What is that bird? Molting at your backyard feeders 

Plumage is the word used to describe the feathers on a bird. It is the variety of plumages we see on bird species that attract us, from the bright yellow of a male American goldfinch in the summer, to the mottled brown and greys of a great horned owl.  Possessing feathers makes birds unique from all other animals, as they are the only animal world-wide that has feathers.

                Birds around the world have a variety of different plumages, ranging from very colourful to very subdued, and each variation has its own purpose. Plumage colour can vary from species to species, or differ between males, females, or juveniles of the same species. For example, male house finches are a striking peachy-red in your backyard, while the females have predominantly grey/ brown streaks for colouring. Spotted Towhees and Dark-eyed Juncos are great examples of birds where the juvenile appears similar to the adults but also different as the juveniles have a surplus of brown streaks compared to their adult counterparts.

                For some species of birds their plumage will change depending on the time of year, with the most noticeable change occurring when birds shed their brightly coloured breeding plumage to don their winter plumage. The bright-coloured plumages we see on some birds in the summer can take a lot of energy to produce, a process made easier when nutritious food is naturally available. But as summer comes to an end birds naturally molt (replace old feathers with new) to become more energy efficient in the fall and winter, when natural food can be hard to find. Sometimes post-molt the birds we recognized so easily in the spring and summer can become harder to identify; for example the once canary-yellow male American goldfinch will become a greyish-yellow in the winter. Or the European starling, recognized for its glossy black iridescent feathers and yellow bill, becomes a black bird with copious white spots and a dark coloured bill in the fall.

Molting American goldfinch (Google)

                Molting for most birds will happen twice a year- in the spring birds will molt from their winter plumage to their breeding plumage, and then in the fall they will lose their breeding plumage in favour of their winter plumage. For juvenile birds they will undergo a molt where they will lose their juvenile plumage and start to look more like the adult of their species. For some birds the transition from juvenile plumage to adult plumage can happen the same year they hatched, or years later after they mature. When birds molt it can sometimes be difficult to identify them, as some birds can naturally lose large patches of feathers before the new feathers grow in, creating bald spots and making them look a little rough. The good news is that although the birds look disheveled, they are still able to fly, even if they’re missing a lot of their feathers.

Molting Bluejay (google)

                For some birds molting is serious business and can make them vulnerable to predation. Most songbirds will undergo a partial molt in which they only molt some feathers, allowing them to still fly. But for some water-fowl, like Mallards and Canadian Geese, undergo a complete molt, where they replace every one of their flight feathers during a single molt period.  During a complete molt you often will find waterfowl staying close to water, as they are unable to fly until their flight feathers grow back. A quick wander around Buttertubs Marsh, you will notice there are no brightly coloured male Mallards or male Wood Ducks, but what looks to be an excess of their female counterparts.  Male ducks have what is known as eclipse plumage, where they closely resemble the females after they have lost their brightly coloured breeding plumage.

Wood duck male in breeding plumage vs. eclipse plumage (Photo:natruallycurious)

                A bird’s plumage serves multiple purposes from courting, camouflage or simply to keep a bird warm when the weather is cold or dry when it rains. Plumage can also be used for communication, especially during territorial disputes. This can be seen with male Red-winged Blackbirds that will use the red and yellow spots on their wings to show dominance in territorial displays with other males.  Biologists have used the patterns of molting feathers to help us understand bird behaviour, changes in nutrition in a bird’s seasonal diet, and to help us understand how old a bird is. There are a lot of reasons why a bird will undergo a molt, and types of molting varies widely across birds species. You can easily witness how birds change their plumage seasonally by watching the birds visiting your backyard feeder. Over the next couple of weeks some signs of molting will be obvious, like the colour change for the male American goldfinch. But for most birds molting will be subtle, perhaps a couple feathers missing here and there as they all prepare for the change in season.

Dark-eyed Junco growing new wing feathers and a red-tailed hawk missing some feathers. Two subtle signs of molting. (Photos: Google)

 Thank you and happy birding!

 Nicole

Are you curious about how changes in plumage can be used for aging birds? Check out the work of VIU Professor Dr. Demers and the VIU Bird Banding Station.