During spring migration, it’s exceedingly difficult to get past the dazzling array of warblers, but mixed flocks are rarely composed only of warblers. Along the Mississippi Flyway Highway, their traveling companions include various vireos, flycatchers, and thrushes, to name a few of the major groups. On the same incredible day, which I’ve thoroughly detailed above, I met with many members from each of these groups. Perhaps my favorite were six species of vireo! This included two—Red-eyed and White-eyed Vireos—that likely ended their migration before my eyes, stopping to breed, and four others that will continue elsewhere—Yellow-throated, Philadelphia, Blue-headed, and Warbling Vireos. The Red-eyed Vireo is a familiar breeder across most of the continent, with its song being an obvious indicator of its presence, often persisting into midday when most other bird activity has ground to a halt. “Where are you? Here I am. Where are you? Here I am.”; the first phrase is ascending in pitch and the second is descending. As you would expect it must, the Red-eyed Vireo has a striking dark red eye, but this is usually difficult to see given that they’re often high in the trees.
Other vireos vocalize during migration, often resulting in baffled observers, as several sound quite similar. Given it’s most familiar, I’ll use Red-eyed Vireo as the baseline. On a good migration day, Philadelphia Vireo might be heard briefly singing. This species can sound very much like Red-eyed, but with a song that is usually slower, as if it had a slight southern drawl. The Philadelphia Vireo is fleeting in the Mississippi Flyway, hightailing it to northern deciduous forests, where it becomes a good example of niche partitioning when its territories overlap with Red-eyed Vireo (Moskoff and Robinson 2020).
Another sound-alike that’s common in the flyway is Blue-headed Vireo. These colorful little vireos have a slurred song that sounds like a Red-eyed Vireo got into the good backwoods hooch somewhere down in the Mississippi swamps. I got good looks at one this spring bashing a caterpillar on a branch before swallowing it whole. What a little brawler. Blue-headed Vireos are the most striking of three closest relatives, others being Cassin’s and Plumbeous Vireos. Once collectively known as Solitary Vireo, they were split into Blue-headed of the east, Cassin’s of the west, and Plumbeous of the southwest late last century. Like Philadelphia Vireo, the Blue-headed doesn’t linger to breed in the flyway, preferring to migrate far north to spruce-fir forest. In winter, Blue-headeds average further north, occurring well inland along the Gulf and Southeast Coasts (Morton and James 2020).
A good set of flycatchers also move up and down the Flyway Highway, a few of which I was able to observe on my productive day. Volumes could be written on flycatchers and the mental trauma that comes from trying to identify them, so I’ll be brief. While there are several obvious species in the flyway, most migrant flycatchers fall into the genus Empidonax, “Empids” for short. In this part of the Mississippi Flyway, there are around nine options, five of them Empids. Empids are some of the most difficult birds to identify by plumage alone and usually require hearing a vocalization. Unlucky for the observer, they often prefer to travel in silence during migration. Great. It’s safe to say probably 30% of the Empids I see during migration get away unidentified, all because of their silence.
Least Flycatchers are one of the most vocal Empids, at least during spring migration. I won’t even get into fall migrating Empids! They’re also one of the smallest and most common members of the whole group. Their simple song, a dry “che-bec”, is diagnostic. Grouped with their telltale vocalization, a defined white eye ring and contrasting white wing bars can be helpful points of identification.
I often hear things like “oh, this is an ABC Flycatcher, just look at all that yellow and the way the wing bars contrast”, or “wow! Look at that eye ring, must be an XYZ Flycatcher!”. Barring a really yellow Yellow-bellied Flycatcher in spring (won’t go there either), plumage coloration and ratio of green to yellow to gray is unreliable on a good day and depends on lighting and individual variation. Contrast of wing bars against the background plumage is also unreliable by itself, but might actually be helpful in narrowing things down to a few options. Though how good are you really at discerning shades of white and gray? Eye ring, or lack thereof is perhaps the most helpful feature in narrowing things down, particularly in the east. West of the Great Plains, birders have their own special issues for the plethora of western Empids and we won’t even talk about the possibility of vagrant species ending up somewhere they’re not supposed to be! Dusky Flycatcher in Virginia anyone? How about Cordilleran Flycatcher in Louisiana? Talk about a nightmare. Ignorance is bliss with Empids.
Acadian Flycatchers are another eye ring-sporting Empid and are common migrants along the Mississippi Flyway. In fact, they even breed in the region, especially in mature deciduous forest. Empid enthusiasts with a discerning eye might say this species appears greener than others, though this can be amplified by light filtering through the green leaves of dense forest. Much better is the aggressive “peet sah!” given readily on breeding territories, and if you’re lucky during migration. Their song sounds as if someone quickly and violently squeezed a dog toy. Acadian Flycatcher nests are really cool and easy to identify if you can find one. Though sort of a weak build overall, the birds adorn the nest with oak tassels.
Empids can be difficult to spot, particularly if they’re not feeling up to talking. You might happen to catch one as it makes a mad dash towards some flying insect, thinking how you can’t believe you missed it perched nearby! But never fear, it’s likely the bird will come right back to the perch it just left to watch for more insects. This exact scenario happened on another particularly good day in the Mississippi Flyway. A large Empid flew just as I spotted it, but came right back and used the same hunting perch for a long time. The Empid had no obvious eye ring and its wing bars blended with the wings. This narrowed the options down to either Alder or Willow Flycatcher. These two are identical in appearance and can’t safely be differentiated without a vocalization. Though this particular Empid was happy to perch at close range, it never said a thing in the time we shared.
Until 1973, Alder and Willow Flycatchers were believed to be a single species (Eisenmann 1973). The Traill’s Flycatcher was first documented by Audubon in the 1820s. It was the only new species he recorded during a stay at Arkansas Post, a bustling trading post at the confluence of the Mississippi and Arkansas Rivers. In his writings, he describes the Traill’s Flycatcher as giving “wheet, wheet” calls, a diagnostic vocalization of the Willow Flycatcher; they also say “fitz-bew” (Sedgwick 2020). Based on Audubon’s description, the birds were probably nesting in grassland of southern Arkansas. Unfortunately, the species has essentially been extirpated from most of its breeding sites in the state. Those that remain are difficult to locate. Its sister species, Alder Flycatcher occasionally gives a “fee-bee-oh” song and breeds much further north, in shrubby wetlands approaching the boreal region (Lowther 2020).
Another significant group of migrants readily observed in the Mississippi Flyway are the thrushes, specifically those in genus Catharus. This genus has twelve species, including five that breed in North America, and a slew of nightingale-thrushes that are resident in Central and South America. Migrant Catharus thrushes can be secretive, not at all like their more common relatives: American Robin and the bluebirds. The dark forests of the Mississippi Delta divulge some of their secrets, but not all of them. Walking through the woods, these thrushes are often such secrets; shadows at the edge of your vision. If you catch one perched, approach carefully and it just might oblige, but more often than not, an approach will send it deeper into the forest.
The Swainson’s Thrush makes up the bulk of Catharus sightings in the region, standing on faded pink legs, brown feathers above, and white below. It’s front is flecked with a field of dark spots; bold near the throat, and more obscure towards the flanks. It also has a bold, tan-colored eye ring and a tan wash to the cheeks. The Swainson’s Thrush is a common sound in a migrant-filled forest, readily giving “wit” calls and singing their haunting flutelike song in a series of ascending notes.
If the Swainson’s Thrush makes up about 80 percent of Catharus in the central Mississippi Flyway, then Gray-cheeked Thrush makes up about 15 percent. They’re less abundant, but usually present on good migration days. Care must be taken when identifying Gray-cheeked and Swainson’s, as the two are shockingly similar. Overall, the browns of a Gray-cheeked Thrush can appear more gray, but that can be difficult to discern under the forest’s canopy. Better is the Gray-cheeked’s lack of tan hue on the cheeks, with no obvious eye ring. Gray-cheekeds also have a subtle stippling of white feathers on the side of their face that lends them their name. They’re also quite vocal, happy to give a zippy “zweer” call, or a flutey song in a series of descending notes. Gray-cheeked Thrushes breed further North than their relatives, not stopping until they reach the taiga. Some breeders range north of the Arctic Circle and even cross the Bering Sea to nest in eastern Siberia (Whitaker et al. 2020)!
With the Swainson’s Thrush’s 80 percent and the Gray-cheeked Thrush’s 15 percent, that leaves us a miniscule 5 percent of Catharus left for seeing a Veery in the region. They’re around, but won’t be recorded on every migration outing. This thrush stands out from its congeners by being very orange, rather than shades of brown, and lacking bold, dark speckling on the throat and breast. I’ve rarely heard them during migration in the region, but that’s likely because there are relatively few of them. Their calls are similar to Gray-cheeked, but deeper and full-bodied. Like most of their relatives, the Veery’s song is flutey, too. Similar to Gray-cheeked, but less nuanced and more insistent.
I can’t end without at least giving a shoutout to a small smattering of other favorite migrants. One of the most jaw-dropping is the Scarlet Tanager. This tanager is quite the long distance traveler, with southernmost wintering populations in Bolivia and northernmost breeders in southeastern Canada. Scarlet Tanagers are common along the Mississippi Flyway Highway, as they use the route to infiltrate the eastern deciduous forest. Males are quintessential ruby red with black wings. Though I tend to see them less, as it’s the males who mark territory in a more obvious manner, females are striking too: yellow with dark wings. Their range has near total overlap with the more abundant Summer Tanager. The two have songs that sound quite similar, but thankfully they commonly make different calls. Compare the Scarlet’s throaty “chick-burr”, to the Summer’s “pit-ti-tuck”.
Not only do Scarlet Tanagers make the list because of their beauty, but over the years I’ve been fascinated by a few individuals I’ve seen with aberrant plumage. I don’t know how common it is range-wide, but several times in my region I’ve observed male Scarlet Tanagers that are bright orange when they should be red. You never know what you’re going to get with birds!
Up the tree with Scarlet Tanagers are Yellow-billed Cuckoos, one of the largest songbirds breeding in the eastern deciduous forest. Though I should note, they aren’t even close to the largest member of their family, Channel-billed Cuckoo, which clocks in at up to 11 times heavier than our “little” bird! Cuckoos overall are known for being brood parasites, meaning they lay their eggs in the nests of other birds. However, neither of our two main North American cuckoos—Yellow-billed and Black-billed—as actively parasitize other nests as do some of their relatives. In fact, both most commonly build their own nests and care for their own young. If any eggs get laid in another bird’s nest, it’s likely to be another cuckoo and only during years of food abundance (Hughes 2020). Here at least, you probably won’t see a tiny warbler raising a massive cuckoo baby, as you might in some of the European relatives. Fitting perfectly with the family stereotype, Yellow-billed Cuckoos are difficult to spot unless you hear them first; often choosing to perch for long periods in one place. When you do hear them, a deep and loud “ka, ka, ka, ka, kow, kow, kow, kow, kow” is unmistakable.
Is it a cliché to end with Ruby-throated Hummingbird? I don’t care. I love hummingbirds and while our diversity is incredibly low here in eastern North America (one species), I can still dream of the times I’ve seen 20 species on a good day in the tropics. Hummingbirds are something for us Americans (as in all of the “Americas”) to hold onto. Nobody else in the world has them! They’re unique to our two continents and associated islands. They also have high endemism, which means there are a lot of species that occur in very geographically small areas; island endemics in the Caribbean, for example. Hummingbirds are such intriguing little creatures. How they don’t just explode from their high energy is nothing short of a miracle, as is their ability to migrate thousands of miles. Our Ruby-throated Hummer is one of the most widespread, breeding throughout eastern North America. It’s safe to say I probably see hundreds in a season, but each time I catch a glimpse of a male’s crimson gorget, or the green-blue iridescence at the base of a female’s tail, I find myself drawing a quick breath. Ruby-throated Hummers aren’t really picky when it comes to habitat preferences, occurring in a range of places from suburban thickets to remote woodland. It doesn’t take much of a twig for them to build a walnut-sized nest and raise young.
Though spring migration has come and gone, I’m still haunted by the birds that took the dangerous journey, whether innate or learned; both methods occur. Getting to watch birds year-round has long been a source of respite for me, but no time more-so than spring migration. Maybe it’s the intrigue of rarity, or the hope of new life. Regardless, I’m drawn to this time of year. Though the passage of migrants may be through for now, they’re all around us. I may not get to enjoy some of the boreal-breeders I get attached to during migration, but I’m awestruck by the breeding residents in my own region. It will get hot—it hasn’t yet in Arkansas—and it will get buggy, greatly reducing some of our desires to go out, but I encourage you to stay the course. The migrants are among us for a short while and can’t be tied down, eternally drawn by innate desire, magnetic fields, day length, what-have-you. Enjoy the mutual and miraculous time we can share together.
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