brood sizes, duckling survival and production for this species. Over three years (1981-83), most breeding was during the spring, ducklings hatching between late August and late November. Some autumn (March-May) breeding also occurred. Timing of breeding appeared to be more closely related to the abundance of food than to rainfall alone. There were clear differences in reproductive success between the drought year of 1982 and the two years of similar weather, 1981 and 1983. Breeding began later in 1982, with a mean hatch date of 18 � 5.1 November, compared with 7 � 3.6 October in 1981 and 21 � 5.1 September in 1983. Broods hatched over 43 days in 1982 compared with 69 days in 1981 and 101 days in 1983. Also, duckling survival was lowest in 1982, with about a 20% probability of survival to fledging compared with 89% in 1981 and 82% in 1983. Only six broods were found in 1982 compared with 33 in 1981 and 30 in 1983. An estimated 158 and 176 ducklings survived to fledging compared with seven in 1982. Brood sizes at hatching did not show the same clear annual differences. In 1981 and 1983 there were seasonal differences in brood size at hatching. Broods were smaller late in the season (4.1) compared with early (7.2) and mid-season (7.2). Broods were also larger in 1983 (7.2) than in 1981 (5.4). Brood size at hatching in 1982 was 6.0.

Survival of Juvenile Ring-Necked Ducks on Wetlands of Different pH

Brood and duckling survival of ring-necked ducks (Aythya collaris) was examined in relation to wetland water chemistry in eastcentral Maine during 1983-85. Daily survival rates (DSR) of broods and ducklings were determined for 381 ducklings from 64 broods by counts of each brood at 6-10-day intervals during broodrearing. Twelve of 64 females lost entire broods. Only 176 of 381 (46%) ducklings survived to fledge. Brood survival for the 45-day rearing period was 0.7731; duckling survival was 0.3707. Young ducklings ( 6.1) wetlands (0.9816/day) (P = 0.049). Class IIb-III (25-45 days old) ducklings from the lowest-pH wetlands ( 6.5) had the highest DSR (0.9856) (P = 0.009). J. WILDL. MANAGE. 52(2): 169-176 Ring-necked ducks have fairly high annual harvest rates, though populations on wintering areas may be declining (Conroy and Eberhardt 1983; U.S. Fish and Wildl. Serv., Off. Migr. Bird Manage., unpubl. data). Conroy and Eberhardt (1983) reported that age ratios for ring-necked ducks harvested in fall in the Atlantic Flyway (1961-81) were lower than those from the Mississippi Flyway (1.18 vs. 1.29 young/ad). The northeast receives acidic precipitation (Cowling 1982); almost 17% of the 3,100,000 km2 of breeding area of the ring-necked duck is vulnerable to acidification and up to 34,000 pairs could be affected (Longcore et al. 1987). Wetland acidification could adversely affect waterfowl by lowering diversity or biomass of invertebrates in wetlands used by breeding adults or ducklings. Female ducks rely on protein-rich invertebrates for egg laying, and ducklings require ample protein and nutrients for growth (Swanson and Meyer 1973, Krapu 1974, Reinecke 1979). Reductions in invertebrates during broodrearing may lower survival of ducklings and reduce recruitment. Brood surveys are used to estimate production and apparent survival rates (ASR) of ducklings. However, estimates from this method overestimate production because there is no accounting for loss of entire broods (Ball et al. 1975, Reed 1975, Ringelman and Longcore 1982, Talent et al. 1983). We estimated survival rates of ring-necked duck broods and ducklings in eastcentral Maine by relocating broods at regular intervals and recording duckling attrition over time. We estimated survival rates of older and younger ducklings and related differences in survival to differences in pH and alkalinity of the broodrearing wetland. We thank A. G. LaRochelle, P. E. Malicky, C. J. Reid, D. D. Eggeman, R. R. Roy, J. R. Kelly, R. D. Stratton, J. C. Lewis, J. D. Stanton III, J. P. Gibbs, T. P. Hodgeman, and J. A. Barker for assistance with brood surveys and sorting invertebrates. T. M. Mingo and C. J. Reid identified invertebrates. K. L. Stromborg analyzed water samples. J. D. Nichols gave helpful advice during the planning stages and on analyses of survival rates. C. M. Bunck, G. W. Pendleton, P. H. Geissler, and L. M. Moyer helped with statistical analyses of invertebrate data. J. E. Hines and R. E. Munro gave programming support. Helpful comments on early drafts of this manuscript were made by J. D. Nichols, G. M. Haramis, M. A. Howe, D. H. White, M. J. Conroy, and an anonymous referee. STUDY AREA AND METHODS About 17% (15,000 km2) of the land area of Maine has low to no acid-neutralizing capacity [ANC] (i.e., sensitivity Class 1 [Norton 1980: 524]). Our study areas were selected to represent Class 1 and Class 2 (low-moderate ANC) terrain and consisted mostly of wetlands in Hancock and Washington counties in eastcentral Maine. The 66-km2 Cherryfield study area was located

Nest-Site Distribution and Overland Brood Movements of Northern Pintails in Alberta

Distribution of nests of northern pintails (Anas acuta) was examined around shallow waterbodies on grazed, mixed prairie in southern Alberta. Pintails were the most common ducks nesting on the mainland prairie but not on the more densely vegetated artificial islands. Nest density on the islands for pintails (10.4/ ha) and all duck species combined (80.0/ha) was much greater than that on the mainland (pintails = 0.160.17/ha and all = 0.26-0.31/ha). Hatching sucess of pintail nests on the prairie appeared to be relatively high, probably a result of nests being widely dispersed over large areas of suitable habitat. Pintail nests on the prairie were most commonly situated 1-2 km from water. A hypothesis that pintails nest far from water to avoid male-chasing was repudiated in favor of one that such behavior reduces nest predation. Substantial overland travel by pintail broods is common, necessitated by the distance that hens nest from water. Simulated 3-km nest-to-water movements of pintail ducklings did not deplete their lipid reserves or impair growth. J. WILDL. MANAGE. 51(4):716-723 The importance of prairie breeding habitat to the overall productivity of northern pintails is evidenced by the low apparent reproductive output of arctic-nesting birds (Calverley and Boag 1977, Derksen and Eldridge 1980) and the positive correlation between continental recruitment and the relative proportion of birds inhabiting the prairies (Smith 1970). Within the prairies, the grasslands of southern Alberta support higher densities of breeding pintails than any other region (Vermeer 1972, Bellrose 1979). Much of this area is rangeland, and consequently, many of the birds breeding there nest on grazed prairie. Most information on the location of nest sites of pintails has come from Manitoba and North Dakota where pintails frequently nest, often unsuccessfully, in cultivated fields (Sowls 1955:66, Milonski 1958, Higgins 1977, Krapu 1977). Pintails reportedly nest farther from water than other ducks (Keith 1961, Bellrose 1980: 271), but no systematic searches have been conducted to determine the distribution of their nests relative to water. Nests placed far from water are often thought to result in reduced duckling survival because of the extended overland travel required to get to water; e.g., Sayler 1962, Dzubin and Gollop 1972. In areas where artificial islands have been created, the distribution of nests on the mainland can be compared to that on islands to evaluate the efficacy of the islands in increasing waterfowl production. This study examined the location of pintail nests around a number of shallow basins in grazed prairie near Brooks, Alberta. Pintail use of artificial islands for nesting sites was compared to that of the mainland and contrasted with that of other duck species. The distance of pintail nests from water was determined, and the hypothesis that male pursuit flights cause hens to nest far from water was considered. The consequences of nesting far from water were examined, particularly the effect of overland movement on the condition of ducklings. Financial support of this study was provided by grants to D. A. Boag from the Nat. Sci. and Eng. Res. Counc., and Can. Natl. Sportmen's Fund. Ducks Unlimited Can. and the Brooks Wildl. Cent. of the Gov. Alberta provided invaluable logistic support. Thanks to T. S. Coleman, R. Cotter, G. G. Gregoire, A. J. Murphy, and T. D. Sorochan for their assistance in the field. Special thanks to D. A. Boag for his comments on the manuscript and also to C. D. Ankney, S. J. Hannon, V. Lewin, A. R. Palmer, A. Shires, W. D. Wishart, and P. M. Woodard. The Bamfield Mar. Stn. provided the facilities and personal support for revision of this paper. STUDY AREA AND METHODS The study was conducted in an area of grazed prairie about 35 km southeast of Brooks, Alberta, from 1981 to 1984. The study area included 4 impoundments that are managed for waterfowl production by Ducks Unlimited, Canada. These impoundments (Tilley O, Tilley P, Kininvie F, and Kininvie S) were described by Giroux (1981). At high water levels, the areas Present address: Bamfield Marine Station, Box 99, Bamfield, British Columbia VOR 1BO, Canada.

Brood territories in buffleheads: determinants and correlates of territory size

In most species of ducks, only females tend the brood, and they do not defend brood territories. However, in buffleheads (Bucephala albeola), females strongly defend brood territories. I examined factors affecting territory size of broods, and their consequences for growth rate and survival of ducklings. Brood density tended to be higher on ponds with higher food density. Territory size was inversely correlated with both food abundance in the territory and brood density on the pond. The slope of the relationship between territory size and food did not differ significantly from −1, the slope expected if females adjust territory size to maintain a constant food supply. Partial correlation analysis, however, revealed that brood density may be a more important proximate determinant of territory size than food. Growth rates of ducklings were not affected by food density but were depressed at high brood density in one year. Duckling survival increased with food density in the first year but was depressed at high brood density in the next. I suggest that females select a brood territory and that the size of that territory varies according to both food and brood density. This apparently buffers the effects of variation in food and brood density on growth and survival of ducklings.

Reproduction in mallards fed selenium

Mallards (Anas platyrhynchos) were fed diets containing 1, 5, 10, 25 or 100 ppm selenium as sodium selenite, a diet containing 10 ppm selenium as seleno-DL-methionine or a control diet. There were no effects of 1, 5 or 10 ppm selenium as sodium selenite on either weight or survival of adults or on reproductive success, and there did not appear to be a dose-response relationship at these lower levels. The 100 ppm selenium diet killed 11 of 12 adults; one adult male fed 25 ppm selenium died. Selenium at 25 and 100 ppm caused weight loss in adults. Females fed 25 ppm selenium took longer to begin laying eggs and intervals between eggs were longer than in females in other treatment groups. Hatching success appeared to be reduced in birds fed 10 ppm selenium as selenomethionine, but the reduction was not statistically significant. The survival of ducklings and the mean number of 21-d-old ducklings produced per female were reduced in the 25 ppm selenium as sodium selenite group and the 10 ppm selenium as selenomethionine group. Egg weights were not affected by any selenium treatment, but 25 ppm selenium lowered the Ratcliffe Index. Duckling weights at hatching and at 21 d of age were reduced 28 and 36%, respectively, in birds fed 25 ppm selenium, as compared with controls. Body weights measured on day 21 were lower for ducklings fed 10 ppm selenium as selenomethionine than in some other groups. Selenium in concentrations of 10 and 25 ppm as sodium selenite caused mainly embryotoxic effects, whereas 10 ppm as selenomethionine was more teratogenic, causing hydrocephaly, bill defects, eye defects (microphthalmia and anophthalmia) and foot and toe defects, including ectrodactyly. Selenomethionine was much more readily taken up by mallards and passed into their eggs than was sodium selenite, and a greater proportion of the selenium in the eggs ended up in the white when selenomethionine was fed. Adult males accumulated more selenium than did females, probably because of the females' ability to eliminate selenium in their eggs.

Survival of Mallard ducklings Anas platyrhynchos and competition with fish for invertebrates on a flooded gravel quarry in England

The survival of Mallard Anas platyrhynchos ducklings was studied on a complex of flooded gravel quarries in England and their weight changes in response to invertebrate predation by fish were studied by experiment. The majority of duckling loss occurred during the first 12 days after hatching but those feeding on the river where fish were scarce survived better than those feeding on lakes where fish density was high. Duckling mortality was higher in broods with large home ranges. In the experimental trials an increase in fish density was related to a reduction in both the number of emerging invertebrates and the biomass of aquatic macrophytes. Ducklings feeding in these ponds travelled further and gained less weight than on the pond with a low fish density where the number of emerging invertebrates was higher.

Factors affecting duckling survival of Eiders Somateria mollissima in northeast Scotland

Mortality factors affecting Eider ducklings Somateria mollissima and their impact with respect to age were studied on the Ythan estuary, Aberdeenshire, Scotland. Survival from hatching to fledging averaged 10.4% over 13 years; numbers declined steeply during the first three to four weeks and slowly thereafter. Growth of tagged young varied considerably between broods. Mortality was not correlated with numbers of ducklings or adults.Predation in 1974 averaged 13.6% per day during the first two weeks, and accounted for most mortality. Herring Gulls Larus argentatus were the principal predators. Predation was 2.5 times as high in rainy, windy weather as in fine, calm weather. Weather, primarily mean rainfall and wind speed, during early life accounted for over 90% of all variation in survival during eight of nine years. Predation was considered the proximate factor in most weather‐related mortality. High survival in 1971 was not explained by weather. An estimated 25–40% of mortality during the second week of life was from renal coccidiosis Eimeria somateriae. Reproductive output of the Ythan population probably limits the rate of population growth, but numbers of breeding birds seem to be regulated by other factors acting after fledging.

Toxicity of abate® 4E (temephos) in mallard ducklings and the influence of cold

AbstractDiets mixed to contain 0, 0.1, 1.0, 10 and 100 ppm temephos (determined chemically to contain less than 0.5, less than 0.5, 0.89, 6.0 and 59 ppm temephos, respectively) in an Abate® 4E formulation, were fed to mallard (Anas platyrhynchos) ducklings for 7 d. During this period, half of the ducklings in each dietary treatment group were housed in a heated brooder (39 to 41 °C) and half were housed in an unheated brooder (10 to 18°C). Mortality in all dietary groups in the unheated brooder was higher than in the heated brooder. High temephos‐related mortality occurred in the 100 ppm group in the unheated brooder but not in any other diet‐temperature groups. Ingestion of the 100 ppm temephos diet inhibited plasma Cholinesterase (ChE) activity and elevated plasma corticosterone concentration and creatine phosphokinase activity, but other selected plasma chemistries were not affected in a dose‐related manner. Brain ChE activity was depressed only in the 100 ppm dietary groups; maximum inhibition of brain ChE activity was 48%. These findings suggest that diets containing up to 10 ppm temephos do not directly affect duckling survival during the first week of life and that the toxicity of 100 ppm temephos is markedly enhanced by cold.

The population dynamics of the Eider Duck Somateria mollissima and evidence of extensive non‐breeding by adult ducks

The dynamics of an Eider Duck population have been investigated over 25 years, using census and capture‐mark‐recapture methods. During the study the population increased two and a half fold, with two periods of major increases in numbers, giving a stepped growth pattern. Mean clutch size showed considerable annual variation, the extremes being 5.40 and 3.78 eggs. The variation in clutch size was greater than that recorded in the Netherlands. Adult female Eiders had a high annual survival rate, averaging 0.895, and varying between 0.75 and 1.00 in individual years. The survival rate decreased markedly in the old ducks. There was no indication of any change in the survival rate during the study. Recruitment of ducks to the breeding group was irregular, with most years showing little recruitment and a few years high recruitment. However, recruitment, associated with good duckling survival, appears to have been the main factor associated with increase in the population. In many years, an appreciable proportion of the surviving ducks, which had already bred in a previous year, failed to nest. The extent of non‐breeding increased during the study and in one year, 1973, this reached 65%. Lower clutch size and adult survival were associated with years of high non‐breeding. The ‘red‐tides’ in 1968 and 1975 appeared to have little effect on the Eider. It is suggested that the Eider missed breeding in years in which its survival was potentially poor, in order to maximize its reproductive output during its life span. This is supported by the smaller clutch size laid by those females which nest in years when many females fail to breed. It is suggested that young ducks may also miss breeding in the year after first nesting but this is not associated with the non‐breeding in older ducks, although it may he related to body condition. It is suggested that non‐breeding by adults of long‐lived birds may be widespread. This has important implications in survey work based on nest counts.

Effects of dietary ABATE on reproductive success, duckling survival, behavior, and clinical pathology in game-farm mallards.

Forty-four pairs of game-farm mallards (Anas platyrhynchos) were fed ABATE® 4E (temephos) to yield 0, 1, or 10 ppm ABATE® beginning before the initiation of lay, and terminating when ducklings were 21 days of age. The mean interval between eggs laid was greater for hens fed 10 ppm ABATE® than for controls. Clutch size, fertility, hatchability, nest attentiveness of incubating hens, and avoidance behavior of ducklings were not significantly affected by ABATE® ingestion. The percentage survival of ducklings to 21 days of age was significantly lower in both treated groups than in controls, but brain acetylcholinesterase (AChE) activity was not inhibited in young which died before termination of the study. In 21-day-old ducklings, aspartate aminotransferase (AST) activity increased and plasma nonspecific cholinesterase (ChE) activity was inhibited by about 20% in both treatment groups, but there were no significant differences in brain AChE or plasma alanine aminotransferase (ALT) activities, or plasma uric acid concentration. Clinical chemistry values of adults were not affected. No ABATE®, ABATE® sulfoxide, or ABATE® sulfone residues were found in eggs or tissue samples.

Effects of dietary nickel on survival and growth of mallard ducklings.

Mallard (Anas platyrhynchos) ducklings were fed nickel sulphate in their diet from day one to 90 days of age. Ducklings fed 1,200 ppm nickel began to tremor and show signs of paresis after 14 days of dosage (age) and 71% of this group died within 60 days of age. Birds fed 1,200 ppm nickel weighed significantly less (P less than 0.05) at 28 days of age than birds fed the other diets. Weights of ducklings fed untreated food or dietary dosages of 200 and 800 ppm nickel diets were not significantly different (P less than 0.05). The weight/length ratio of the humerus (an expression of bone density) from the 800 ppm diet females was significantly lower (P less than 0.05) than the control fed females at 30 and 60 days and for all ducklings fed 1,200 ppm at 30 days of age. The organ-weight/body-weight ratios for heart, liver, and gizzard did not differ from controls or between any dosage group. Liver nickel residues from ducklings that died during this study ranged between 1.0 to 22.7 ppm and kidney residues ranged between 2.7 and 74.4 ppm. Liver and kidney tissues from all ducklings that survived to 90 days of age contained less than 1.0 ppm nickel.

Effects of dietary nickel on mallards.

Thirty breeding pairs of mallards (Anas platyrhynchos) were randomly assigned to one of five treatment groups and were fed breeder mash containing 0, 12.5, 50.0, 200.0, or 800.0 ppm Ni (as the sulfate) for 90 d. Ni ingestion had no effect on egg production, hatchability, or survival of ducklings. After 90 d birds were bled, sacrificed, and necropsied. There were no significant differences in hematocrit; concentrations of hemoglobin, plasma triglyceride, and cholesterol; of plasma activities of ornithine carbamoyltransferase and alanine aminotransferase. A black tarry feces was noted in the high Ni dose group at necropsy, but no gross or histopathologic lesions were observed. Although absolute concentrations of Ni in tissues were low, there were significant accumulations in kidneys of birds fed Ni at all dietary levels and in feathers, blood, and livers of birds fed high doses of Ni compared with controls.

Reproductive success and nest attentiveness of mallard ducks fed Aroclor 1254

A dietary dosage of 25 ppm Aroclor 1254 fed to nine-month-old mallards Anas platyrhynchos for at least a month before egg-laying had no detrimental effect on reproductive success or nest attentiveness when hens were allowed to incubate their own eggs. The treatment caused no effect on number of hens laying, date of first egg laid or clutch size. Fertility of eggs was greater among Aroclor-treated birds (87·7%) than among controls (73·2%). Aroclor may have stimulated males to come into reproductive condition sooner than controls. Hatching of fertile eggs and survival of ducklings to 3 weeks of age were similar in treated and control groups. The number of times off the nest per day and total time off the nest per day were the same for control and Aroclor-treated hens in days 14–17 of incubation.

Survival and reproductive success of black ducks fed methyl mercury

A diet containing 3 ppm mercury was fed to black ducks ( Anas rubripes) for periods of 28 weeks during two consecutive breeding seasons. Clutch size, egg production, number of eggs incubated, hatchability and survival of ducklings were lower during both years in hens fed mercury. Reduced hatchability and poor duckling survival were the most harmful effects. During 2 years, 13 pairs of breeders fed mercury produced only 16 ducklings that survived 1 week compared with 73 ducklings from 13 pairs of controls. Mercury residues in eggs, embryos and ducklings averaged about 30% lower during the second breeding season compared with first year results. Third eggs laid by treated hens contained a mean of 6·14 and 3·86 ppm mercury during the first and second years. Whole embryos that failed to hatch contained means of 9·62 and 6·08 ppm mercury during the first and second years. Brains of dead ducklings contained between 3·25 and 6·98 ppm mercury and exhibited lesions characteristic of mercury poisoning. Relative tissue mercury levels for treated adult breeders were: feathers > liver > kidney > breast muscle > brain. Mercury levels in males and females did not differ.

Survival of Wood Duck and Mallard Broods in North-Central Minnesota

Duckling survival in wood duck (Aix sponsa) and mallard (Anas platyrhynchos) broods was estimated from data obtained from 71 radio-marked brood hens on a study area in north-central Minnesota. Radio-marked hens produced 30 broods during the study, and 41 hens already leading broods were captured and radio-marked. Production estimates based on brood size counts were inflated by about 38 percent for wood ducks and 30 percent for mallards if total-brood losses were not taken into account. Mortality during the first 2 weeks of life was most severe, accounting for 86 percent of total recorded mortality in wood ducks and 70 percent in mallards. Rearing success was about 41 percent for wood ducks and 44 percent for mallards. Duckling survival was negatively correlated with distance of overland travel by young broods. Wood ducks had a shorter hen-brood bond than mallards, and presence of the hen appeared to affect duckling survival less in wood duck broods than in mallards.