Male Black Ducks Research Articles

Mallard–Black Duck Hybridization and Population Genetic Structure in North Carolina

ABSTRACTNorth Carolina, USA, represents the southern extent of the American black duck's (Anas rubripes) breeding range. Mallards (A. platyrhynchos) are present on the breeding grounds of the American black duck and hybridization is observed between these species; therefore, we assessed the genetic integrity, hybridization rates, and population structure of this local breeding population. We extracted genomic and mitochondrial DNA from chorioallantoic membranes and contour feathers from monitored black duck nests. We then prepared the extracted DNA for analysis using high‐throughput DNA sequencing methods (ddRAD‐seq). First, we assessed nuclear and mitochondrial population structure, genetic diversity, and differentiation across samples from North Carolina, and compared them against 199 genetically vetted mallards, black ducks, and mallard × black duck hybrids that served as genetic references. Next, we tested for parentage and sibling relationship and overall relatedness of black ducks in North Carolina. We recovered strong population structure and high co‐ancestry across genetic markers due to interrelatedness among sampled nests in North Carolina and concluded that black ducks have been locally breeding in this area for a prolonged period of time. Despite a high level of interrelatedness among our samples, nucleotide diversity was similar to the reference continental black duck population, suggesting little effect of genetic drift, including inbreeding. Additionally, we conclude that molecular diversity of black ducks in North Carolina is maintained at reference population levels through the influx of genetic material from unrelated, migrating male black ducks. Finally, we report a hybridization level of 47.5%, covering 3 filial generations. Of identified hybrids, 54.7% and 53% were the direct result of interbreeding between black ducks and captive‐reared or wild mallards, respectively. We conclude that because of high rates of interspecific hybridization and successive backcrossing events, introgression from wild and feral mallards is occurring into this population of breeding black ducks and requires careful consideration in future management efforts. © 2021 The Wildlife Society.

Condition Indices of Live-Trapped American Black Ducks and Mallards

We compared condition indices of interacting American black ducks (Anas rubripes) and mallards (A. platyrhynchos) during staging to contrast changes in energy reserves that potentially influence survival or other population parameters. We live-trapped and banded 1,126 black ducks and 1,292 mallards from October through January during 1990-1993 on Ottawa National Wildlife Refuge (NWR) in Ohio, USA. Ducks were aged, sexed, and weighed; total body length, wing chord, culmen, and tarsus were measured to compute condition indices. The condition indices were used as dependent variables in multiple regression models to measure influences of annual date, species, and ambient temperature for each age-sex class. Adult male black ducks usually had slightly higher (1% to 3%) condition indices than adult male mallards. Initially, in 1990 and 1992, juvenile female mallards had 6% higher condition indices than juvenile female black ducks, but during these 2 years, black duck juvenile females improved condition at higher rates than their mallard counterparts. Temperature effects on condition of live-trapped birds were noted, especially during November 1991, when decreased body weights corresponded with frozen wetland foraging areas. Daily temperature similarly influenced black duck and mallard egress from the Lake Erie marshes. Species differences in breeding chronology and breeding ground productivity could influence the body condition of these birds and the observed seasonal trends. The poor body condition of juvenile black duck females observed during some years could possibly contribute to lower survival and reproductive performance during the following spring if these differences continue through the remainder of the winter.

Forced copulation in sympatric American black ducks and mallards in Nova Scotia

Observations of primarily identifiable wild black ducks and mallards provided qualitative and quantitative descriptions of interactions within and between intraspecific, interspecific, and heterospecific pairs throughout the breeding season. The study was carried out in a watershed on the St. Lawrence estuary shore of Nova Scotia from 1972 to 1988. Attempted forced copulation and forced pair copulation were rare among black ducks at any time throughout the breeding period. Only two apparently successful forced copulations were observed. Territorial males chased both female black ducks and mallards, and these chases appeared motivated by hostility. Males that had left their mates/territories did not attempt forced copulation with other females. Females sometimes avoided strange males, particularly when they returned to territories from their nests. Paired males rarely approached females with broods. Male mallards chased both female mallards and black ducks, and did not appear to discriminate between species when attempting forced copulation. Male mallards were more persistent and vigorous in their chases than black ducks, and they attempted forced copulation, whether with black ducks or mallards, more frequently than male black ducks did. Apparently successful forced copulation between a male mallard and female black duck occurred on three occasions.

Survival and Movements of Molting Male Black Ducks in Labrador

Suivi par telemetrie de 26 mâles de canards noirâtres (Anas rubripes) pendant la mue post-nuptiale sur la cote nord du Labrador afin de determiner leur survie et d'etudier leurs deplacements

Social experience influences preferences in black ducks and mallards

The influence of social experience on the preferences for a potential mate in a captive population of black ducks, Anas rubripes, and mallards, Anas platyrhynchos, was examined. Birds were reared from hatching with conspecifics (i.e., female black ducks with male black ducks, female mallards with male mallards), or were cross-fostered with the other species (i.e., female black ducks with male mallards, female mallards with male black ducks). Preferences of individuals were tested in a chamber containing caged black ducks and mallards of the opposite sex. In over 90% (100/109) of the trials, males and females preferred the species that they were raised with since hatching, whether they were of the same species or not. These results demonstrate that social experience influences the social preferences of male and female black ducks and mallards.

The influence of male dominance on social interactions in black ducks and mallards

The influence of male dominance on male-female social interactions was examined in black ducks, Anas rubripes, and mallards, A. platyrhynchos, that were raised from hatch in four different groups (male and female mallards; male and female black ducks; male mallards and female black ducks; male black ducks and female mallards). The mate preference of females, independent of the influence of male dominance, was determined by exposing females to four caged, isolated males, one from each different group. All females preferred the type of male they had been raised with since hatch. Females were then exposed to the same four males, now free-swimming, to determine how male dominance influenced the initial preference. Under these conditions, each female associated primarily with the most dominant of the four males, regardless of her initial mate preference. Mallards were the most dominant males in all tests. These results demonstrate that male dominance influences social interactions and is one factor contributing to hybridization between these two species.

Survival and Band Recovery Rates of Sympatric American Black Ducks and Mallards

Survival and Band Recovery Rates of Sympatric American Black Ducks and Mallards

Breeding habitat selection and home range of radio-marked black ducks (Anas rubripes) in Maine

Telemetry techniques were used to monitor the movements and habitat use of 13 female and 7 male black ducks (Anas rubripes) in an inland breeding region of south central Maine in 1977–1980. Black ducks preferred persistent emergent, broad-leaved deciduous forested, and broad-leaved deciduous scrub–shrub wetlands over unconsolidated organic bottom, needle-leaved evergreen forested, and broad-leaved evergreen scrub–shrub ponds. Birds also made frequent use of small ephemeral pools and streams throughout the breeding period. Nests were located in several habitats ranging from wetland sites to upland areas 1.5 km from the most frequently used pond. Home range size averaged 119 ha for females and 231 ha for males and did not differ by reproductive stage. Three pairs used only a single pond during the incubation period. Home ranges were linear (linearity index = 2.8), averaging 1956 m long for females and 2755 m for males. Wetlands used most by hens during incubation recesses were not always those located closest to the nest. Radio-marked ducks that returned in subsequent breeding seasons demonstrated fidelity to the previously used home range. Pair bonds of marked birds lasted until day 19 or 20 of incubation for initial nesting attempts.

Behaviour of unpaired male black ducks (Anas rubripes) during the breeding season in a Nova Scotia tidal marsh

Behaviour of unpaired male black ducks throughout the breeding season was studied for 3 years (1973, 1974, 1978) in the marsh of a tidal estuary near Antigonish, Nova Scotia. Males remained primarily on a communal area in the marsh. Reproductively oriented activities occurred from late March until late May and peaked in frequency and intensity in early April. Most frequently daily display occurred from 0800 to 1300 hours. Unpaired males joined pairs singly or in groups but only grouped birds courted females. Unpaired males were tolerated on territories and some single males associated with pairs for several days. Groups joined pairs that foraged on the communal area, often persisting with them and disrupting their activity. Males appeared to prefer to court introduced unpaired females over paired females, which were always with their mates. Some males appeared successful in forming pair bonds with introduced females. Males did not attempt to rape females either on territories or the communal area and mallard (A. platyrhynchos) and pintail (A. acuta) males courted female black ducks.

Metabolic rates and heart rate-metabolism relationships in the black duck ( Anas rubripes)

1. 1. All ducks exhibited a linear inverse relationship between metabolism and temperature below the lower critical temperature. 2. 2. Heavier male black ducks had a higher heat production on a per bird basis that did females. 3. 3. Heat production of ducks acclimated to 19°C was greater than that of birds acclimated to 5°C. 4. 4. Resting metabolism of ducks equipped with small radio transmitters was 19% higher than that of birds without radios. 5. 5. Significant correlations between heart rate and metabolism existed for most ducks.