Black ducks and Mallards are two of the most common duck species found across North America. They belong to the same genus, Anas, and have similar appearances with green heads and grey bodies. However, there are some key differences between black ducks and Mallards when it comes to their size and mass.
In the opening paragraphs, it’s quick to answer that on average, Mallards are slightly bigger than black ducks. The male Mallard is typically larger than the female, but even Mallard hens tend to be bigger overall than black ducks of either sex. Exact size ranges are explored in more detail throughout this article.
Detailed Size Comparison
Mallards are considered a large duck species, with some of the highest weight and length measurements among common ducks. Black ducks, while a good-sized duck, usually fall just short of Mallard size benchmarks. Here is a more detailed look at how the two ducks match up in terms of length, wingspan, mass, and other size metrics:
Length
– Mallard Length: Males reach 21-26 inches long on average, while females are typically 20-24 inches. Overall Mallard lengths span 18-28 inches.
– Black Duck Length: Black duck lengths range from 19-25 inches. On average, males grow to 21-23 inches and females reach 20-22 inches.
So while the length range overlaps between the species, Mallards on the high end can get almost 10% longer than the biggest black ducks. The Mallard’s length advantage is most pronounced among drakes versus female and juvenile ducks of both species.
Wingspan
– Mallard Wingspan: Around 32 inches on average, but can reach 36 inches.
– Black Duck Wingspan: Typical wingspan of 28-30 inches, up to 34 inches maximum.
The wingspans highlight another size difference favoring Mallards by a few inches on average. Both ducks need wide wings to generate lift and thrust to stay aloft during flight. But the broader Mallard wings allow it to fly faster with more power.
Mass and Weight
The mass and weight numbers further confirm the Mallard’s size advantage:
Species | Male Weight | Female Weight |
---|---|---|
Mallard | 2.8-3.2 lbs | 1.5-2.2 lbs |
Black Duck | 2.2-2.8 lbs | 1.3-1.8 lbs |
– Mallard Weight: Males are about 2.8-3.2 lbs on average compared to 1.5-2.2 lbs for females.
– Black Duck Weight: Male black duck weights run around 2.2-2.8 lbs, while females are 1.3-1.8 lbs typically.
The male Mallard can outweigh even the heaviest male black ducks by 0.5 lb or more. Among females, the mass difference is less pronounced but still favors the Mallards on average. Higher weight correlates to greater overall body size and bulk.
Other Size Characteristics
Looking beyond length, wingspan, and mass reveals a couple more size differences:
– Bill Length: Mallards have longer bills (2.3 inches average) than black ducks for feeding preferences.
– Plumage Dimensions: Mallard’s broad tail and thick belly feathers increase apparent body size.
– Skeleton Size: Mallards have bigger foot bones and skulls than black ducks on average.
While less significant individually than weight and length, these other structural size markers add to the Mallard’s cumulative size advantage across most physical metrics. Exceptions may occur among especially large black duck specimens.
Growth Rate and Sexual Dimorphism
Two duck biology factors that influence size are growth rates and sexual dimorphism between males and females:
– Faster Growth: Mallard ducklings grow quicker than black ducklings, resulting in larger juvenile and adult sizes.
– Greater Sexual Dimorphism: Male Mallards are more than 20% larger than females. Black ducks show less size divergence between sexes.
So Mallard ducks start bigger as ducklings and then male Mallards keep growing compared to females. The combination allows Mallards to exceed black duck sizes through most life stages after hatching.
Diet and Habitat Influences on Size
Beyond growth patterns, access to food resources in their habitats can also impact duck size:
– High-Protein Diet: Mallards thrive on protein-rich aquatic invertebrates that fuel growth.
– Ideal Wetland Habitat: Mallards occupy diverse wetlands with abundant food sources.
– Generalist Foraging: Mallards eat diverse plant and animal foods, taking advantage of seasonal abundance.
– Declining Habitat Quality: Black ducks are losing ideal food-rich habitat due to wetland loss and degradation.
On the whole, Mallard habitat and dietary adaptations give them better access to the high-protein resources needed to reach their full size potential. Black ducks are constrained by declining wetland foraging opportunities.
Geographic Variations in Size
Both Mallards and black ducks show some natural geographic variations in size:
– Northern Populations: Larger body sizes occur in northern latitudes following Bergmann’s rule. More insulation conserves heat.
– Captive Mallards: Artificial feeding and breeding boosts size beyond wild Mallards.
– Eastern Black Ducks: Tend to be slightly larger than inland populations on average.
– Western Black Ducks: Have smaller body size metrics like mass and wingspan.
But the regional fluctuations don’t change the overall species advantages favoring Mallard size. Even small southern Mallards exceed northern black duck sizes.
Hybrid Influence on Size
There is significant hybridization between Mallards and black ducks where their ranges overlap:
– Eastern Hybrids More Common: Mallards expanding eastward creates more hybrid zone.
– Hybrid Sizes Intermediate: Hybrids tend to be intermediate in size between parental species.
– Male Hybrids Larger: It’s been suggested hybrid males can grow bigger than pure black ducks.
– Hybrid Viability: Most hybrids seem healthy and able to breed.
The ongoing hybridization makes size comparisons more complex. But currently there’s limited evidence of hybrid influence expanding black duck sizes beyond pure Mallard dimensions.
Conclusion
Based on a detailed look at length measurements, mass and weight data, wingspans, and other physical attributes, Mallard ducks do generally exceed black duck sizes by slight but significant margins. The differences become most pronounced when comparing large male Mallards versus small female black ducks. However, there is some overlap between the species, and regional size variations occur across populations. Ongoing Mallard-black duck hybridization may also be impacting relative body size, but not enough to offset the innate size advantage of Mallards. While black ducks are a large duck species in their own right, the typical Mallard is bigger by almost any size metric.