Birds eat all kinds of foods, some of which are very appealing to our own palates, particularly things like fruits, berries, nuts, corn, and maybe even fish, crabs, mollusks, and crustaceans. Sushi lovers aside, though, most of us prefer the latter types of food in an at least partially cooked format. Then there are those birds that eat things that almost everyone finds downright repulsive.
It is doubtful that you know even a few people who salivate over raw meat of any kind or have an appetite for insects or slimy invertebrates, let alone carrion. Sure there are plenty of people on this word who eat roadkill and other things firmly planted in the weird category, but broadly speaking we can chalk this up to cultural differences or isolated world oddities.
One thing that some birds are known to eat that humans simply don’t consume, at least not as food, is wax. Wax in the general and naturally occurring sense refers to a class of organic compounds that are insoluble in water, solid and brittle when cold, solid but malleable at room temperature, and melt into a low-viscosity liquid at higher temperatures. Wax consists of long-chain fatty acids and is very difficult for most organisms to digest. Aside from its limited appearance in things like chewing gum or wrapping some types of cheese, wax is not something we eat, but rather something for which we have found all sorts of creative practical applications. Birds can always be counted on to defy basic logic or provide exceptions to general rules, and eating wax is no exception.
There are actually several groups of birds that eat on purpose and can metabolize wax. Many seabirds, for example, such as petrels and razorbills, derive energy indirectly from wax found in the crustaceans they eat. Then there are a handful of land birds, such as certain species of warblers and swallows, that gorge themselves on waxy berries. The digestive tracts of these rare birds are characterized by higher concentrations of secretions from the gallbladder, higher concentrations of bile salts in the intestines, and a relatively slower rate of passage of lipids acquired from food. There is also some evidence that these birds are like ruminators, like cows, so that the partially digested waxy compounds somehow make their way back to the gizzard from the small intestine for a second or third round of digestion.
Unbelievable as it may seem, none of these birds are eating wax directly, they are simply forced to consume it because it is an unavoidable part of their preferred foods. Enter the Honeyguides (Indicatoridae), a family of 17 species found only in Africa and ranked in the same order as woodpeckers (Piciformes). Rather unspectacular in appearance and basically the size of a songbird, these birds are mostly insectivorous, but are famous for their curious behavior of eating the pure wax from the combs. In addition, these strange birds enlist the help of honey-loving animals such as honey badgers and even humans, drawing their attention to the location of a hive so that their assistant opens the hive to take the honey and leave the waxy comb and bee larvae to the honey guide.
