Written for rehab volunteers, this page covers birds that commonly appear in rehab that haven’t been “lumped” into broader categories: Barn Swallow, American Robin, Black-headed Grosbeak, and Dark-eyed Junco.
Although the U.S. hosts 8 species of swallows, the Barn Swallow is the most abundant and most widely distributed swallow in the world, found on every continent except Antarctica. For once, the species’ scientific name needs little explanation: Hirundo rustica in Latin literally means “swallow of the country.” The Barn Swallow is the only swallow that has a true “swallow tail,” deeply forked and streaming behind. In the 1800s, this species experienced mass destruction so that those beautiful tail feathers could decorate ladies’ hats. An editorial decrying this practice in Forest and Stream in 1886 led directly to the foundation of the first Audubon Society and to saving this species in the US. Here’s a photo of an adult feeding one fledgling while another waits impatiently. Generally, Barn Swallows reside in Colorado between mid-May and early September.
Flying equals life for Barn Swallows. They are believed to be the fastest swallow; one was clocked at 46 mph! Swallows dine exclusively on flying insects, usually foraging within 30 feet of the ground. They also drink on the wing, lightly dipping to the water’s surface with their lower mandibles (jaws). They may fly 600 miles a day while feeding their young. The parent gathers small insects in flight, compresses them into a pellet in its throat, and deposits it in a nestling’s mouth. One study estimated that one Barn Swallow made an average of 29 visits to its nest each hour of daylight—that would be over 400 trips a day! Each pellet can contain as many as 20 insects and weighs on average about 70 mg. So each day, one Barn Swallow can remove 28 grams of insects from the environment-nearly 800 grams over a month of feeding nestlings and fledglings. And this doesn’t even take into account the many insects they eat themselves!
Building mud nests fastened to walls or horizontal ledges of just about any structure, nothing says Barn Swallow nest more than feathers, feathers, feathers! (This photo also shows some brand-new hatchlings and a couple of eggs.) After leaving the nest (about 20 days after hatching), the fledglings are fed by the parents for about a week. The kids soon fly out to meet the parents, who transfer food mid-air. Not long after honing this skill, the babies begin to catch their own food, launching into their own, independent lives on the wing.
And while we’re on the topic of swallows–although not common in rehab in CO, we have many Cliff Swallows in the Coaldale area. When we were atlasing our area for the CO Breeding Bird Atlas, we estimated 450 active CLSW nests on the Vallie Bridge, over the Arkansas River. I did some sleuthing on this and, putting some pieces together, I came up with the following calculations. Both parents together make up to 18 visits to a nest per hour during daylight hours in large colonies; I figured at least 14 hours of daylight during the time they’re nesting; an adult can deliver a “serving” of as much as 0.8 grams of insects compressed in its throat; kids are on the nest for around 20 days and the parents continue to feed them for another 5 days. Thus—18 * 14* 0.8 * 25 = 5,040 grams. So each nesting pair could remove as many as 5 kilos of bugs per breeding season—and that doesn’t count what they themselves are eating. (I’m not sure how many nests were at the firehouse, but we estimated 425 active nests on Valiie Bridge.) Swallows don’t eat very many mosquitoes (drat!) because the mosquitoes are most active at dawn and dusk, not during the broad daylight hours that swallows are foraging; in addition, mosquitoes don’t provide much nutrition. But CLSWs do eat lots of bees and wasps, aphids and planthoppers, flies, beetles—and just about any other insects that concentrate in aerial swarms.
American Robin—the original early bird
Can you imagine a spring without robins, singing their bright “cheerily, cheer up” song? Michigan State University (my alma mater—go Spartans!) faced this catastrophe in 1959. In the early 1950s, arbor specialists began trying to eradicate Dutch elm disease on campus by spraying the many elm trees with DDT. The insecticide manufacturer had assured them that the spray was not harmful to birds. But the oily residue stayed on the leaves; the leaves fell to the ground; the earthworms ate the leaves; the robins ate the earthworms. Within a week after each new wave of migrants arrived in the spring, all of the robins were dead. By 1959, robins had been completely extirpated on the vast, bucolic campus. Faculty ornithologists eventually identified the culprit—as few as 11 earthworms delivered a lethal dose of poison to a robin—and stopped the use of DDT locally. This investigation was one of the cornerstones of Rachel Carson’s powerful and ground-breaking Silent Spring, which resulted in the banning of DDT as a pesticide throughout the U.S. And happily, the MSU robin population had returned to its pre-1950s level by 1979.
The American Robin is the largest species in the thrush family, which includes not only all bluebird species but also some of the most talented songsters in the avian world. The only areas of Colorado where robins don’t breed are those without trees—croplands, grazing lands, or agricultural fields, for instance. Saddled with the easily ridiculed scientific name of Turdus migratorius, its name derives from the Latin term for “wandering” (migratorius) and “thrush” (turdus). (Since most thrushes wander (migrate), it’s not really clear why the robin was singled out for this particular moniker.) Its common name arose from homesick European settlers in the U.S., who thought the birds looked like the English Robin, commonly found in Europe (but to which our robins are not closely related). Adult males and females look quite a lot alike, although you can often differentiate them by the color of their heads: A male’s head is much darker—almost black—while a female’s head is more gray. Juveniles are easy to identify—they have black spots on their breasts and pale spotting on their upperparts.
Both parents take an active role in feeding nestlings. For the first few days after hatching, parents regurgitate soft invertebrates (e.g., grubs), parts of worms, and even some plant material (e.g., fruit) for the babies. (This is why we feed mashed soft-bodied insects to these hatchlings for their first few days with us.) After that, the parents just directly fill the gaping mouths with a variety of invertebrates and, occasionally, small fruit. Nestlings fledge about 13 days after hatching and are fed by their parents for at least another 3 weeks. A robin’s fall and winter diet is 90% fruit; but in spring and summer, it flips to 90% invertebrates—especially earthworms. When a robin is hunting earthworms, it looks like it is listening for them, cocking its head to one side and then to the other before pouncing. But the noise that earthworms make is too faint to be heard above ambient sound. Robins are really using visual cues to detect the worms under the soil. Studies of captive robins indicate that they seem to prefer blue and red fruits (e.g., blueberries, strawberries) over yellow or green fruits (e.g., green grapes). Robins do not eat seeds at all; if they ingest seeds with fruit, either they regurgitate them or the seeds pass through their systems completely undigested. Save some money and don’t give robins any bird seed! Also, robins love bathing in water. So as the young robins get bigger and move to larger cages, consider putting in a medium-sized shallow pan with fresh water. Then stand back and watch the droplets fly!
During breeding season, robins are the last to sing in the evening twilight after sunset. And they greet the morning long before most humans and other birds are up—as much as an hour before dawn. In fact, this characteristic gave rise to the adage “The early bird catches the worm.”
No doubts when young Black-headed Grosbeaks are “in the house!”
For the past few weeks, anyone in the baby bird room has heard the soft, descending “whee-urr” calls of the pair of baby Black-headed Grosbeaks. Even in the wild, the babies emit this call continuously from the nest, cranking it up to loud begging when a parent (or a human carrying a syringe of formula) appears. Officially entitled Pheucticus melanocephalus, the species name seems obvious—from Greek for “black” (melano) and “head” (cephalus). But the genus name Pheucticus—“painted with cosmetics”—is a bit odd. It likely was first applied to the Rose-breasted Grosbeak—a very close relative of our Black-headed guests—which has a brilliant red “bib” on its otherwise white chest. The common name—grosbeak—derives from French for “large beak,” which indeed they have. Members of the Cardinalidae family along with cardinals and buntings, here are photos of an adult male and female. (Juveniles look like females.) These birds arrive in Colorado in late April or early May and stay until mid-August before heading back to their wintering grounds in Mexico and Central America. Once there, they are one of only a few species that eat Monarch butterflies, despite the fact that Monarchs contain toxins deadly to most birds. Grosbeaks never eat the wings, which contain the greatest concentration of the toxins—so perhaps that’s part of how they limit their ingestion of toxins.
Black-headed Grosbeaks can be found in many different kinds of habitats. About 60% of their diet is insects and spiders; the rest, fruit and seeds. Babies hatch after about 2 weeks and crawl out of their nests to perch in trees 10 – 14 days after hatching—a good 2 weeks before they can fly! The babies then sit very quietly on tree limbs and the parents keep track of whom to feed by remembering where the kids are. Once the fledglings can fly, they again communicate constantly with their parents using that “whee-urr” call we all know so well now. Given that the babies spend so much time out of the nest before they can get around well, it’s amazing that we don’t have more people bringing in baby Black-headed Grosbeaks—a testament to skilled parenting and good-gripping baby feet!
Dark-eyed Junco—a rare visit from a clutch of “snowbirds”
The Dark-eyed Junco is a common and conspicuous bird at winter bird feeders in Colorado. John Jay Audubon once referred to the junco as “the little Snowbird,” and many people today think that that’s its name (unless they’re referring to the Northerners who winter in Florida and summer in cooler climes—also called, rather derogatorily, snowbirds). Juncos nest in upland coniferous forests more so than any other habitat; spruce and fir figure importantly in their breeding grounds. Their scientific name is Junco hyemalis, which derives from the Latin for the European “reed bunting” (a bird they resemble and based on the Latin term “iuncus,” for a reed) and “of or belonging to winter,” because in Sweden (where Carl Linnaeus lived and named the bird), the bird was only seen in the winter. It’s therefore easy to see where the common name of “junco” came from; and they are referred to as Dark-eyed Juncos to differentiate them from the Yellow-eyed Juncos found in Mexico and occasionally in extreme southeastern Arizona.
The junco can be identified by its white tail edgings that flash brilliantly as it flies away; it’s a long-tailed, small-bodied sparrow that usually has a dark “hood” (head, throat, nape) and a dark back that contrasts sharply with a white chest and belly. I say usually because the species is made up of 4 (although some consider it 5) subspecies that were once considered separate species. Colorado’s most common breeding junco is the “gray-headed junco,” with a brown patch on its shoulder on an overall gray back and gray sides (one of the best clues for differentiating this subspecies, if you’re into that sort of thing). But in the winter, you might find any of the other 3 subspecies at your feeder at any time. The next most common is the “oregon junco,” which has a dark gray or black hood (males) or dark brown hood (females) with pink sides and a gray back. (Some consider the “pink-sided junco” to be a pale variant of the oregon subspecies; others consider it a separate subspecies. Indeed, it can often be a real challenge to differentiate pink-sideds from oregons, since you mostly are looking to see how dark their heads are. If the head is so dark that you can’t see the black around their eyes, it’s probably—PROBABLY—an oregon. If you can see black around the eyes, pink-sided is a good guess) The last 2 subspecies aren’t as common in CO as the previous ones, although they are among the most stunning. The “slate-colored junco” has a uniformly dark gray head and back, with the gray stretching to the chest as well. And finally, the “white-winged junco“—pretty uncommon in our area—looks like a light version of a slate-colored, except that you can see white wing bars. Of course, just to keep things dicey, slate-coloreds can have small white wing bars too. And the various subspecies can hybridize, so you can get lots of variations on the “junco” theme. Oh, well—thank heaven they have all been lumped into one super-species of Dark-eyed Junco and only the truly obsessed need to worry about all of this.
Adult juncos have a diet that is roughly 25% insect matter (primarily arthropods—insects and spiders) and 75% vegetable matter (seeds). But parents feed their nestlings primarily arthropods. Nestlings grow up quickly, leaving the nest 9 – 11 days after hatching; about 2 weeks after fledging, they are self-feeding and fly as well as adults.
Juncos—especially nestlings—are not a common guest here, in large part because they typically nest at much higher altitudes than most humans visit. In fact, when we were planning the baby bird CD, I had originally included juncos in my list of birds I thought might show up at the center—and the consensus was loud and clear that young juncos were such a rare occurrence that we needn’t use up valuable space for them on the CD. They begin singing their lovely bell-like songs when they’re still in our area in late winter—keep your ears tuned for its tinkling wafting through the air on warm winter days.
© 2009 Tina Mitchell
