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?

 

About Roger Gosden

British-born scientist specializing in reproduction & embryology. Career as professor & research director spanned from Cambridge to Cornell's Weill Medical College in NYC. Married to Lucinda Veeck Gosden, embryologist for the first successful IVF team in America. Retired early to Williamsburg, Virginia, to write and recover from 'nature deficit disorder'. Currently a visiting scholar at William & Mary. https://en.wikipedia.org/wiki/Roger_Gosden
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