Lophodytes Research Articles

Interspecific Mate Choice and Hybridism in the Bufflehead, <em>Bucephala albeola</em>

Observations of a male Bufflehead (Bucephela albeola) paired with a female Common Goldeneye (Bucephela clangula) in northern Alberta in 1995 and of a hybrid male Common Goldeneye × Bufflehead photographed near Victoria, British Columbia, in March 2009 provide the first combined evidence of interspecific mate choice and out-crossing in Bucephala albeola. Since 1999, there have been at least 10 unofficial records, including photographs, of Common Goldeneye × Bufflehead hybrids posted on the Internet, as well as 6 records of hybridization with Hooded Mergansers (Lophodytes cucullatus). In all cases, where evident in Common Goldeneye × Buffleheads, gold eyes and pink feet were expressed and social affiliation was with Common Goldeneyes, suggesting matrilineage with that species. Because most attention is given to the hybrid - and to male hybrids at that - rather than to the progenitors, the theory of mate attraction, through sexual imprinting of males, is biased toward the paternal viewpoint. It appears that there is more plasticity in mate choice, particularly by the female. The opportunity to observe mate choice is much rarer than the hybrid outcome, while the odds of the latter have increased many fold in the last decade due to advances in Internet communication and digital photography. This exercise illustrates the ability of the Internet to amplify the prevalence of rare phenomena many fold over historical records.

Two Cases of Neoplasia of Basal Cell Origin Affecting the Axillary Region in Anseriform Species

Neoplasms of the skin are occasionally seen in domestic birds but are uncommon in nondomestic birds. An 8-year-old male hooded merganser (Lophodytes cucullatus) was presented with bilateral axillary ulcerative lesions that improved but did not resolve with empiric antibiotic and antifungal therapy. Skin biopsies were taken, and bilateral feather folliculomas were diagnosed on histopathologic examination. The duck was euthanatized because of the poor prognosis. A 9-year-old Indian runner duck (Anas platyrhynchos) was presented with an ulcerative lesion, with pseudomembrane and serocellular crust affecting the axillary region. This mass was diagnosed as a basosquamous carcinoma. The mass was surgically excised, and no recurrence was observed. Feather folliculomas are usually considered benign neoplasms in domestic birds and may be primarily ulcerative, exudative, bilateral, and symmetric in location. Basosquamous carcinoma may have a similar gross appearance. It is unknown if the axillary region may be an area with increased incidence of neoplasia in birds. This appears to be the first report of feather folliculoma and basosquamous carcinoma in Anseriforme species. Feather folliculomas and other neoplasms, such as basosquamous carcinoma, should be considered as a differential diagnosis in ulcerative or proliferative skin lesions in birds.

Estimating Waterfowl Densities in a Flooded Forest: A Comparison of Methods

During winter, aerial surveys are used to estimate densities of ducks that occupy open-water habitats. However, such surveys are ineffective for sampling forest-dwelling species, especially Aix sponsa (Wood Ducks), Anas platyrhynchos (Mallards), and Lophodytes cucullatus (Hooded Mergansers). We evaluated fixed-radius plot (FRP) and Reynolds and Goodrum variable-radius plot (VRP) methods for estimating waterfowl densities in a flooded hardwood bottomland. We constructed 15 elevated blinds on the Angelina River flood plain in eastern Texas and established a 1-ha FRP around each blind; color-coded markers were placed at fixed intervals from each blind. Observers surveyed waterfowl from blinds for 21 mornings during January–March, 1990. For FRPs, species, sex, and time a bird entered and exited the plot were recorded. For VRPs, similar data and estimated observer-to-bird distance were recorded. Data were arranged in a randomized block design and tested using 1-way analyses of variances. Wood Ducks, Mallards, and Hooded Mergansers comprised 68, 18, and 10% of the birds recorded, respectively. Wood Duck density estimates (per ha) for FRP, Reynolds VRP, and Goodrum VRP methods were 0.65, 0.49, and 1.00 (P < 0.001), respectively; for Mallards, estimates were 0.27, 0.20, and 0.33 (P < 0.001), respectively; and estimates were 0.09, 0.13, and 0.15 (P = 0.003) for Hooded Mergansers, respectively. Based on ease of implementation, complexity of data analyses, and precision of density estimates, the FRP and Goodrum VRP methods are recommended for sampling waterfowl in flooded forests.

Estimating Waterfowl Densities in a Flooded Forest: A Comparison of Methods

Abstract During winter, aerial surveys are used to estimate densities of ducks that occupy open-water habitats. However, such surveys are ineffective for sampling forest-dwelling species, especially Aix sponsa (Wood Ducks), Anas platyrhynchos (Mallards), and Lophodytes cucullatus (Hooded Mergansers). We evaluated fixed-radius plot (FRP) and Reynolds and Goodrum variable-radius plot (VRP) methods for estimating waterfowl densities in a flooded hardwood bottomland. We constructed 15 elevated blinds on the Angelina River flood plain in eastern Texas and established a 1-ha FRP around each blind; color-coded markers were placed at fixed intervals from each blind. Observers surveyed waterfowl from blinds for 21 mornings during January–March, 1990. For FRPs, species, sex, and time a bird entered and exited the plot were recorded. For VRPs, similar data and estimated observer-to-bird distance were recorded. Data were arranged in a randomized block design and tested using 1-way analyses of variances. Wood Ducks, M...

British Ornithologists’ Union Records Committee: 37th Report (October 2008)

British Ornithologists’ Union Records Committee: 37th Report (October 2008)

Nesting ecology of Common Goldeneyes and Hooded Mergansers in a boreal river system

Common Goldeneyes (Bucephala clangula) and Hooded Mergansers (Lophodytes cucullatus) are common cavity-nesting ducks but the importance of fast-flowing rivers as suitable nesting habitat may have been overlooked. We monitored the use of >90 nest boxes installed along a boreal forest river over a 5-year period. A high nest box occupancy rate was reached in the second year (40%) and was maintained thereafter (48 to 55%). On average, 35 nest boxes were occupied by goldeneyes and 11 by mergansers each year. Laying date was similar between the two species but merganser nests hatched slightly later. Both species had similar clutch sizes but merganser nests contained more eggs than goldeneye nests when heterospecific parasitic eggs were included. On average, 16% of goldeneye nests were parasitized by mergansers, and 49% of merganser nests were parasitized by goldeneyes. Density of suitable natural cavities in the area was relatively low suggesting the high occupancy rate of nest boxes may be a response to lack of suitable cavities. Nest box use was positively related to the total surface area of ponds in the vicinity and negatively to distance to the river. Use of nest sites along fast-flowing rivers appears to be an opportunistic strategy and may be dependant on the presence of nearby ponds and lakes.

SITE FIDELITY IS AN INCONSISTENT DETERMINANT OF POPULATION STRUCTURE IN THE HOODED MERGANSER (LOPHODYTES CUCULLATUS): EVIDENCE FROM GENETIC, MARK–RECAPTURE, AND COMPARATIVE DATA

Abstract The level of site fidelity in birds is often characterized as on the basis of rates of return or homing from mark–recapture data. For species that exhibit site fidelity, subsequent biological assumptions have included population structure, demographic independence, and that the extirpation of a site-faithful group might be irreversible because of low immigration. Yet several genetic studies have observed patterns of population differentiation that are incongruous with strong site fidelity, which suggests recent isolation, gene flow, or both. Using a 13-year live-recapture and dead-recovery data set, as well as nuclear and mitochondrial DNA collected across the range of the Hooded Merganser (Lophodytes cucullatus), an obligate cavity-nester endemic to North America, we found evidence that gene flow persists across portions of the species' range even though the probability of female breeding-site fidelity is high (0.92; 95% confidence interval [CI]: 0.64–0.98) and disjunct breeding ranges of...

Species Differences in the Sensitivity of Avian Embryos to Methylmercury

We injected doses of methylmercury into the air cells of eggs of 26 species of birds and examined the dose-response curves of embryo survival. For 23 species we had adequate data to calculate the median lethal concentration (LC(50)). Based on the dose-response curves and LC(50)s, we ranked species according to their sensitivity to injected methylmercury. Although the previously published embryotoxic threshold of mercury in game farm mallards (Anas platyrhynchos) has been used as a default value to protect wild species of birds, we found that, relative to other species, mallard embryos are not very sensitive to injected methylmercury; their LC(50 )was 1.79 microg/g mercury on a wet-weight basis. Other species we categorized as also exhibiting relatively low sensitivity to injected methylmercury (their LC(50)s were 1 microg/g mercury or higher) were the hooded merganser (Lophodytes cucullatus), lesser scaup (Aythya affinis), Canada goose (Branta canadensis), double-crested cormorant (Phalacrocorax auritus), and laughing gull (Larus atricilla). Species we categorized as having medium sensitivity (their LC(50)s were greater than 0.25 microg/g mercury but less than 1 microg/g mercury) were the clapper rail (Rallus longirostris), sandhill crane (Grus canadensis), ring-necked pheasant (Phasianus colchicus), chicken (Gallus gallus), common grackle (Quiscalus quiscula), tree swallow (Tachycineta bicolor), herring gull (Larus argentatus), common tern (Sterna hirundo), royal tern (Sterna maxima), Caspian tern (Sterna caspia), great egret (Ardea alba), brown pelican (Pelecanus occidentalis), and anhinga (Anhinga anhinga). Species we categorized as exhibiting high sensitivity (their LC(50)s were less than 0.25 microg/g mercury) were the American kestrel (Falco sparverius), osprey (Pandion haliaetus), white ibis (Eudocimus albus), snowy egret (Egretta thula), and tri-colored heron (Egretta tricolor). For mallards, chickens, and ring-necked pheasants (all species for which we could compare the toxicity of our injected methylmercury with that of published reports where methylmercury was fed to breeding adults and was deposited into the egg by the mother), we found the injected mercury to be more toxic than the same amount of mercury deposited naturally by the mother. The rank order of sensitivity of these same three species to methylmercury was, however, the same whether the methylmercury was injected or maternally deposited in the egg (i.e., the ring-necked pheasant was more sensitive than the chicken, which was more sensitive than the mallard). It is important to note that the dose-response curves and LC(50)s derived from our egg injections are useful for ranking the sensitivities of various species but are not identical to the LC(50)s that would be observed if the mother bird had put the same concentrations of mercury into her eggs; the LC(50)s of maternally deposited methylmercury would be higher.

Enhanced C‐Type Lysozyme Content of Wood Duck (Aix sponsa) Egg White: An Adaptation to Cavity Nesting?

Abstract Wild waterfowl species often nest in conditions where high humidity and microbial contamination may influence egg survival and quality. Albumen is traditionally regarded as the major impediment to microbial contamination of eggs, and its composition and activity may be selected by environmental pressures. Egg white protein from the eggs of wood duck (Aix sponsa), hooded merganser (Lophodytes cucullatus), Canada goose (Branta canadensis), and mute swan (Cygnus olor) was evaluated in order to compare the antimicrobial defenses of these species. Ovotransferrin and ovalbumin were identified in all species, but c-type lysozyme was present only in wood duck and hooded merganser egg white samples. Wood duck egg white showed the greatest bacterial activity as well as the highest lysozyme content. Egg white from wood duck and hooded merganser possessed greater lysozyme activity under acidic conditions, suggesting a c-type lysozyme with a pH optimum lower than that of Gallus gallus c-type lysozyme or the presence of g-type lysozyme. Ovotransferrin bacteriostatic activity appeared to be similar across the species investigated. The results suggest that lysozyme and ovotransferrin play a role in the antimicrobial defense of the avian egg. High levels of the broad-acting c-type lysozyme appear to have evolved in the albumen of the wood duck in order to ensure proper development of the embryo in the humid conditions of the cavity nest.

Antimicrobial activity of the Anseriform outer eggshell and cuticle

The avian eggshell is a complex, multifunctional biomineral composed of a calcium carbonate mineral phase and an organic phase of lipids and proteins. The outermost layer of the eggshell, the eggshell cuticle, is an organic layer of variable thickness composed of polysaccharides, hydroxyapatite crystals, lipids and glycoprotein. In addition to regulating gas exchanges, the eggshell cuticle may contain antimicrobial elements. In this study, we investigated the antimicrobial activity of eggshell cuticle and outer eggshell protein extracts from four Anseriform species: wood duck (Aix sponsa), hooded merganser (Lophodytes cucullatus), Canada goose (Branta canadensis) and mute swan (Cygnus olor). Cuticle and outer eggshell protein was extracted by urea or HCl treatment of eggs. C-type lysozyme, ovotransferrin and an ovocalyxin-32-like protein were detected in all extracts. Cuticle and outer eggshell protein extracts inhibited the growth of Staphylococcus aureus, Escherichia coli D31, Pseudomonas aeruginosa and Bacillus subtilis. The presence of active antimicrobial proteins within the avian cuticle and outer eggshell suggests a role in antimicrobial defense. Protein extracts from the cavity nesting hooded merganser were especially potent. The unique environmental pressures exerted on cavity-nesting species may have led to the evolution of potent antimicrobial defenses.

FACTORS INFLUENCING INCUBATION EGG-MASS LOSS FOR THREE SPECIES OF WATERFOWL

Abstract Many bird eggs lose ∼15% of their fresh mass before pipping, but individual species have been reported to lose 10–23%. Most published estimates have been imprecise due to small sample sizes. Moreover, published estimates of within- or among-species variance components of mass loss are virtually unknown. We modeled the influence of nest type, clutch size, and egg size on daily mass loss of Mallard (Anas platyrhynchos), Common Goldeneye (Bucephala clangula), and Hooded Merganser (Lophodytes cucullatus) eggs and compared fractional mass loss among species. Mallard eggs in artificial nest cylinders lost more mass than those in ground nests, but were unaffected by nest initiation date. Average-sized eggs in Mallard ground nests, Mallard cylinder nests, and Common Goldeneye and Hooded Merganser nest boxes lost 7.9 g (15.2%), 10.8 g (20.3%), 10.3 g (15.5%), and 9.2 g (15.8%) of fresh mass, respectively. For all species, daily mass loss increased as incubation progressed and was affected by an interactio...

Dioxins and congener-specific polychlorinated biphenyls in three avian species from the Wisconsin River, Wisconsin

Sediments from the Wisconsin River, WI, USA are contaminated with 2,3,7,8-tetrachloro- p-dioxin (TCDD) and polychlorinated biphenyls (PCBs). Wet weight concentrations of TCDD and PCBs in eggs were at background levels and highest in the piscivorous hooded merganser ( Lophodytes cucullatus; geometric mean=7 pg/g TCDD and 0.92 μg/g PCBs) and lowest in the omnivorous wood duck ( Aix sponsa) (<1 pg/g and 0.07 μg/g); concentrations in eggs of the insectivorous tree swallow ( Tachycineta bicolor) were intermediate (<1 pg/g and 0.33 μg/g). Positive accumulation rates of TCDD (8–19 pg/day) and PCBs (0.4–0.7 μg/day) in tree swallow nestlings suggest that the Wisconsin River is the source of these contaminants for tree swallow nestlings. The lower representation of trichlorobiphenyls and tetrachorobiphenyls in hooded merganser eggs compared to wood duck or tree swallow eggs suggests that the hooded merganser or its diet has a greater ability to metabolize lower-numbered PCB congeners than wood ducks or tree swallows.

British Ornithologists’ Union Records Committee: 28th Report (October 2001)

British Ornithologists’ Union Records Committee: 28th Report (October 2001)

Evidence of an Increasing Hooded Merganser Population in Massachusetts

The number of Hooded Merganser (Lophodytes cucullatus) broods hatching in nest houses on 53 study areas in Massachusetts increased by 289% from 1979–1983 to 1994–1998 and the number of areas used increased from 9 of 53 in 1979 to 26 of 53 by 1998. The number of Hooded Mergansers counted on 21 Massachusetts Christmas Bird Count circles from 1979–1983 to 1994–1998 increased by 225%. The increasing trend lines did not match, suggesting different populations. This appears to support reports of increasing Hooded Merganser populations by other northeastern state waterfowl biologists.

Factors Affecting the Pairing Chronologies of Three Species of Mergansers in Southwest British Columbia

-Most Northern Hemisphere ducks form pairs on the wintering grounds, and timing of pairing varies considerably among species and populations. Hypotheses to explain variation in pairing chronology utilize sex-specific cost-benefit frameworks. These hypotheses have not been adequately tested, largely because of inadequate sample size of pairing chronologies, especially within the tribe Mergini. Wintering Common (Mergus merganser), Hooded (Lophodytes cucullatus), and Red-breasted mergansers (M. serratus) were observed at several sites in southwest British Columbia to determine pairing chronology. Courtship displays of Hooded Mergansers occurred significantly earlier than those of Red-breasted Mergansers. Hooded Mergansers began to pair in mid-November, Redbreasted Mergansers in early February, and Common Mergansers in late February. We tested the prediction that the largest species of ducks pair earliest. This could occur if females derive energetic benefits as a result of pairing, and females of larger species begin to accumulate endogenous nutrients earlier. It could also occur if pairing exerts an energetic cost on males, such that males of smaller species are more prone to winter mortality as a result of fluctuations in energy demand. The much earlier pairing of the smallest species (Hooded Mergansers) is inconsistent with either scenario. We suggest that between-species differences in pairing chronology may be better explained by the constraints imposed by sexual segregation during winter. Received 29 March 1999, accepted 29June 1999.

Response of Female Hooded Mergansers to Eggs of an Interspecific Brood Parasite

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Risk-Taking by Incubating Common Goldeneyes and Hooded Mergansers

We studied nest defense by Common Goldeneyes (Bucephala clangula) and Hooded Mergansers (Lophodytes cucullatus) nesting near Sudbury, Canada between 1989-1995. As incubation proceeded, female Common Goldeneyes took greater risks by allowing the observer to approach the nest more closely before flushing, landing closer to the nest after flushing, vocalizing more commonly when flushed, and giving more broken wing or distraction displays. Hooded Merganser females exhibited relatively strong defense at all stages, including giving distraction displays much earlier in incubation. An index of all four behaviors increased for each species as incubation proceeded. Nest defense by these cavity-nesting ducks differed from patterns known for ground-nesting waterfowl, perhaps due to effects of nest location, predation type and intensity, and nest parasitism. Future nest defense studies should consider the overall suite of behaviors that comprise parental strategies for defending their nests and/or offspring.

Monitoring nest box use by cavity‐nesting ducks on acid‐stressed lakes in Ontario, Canada

Nest boxes erected on 75 small lakes near Sudbury, Canada were monitored annually between 1987 and 1996 to measure the response of cavity‐nesting waterfowl to changing chemical and biological conditions of their nesting habitat from the effects of acidification. Nest boxes were used mainly by common goldeneyes Bucephala clangula and hooded mergansers Lophodytes cucullatus, although a few were occupied by common mergansers Mergus merganser and wood ducks Aix sponsa. Use by hooded mergansers and wood ducks increased from 1987 to 1996, while use by goldeneyes remained stable. Patterns in nest box use reflected general population trends observed in the area. Interspecific nest parasitism also increased to 33% of all nests in 1996, probably a consequence of more hooded merganser nests. Clutch size, nesting and hatching success of goldeneye and hooded merganser eggs were similar to values reported for conspecifics in other studies. Overall, interspecific nest parasitism did not appear to affect the nesting success of either species. Although goldeneyes nested more often on fishless lakes early in the study, overall, fish presence, pH‐value, lake area and connectivity were not related to nesting attempts or measures of nesting success for either species. Therefore, it is believed that for common goldeneyes and hooded mergansers currently breeding in the acid‐stressed Sudbury area, habitat characteristics have little influence on nest site selection, particularly when compared to their documented effects on brood‐rearing. However, monitoring of nest boxes may prove a less expensive method than aerial surveys to track population responses of cavity‐nesting species to chemical improvements.

Female Hooded Merganser Body Mass during Nesting

Body mass of female Hooded Mergansers (Lophodytes cucullatus) nesting in widely dispersed and newly erected wooden nest boxes in northcentral Minnesota was measured in 1982-1985. Median body mass during egg-laying was 635 g. Female mass during incubation varied significantly among years, but decreased monotonically at the same rate (1.0 g day-1) each year. Mass at the end of incubation (519-494 g) was 5.7 to 6.0% less than when incubation began. There was no indication that females having the greatest body mass began nesting earliest. However, females with the greatest body mass incubated the largest clutches and hatched the most young. Comparison of the observed body mass-clutch size relationship with one assumed to exist in the absence of intraspecific brood parasitism indicated that more parasitic eggs were laid in nests incubated by heavier females.

An Occurrence of Avian Tuberculosis in Hooded Merganser (Lophodytes cucullatus)

Two imported male hooded mergansers (Lophodytes cucullatus) were introduced into a zoological aviary in Japan, and one of them died 10 mo later. Postmortem revealed numerous white yellowish nodules of various sizes in the liver. Two large nodules were also observed below the right lung and on the top of the left kidney. Histopathologically, a large number of tubercles with acid-fast bacilli were seen in the liver. The amyloid was deposited in the connective tissue of the tubercles. Bacteriologically, Mycobacterium avium serovar 1 was isolated from the liver.