Summer is in full swing by July and most people see and feel the changes in their environment. The sun is higher in the sky, the trees are full, the mosquitos are everywhere, and the air is heavy with humidity. If you’re a birdwatcher, you’ll probably notice a difference in the appearance of the birds at your backyard feeders.
Molting season for many North American birds begins in July. Because molting is energetically expensive for birds, Mother Nature timed it just right so that it would not interfere with other energy-expending activities such as migration and breeding. Molting takes place after fall migration, spring breeding, and the subsequent tending to chicks. The timing of this cycle is yet another one of nature’s miracles.
See also: Five Birds to Find in July
What Does Molting Mean?
Molting is the process of a bird shedding old, worn feathers to be replaced with a fresh plumage. Depending on the species of bird, a molt may be partial and replace some of the bird’s feathers or a complete replacement. As a rule, smaller species of birds tend to replace their feathers all at once, often replacing some feathers twice. The larger the bird, the more energy-taxing the molting process will be. Large species, such as eagles, will not grow a new set of flight feathers annually. Molting restores individual primary and secondary feathers on their wings, often in a staggered process that takes years to complete. For other species, the complete molting can take as little as two weeks.
Four Types of Molting
You might be wondering why a bird needs to molt its feathers. Like our hair and fingernails, feathers are composed of a protein called keratin. This material is under constant stress and subject to a great deal of damage over time.
Like the daily activities of human life that wear our human bodies, many activities of the bird’s daily life wear feathers. Activities such as rubbing against bushes, preening, flying, and even the necessary dust bath, cause friction that causes wear. The keratin weakens as the feathers age, but unlike our hair and fingernails that are capable of regenerating, a feather will no longer grow after reaching its full size.
The accumulation of this damage affects the feather’s aerodynamic properties as well as its ability to insulate the bird in all types of weather. The feather must be shed so that a new stronger feather can take its place. There are four types of molting in the life cycle of most species of birds:
- Juvenile to Adult: Young birds must shed their down feathers and subadult plumages as they mature. This is also important so they can develop their adult coloration and distinct markings. Larger species will take several molt cycles in order to reach their mature plumage.
- Breeding to Non-Breeding: In order to attract a mate, many birds will entice potential mates with their bright breeding plumage. Once the breeding season ends, however, these birds will molt into camouflaged colors. Additionally, this plumage will also feature feathers that offer better insulation for the coming winter season.
- Non-Breeding to Breeding: In the reverse of the above, after winter’s dull plumage, molting allows for the bird to prepare for mating season with a fresh, colorful plumage of feathers. Scientific studies have discovered that birds with brighter plumage are most successful at breeding.
- General Feather Replacement: For species that do not specifically molt to change color for breeding, replacement of worn feathers is an important molt that most species of birds must undergo to maintain their healthy plumage.