Mallards are a common type of duck found across North America, Europe, Asia, and Australia. Like most ducks, mallards build nests and lay eggs in the springtime. This raises the question – do mallards sit on their eggs to incubate them until they hatch? The short answer is yes, female mallards do sit on their eggs to keep them warm and allow the ducklings to develop.
Mallard Nesting Behavior
Mallards build nests on the ground near water, often concealed in vegetation. The nests are bowl-shaped and lined with down feathers plucked from the female’s breast. Mallards lay between 5-13 pale greenish-blue eggs. Once all the eggs have been laid, the female mallard will begin incubating them. Incubation lasts for 28 days before the eggs begin to hatch.
The female mallard plucks down from her breast to line the nest and cover the eggs when she leaves to feed. This helps insulate the eggs and keep them at the proper temperature of around 99°F needed for development. The female will sit tightly on the nest to provide warmth through contact with her body.
Mallard pairs are generally thought to be monogamous during each breeding season. Once the female begins incubating the eggs, the male mallard may leave the female or stay nearby to stand guard and defend the nest site. However, the male does not aid in incubating the eggs. The female leaves the nest only briefly once or twice a day to feed nearby.
Importance of Incubation
Incubation serves several important purposes for bird eggs:
- Provides warmth – Bird eggs need to be kept at a temperature between 99-102°F for proper embryonic development.
- Protects the eggs – Sitting on the nest prevents eggs from getting chilled, overheated, or damaged.
- Allows embryo to develop – The warm temperature triggers physical and chemical changes needed for cell division and growth.
- Hatches the eggs – The incubating parent will help the hatchlings emerge by pecking away the shell.
Without a parent sitting on the nest, the eggs would quickly cool and the duckling embryos would die. Therefore, incubation behavior is essential for mallards and other bird species to successfully hatch their young.
Sitting on the Nest
When sitting on the nest, the female mallard will position herself over the eggs with her body centered and wings loosely folded. The female plucks down feathers from her breast to line the nest bowl beneath the eggs and create an insulating layer up to 5 inches thick. The down helps retain heat from the parent’s body and keep the eggs at the ideal temperature.
The female mallard rotates the eggs periodically using her bill to ensure even heating. However, she needs to minimize shifting her position to prevent the eggs from cooling or getting exposed. Too much disturbance or leaving the eggs uncovered for more than 15-20 minutes can jeopardize their development.
To incubate successfully, the female must sit on the nest for at least 90% of the 28-day incubation period. Mallards are patient and persistent nest sitters, only leaving the nest for brief periods each day to drink, bathe, and feed close by. However, predators, disturbance, starvation, or poor weather may disrupt incubation in the wild and cause a nest to fail.
Brooding Ducklings
Once the ducklings start hatching, the female mallard continues to brood them on the nest. The chicks are covered in down but have very limited temperature regulation for the first 2-3 weeks after hatching. The mother duck provides warmth essential to their survival during this fragile period until the ducklings develop waterproof feathers for insulation.
Do Other Duck Species Incubate Their Eggs?
Almost all ducks incubate their eggs by sitting on the nest. Dabbling ducks like mallards, wood ducks, teals, wigeons, gadwalls, shovelers, and pintails all build ground nests and brood eggs. In contrast, diving ducks like canvasbacks, scaups, mergansers, scoters, and eiders nest in elevated sites like tree cavities or rocky crevices. But they also rely on contact incubation by the female.
A few unique exceptions include:
- Black-headed ducks – Females incubate while males brood and protect hatchlings.
- Steamer ducks – Males incubate and care for young while females defend territory.
- White-backed ducks – Eggs are often left unattended for hours, suggesting lower incubation commitment.
For most duck species, however, the female sitting on the nest for long bouts each day is critical to warm the eggs and allow them to successfully hatch.
Reasons for Sitting on Eggs
Why do ducks go to such great efforts to sit on their eggs for up to a month? Incubation behavior likely evolved in birds for several reasons:
- Insulates eggs and provides warmth
- Protects eggs from predators and elements
- Allows close monitoring of embryo development
- Facilitates bonding between parents and offspring
- Increases survival of vulnerable hatchlings
Sitting on eggs was favored by natural selection as it improved the hatching success and survival rates of offspring. It’s an essential part of the reproductive strategy of not just ducks but most bird species.
Do Other Animals Sit on Their Eggs?
While incubation behavior is ubiquitous in birds, some reptiles, fish, and invertebrate animals also sit on their eggs to enhance their development:
- Crocodilians – Females guard nests and provide some parental care.
- Snakes – Pythons and some other snakes brood egg clutches.
- Fish – Cichlids and catfish fan and guard eggs and fry.
- Insects – Some beetles watch over eggs laid in dung or carrion.
However, stable warm-blooded body temperature makes birds better adapted to closely regulate egg temperature than cold-blooded animals. This allows more advanced development in bird eggs prior to hatching.
Why Don’t Mammals Sit on Their Eggs?
Unlike birds, mammals do not incubate their eggs for several reasons:
- Most mammals do not lay eggs – They give live birth to young.
- Placenta provides warmth – Eliminates need to sit on eggs.
- Eggs are retained internally – So outside incubation not needed.
- Marsupials have short gestation – Hatchlings complete development nursing in the mother’s pouch.
- Mammals lack a cloaca – Makes egg-laying anatomically difficult.
- Hair offers insulation – Replaces need for brooding external eggs.
The few mammals that do lay eggs (monotremes like platypuses and echidnas) lack dedicated incubation behavior. Their eggs develop for a short time in simple nests before hatching.
Incubation Periods for Waterfowl
Different waterfowl species have varying incubation periods:
Species | Incubation Period |
---|---|
Mallard | 28 days |
Canada Goose | 28-30 days |
Wood Duck | 28-37 days |
Canvasback | 24-29 days |
Redhead | 24-28 days |
Ruddy Duck | 23-26 days |
The longer incubation periods of mallards, geese, and wood ducks reflect their larger egg size compared to diving ducks. However, most dabbling and diving ducks complete incubation in 24-30 days.
Daily Nest Attendance for Mallards
Researchers have quantified time spent on the nest by female mallards:
Nest Attendance | Proportion of Day |
---|---|
On nest overnight | 76% |
On nest during day | 84% |
Off nest on recess | 16% |
Total daily nest attendance | 80% |
This shows mallards spend about 80% of daylight hours sitting on the nest. Females take brief recess periods off the eggs to feed and bathe. But long attentive periods on the nest are vital to keep the eggs in proper condition.
Conclusion
In summary, female mallards do regularly sit on their nest for up to a month to successfully incubate eggs and hatch ducklings. Contact incubation provides essential warmth, protection, and bonding critical to the survival of vulnerable developing embryos and young. Mallards share this nesting strategy with most other ducks and bird species. Incubation behavior is a defining feature of avian reproduction and was favored by natural selection to maximize the hatching success of chicks.