Loves Water, Eats Bees

COURTESY MARY KEIM
I await the arrival of the phoebe who used to nest in our garage but now seems to live in the nearby barn. Unlike the previous tenants, we actually park in the garage. This was a little much for even so bold a bird as an eastern phoebe (Sayornis phoebe). When we moved in there was an old nest on one of the rafters, and I left it there in case she wanted to re-use it. Although, the first spring we were here, she hovered around the old site for a while, she did not re-occupy it or build elsewhere in the garage. Happily, the pair has remained in the immediate vicinity, so we continue to get the pleasure of their company.

I have begun to see reports of returning phoebes in New Hampshire. It has been suggested that they follow the frost line northward, so March arrivals make sense, as long as there are insects to eat. Over the last two weeks I have seen flying insects about and, even if there is a lot of snow on the ground, especially on north-facing slopes, there are plenty of melted areas. And although the lakes and ponds are still frozen, the streams are running.

Hardly anything is known about phoebe migration. It is apparently solitary, as flocks are never seen. It is apparently diurnal because dead phoebes are not found at the base of television towers and the like. It is thought that males arrive north slightly ahead of the females, but researchers are not sure because the sexes look alike, and the males sing so much it is hard to miss them.

Phoebes generally raise two broods each year. The first is fledged sometime in May and the second sometime in July. When they finish breeding, they often vanish from their breeding territory, but they do not migrate south at that time. No one, however, is sure where they go. Fall migration generally takes place in September and most of the population winters in the southeastern United States, but some will get as far as northeastern Mexico.

A small brook runs through my property and there is a fire pond elsewhere on the lot as well. During the breeding season eastern phoebes are strongly associated with water, but less so during other times of the year. They usually use built structures as nesting sites. Before European settlement they nested on rock ledges, and some still do so. Although they have a wide distribution, there are large gaps in it in the midwestern U.S. and Canada where there are no built structures, no rock outcrops, and very little water.

This predilection for nesting on man-made structures make the phoebe one of the most familiar of tyrant flycatchers. The eastern wood-pewee (Contopus virens) has a broadly overlapping range, is similar in size with similar behavior, and is actually fairly closely related (same subfamily), but—during the breeding season—you will rarely see the two species together, and you will see phoebes more often than pewees. True to its name, the wood-pewee is a creature of the forest edges and clearings. I would never expect to see one perched on a low limb over my driveway, while I routinely see our phoebes between April and July when I walk to and from my car.

This is a good example of resource partitioning. In this part of New Hampshire, you can find eight species of tyrant flycatcher. Two of them (great crested flycatcher and eastern kingbird) are larger than the phoebe, and four of them (the Empidonax species) are smaller, but all feed by hawking flying insects. They divide up their resources by specializing in varying habitats and emphasizing pursuit of different flying insects.

We have a pair of great crested flycatchers in my neighborhood, but I rarely see them because they never come down from the top of the canopy. In contrast, when I encounter “my” phoebes, they are often at or slightly above eye level. To see an alder flycatcher (one of the Empidonax species) I must go up to Stearns Road to the beaver pond where the alders grow. To find pewees, I need to hike in the extensive woodland along New London/Wilmot border where clearings are created by logging and beaver ponds.

The diet of phoebes was studied by F.E. Beal 120 years ago. He looked at 370 stomachs and found the largest portion (26%) consists of Hymenoptera (bees and wasps). Wood-pewees, who segregate themselves from phoebes laterally, eat far more Lepidoptera (moths and butterflies; up to 30%) and Diptera (true bugs; up to 25%). The great crested flycatchers, who segregate themselves vertically from my phoebes, eat mostly lepidopterans (22%) and Coleoptera (beetles; 17%).

There are two other species of phoebe. Say’s phoebe (S. saya) is broadly distributed in the western U.S., essentially complementing the range of S. phoebe. The black phoebe (S. nigricans) is a more southern bird, found throughout Mexico and ranging up into the U.S. Southwest and through California. These two western species have a broad overlap in their distributions. Mitochondrial DNA studies have shown that the eastern and black phoebes are sister taxa and that the Say’s is sister to both, which is to say, less closely related to them than they are to each other.

Within the overlapping range of the Say’s and black phoebe, hybrids have been documented but they are rare. The eastern phoebe has been extending its range westward and in 1984 a possible Say’s/eastern hybrid was found in Utah. Say’s phoebe actually avoids water and prefers to nest in very dry places, while the black phoebe is invariably associated with water. That is, the Say’s evolved a different habitat preference to prevent hybridization, and the black and eastern, while more closely related and ecologically similar, remain distinct by being geographically separate.

Bill Chaisson has been a birdwatcher for over 50 years. He lives and works in Wilmot.