Loons, also known as divers, are large waterbirds in the genus Gavia found primarily in North America and Eurasia. There are five living species of loons, with the Common Loon being the most widespread and familiar in North America.
Quick Facts on Loon Egg Laying
Here are some quick facts about how many times loons lay eggs:
- Loons typically lay two eggs per clutch.
- They lay one clutch per breeding season.
- So in a typical breeding season, a loon pair will lay two eggs.
- Occasionally, a loon may lay only one egg or three eggs in a clutch.
- Loons build their nests very close to the water’s edge.
- Both the male and female loon incubate the eggs for around 28 days until they hatch.
- Loons are monogamous and mate for life. A breeding pair will often return to the same breeding territory year after year.
- Most loons reach sexual maturity and begin breeding around 3-4 years of age.
- Loons that lose a clutch early in the breeding season may re-nest and lay another clutch.
Typical Loon Breeding and Egg Laying
During the typical loon breeding season, which occurs between April and August depending on latitude, a mated pair of loons will build a nest very close to the edge of a lake, pond, or other body of freshwater. Most loon nests are situated within just a few feet of the water.
Loon pairs usually lay two eggs, though clutch sizes can range from one to three eggs. The eggs are olive to brownish-black in color with dark brown or black splotches for camouflage. Loon eggs are relatively large, approximately 3 inches long with a width of 2 inches.
Both the male and female loon will incubate the eggs for around 28 days until they hatch. Loon chicks are precocial, meaning they are able to swim and dive right away after hatching. The parents will care for the chicks for the first 6-7 weeks until the chicks are able to fly and fish independently.
In a typical breeding season, most loon pairs will successfully hatch around 1-2 chicks. Loon eggs and chicks have many natural predators including gulls, crows, raccoons, foxes, snapping turtles, and bald eagles. Adult loons may abandon a nest if disturbed by human activity.
One Clutch Per Season
Loons typically only lay one clutch of 1-3 eggs per breeding season. However, if a loon pair loses their eggs very early in the season, they may re-nest and lay another clutch. Most loons breed for the first time between 3-4 years of age and the typical breeding lifespan is around 15 years.
Exceptions and Abnormalities
While most loons lay two eggs per clutch, some exceptions may occur:
- Occasionally loons may lay only one egg. This could be due to suboptimal health or nutrition of one member of the pair.
- Rarely, loons may lay three eggs in a clutch. Three-egg clutches are not typical and are likely stressful for the parents to incubate.
- Damaged eggs or infertility can reduce normal two-egg clutches down to only one viable egg.
- Interspecies nest parasitism between Common Loons and Red-throated Loons can result in abnormal clutch sizes.
Additionally, first-time breeding loons may lay smaller clutches or struggle with proper incubation. Older breeding loons that have passed their prime breeding years may also lay fewer or smaller eggs per clutch.
Detailed Stages of the Loon Breeding and Egg Laying Process
Loons go through very defined stages throughout the breeding and egg laying process. Here are the key stages:
Stage 1: Spring Migration to Breeding Grounds
Loons migrate from their wintering habitats along the coasts to inland lakes and ponds where they breed. In March and April, loons will return to the same breeding territories they inhabited in previous years, often migrating thousands of miles. Loons mate for life so they reunite with their long-term mate at the breeding area.
Stage 2: Courtship and Pair Bonding
From April through May, loon pairs engage in courtship behaviors to reestablish their bond. This includes territorial yodeling, diving and splashing displays, preening each other’s feathers, and more. These rituals help synchronize their reproductive systems for egg laying.
Stage 3: Nest Building
By May, the pair starts building a nest very close to the water’s edge. Loon nests are made of vegetation and often measure 1-3 feet in diameter. Nest building may take 1-2 weeks to complete. Nests are reused and added to each year.
Stage 4: Egg Laying
Egg laying starts in late May or early June. Eggs are laid every 1-2 days until the clutch of 1-3 eggs is complete. Larger clutches correspond with better health and foraging resources that year.
Stage 5: Incubation
Both male and female loons incubate the eggs for about 28 days until they hatch. Parents rotate incubation duties while the other parent feeds. Loons may briefly abandon the nest if threatened by predators.
Stage 6: Hatching
Loon chicks start hatching in late June or early July. Like all precocial birds, loon chicks can swim and dive right away. Parents will feed and protect the chicks for 6-7 weeks until fledging.
Stage 7: Fledging and Independence
By late August or September, loon chicks are able to fly and fish on their own. They will stay with their parents during the fall migration before dispersing to adult wintering grounds along the coasts.
How Many Times Can Loons Re-Nest?
If loons lose their eggs very early in the breeding season, they may re-nest and lay a second or even third clutch. However, re-nesting becomes less likely later in the season and most loons only lay one clutch per breeding season.
Here are some key points about loon re-nesting:
- Loons can re-nest up to two times if they lose eggs early in the season.
- The later in the season, the less likely loons are to re-nest if eggs are lost.
- Re-nesting requires 28+ days of re COURTSHIP and egg laying, so late season re-nests often fail.
- Only about 10-15% of loon pairs that lose a clutch will go on to re-nest.
- Re-nesting rates depend on food supply and the health of the breeding pair.
- Loons that re-nest often lay only 1-2 eggs in subsequent clutches due to time constraints.
While loons can lay up to three clutches in a season, most do not re-nest after a failed clutch due to the amount of energy required. The majority of loons will lay just a single clutch of 1-3 eggs each breeding season.
How Many Chicks Do Loons Fledge?
While loon pairs may lay 1-3 eggs per clutch, on average only 1-2 chicks will survive to fledging age. Here’s an overview of loon chick survival:
- From 2-egg clutches, an average of 1.4 chicks will hatch.
- From 3-egg clutches, around 2.1 chicks will hatch.
- Chick mortality is around 29% in the first two weeks after hatching.
- Predators like eagles and snapping turtles take many chicks.
- An estimated 41% of hatched chicks survive to fledge at 6-7 weeks.
- So the average is around 0.6 chicks fledged per nesting attempt.
With one clutch per season, most loon pairs that hatch chicks will successfully fledge just one single chick. Productivity can be reduced by human disturbance, pollution, habitat loss, and increased predation.
How Long Do Loons Live?
Loons are relatively long-lived birds. Lifespans in the wild vary from 10 to over 30 years. Here are some key facts about loon longevity:
- The oldest known wild Common Loon was at least 31 years old.
- Average lifespans in the wild are around 15 years.
- Adult loon annual survival rates are estimated between 85-95%.
- The longest-lived captive loon reached age 33.
- Loons reach sexual maturity and begin breeding around 3-4 years old.
- Peak breeding age is 5-12 years when clutch sizes are largest.
- Loons may continue breeding up to about age 25.
The long lives of loons contribute to pair bonding, nest site fidelity, and repeated successful breeding efforts over many years. Their longevity allows loons to produce many fledglings over their lifetimes despite modest productivity each season.
How Does Human Activity Impact Loon Nesting?
Because loons build very exposed nests right along lake and pond shorelines, they are vulnerable to disturbances from human recreation and development. Here are some key impacts:
- Boating too close can flood nests with wakes, drowning eggs.
- Fishing lines and tackle can entangle incubating parents.
- Nests abandoned due to disturbance likely fail.
- Shoreline development removes nesting habitat.
- Pollution and runoff reduce fish populations loons depend on.
- Lead fishing tackle poisons loons and chicks.
Many reservoirs, lakes, and ponds used heavily by humans have seen reduced loon nesting success and productivity. Mitigating recreational impacts during breeding season gives loons their best chance at successfully raising chicks.
Conclusion
In summary, loons are dedicated parents that go through elaborate breeding rituals every spring to hatch and raise the next generation. Most loons lay two egg clutches, occasionally one or three. Both parents incubate the eggs for about four weeks until they hatch. Despite devoted care by loon parents, predators and human disturbance take a toll, resulting in only one or two chicks fledged per breeding pair. Management efforts focused on protecting shoreline habitats and minimizing recreational impacts during breeding season can help loon populations thrive.