It’s a day in late May and already the nests of our eastern phoebes are bursting with nestlings preparing to fledge. Over the 47 years we have lived on our mountain, our buildings have hosted many eastern phoebe nests.
Some buildings, such as the guesthouse portico and the old outhouse, contained nests for several decades, but the outhouse finally collapsed and the phoebes deserted the guesthouse portico after years of successful fledgings. They continue to use either the outside or inside of the small springhouse, while the barn overhang has become a more recent popular nesting place.
Still, there has never been a year when phoebes have not used the top of a veranda column and one of the garage beams to raise families, even though we tried to discourage the veranda column nest sites when we had it repaired and painted by blocking in the flattened tops of the columns. Undeterred, phoebes molded their nests around the obstructions.
Eastern phoebes have been building their nests on human homes and outbuildings for centuries and were known in the 19th century as “barn pewees” as well as “bridge pewees” because they also favor the undersides of bridges. Before the advent of human dwellings and even today, they will build nests in natural rock outcroppings. All such choices protect their nestlings from the weather and often predators as well.
Members of the Tyrant Flycatcher family, eastern phoebes follow the first flush of insects north from their winter homes in the southern United States, Texas, and Mexico, often arriving in Pennsylvania in early March and leaving in late October. Sometimes they must survive late spring snow storms and are able to subsist on small fruits instead of insects until the weather improves.
These gray-brown birds with off-white throats and bellies are the first songbirds to arrive on our mountain around March 15. When I hear the raspy “fee-bee” of a male phoebe and see this tail-flicking flycatcher on a wire near the barn catching insects from the sunny side of the building, I know that spring is here.
In scientific circles, eastern phoebes are known as “suboscine” birds because their songs are innate instead of learned like those of “oscine” birds such as wood thrushes. But lately bioacoustic studies of their songs detected variations among male song characteristics that are not obvious to our ears but are to those of the birds.
Eastern phoebes should be credited with first arousing bird artist John James Audubon’s interest in birds. When he was a youth, he lived at Mill Grove on the Perkiomen Creek in Chester County. Early in the spring of 1804, he found the empty nest of the bird he called “Pewee” or “Pewit flycatchier,” fastened to a rock in a cave on his property.
When the cave phoebes returned, he spent many hours watching them as they went about their phoebe business. “Before a week had elapsed,” he wrote in his Ornithological Biography, “the Pewees and myself were quite on terms of intimacy.”
Beginning on the tenth of April, he watched them repair their old nest as “they brought fresh materials, lined the nest anew, and made it warm by adding a few soft feathers of the Common Goose which were strewn along the edge of the creek water.”
Even today, eastern phoebes often refurbish old nests instead of building new ones, since building a new nest takes five to 14 days and refurbishing an old one four days or less. One recent study found that new nest builders finished their first clutches later, were less likely to raise a second family, and lost their nesting attempts more often because of fallen nest structures, all of which led to “lower seasonal reproductive effort,” the scientists concluded.
Audubon’s close observations of phoebes’ family life reminded me of the time I spent watching a guesthouse portico family back in the early 1980s. The female refurbished an old nest and she then laid five white eggs.
I sat inside the front door of the guesthouse and watched the family through the portico window, but I also climbed up on a chair outside and held a mirror above the nest to check the eggs. The female is the sole incubator, even sleeping in the nest overnight. It takes 16 days until the eggs hatch, and most eggs in a single nest, including the ones I watched, hatch within 24 hours.
Audubon’s eggs hatched on the thirteenth day and in his nest of six eggs one did not hatch just as in the nest of five that I watched one never hatched. In both cases a parent removed the egg. Audubon opened the rejected egg and “found the embryo of a bird partly dried up, with its vertebrae attached to the shell…”
Since the hatchlings are helpless, almost naked, and in need of nearly constant brooding, I waited until they were 11 days old, fully feathered, and active before spending an hour every day watching the nest and recording the number of feedings. For four days they averaged 25 feedings, but when they reached 16 days of age, the feedings diminished to 15 an hour. A recent study showed that parents adjust their feeding rates according to the begging rates of their nestlings.
By then the nestlings were flexing their wings or standing on the edge of the nest and beating them. When they were 17 days old, the female parent appeared with nesting materials in her beak and, despite screams of hunger from the nestlings, proceeded to build a second nest beside the first one, yanking nesting materials from the side and top of the first nest as the youngsters watched.
While she worked on construction, the male fed the nestlings. But sometimes when they begged, she tried to push construction materials down their throats which they promptly spat out. They even jumped back and forth between the old and new nests but settled into the old nest by nightfall. The following morning, at 9:30 a.m., they all fledged at once. Usually though phoebes fledge one at a time over an hour or so as the veranda column nestlings do.
While I kept a “hands off” approach to the young, Audubon spent his time gaining the trust of both parents and nestlings so that they tolerated the light silver thread he fastened to the leg of each nestling before they fledged. This was the first time that birds had been banded in North America.
His banding proved the following year that phoebes return to their same nesting site and even nest, writing, “When the Pewees returned to Pennsylvania I had the satisfaction of observing them again, in and about the cave. There again in the very same nest two broods were raised…Several of these birds which I caught on the nest had the little banding ring on the leg…”
He assumed many of the pairs he observed, not only in the cave, but on farm buildings and his mill nearby remained faithful during one breeding season and from year to year. Recently, two studies found that most pairs were both socially and genetically monogamous within a breeding season. In one case in Indiana only 15 of 87 families had extra-pair young in at least one brood, most commonly the second brood.
Those researchers followed up with a second study in which they captured and color-banded 198 males and 237 females, studied them for three seasons, and discovered that they were faithful to their territories, nest sites, and mates within and between years with 85.5% of males and 92% of females mating with the same mate during multiple breeding attempts. But mates were replaced following their disappearance and probable deaths.
A study of infanticide in Kentucky by an unrelated male phoebe even while the female continued feeding her nestlings, resulted in the death of all the nestlings. The researchers hypothesized that the male parent of the nestlings had died or disappeared and that it was a way for a non-breeding male to obtain a mate and start his own family.
A greater threat to breeding phoebes has been repeated brood parasitism by brown-headed cowbirds. I’ve occasionally observed cowbird parasitism in our nests over the years, but never in the veranda column nests. A study of cowbird parasitism in New York State concluded that even over generations of birds, cowbirds prefer particular eastern phoebe sites, such as our old outhouse.
Other threats to phoebe eggs and nestlings are black rat snakes, raccoons, coyotes, blue jays, American crows, chipmunks, and house wrens, but not one of those predators has climbed or flown into the veranda column nests.
Overall, phoebes are incredibly successful throughout their range including Pennsylvania where they live everywhere except for the urban cores of Philadelphia and Pittsburgh. Although our songbird population has dwindled since the 1970s, it is comforting to know that eastern phoebes continue to thrive and are able to quickly adapt manmade structures for their own purposes.