Pelicans are large waterbirds with distinctive pouches for catching fish. They are found in lakes, rivers, coastlines and estuaries around the world. Pelicans belong to the order Pelecaniformes and the family Pelecanidae. There are 8 living species of pelicans.
Pelicans are colonial nesters, often breeding in flocks numbering in the hundreds. They build nests out of sticks, grass, or reeds on islands, mangrove forests, or inshore cliffs. During breeding season, the skin around their beaks (called the “gular” pouch) changes dramatically in color. The breeding ritual involves pairing, nest-building, egg-laying, incubation, and raising the young.
Courtship and Pairing
The courtship and pairing process begins several months prior to breeding season. Male pelicans will establish and defend nesting territories from other males. When females arrive, the male will strut, vocalize, and point his bill up to attract a mate. Once paired, the male and female reinforce their bond by preening each other’s feathers and performing synchronized movements like head-swaying. Pairs will often reuse the same nesting site year after year.
Nest Building
Pelicans build nests out of whatever materials are available near the breeding colony. The nests are simple depressions in the ground lined with sticks, grass, seaweed, or reeds. Both the male and female participate in nest building, though the male does the majority of the work. The nests are usually built right on the ground, though some species nest in trees, cliff ledges or on elevated platforms in mangroves. Ground nests are very susceptible to flooding, so pelicans prefer elevated sites when available.
Egg Laying and Incubation
Once paired, the female will lay a clutch of 2-3 eggs over a period of 2-4 days. The eggs are chalky white in color and elliptical in shape. On average, pelican eggs are around 10 cm long and weigh about 150 grams. The female begins incubating the eggs as soon as the first one is laid. Both parents take turns sitting on the nest and incubating the eggs. The eggs hatch asynchronously over a period of 1-3 days after an incubation period of 28-36 days.
Raising the Young
Pelican chicks are altricial, meaning they are helpless at hatching. Their eyes are closed and they have no feathers. The parents brood the semi-naked chicks for warmth and protection. After about a week, the chicks open their eyes. They develop a grayish down within 2-3 weeks. Both parents feed the chicks by regurgitating food into their gaping beaks. Initially the diet is mostly liquid, then progresses to solid food like fish.
Fledging occurs between 63-88 days after hatching. The fledglings will remain near the nest for some time, relying on their parents for food. They gradually become more independent and venture further away from the nest. Pelicans reach sexual maturity between 2-5 years old. Some pelicans may live over 25 years in the wild.
Unique Aspects of Pelican Reproduction
There are a few unique aspects of pelican reproduction compared to other birds:
Synchronized Breeding
Pelicans in a colony tend to breed in synchrony. Females lay eggs within a few days of each other. This results in chicks hatching around the same time. Synchronous breeding may confer advantages like shared anti-predator defense and social learning.
Rapid Chick Development
Pelican chicks develop very rapidly compared to many other birds. They are able to leave the nest after just 9-12 weeks. This rapid growth requires huge amounts of fish provided by the parents. It may be an adaptation to allow breeding in temporary or unstable habitats.
Long-term Monogamy
Pelicans are predominantly monogamous. Pairs typically stay together for many breeding seasons, often reusing the same nest site. Some pairs may stay together for over 15 years. Mate fidelity means both parents invest in raising the young. Pelican divorce rates are estimated to be less than 3%.
Rare Twinning
While most pelican eggs hatch one by one, on very rare occasions two chicks may hatch from the same egg. Twinning has been observed in American white pelicans and great white pelicans. The twin chicks frequently do not survive to fledging due to the difficulty of two chicks sharing one pouch.
Breeding Seasonality and Location
The breeding season and location varies across pelican species:
| Species | Breeding Season | Location |
|---|---|---|
| American white pelican | April – August | Interior lakes and swamps in western North America |
| Brown pelican | February – May | Coastal islands from North Carolina to Venezuela |
| Great white pelican | August – December | Freshwater lakes and marshes in Africa, southeast Europe, and southern Asia |
| Pink-backed pelican | Year-round | Swamps and lakes in sub-Saharan Africa |
| Spot-billed pelican | October – April | Lakes, rivers and estuaries in southern Asia |
Pelican species in temperate climates breed during spring and summer, while tropical species may nest year-round. Many pelicans migrate after breeding season to find food. The nesting habitat varies by species, but pelicans favor islands for protection from land predators.
Mating Behavior
Pelicans have some interesting mating behaviors and adaptations:
Courtship Displays
Male pelicans perform elaborate courtship displays to attract females. Displays include vocalizations, feather posturing, waving the bill, and ritualized preening of the female. These behaviors strengthen the pair bond.
Mate Guarding
Mate guarding helps ensure paternity. Males will stay close to the female and chase away intruders. Males may also frequently copulate with the female to discourage her from seeking other partners.
Extra-pair Copulations
While social monogamy is the norm, extra-pair mating does occur. Both males and females may briefly mate with neighbors during the breeding season. The frequency ranges from 5-15% in different pelican species.
Cloacal Kissing
Pelicans touch cloacal openings in a gesture called a “cloacal kiss”. It may help strengthen the pair bond and assess reproductive status. The male will often initiate kissing before copulation.
Mate Replacement
If a mate dies during breeding season, the surviving pelican may acquire a new partner within days. Rapid mate replacement ensures they can still reproduce that year. Widowed pelicans may return to the same colony the following year to re-pair with a previous mate.
Copulation
Pelicans typically begin copulating 1-2 weeks before the first eggs are laid. The male initiates copulation by vocalizing and pointing his bill up. He then mounts the female from behind and briefly balances on her back. Before cloacal contact, the male may engage in rapid bill-flicking against the female’s head.
During cloacal contact, the male stands with his belly lowered onto the female’s raised rump. The male’s wings are slightly lifted for balance. Copulation lasts only 1-5 seconds, as their cloacae make momentary contact for sperm transfer. Pelicans may copulate repeatedly within a few hours to ensure fertilization.
Egg Formation and Laying
Approximately 5-14 days before egg laying, the female’s oviduct starts forming egg components. The ovum is fertilized by sperm stored in sperm storage tubules lining the oviduct. It takes 24-36 hours for an egg to progress through the oviduct and develop shell membranes and a hard shell.
Pigments like biliverdin (blue-green) and porphyrin (reddish-brown) are deposited into the shell, giving pelican eggs their colored appearance. The completed egg detaches from the oviduct and enters the uterus. Contractions of the uterus muscle finally push the egg out through the cloaca.
The female delicately picks up the emerged egg with her beak and deposits it into the center of the nest. The egg laying process repeats every 1-3 days until the clutch of 2-3 eggs is complete.
Incubation
Pelican parents share incubation duties, but the female does the majority. The parent sits directly atop the eggs, providing warmth and humidity for embryonic development. Their webbed feet help rotate the eggs. Incubation lasts 28-36 days depending on species. The eggs hatch asynchronously over 1-4 days.
Both parents develop oval incubating patches on their bellies – areas of bare skin with an extensive blood vessel network. The warm blood vessels help transfer heat to the eggs. The eggs will chill and fail to develop if not continuously incubated. Parents exchange incubation duties every 1-3 days.
Hatching
Pelican eggs hatch after 28-36 days of incubation. The chick starts the hatching process by using its egg tooth to puncture a hole in the shell. It then pecks off pieces of shell over 10-36 hours until it fully emerges. The hatching success rate is around 50-60% in the wild.
Newly hatched chicks are semi-altricial – blind, mostly naked, and helpless. They have some gray down on their heads and backs. The parents brooding keeps them warm until their insulation and mobility improves. Within 1-2 days, the chicks gain the strength to stand, walk, and beg for food.
Fledging and Dispersal
After 63-88 days, pelican chicks are ready to fledge. Fledging is the stage where juveniles make their first flight and leave the nest. Pelican chicks may take several short practice flights around the nest or colony before fully fledging. Parents continue to feed and protect the fledglings until independence.
Juveniles remain near their natal colony for several months after fledging. They join groups of other young pelicans for protection. Juveniles start dispersing from the colony during their first fall migration. Most pelicans return to breed at their natal colony 2-5 years later upon reaching maturity.
Threats to Breeding
Pelican breeding faces a number of natural threats and human-related threats:
Natural Threats
– Nest flooding – Storms or high tides can wipe out ground nests
– Predators – Gulls, ravens, eagles, foxes, raccoons eat eggs and chicks
– Disease – Salmonella, botulism, avian influenza can kill chicks
– Starvation – Limited fish supply affects chick survival
Human Threats
– Habitat destruction – Draining wetlands removes nesting sites
– Human disturbance – Tourism or recreation can disrupt breeding
– Pollution – Pesticides, hydrocarbon spills, plastics affect reproduction
– Fisheries impacts – Overfishing depletes food resources
Climate change is likely increasing the impacts of severe weather, disease, and prey availability on pelican breeding success. Protecting breeding sites from human disturbance is key during the critical nesting season.
Evolution of Pelican Reproduction
Pelicans share several reproductive traits with related bird groups:
Pelecaniformes
Pelicans belong to the order Pelecaniformes, along with cormorants, gannets, boobies, and frigatebirds. Shared traits include:
– Altricial chicks requiring extended parental care
– Both parents incubating eggs and feeding young
– Building nests on cliffs, trees, or ground islands
– Laying small clutches of 1-3 eggs
Seabirds
Many seabirds have life histories similar to pelicans:
– Delayed sexual maturity
– Long-term monogamy with mate fidelity
– Breeding in dense colonies
– Synchronized breeding seasons
– Males display and defend nest sites
These reproductive strategies evolved for success in marine environments. Long-lived monogamy produces the highest lifetime reproductive success in seabirds.
Wading Birds
As wading birds, pelicans share traits with herons, storks, ibises, and spoonbills:
– Nests built of sticks located near water
– Clutches of 2-6 eggs laid on successive days
– Incubation alternating between both parents
– Defense of breeding territories
– Formation of breeding colonies
These adaptations suit wetland-nesting birds that feed on aquatic prey like fish. Pelicans essentially amplified these key reproductive behaviors.
Unique Adaptations for Reproduction
Beyond their bird family traits, pelicans have evolved some special adaptations just for their lifestyle and feeding:
Synchronized Breeding
Mass synchronized breeding improves group anti-predator defense. It may also exploit a temporary abundance of fish that provides enough food for all the chicks.
Rapid Chick Growth
The extremely fast growth of pelican chicks allows breeding in temporary wetlands with unpredictable resources. The chicks fledge before the habitat dries up.
Gular Pouch Color Changes
Seasonal changes in gular pouch color signal breeding readiness. The bright colors attract a mate and communicate fitness.
Large Eggs
The large size of pelican eggs requires a huge investment from both parents. But it gives the semi-altricial chicks enough nutrients to grow quickly.
Exclusive Piscivory
Feeding chicks regurgitated fish provides the high-protein diet needed for rapid development. Total reliance on fish constrains pelicans to nesting sites with abundant marine/freshwater food sources.
Conclusion
In summary, pelicans have a complex and synchronized breeding process adapted for their fish-eating lifestyle. Courtship displays lead to monogamous pairing and nest building. Females lay small clutches of 2-3 eggs that both parents incubate. Once hatched, the semi-altricial chicks grow rapidly on a diet of regurgitated fish. After 63-88 days, the young fledge and start gaining independence.
Pelicans face threats to breeding from habitat loss, pollution, human disturbance and climate change. Their unique reproductive adaptations include rapid chick development, gular pouch changes, large eggs, synchronized breeding, and piscivory. Understanding how pelicans breed and the challenges they face can help target conservation efforts for these iconic seabirds.
