Swans are large waterfowl known for their long necks, majestic appearance, and loyalty as mates. Like all birds, swans lay eggs and incubate them until they hatch. But do swans actually sit on their eggs all the time while incubating them? Let’s take a look at the details of swan nesting and incubation behavior to find out.
When do swans lay and incubate their eggs?
The breeding season for swans depends on the species and their geographic location. In temperate climates, most swans nest in the springtime. For example, Mute Swans in North America typically lay their eggs between late March and early May. Tundra Swans nest a bit later from mid-May through June. Trumpeter Swans in Alaska may not start nesting until June.
Once they form a bond and find a suitable nesting site, the female swan will lay a clutch of 3-9 eggs over a period of a few days. She does not start full incubation until all the eggs have been laid. This ensures the cygnets (baby swans) will hatch closer together.
The incubation period lasts about 35-42 days depending on species. Some key facts about swan incubation behavior:
- The female performs most of the incubation during the day, only leaving the nest for brief periods to eat, drink, and preen.
- The male swan may help incubate for short periods, but does most of his sitting at night when the female is sleeping.
- Swans rotate their eggs frequently with their bill and feet to evenly distribute heat.
- If the nest and eggs are disturbed, swans may completely abandon nesting for the season.
Do swans ever leave their nest unattended?
While swans are extremely dedicated to incubating their eggs, the female cannot realistically sit on the nest constantly without ever leaving. However, swans ensure their eggs are attended nearly full-time by coordinating duties between the breeding pair.
During the day, the female swan will take occasional short breaks to feed, bathe, preen her feathers, and stretch her muscles. A sitting swan mostly just changes position atop the nest. But every hour or two, the female will briefly step away for 10-30 minutes before returning. This gives her time to take care of her basic needs without leaving the eggs exposed for too long.
The male swan performs his share of nest protection by taking the night shift. He will often sleep right alongside the nest or floating in the water immediately nearby. Having the male there allows the female to sleep comfortably on the shore knowing her eggs are safe.
How do swans adapt their behavior in extreme weather?
Swans have evolved to withstand challenging weather while incubating. During extreme cold, they fluff their feathers to retain body heat on the nest. In windy conditions, they turn their backs to the wind and cover the eggs with their wings and belly feathers. In wet weather, the oils in their feathers provide a waterproof barrier. And in hot sun, they shade themselves and the eggs by tucking their head over their back.
Still, harsh weather does force swans to adapt their nesting habits. In very cold climates, the female cannot sit constantly overnight without risk of freezing. So the male takes over more overnight duties. In severe storms, one swan may have to remain on the nest at all times to prevent eggs blowing away. And in heavy rain, the swans keep the eggs warm and dry by lying over them despite being soaked themselves.
Do swans ever synchronize incubation?
Because swans form monogamous pair bonds, the breeding pair works together to share the incubation duties. They coordinate their efforts based on the circumstances to ensure their eggs are attended full-time.
Swans demonstrate a notable synchronization when it’s time to hatch the cygnets. In the final days before hatching, the adults become much more attentive. When the first baby emerges, the parents will both assist the cygnet and welcome it under their wings. This close teamwork continues until all the cygnets have hatched and left the nest.
How do swans know when to incubate their eggs?
Swans rely heavily on instinct and hormones to direct their breeding and nesting behaviors. Their hormones shift as winter turns to spring, stimulating the adults to seek mates, establish territories, build nests, lay eggs, and sit. They feel a strong biological urge to nurture their clutch.
Swans also watch for visual cues that their eggs are ready for constant warmth. If eggs are left alone too early, embryos may not develop. And if incubation starts too late, some eggs may not be viable. When the female has laid the last egg, hormonal signals prompt her to remain on the nest for good.
Throughout incubation, the adults continue to watch for signs of distress in the eggs. Unusual vocalizations, movements, or damage trigger the swans to adjust position, breathe on the eggs for warmth, or call their mate for assistance.
Do swan parents ever damage their own eggs?
It is very rare for swan parents to intentionally damage their own eggs. They have excellent coordination and perception to avoid harming the clutch when moving on the nest. Swans use their soft breast feathers to gently surround and cushion the eggs underneath them.
However, accidents may still happen on occasion. Eggs can crack if a nest collapses unexpectedly or the adult startles and steps on the clutch. Abandonment may follow since damaged eggs have lower hatching success. Yet overall, swans are incredibly dedicated and attentive parents.
How do swan parents work together to incubate eggs?
Swan pairs coordinate their incubation responsibilities in a well-timed routine:
- The female incubates throughout the day, briefly leaving every 1-2 hours to feed and preen.
- As evening approaches, the male swan arrives to take the first overnight shift.
- The female returns to sleep floating on the water near the nest.
- In the early morning hours, the male wakes the female to resume daytime duties.
- The male swan then retires until late afternoon when he will relieve his mate again.
This constant trade-off enables the swan parents to attend the nest virtually around the clock while also meeting their own biological needs. The female does bear the bulk of incubation during the most active daylight hours when feeding is easiest. But the male contributes significantly by monitoring the eggs all night when the risk of nocturnal predators is highest.
Do swans ever take breaks from incubation together?
Swan pairs rarely, if ever, leave their nest fully unattended. One adult always remains to protect the vulnerable eggs and embryos.
However, the male and female swan may briefly be off the nest at the same time during shift changes. These transitions happen twice daily – at dawn when the female relieves the male, and again at dusk when the male comes to take over the night watch. But even during exchanges lasting just minutes, one of the swans typically remains within sight of the nest.
These brief periods of joint activity allow the mated pair to communicate and synchronize their incubation duties. The swans reaffirm their pair bond while checking that their mate is healthy and prepared for the next sitting shift.
Do swans lose their eggs if they don’t sit on the nest?
If swan eggs are left alone for too long, they will certainly fail to hatch. Embryo development stops without the warmth and protection provided by the incubating parents.
Eggs can only survive unincubated for a short while. The embryos are somewhat resilient for the first few days after laying while they draw sustenance from egg yolk. But they soon reach a critical stage where constant heat is vital to continue growing.
By a week after the last egg appears, the clutch must receive nearly full-time incubation. Partial or inconsistent coverage will not be adequate. So if the swan pair abandons the nest at this point, the eggs will no longer be viable.
Do swans ever take turns incubating with other birds?
No, swans do not take turns incubating eggs with other waterfowl species. They solely rely on their own mated pair bond.
However, some other bird groups do demonstrate joint nesting and egg-sitting duties. Examples include:
- Penguins – Both parents incubate and protect the egg by balancing it on their feet.
- Parrots – Pairs coordinate duties, and often other family members or flockmates also help incubate.
- Ostriches – Females incubate by day; males incubate at night.
- Passerines – Both sexes develop brood patches and share relatively equal roles.
But swans stick to their tried-and-true system of the female incubating by day with the male substituting at night. Their solitary nesting behaviors help ensure safety and breeding success.
How long can a swan keep eggs warm if the mate disappears?
If one mate suddenly disappears or dies during incubation, the remaining swan will try its best to continue warming the eggs 24/7. However, solo incubation severely taxes the lone parent.
The female is better equipped than the male to sustain incubation alone. With ample food nearby, the female may successfully hatch some cygnets. But solitary incubation is extremely difficult for a lone female even for a few days. Doing so for weeks until hatching is rare.
A male left on his own has almost no chance of keeping the eggs viable without the female sharing duties. He may temporarily maintain the nest but is unlikely to adequately incubate the eggs around the clock.
In most cases, the swan pair’s breeding attempt will fail if one mate vanishes. But the remaining adult will still feel compelled to continue sitting for some time before finally abandoning the clutch.
Do swan parents ever sit on eggs laid by other swans?
It is highly unusual for a swan pair to adopt eggs laid by another pair. Swans have strong territorial instincts and typically reject foreign eggs introduced into their nest.
However, egg transfer between nests has been performed intentionally by biologists trying to bolster small swan populations. When artificially adding eggs, human handlers must be very careful to mask human scents. The receiving pair will often kick out or abandon unfamiliar smelling eggs.
Adoption success is somewhat higher when transferring lone natural eggs that roll into another pair’s territory. But overall, swans strongly prefer incubating eggs from their own mated pair bond.
Conclusion
Swans demonstrate impressive dedication to incubating their eggs in order to hatch their cygnets. The breeding pair works in excellent coordination to keep the eggs warm for 35-42 straight days until hatching.
While swans do not literally sit on the nest 100% of the time, their care of the clutch is virtually non-stop. The female incubates throughout the day with the male substituting at night. Brief exchanges occur at dawn and dusk so both parents can take care of their own health and nutrition.
This constant vigilance ensures the vulnerable eggs and embryos are protected 24 hours a day. Both swan parents feel a strong biological drive to nurture their offspring. So even in poor weather and other challenges, they adapt their diligent nesting behaviors to successfully hatch their new brood.
