Loons are unique waterbirds that are known for their striking plumage and haunting calls. They breed on freshwater lakes across North America and spend their winters along coastlines from the southern United States to Central America. Loons have very specific habitat requirements for breeding and their reproductive activities are closely tied to the seasons.
Breeding Season
The breeding season for loons depends on their geographic location:
- Northern loons in Alaska and Canada breed from May through August.
- Loons in the northern United States breed between April and July.
- Southern loons in the Upper Midwest and Northeast breed earlier, from March through June.
In general, loons migrate back to their breeding lakes in the spring as soon as the ice melts. Egg laying usually begins within two weeks after the loons return. The timing ensures that young loons hatch at the best time to take advantage of abundant food resources like small fish, frogs, and aquatic invertebrates over the summer.
Pair Formation
Loons form long-term pair bonds that can last over 15 years. Pairs reunite each spring at their breeding lakes and re-establish their bond through elaborate courtship displays. These rituals involving splashing, diving, and distinctive vocalizations help pairs assess each other’s fitness and synchronize their breeding efforts.
If one member of a mated pair dies, the surviving bird will find a new mate. Immature loons between 3-5 years old also attempt to establish pairs for the first time during the breeding season. Floating solitary loons called “rafting singles” often gather at staging lakes to meet potential mates.
Nest Building
Loons build their nests very close to the water’s edge, providing easy access for swimming. Nests are made from vegetation and mud scraped from the lake bottom. Vegetation might include bulrushes, cattails, pondweed, and horsetails arranged in a mound or floating platform.
Both male and female loons contribute to nest building. They may assess several potential sites before selecting one and remodeling it to suit their preferences. Most nest building takes place from late April through May.
Egg Laying and Incubation
Egg laying starts 1-2 weeks after nest building. The female lays one egg every 1-2 days, until the complete clutch of 2 eggs is produced. Egg laying occurs from May through June. Both parents incubate the eggs for 27-29 days until they hatch, usually in June or July.
Loons have very specific egg care duties during incubation:
- The female loon incubates the eggs at night.
- The male incubates during the day.
- Parents exchange roles in an elaborate ceremony called a “circle run”.
- Eggs left unattended even briefly may overheat or freeze.
If the eggs are lost early in incubation, the female can lay another clutch. But there is only time for one successful brood per year.
Hatching
Loon eggs hatch asynchronously, meaning the chicks emerge up to 48 hours apart. The soft, downy chicks are able to swim and dive almost immediately. The parents protect them from predators and teach them to feed themselves.
Fledging
Loon chicks fledge at 11-12 weeks old. Fledging refers to the time when juveniles develop wing feathers large enough for flight and leave the nest permanently. Parents continue to protect and feed the fledglings for another 6-8 weeks, until they are capable of sustained flight.
Fall Migration
By late September through October, loons have completed their breeding duties. Lakes start to freeze over and food becomes scarce. This triggers both adults and juveniles to migrate south to their wintering grounds.
Some key points in the loon breeding and reproductive timeline:
| Breeding Stage | Timeframe |
|---|---|
| Spring Migration to Breeding Lakes | March – May |
| Pair Formation and Courtship | April – May |
| Nest Building | Late April – May |
| Egg Laying and Incubation | May – June |
| Hatching | June – July |
| Fledging | July – September |
| Fall Migration | September – October |
Conclusion
In summary, loons have a distinct breeding season that is timed to make the most of abundant summer resources. Their reproductive activities span spring through fall, including pair bonding displays, nest building, egg laying and incubation, chick rearing, and fledging of juvenile birds. The exact timing varies across their breeding range but is generally confined to March through October, culminating in fall migration back to wintering areas.
Loons demonstrate a strong breeding site fidelity and mate fidelity from year to year. Their seasonal reproductive cycle enables loons to maximize their reproductive success and renew their populations each year across North America. Monitoring changes in loon breeding phenology and success provides an important indicator of the health of freshwater lakes.
Protecting loon habitat requirements, especially clean water, quiet sheltered bays, and shoreline vegetation, is key to supporting successful breeding. Public education efforts continue to reduce disturbance of loon nesting areas during the breeding season. With vigilance and conservation action, these iconic waterbirds can continue thriving each summer across their traditional breeding lakes and ponds.
So the key period when loons can successfully reproduce runs from March through October, following their intricate seasonal dance of pair bonding, nesting, raising young, and migrating. Their breeding schedule is timed to make the best use of temporary abundant resources, while their longevity and site faithfulness allow loons to reuse successful nesting locations year after year.
Spring migration
Loons migrate back to their breeding lakes in spring as soon as the ice melts, usually March through May depending on latitude. Early arrival ensures they have time to establish territories, find mates, and build nests before egg-laying begins.
Courtship and pair bonding
Most loon pairs reunite at breeding sites from previous years. Surviving members will seek new mates if needed. Young loons 3-5 years old also try to form pairs for the first time. Courtship displays like yodeling calls, splashing, and diving help reestablish bonds and synchronize breeding.
Nest building
Both male and female loons build the nest from available vegetation near the water’s edge, providing easy access. Nest building occurs from late April through May as pair bonds strengthen. Several sites may be assessed before choosing one to remodel.
Egg laying and incubation
The female lays one egg every 1-2 days until the complete clutch of 2 eggs is produced in May/June. Parents incubate eggs in shifts, with females at night. This continues for 27-29 days until hatching in June/July.
Hatching
Loon eggs hatch asynchronously up to 48 hours apart. Downy chicks can swim and dive nearly instantly. Parents protect and teach chicks how to feed themselves at first.
Fledging
At 11-12 weeks old, loon chicks develop enough wing feathers to fly and leave the nest for good. Parents still help feed fledglings for 6-8 more weeks until they are strong fliers.
Fall migration
By late September through October, food becomes scarce as lakes freeze over. This triggers migration back to wintering grounds. The breeding cycle ends until next spring.
So in summary, the key breeding and reproductive period for loons spans from March through October. Their seasonal activities are precisely adapted to take advantage of short-term abundant resources for successful breeding each year.
Loons have very specific habitat requirements and face various threats during the breeding season. Some important conservation measures for supporting loon reproduction include:
- Protecting shoreline vegetation that loons need for nest building
- Preventing lakeshore development that encroaches on nesting areas
- Reducing boating traffic and fishing near nest sites during breeding
- Keeping water quality high by limiting pollution and runoff
- Letting water levels stabilize by late April when nesting begins
- Promoting public awareness to avoid disturbances
With vigilance and dedicated conservation efforts, the unique reproductive behaviors and habitats of loons can continue being supported each year.
Spring migration timing
Loons migrate back to breeding lakes as soon as ice melts, which may vary from March through May depending on latitude and seasonal variations. Early arrival ensures time for courtship, pair bonding, and nest site selection before egg laying must begin. Their internal clocks are precisely tuned to seasonal cues that initiate migration.
Courtship displays and vocalizations
Loons use complex visual and vocal displays to reestablish pair bonds. These include the “circle dance,” splashing, “bobbing,” and distinctive calls like yodeling, wailing, and tremolo calls. Performing these elaborate rituals signals readiness to breed and synchronizes the pair’s reproductive efforts.
Nest site selection
Loons evaluate multiple potential nest sites before choosing one. Ideal sites have vegetation like bulrushes or cattails growing in shallow water near shore. This provides cover while allowing easy access between nest and water. Both male and female loons collect vegetation and mud to create the nest platform.
Egg laying intervals
The female lays eggs every 1-2 days, until a complete clutch of 2 eggs is laid in May or June. Larger clutches of 3-4 eggs occur in rare cases, but 2 is typical. The interval between eggs allows time for the female to replenish lost calcium for egg shell formation.
Incubation shifts
Loons share incubation duties, with females incubating eggs at night and males incubating by day. They exchange roles in an elaborate ceremony called the “circle run” to ensure eggs are never unattended. Both parents develop brood patches for egg warming.
Asynchronous hatching
Loon eggs hatch up to 48 hours apart due to staggered laying intervals. This size difference can help the elder chick compete for food later on. The downy chicks can swim and dive almost instantly after hatching.
Fledging age
Loon chicks fledge at 11-12 weeks once they’ve developed enough wing feathers for flight. Parents still help feed them for 6-8 more weeks until juvenile loons become fully independent and capable of migration.
In summary, understanding the intricacies of loon breeding biology and seasonal timelines helps inform conservation. Supporting their habitat needs during the reproductive period aids populations.
Here is a review of key details about loon breeding phenology and requirements:
- Breeding season ranges from March-October depending on latitude
- Spring migration timed around ice-out on lakes
- Reestablishing pair bonds critical first step
- Nest site selection key, near shore with vegetation
- Egg laying in May-June, interval allows calcium replenishment
- Shared incubation duties, synchronization critical
- Chicks hatch asynchronously to give eldest advantage
- 11-12 week fledging period once flight feathers develop
- Food abundance on lakes critical for chick survival
Understanding these details helps inform conservation strategies like protecting shoreline habitat, managing water levels, enforcing boating restrictions, and keeping the water clean. With proper management informed by loon reproductive biology, populations can remain resilient across their breeding range.
