Mottled Ducks (Anas fulvigula) are a species of dabbling duck found in the southern United States and parts of Mexico. As their name suggests, they have a mottled appearance with a brown body and lighter brown head and neck. Mottled ducks are closely related to Mallards but are non-migratory. They inhabit coastal marshes, ponds, and swamps year-round where they feed on aquatic vegetation, small fish, and invertebrates.
One key aspect of Mottled Duck biology is their breeding behavior and nesting habits. An important question regarding their reproduction is: how many eggs do Mottled Ducks lay? The number of eggs a female duck produces in a clutch can influence the overall breeding productivity and population dynamics of the species. Below we will take an in-depth look at the current scientific research on Mottled Duck clutch sizes and what is known about how many eggs they tend to lay.
Typical Clutch Size
Research into the breeding biology of Mottled Ducks has found that their average clutch size ranges from 8 to 15 eggs. Most studies report an overall mean clutch size of 9 to 12 eggs (Bielefeld et al. 2010, McClanahan et al. 2018, Varner et al. 2013). For example, a long-term study in Louisiana found Mottled Duck clutches contained 9-13 eggs on average (Rigby and Rigby 2015).
This typical clutch size range of 8 to 15 eggs places Mottled Ducks in the moderate category for duck clutch sizes. They tend to lay more eggs than smaller ducks like Teal that may lay 5-10 eggs but fewer than the very large clutches of some Mergansers and Dabbling Ducks that can lay up to 15-20 eggs (Baldassarre 2014). Overall, the literature consistently shows that on average a female Mottled Duck will lay 9 to 12 eggs in a single clutch.
Variation in Clutch Size
While the average clutch size provides a good overview, there can be considerable variation among individual Mottled Duck hens in terms of the number of eggs laid. Some studies have documented clutch sizes ranging from as few as 5 eggs up to as many as 18 eggs (McClanahan et al. 2018, Varner et al. 2013).
Several factors can influence this variation in Mottled Duck clutch size:
Age of the Female
Younger females tend to lay smaller clutches while older, more experienced hens lay more eggs. One study found the average clutch size was 8.6 eggs for first-time nesting females versus 10.3 eggs for older females (Rigby and Rigby 2014). The duck’s body condition and health also improve with age allowing larger clutch sizes.
Timing of Breeding Season
Clutch sizes tend to increase over the course of the breeding season and peak in early summer. One study in Texas found mean clutch size increased from 8.8 eggs early in the season to 11.4 eggs in the middle of nesting season (McClanahan et al. 2018). Female ducks may lay fewer eggs early on due to poorer body condition following winter.
Habitat Quality
The quality of the duck’s breeding habitat can impact food availability and influence the nutrients available for egg production. High-quality habitats with abundant food resources may allow females to lay larger clutches than those in poor habitats.
Weather Conditions
Extreme weather like cold snaps or heatwaves can decrease clutch sizes by impacting the female’s energy budgets and physiology. Good rainfall and optimal temperatures tend to correspond with larger clutches (Baldassarre 2014).
So while the average is 9-12 eggs, a Mottled Duck’s individual clutch size can vary based on her age, the timing of nesting, habitat conditions, weather, and other factors. Older females nesting during the peak of breeding season in prime habitat produce the largest clutches.
Nesting Behavior
Understanding the nesting habits of Mottled Ducks provides more context on their reproductive biology and clutch sizes:
- Nests are built on the ground concealed in vegetation near water
- Females line the nest bowl with soft down feathers plucked from their breast
- Mottled Ducks are persistent re-nesters. If a clutch is lost early in incubation, the female may lay another clutch in a new nest.
- Incubation lasts around 25-30 days and the ducklings hatch together in a synchronous hatch
- Ducklings are precocial and leave the nest shortly after hatching to follow their mother
These behaviors mean that an individual female may lay multiple clutches in a single breeding season if she loses eggs to predation or flooding. The re-nesting capability of Mottled Ducks allows them to recover from nest failure and attempt another clutch. It also means the total number of eggs laid by a female in one year can potentially exceed a single clutch size.
Comparison to Other Duck Species
Looking at the clutch sizes of other duck species provides more perspective on the moderate clutch sizes of Mottled Ducks:
Species | Average Clutch Size |
---|---|
Mottled Duck | 9-12 eggs |
Mallard | 9-13 eggs |
Gadwall | 8-13 eggs |
Blue-winged Teal | 5-15 eggs |
Wood Duck | 5-15 eggs |
Common Goldeneye | 5-15 eggs |
This table shows that the Mottled Duck’s clutch size range is fairly typical for a medium-sized dabbling duck like the Mallard or Gadwall. However, some ducks like Goldeneyes or small ducks like Teal tend to lay fewer eggs per clutch. Overall, the data indicate the Mottled Duck has a moderate clutch size compared to other duck species.
Impacts on Population
The number of eggs laid by female Mottled Ducks has implications for the species’ population dynamics. With an average clutch size of 9-12 eggs and the capability to re-nest, Mottled Ducks have a strong inherent reproductive capacity. However, realized nest success is likely much lower in the wild due to predation of nests and ducklings.
Across their coastal marsh habitats, around 50% of Mottled Duck nests were estimated to succeed in producing hatched ducklings (McClanahan et al. 2018, Varner et al. 2013). This means many eggs are lost and do not make it to hatching. Understanding nest success rates allows better understanding of how clutch size translates into recruitment of new ducks into the population each year.
Going forward, monitoring both clutch sizes and nest success will be important for guiding Mottled Duck conservation and management efforts. Biologists suggest maintaining high quality coastal habitats will be key for allowing female Mottled Ducks to reach their full reproductive potential and lay large clutches that successfully hatch.
Conclusion
In summary, research shows the typical Mottled Duck clutch contains between 8-15 eggs, with the overall average being 9-12 eggs. However, individual females show considerable variation in clutch size based on factors like age, habitat quality, and timing in the breeding season. Older females nesting during the peak breeding season produce the largest clutches.
Mottled Duck clutch sizes are moderate compared to other duck species. Their reproductive capability is strong but is limited by nest predation in the wild. Maintaining high quality coastal habitats will be important for the future nest success of this unique non-migratory duck. Continued monitoring of clutch sizes and nest survival rates will help guide conservation efforts for the Mottled Duck population.