A Nose for Good or Evil

Turkey Vulture
Photo: Inge Curtis

Imagine my shock. I poured a glass of fine wine for a French neighbor in New York and, before showing him the bottle, he identified it by a sniff – the region, vineyard, and almost got the vintage. My nose humbled by this feat, I gazed at a man who missed a vocation as a master sommelier.

Smell is our least sense (same for apes) that never garnered much public attention until becoming a symptom of covid-19 infection. An odor must be pungent for my nose to take notice, so I didn’t detect anything unusual in the air in our back forty. But my heart missed a beat when a dozen Black Vultures flew up on heavy wingbeats from behind a brush pile, looking like medieval plague doctors with a hooded beak.

I found a white-tailed deer lying on the ground, so recently dead that ants hadn’t found it yet. After moaning about the population boom of hooved locusts that devastate gardens and farms, I felt sad to see the beautiful animal, whose death is still a mystery. I left to bury it another day.

Black Vulture

The story goes that birds, including Black Vultures, have a poor a sense of smell like us. But for every rule there seems an exception, and in this case several. The obvious one is the Brown Kiwi with nares at the tip of its long bill for sniffing earthworms in the dirt. Olfaction makes sense for a nocturnal species. The Turkey Vulture is a diurnal counterpart, and seldom is the hour when one isn’t patrolling overhead in wobbly flight.

Their large olfactory bulb with dense connections to receptors suggests an acute sense of smell. But discovery of their talent for smelling carrion up to a mile away came not from dissection but more serendipitously in 1938. They were spotted gathering at the site of a gas leak from pipes of the Union Oil Company, attracted by traces of mercaptan, a sulphurous additive that smells like rotten eggs.

Turkey Vultures are often first to find a meal not in plain sight, and Black Vultures tagging along never needed to evolve olfactory acuity.

Both species returned to feed, and repeatedly. They hadn’t waited for the meat to be tenderized, not because their stomachs can’t sterilize rotted food, but other scavengers might get there first. In four days, the deer weighing about 150 pounds was reduced to bare bones by the most efficient and discreet disposal agents around town.  On average, each vulture feasted on a few pounds each day. They saved me the trouble of burying a corpse before neighbors with a finer sense of smell than mine complained.

There’ll Be Bluebirds Over

The American composer of “There’ll be Bluebirds over the White Cliffs of Dover” either had the excuse of poetic license or didn’t know that bluebirds are absent from the British Isles. But the song became one of one of Dame Vera Lynn’s signature performances for stirring patriotic hope in 1942.

There are three species of bluebird in North America (all thrushes). Someone who grew up in Tidewater Virginia doesn’t remember seeing Eastern bluebirds here in the 1960s, probably because urban sprawl and competition from introduced species robbed them of natural cavities to make home. But no longer.

nestboxes
Male Eastern bluebird (photo: Inge Curtis)

The friendly songsters are now common in local meadows and suburban gardens thanks to human interference, sponsored by the Virginia Bluebird Society and kindly people who provide nestboxes. The best boxes are not the kind found in knickknack stores, gaily painted (for predators to find) and with a perch close to the entrance hole (to help predators look inside). Constructed of rot resistant cedar, an ideal box has a 1.5” entrance hole protected by a wire mesh predator guard and a snake guard on the pole. While these safeguards are not 100% effective, most broods reach the fledgling stage for the most dangerous days of their lives.

Bluebirds are nesting in two of our four boxes, each with five sky blue eggs. I don’t peep inside again until the chicks have flown after gorging on countless insects and arachnids brought by doting parents. Then, I clean out old nests that might harbor parasites, and usually find the lodgers have made new ones of pine straw and small sticks a few days later for a second brood. Even if I trained for months using forceps to weave the straw I doubt I could craft anything that would pass a bird’s inspection.

Our third box is still vacant and the fourth has a house wren sitting on brown speckled eggs.

Bird eggs are among the most beautiful objects in nature. They are delicate works of art, sometimes decorated with pigments as if squirted from paint guns in the oviduct on the day before laying. It is no surprise that ground-nesters have camouflaged eggs or that eggs laid further north tend to be darker to absorb more heat. We might expect cavity nesters, such as owls, kingfishers, woodpeckers, and wood ducks, would have pure white or buff eggs as coloring provides no obvious advantage. The colors of bluebird and wren eggs are among the exceptions, which goes to prove that nature hates uniformity and ruins our simple hypotheses.

Box taken over by house wrens
Adopted by house wrens

Data from over 4,500 nestboxes on 410 trails across Virginia are compiled by the Bluebird Society. Our local chapter of Master Naturalists monitors a few hundred boxes in parks and around golf courses every week between March and July. On a trail where I help to monitor 41 nestboxes, there were 63 bluebird fledglings in 2018  (a wet spring) and 97 last year, plus a few broods of chickadees and tufted titmice. Nestboxes raise thousands of extra birds.

This year the coronavirus pandemic disrupted our survey, but not the breeding season, which may even benefit from less human traffic and noise. But human nature doesn’t seem to change as I heard that three of our boxes have been vandalized. Who could do that to bluebirds?