The brown pelican (Pelecanus occidentalis) is a large seabird found on the Atlantic and Pacific coasts of North and South America. Brown pelicans are famous for their oversized bill and large throat pouch used for catching fish. Like many birds, brown pelicans have different plumages depending on whether they are breeding or not. The non-breeding plumage of brown pelicans differs noticeably from the breeding plumage and serves an important function for the birds. In this article, we will explore what exactly is the non-breeding plumage of the brown pelican, how it differs from the breeding plumage, the purpose it serves, and some key facts about moulting and plumage in brown pelicans.
What is Non-Breeding Plumage?
The non-breeding plumage, also called the basic or winter plumage, refers to the feathers and coloration pattern that brown pelicans sport outside of the breeding season. The breeding season for brown pelicans occurs during spring and summer months. During this time, they acquire their bold breeding plumage with stark brown and white markings, as well as a bright gular pouch and bright yellow head.
In the non-breeding season, which runs from fall through winter, brown pelicans moult these vibrant breeding feathers for a more subdued non-breeding look. The non-breeding plumage has more gray-brown and white feathers overall, with paler and less distinct markings compared to the bold patterns when breeding. The non-breeding plumage serves important functions related to thermoregulation during colder months and reducing conspicuousness while birds are not nesting or courting.
Differences Between Non-Breeding and Breeding Plumage
There are several key differences between the non-breeding and breeding plumage in brown pelicans:
Coloration
– Non-breeding plumage is more gray-brown rather than the rich chocolate brown seen in breeding plumage. The white markings are also duller and less bright than breeding whites.
– The gular pouch is paler yellow or even white in non-breeding plumage versus the bright orange-yellow during breeding.
– The head tends to be white in non-breeding birds rather than the bold yellow head color while breeding.
Patterns
– Feather patterns are subdued and mottled in non-breeding plumage versus the sharply defined blocks of color seen when breeding.
– Dark feathers have white speckles and light feathers have dark edging, creating a muted blurred effect.
– There is heavier streaking on the head and neck feathers. Crest feathers are also streaked.
– The wing linings (underwing coverts) lack the dark carpal bar seen in breeding plumage.
Soft Parts
– The bill often loses its bright yellow color and becomes dusky gray.
– The unfeathered skin around eyes and lores becomes dull grayish in non-breeding birds compared to yellow skin when breeding.
– Legs fade from bright orange to a paler flesh-tone outside breeding season.
Purpose of Non-Breeding Plumage
The drabber non-breeding plumage serves some key functions for brown pelicans:
Thermoregulation
The muted plumage provides better camouflage and less conspicuousness during the non-breeding season. This helps reduce conflict and competition between birds at a time when they are not trying to attract mates or defend nesting territories. The paler plumage also matches the white winter beach landscapes where pelicans often spend time.
Energy Conservation
Duller feathers require less energy production than the richer breeding colors. This saves vital resources during harsher winter months when the birds are not involved in reproductive activities.
Waterproofing
The addition of pale feather edging helps increase water resistance and waterproofing capacity compared to breeding feathers. This aids with water shedding and thermoregulation in cold marine environments.
Abrasion Resistance
The sturdier non-breeding feathers hold up better to abrasion from rocks and coarse sand compared to finer breeding plumage. This helps preserve plumage and reduce wear and tear during winter months.
Moulting and Plumage Cycles
Brown pelicans have complex moulting cycles and strategies to transition between breeding and non-breeding plumages:
Timing
Brown pelicans moult breeding plumage starting in early fall, directly after nesting season ends. Complete transition to non-breeding plumage finishes by late fall or early winter.
The pre-breeding moult occurs in early spring, with full breeding colors usually attained by the onset of the nesting period.
Overlap of Plumages
There is often around a month period of overlap where non-breeding and breeding plumage co-occur in partially moulted birds. For example, a bird may have dull grey feathers mixed with vibrant breeding colors.
Moult Strategies
Brown pelicans moult sequentially, meaning feathers are dropped and replaced in a distinct order over time. They retain flight feathers longest to avoid compromising flight ability.
The post-breeding moult begins at the head and moves down the body, while the pre-breeding moult begins at the body and moves up towards the head.
Gender Differences
Males tend to acquire breeding colors sooner than females in pre-breeding moult. Males also retain breeding colors longer than females in post-breeding moult.
Age-related Variations
Younger birds in their first potential breeding season acquire less bright breeding plumage than mature adults. Their non-breeding plumage also differs by being more brownish overall.
Key Facts About Brown Pelican Non-Breeding Plumage
Here are some key facts about the non-breeding plumage of brown pelicans:
Appearance
– More drab gray-brown plumage with white mottling
– Paler yellow to white gular pouch
– Dull or white head, sometimes with partial yellow
– Dark feathers have pale edging and barring
– Reduced or absent carpal bar on wing lining
Purpose
– Provides camouflage and reduces conspicuousness
– Conserves energy compared to breeding colors
– Enhances waterproofing and abrasion resistance
Molt Patterns
– Acquired via complete molt each fall after breeding
– Shed via another complete molt each spring before breeding
-Transient period with overlapping non-breeding and breeding feathers
-Males complete molts sooner than females
Individual Variation
– Younger birds have less vivid non-breeding plumage
– Males tend to retain breeding colors longer in fall
– Geographic populations may differ slightly in non-breeding appearance
Conclusion
In summary, the non-breeding plumage of the brown pelican is markedly different than its bold and vibrant breeding colors. Drabber grays and browns replace rich chocolate feathers, while white replaces bright yellows on the head and bill. This muted plumage serves important functions related to camouflage, energy conservation and feather durability during the non-breeding season. Complete moults each spring and fall allow the pelicans to transition between their breeding finery and their subtler non-breeding outfit. While variable between individuals, the non-breeding plumage is overall paler, plainer and distinct from the pelican’s iconic breeding costume. Understanding differences in bird plumage and the purposes they serve reveals the intricate strategies and adaptations of avian life.
