Birds can be tough enough to identify – just look at the differences between typical cardinals, with the male at left and a female on the right. Identification can be made even more difficult for any species when plumage abnormalities are present. Associated Press photos

One of the most common questions we receive is about birds that appear to have different plumages or colors. People see a bird that looks like a cardinal or woodpecker but something seems different. Steve Champagne sent a question about an unusual hairy woodpecker, saying “all the parts that are normally white were a distinct yellow … We haven’t been able to find anything about this. Was this some kind of pigment abnormality?”

Plumage anomalies in birds can be really fun and frustrating to decipher. They occur from a variety of causes and present themselves in different ways, from a single feather being ruffled, to a bird being entirely the “wrong” color. Let’s discuss a few causes of these appearance-altering differences.

The most commonly observed “off” plumages are usually caused by genetic anomalies. Albinism is when an organism has a complete lack of any pigments, typically resulting with white (alba, meaning white in Latin) hair or feathers (focusing on birds here). To oversimplify, the opposite of albinism is melanism. Melanistic birds usually appear extra dark from an over-production of melanin, which gives birds most of their blacks, browns, and some shades of yellow.

Within this group of genetically-altered plumages are individuals with partial albinism, known as leucism. Leucistic birds will often have single feathers or patches of feathers that have no pigmentation. Fortunately, for people like me who are often challenged with “can you ID this bird” photos, leucistic birds will often look very much like they “normally” do, while fully albino birds can be a real challenge and are sometimes only identifiable to the family or genus level. Another plumage anomaly in this category is a phenomenon known as xanthochroism, which occurs when there is an overproduction of yellow pigments.

This could be what Steve is reporting with his yellow woodpecker. However, the important distinction is that “all the parts that are normally white were a distinct yellow,” which makes me think we are dealing with an environmental – rather than genetic – cause. The genetic causes all changed pigmented feathers to either lighter, darker, or a different color all together. But when a white feather changes into a color, it’s usually caused by something getting on the feathers.

In the case of woodpeckers, it is helpful to think about what they are doing this time of year: nesting. Since woodpeckers are cavity nesters, they are often going in and out of a hole in a tree, and these oft-repeated trips will result in their feathers becoming stained from tannins from the tree. I first learned about trees staining woodpeckers in a July 2012 Maine Sunday Telegram article by Herb Wilson, the newspaper’s longtime birding columnist.

CYCLE OF LIFE IN THE DEEP WOODS

Another common question I get, especially this time of year when animals are on the move, is about roadkill. Michael Petit sent in a question, however, about dead animals not on the road but in the woods and forests. He’s wondering why he never sees carcasses in the woods and asks, “With millions of animals across the state, there must be a very efficient natural system for keeping the forest floor so ‘clean’. What do we know about this process?” As Michael says, nature provides some “very efficient” cleaning, or even better, recycling systems. This is a big topic to unravel in a short article but thinking about a few different animals’ life cycles may help fill in some gaps.

First, it is worth mentioning that our detections of recently deceased animals are probably really low because of our access (or lack of access) to areas where deaths of all kinds are occurring. The roads and trails that we use to navigate through the wilderness are very different from those used by animals.

Then we should think about the causes of death. Dying of old age is probably incredibly rare in the wild, and even creatures dealing with physical disabilities or disease are very likely to be taken by a predator. Whether it is to feed themselves or their offspring, predators tend to be very efficient, using almost all of their prey. You sometimes come across telltale signs left behind by a few apex predators. Great horned owls, for example, tend to decapitate their prey, though other wildlife will often take advantage of the leftovers.

Recyclers – mainly a diverse and large group of insects – are also hard at work. We tend to be aware of the many insects, especially beetles, that help decompose fallen trees, but among that incredibly broad cast of characters are species like burying or carrion beetles. These small insects can make a carcass 20 times their size disappear in a matter of hours, burying it and laying eggs nearby, so their offspring have a meal ready at birth.

As I said at the beginning, there is a lot more to these life cycles than we can cover here, so I’ll end with a book recommendation from one of the greatest naturalists of our time: Bernd Heinrich’s “Life Everlasting” is a fascinating read about, as Heinrich calls it, “the animal way of death.”

Do you have a nature question for Doug? Email questions to [email protected] and visit maineaudubon.org to learn more about bird walks, community science projects, and other programs about wildlife and habitat.


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