Birds of a Feather

No matter what time of year you ascend the escalator into Level 4 of our Pier 3 building, the Atlantic puffins, black guillemots and razorbills—all seabirds in the family Alcidae—in the Sea Cliffs exhibit are certainly a welcome sight. But the exact sight you're seeing is dependent on the time of year. Alcids—the term for individuals within this family—look much different in the spring and summer than in the fall and winter, and it's mainly due to a process called molting.

All About Molting

When an animal molts, it loses and replaces some type of outer layer, whether that's fur, an exoskeleton, feathers, hair or skin. Many animals throughout the animal kingdom molt, from snakes and crabs to seals and birds. The molting process and purpose differs greatly depending on the animal.

For alcids, which spend much of the year at sea, the timing of feather molting is extremely important to their survival. Seabirds maintain the condition of their feathers through preening, which involves cleaning them with their beak and tongue and secreting oil to help keep them waterproof. Even with this effort to keep feathers in tip-top shape, they eventually become worn and need to be replaced.

Birds don't just go to sleep one night and wake up with a fresh set of feathers; the process is gradual and timed to occur at different periods of the year. For each individual puffin, guillemot and razorbill in our care, the entire process can take several weeks—and the birds don't all molt at the same time, so molting season for these birds lasts a couple months total.

Breeding Plumage vs. Non-Breeding Plumage

Alcids molt twice a year: prior to breeding season in late winter or early spring, and at the end of breeding season in the fall. The molt before breeding season is known as their breeding plumage, and their fall molt gives way to their non-breeding plumage. The birds undergo both full molts and partial molts during the year.

For many birds, breeding season plumage is brighter and more vibrant than the non-breeding plumage—but these new feathers don't serve the sole purpose of attracting a mate.

Since alcids spend the non-breeding months out in the ocean, their plumage in winter provides maximum protection and warmth from the harsh conditions and cold water. In late winter or early spring, before they return to their rocky nesting sites on land, they must replace their worn feathers degraded from living at sea.

One feather change that occurs during breeding season is the development of a brood patch, a bare area of skin on the bird's underside used to cover eggs as they develop. The brood patch allows for direct skin-to-egg contact, which provides extra warmth essential for incubation.

The molting of wing and tail feathers—which renders these birds unable to fly—occurs in the non-breeding months. Full flight capabilities are critical in breeding season so parents can forage for and deliver food to rapidly growing chicks.

A Closer Look at Atlantic Puffins

When breeding season is over, the first feathers that Atlantic puffins lose are the primary feathers—the longest feathers at the end of their wings. Approximately 16 to 21 days after the primary feathers are lost, the secondary feathers—those next to the primary feathers, lining the bottom of the wing—are lost. Fast forward several weeks, and the primary and secondary feathers start to regrow at a rate of 3 to 5 millimeters per day in preparation for their spring breeding plumage. The exact timing of this process depends on the colony's geographic location and varies from one population to another.

It's not just feathers that molt. The most recognizable physical characteristic of the Atlantic puffin may be its striped, brightly colored bill, but it only sports these vibrant colors during breeding season. Bill plates are shed prior to breeding season, revealing brightly colored portions, some of which are photoluminescent. This bright bill indicates to other puffins that the individual is reproductively active. After breeding season, the bill sheds its plates, revealing a duller colored bill underneath. The process begins anew for the next breeding season.

Time to Molt

There are seasonal cues that tell these seabirds it is time to start molting and get ready to breed. Our experts alter the Sea Cliffs environment to replicate these changes and cue these natural processes. Green grasses are added to the rocky decor to mark the beginning of breeding season; the amount of light in the exhibit is gradually increased each day, reaching peak hours in mid-summer; burrows are opened and nesting material is provided. These environmental cues likely aid in triggering hormones that are the catalyst for molting.

By mimicking the conditions found in their natural habitats, our experts prioritize promoting natural behaviors in these birds.