American black ducks (Anas rubripes) are a medium to large-sized duck species native to North America. Their size can vary based on age, sex, and geographic location, but on average, American black ducks reach lengths of 19-25 inches (48-63 cm) and have wingspans of 32-39 inches (81-99 cm).
Average Weight of American Black Ducks
The average weight of American black ducks also varies based on age, sex, and geography. Adult males tend to be the largest, weighing 2.5-3.2 pounds (1.1-1.5 kg) on average. Adult females are a bit smaller, weighing 2.0-2.8 pounds (0.9-1.3 kg).
Immature ducklings and juveniles weigh much less. Newly hatched ducklings may weigh as little as 0.7 ounces (20 grams). By 2-3 months of age, juvenile ducks may reach 1.5-2.0 pounds (0.7-0.9 kg).
American black ducks at more northern latitudes, such as in Canada, tend to be larger than populations further south. This is likely an adaptation to colder climates where larger body size helps retain heat.
Wingspan
As mentioned above, American black ducks typically have wingspans between 32-39 inches (81-99 cm). Males tend to have larger wingspans near the upper end of this range, while females are more likely to be on the smaller end. However, there is considerable overlap between the sexes.
Wingspan reaches full adult size by around 3-4 months of age when flight feathers are fully grown. Ducklings hatch with very small wings relative to their bodies. Their wings grow rapidly in the first few weeks until they are able to take their first flight at 6-9 weeks of age.
Length
From head to tail, American black ducks measure 19-25 inches (48-63 cm) in length. The upper end of this range is composed of large adult males. Females are generally 19-23 inches (48-58 cm). Ducklings hatch at just 2-3 inches (5-8 cm) in length and grow rapidly in their first few months.
Geographic variations exist with a tendency for more northern populations to have greater lengths. As with weight and wingspan, larger size provides an advantage in colder climates.
Other Physical Attributes
In addition to their large size, American black ducks can be identified by a number of other physical traits:
- Predominantly dark brown to black plumage with a purple iridescence
- Light brown head and neck
- Yellowish bill with black markings
- Bright red legs and feet
- White underwings visible during flight
Females tend to have more muted, lighter plumage compared to males. Juveniles resemble adult females until their plumage matures at 4-5 months of age.
Comparison to Other Duck Species
American black ducks are one of the larger duck species found in North America. They are very similar in size to mallards, with nearly identical length, wingspan, and weight ranges.
Some other common duck species comparisons:
| Species | Length (in) | Wingspan (in) | Weight (lbs) |
|---|---|---|---|
| American Black Duck | 19-25 | 32-39 | 2.0-3.2 |
| Mallard | 20-26 | 32-39 | 2.1-3.5 |
| Northern Pintail | 26-30 | 36-42 | 1.6-2.4 |
| Green-winged Teal | 14-18 | 23-27 | 0.7-1.0 |
| Wood Duck | 18-21 | 26-29 | 1.5-1.9 |
As you can see, the American black duck is larger than species like the green-winged teal, but smaller than the elongated northern pintail. Mallards are their closest match in terms of overall body size.
Role of Size in Survival and Reproduction
An American black duck’s large size provides them with some key evolutionary advantages:
- Larger males can compete more effectively for females during breeding season.
- Larger females can lay larger clutches of eggs.
- Larger overall size allows for consumption of a wider array of plant and animal foods.
- Big bodies retain heat better in cold northern climates.
- Large wings provide power for long distance migration.
Their medium to large stature has likely been a key factor in making American black ducks one of the most abundant and successful duck species throughout North America. Changes to their typical size parameters can serve as an important indicator of environmental stressors on duck populations.
Changes Over Time
Some research indicates the average size of American black ducks may be decreasing slightly over the past few decades. However, findings are inconsistent.
One study in New Jersey found that over the past 50 years, wing length declined by 1.5% while body mass declined by 7% in some populations. The reasons for this possible reduction in size are unclear, but could include factors like habitat change, shifts in nutrition, or rising temperatures.
More research is needed to determine if these localized size reductions are occurring on a broader geographic scale. Currently, the best available data suggests American black duck measurements remain largely stable since the early 20th century, with no major shifts in length, wingspan, or weight averages across their full range.
Conclusion
American black ducks are a medium to large-bodied duck species, with grown adults reaching average lengths of 19-25 inches, wingspans of 32-39 inches, and weights between 2.0-3.2 pounds. Males tend to occupy the upper end of these ranges, while females are somewhat smaller. Their large size provides advantages in courtship, reproduction, foraging, migration, and thermoregulation.
While their overall dimensions appear to have remained stable over the last century, some localized declines in body mass and wing length warrant continued monitoring. Tracking shifts in American black duck size over time can reveal important information about the status and health of populations.
