Lake Artemesia is an incredibly popular natural oasis just east of the University of Maryland’s College Park campus. On summer weekends, bikers, joggers and families with children in strollers fill the 1.5-mile path that circles the lake. People fishing and bird watching or just out for a walk join the fun, all enjoying a respite from work, school and Washington, DC, traffic.
The paved paths are ideal for my scooter, allowing me to explore bird habitat that isn’t limited to a few steps from my car. While the lake supports a surprising array of waterfowl, it is the extensive — and paved — Anacostia Trail system bordering the park that reveals the area’s real avian bounty.
We left the multitudes behind and slid off onto the surprisingly quiet trail.
Almost immediately, from high in a sycamore, we could hear a bird’s incessant song. The singer was lost amid the dense foliage, but his song kept me glued to the spot. Finally, I caught a glimpse of the bird hopping from twig to twig.
He had a bold face pattern. A gray cap edged in black sat atop a broad, long white eyebrow. A sharp black line extended from the bill through the eye to the back of the head. His bill was impressive: a long, dark, stout affair. The bird’s undersides were pale from the white chin to the yellow blush under the tail.
As he changed positions again, I caught sight of his olive green back. He wasn’t easy to see, but this was one of the most common birds of the Eastern forests, a red-eyed vireo (Vireo olivaceus).
Those eponymous red eyes are only visible in ideal lighting conditions. The shade provided by the closed canopy kept them hidden this day.
Although both sexes look alike, I knew this merry songster was a male; females don’t sing.
And sing they do! Most species only sing to attract mates and establish and protect territory. After mating and the young have fledged, most birds simply stop singing until next year. Not so with the irrepressible red-eyed vireo. He’ll sing all summer long for hours on end. One researcher counted more than 20,000 songs in a single day from just one bird!
The towering mature trees along the river were perfect habitat. These vireos love deciduous forests and the teeming life that lives in the treetops.
Red-eyes are gleaners, plucking insects from leaves and twigs. Caterpillars are a favorite during spring and summer when they may constitute half of the bird’s diet. And those caterpillars that are lucky to survive to maturity? They continue to be favored prey in the form of moths and butterflies.
Red-eyes also eat a host of other insects and a sizable number of fruits and berries. On their winter habitat in the Amazon basin, their diet is especially heavy with fruit.
Every March, they begin the long migration north. Well-nourished birds take the daunting flight across the open waters of the Gulf of Mexico before fanning out across the landscape. Thinner birds that don’t have the fat reserves required to make that flight, stick to a coastal route along Central America and Mexico. Regardless of the route, they all migrate at night.
About half of all red-eyed vireos fly up to Canada to breed. Another quarter of the population will breed in the United States. The final quarter never leaves South America. This race, called the Chivi, spends its life in the Amazon.
In the Chesapeake, most red-eyes arrive in May. The female red-eyed vireo will lay 3–4 eggs in a nest she constructs 10–15 feet above the ground. In Pennsylvania, red-eyes will produce a single brood, but in Virginia and farther south they may have a second clutch before heading back to South America in September.
Brown cowbirds rely heavily on red-eyed vireos. Cowbirds likely evolved following massive bison herds across the plains of the continent before Europeans arrived. They devised a strategy of laying their eggs in other birds’ nests as the cowbirds continued on with the always-moving herd. Luckily for them, most species treat the eggs as their own and raise the chicks to maturity.
For some strange reason, cowbirds seem to love red-eyed vireo nests. In many forests examined by ornithologists, one or more cowbird eggs were found in half of the vireo nests examined. Although they compete for food as fledglings, brown cowbirds fill a different ecological niche as adults, leaving the dense forests to their foster families.
As I thought about this odd dynamic, my mind went back to the diverse crowd circling the lake. How many nannies were pushing other people’s children in strollers? How many adopted kids were riding bikes? How many blended families were out for a walk? All permutations seemed both possible and entirely normal. Caring for nonbiological children is increasingly common. I realized that all a child needs is a family willing to ignore unimportant differences.
That strange bond between cowbird and red-eyed vireo suddenly seemed not so strange after all.