There's Something in the Air

Autumn is only now truly settling in, but the birds have been on the move for months.  In the previous post, I talked about some of the migrating species I’d seen, and now I’m overdue to discuss even more of them!  Frustratingly, not all of these birds are easy to see.  Some of them—particularly the warblers—are notoriously uncooperative.  The photos I manage to snap of these feathered sprites have an unfortunate tendency to recall Where’s Waldo? illustrations.

Where’s the warbler?

In the case of this picture of an adult male American Redstart, you have to look far over to the right to see the bird, displaying his gorgeous orange-on-black plumage.

Immature male redstart

This photo of an immature male redstart (with yellow-and-gray feathers) is identifiable, but not much else.  These tiny birds repeatedly thwarted my attempts to capture them on camera!  Although redstarts are breeding birds in a few locations in my area, they are much more common in the fall, when they can be expected to be seen in almost any wooded habitat from about September through mid-October.

Tennessee Warbler -- with food!

Tennessee Warbler -- note the facial markings.

Tennessee Warblers are also quite abundant fall migrants.  Their foraging behavior of methodically probing clusters of leaves for insects makes them a little easier to photograph than restarts, which flit around in thickets, catching a lot of their food on the wing.  “Tennessee Warbler” is really a misnomer, since this species nests nowhere near Tennessee; Alexander Wilson, an early ornithologist, just happened to discover it in that state during migration, so the name stuck.  Tennessee Warblers are pretty drab, but they always show pale “eyebrow” markings and white undertail coverts.

Tennessee Warbler -- note the yellow breast and the white undertail coverts.

One of the warblers that arrives in this part of the world in October and stays through the winter, instead of continuing farther south, is the Yellow-rumped Warbler.  These tough little guys increase their consumption of berries—including those of wax myrtle and poison ivy—during the colder months, when insect prey are harder to find. 

Yellow-rumped Warbler

Yellow-rumped Warbler.  The yellow patches on the birds' sides are noticeable even when the yellow rump patches are hidden from view.

Of course, warblers are far from the only birds migrating right now.  Yellow-bellied Sapsuckers (the name that sounds almost too silly to be true) have arrived for the winter, joining the permanent-resident woodpeckers, such as the extremely common Red-bellied and Downy Woodpeckers.  Sapsuckers have bold white wing stripes and a mewling call, which make them fairly easy to identify.  

This Yellow-bellied Sapsucker is a juvenile, which is why it has brownish markings on its head instead of bolder black, white, and red ones.

For the sake of comparison, here’s a Red-bellied Woodpecker (another name that can cause some confusion, since the red on the crown and nape is far more prominent than the few reddish feathers on the belly):

Red-bellied Woodpecker clinging.

And preening.  The red forehead indicates that this bird is a male.

And here’s a Downy Woodpecker, with its spotted wings and white back:

Downy Woodpecker

The red spot on this Downy's head marks it as a male.

Another overwintering migrant is the Red-breasted Nuthatch, a tiny bird that moves south in larger numbers during years in which conifer seed production is low.  This is referred to as irruptive behavior, and is exhibited by many other species, including Purple Finch, Evening Grosbeak, and Pine Siskin.  I was lucky with the bird below; it had apparently just recently arrived, and seemed somewhat disoriented—darting under the roof of the patio and landing on the rocks beside the goldfish pond.  I haven’t seen it since, though, and I wonder if it continued farther south.

Red-breasted Nuthatch

Finally, what about that quintessential image of fall migration: a flock of geese?  The ones in this photo are Greater White-fronted Geese instead of the more familiar Canadas, but, because large numbers of them have been flying through northeast Mississippi since the last week or so of this month, their piping calls piercing the somewhat colder, mid-autumn air, I think they exemplify the mood of the season.

Greater White-fronted Geese at Sam D. Hamilton Noxubee NWR.

This is just a small sampling of the avian life moving through the Southeast.  Every day seems to bring something new and interesting!  There's a lot in the air...

Snapshot of Autumn

There are so many rapid changes in the fall season that it can be hard to keep up with them all: temperatures decreasing; daylight hours steadily shortening; leaves turning yellow, red, orange, and brown; herbaceous plants dying in the fields; birds, butterflies, and dragonflies migrating; animals of all sorts fattening up; etc.  Taking photographs of nature helps me to track some of these ecosystem-level changes and cycles.  In the neighborhood, many of the wildflowers, including giant ironweed (Vernonia gigantea), a gorgeous native plant, have gone to seed.  

 

giant ironweed with seeds

 In August, these ironweed plants looked like this:

ironweed in August

However, as you can see in both the top photo and the one below, some of the ironweed is still flowering.  This species blooms through the late summer and into the fall.  Its flowers and leaves provide food for insects, and the seeds attract several species of birds.

September ironweed blossoms

Not all of the wildflowers are past their peak.  The goldenrod (which is probably the tall goldenrod, Solidago altissima), growing among the greenery of the woodland edges, has such vivid yellow flowers that it almost seems to glow.  These autumnal plants will probably continue to bloom for at least another month.

goldenrod

The toll that the long season has taken on some of the insects and spiders in the area can be clearly seen.  A common wood-nymph butterfly, a species typically found around shaded forest edges, looks a little the worse for wear.  The damage to its wings is, in all likelihood, the result of a few narrow escapes from birds.

common wood-nymph

One of the many orb-weaver spiders hanging around in the mid-level vegetation is missing legs: two of them seem to be entirely gone, and about half of a third one has also been amputated.  I don’t know whether this damage is from a bird or from something else, but, despite its disability, the arachnid is apparently still managing to eke out a living.

orb-weaver

Even though I don’t know for certain what caused the spider’s injuries, it’s fun to speculate.  Who knows what the culprit might have been?  While a lot of the birds around here feed on seeds and fruits, many more are either partly or exclusively insectivorous—or, since spiders aren’t insects, maybe the more accurate term would be invertivorous (invertebrate-eating).  Anyway, Red-bellied Woodpeckers certainly could be fierce and daring enough to have done it, from what I’ve observed.  I doubt that I’ll ever forget the afternoon at Noxubee National Wildlife Refuge, over a decade ago, when I saw a Red-bellied Woodpecker and a Northern Cardinal zipping through the woods in hungry pursuit of a Luna moth.  Woodpeckers might not seem like the most agile of birds, but I can attest that this Red-bellied was quite maneuverable!  I never saw what became of the Luna moth, but maybe it managed to evade the predators.  

A much less hurried—for now, at least—Red-bellied Woodpecker clings to a lichen-covered branch.  No need to chase moths or nab giant spiders—there must be plenty of food to discover beneath the tree bark.

Red-bellied Woodpecker on branch

Eastern Bluebirds patrol the grassy areas under the power lines, hunting for insects.  Their large, dark eyes and “open” faces give bluebirds an appearance of inquisitiveness.  That may not be entirely a fanciful notion, though, since bluebirds are great at investigating every inch of their environment for food and nesting places.  Any crack, crevice, or hole of sufficient size in a tree, box, or fencepost might serve as a suitable bluebird nest spot, and all sorts of arthropods and fruits make up the species’ diet.

Eastern Bluebird

A short, squeaky sound that recalls the noise made by sneakers on a gym floor alerts me to the arrival of a Rose-breasted Grosbeak.  Then another one flies in, landing very close to the first.  It’s the peak migration time for this species, and these two individuals seem to be merely stopping over for a brief spell.  They remain in the tops of the trees along the creek run for only a few minutes before flying away.

The first of the grosbeaks lands.

Two grosbeaks -- the earlier bird is on the right.

The lower photo provides an interesting comparison between the two individuals.  The bird at the right is definitely a male, and at least two years old, given that it has bold black-and-white wings, extensive dark feathering on the head, and a very distinct breast patch.  However, I’m not so certain about the bird on the left.  It’s either a female or a hatching-year male.  In the spring and summer, older male Rose-breasted Grosbeaks have entirely black heads and bright rose-pink breast patches.  The McGill Bird Observatory does an excellent job of describing the variation in these birds’ plumages (http://www.migrationresearch.org/mbo/id/rbgr.html#ahymb), and their website is one of the sources I’ve perused in my attempts to figure out the age and sex of birds that I’ve seen.  As I’ve learned over the years, though, ageing and sexing birds isn’t always possible in the field.  Obviously, birds that don’t display sexual dimorphism, such as Northern Mockingbirds, can’t be definitively sexed in the field under most circumstances (including when they are singing, apparently, since both males and females participate in that activity), but there are more sexually dimorphic species than you might think that can nevertheless befuddle observers.

Speaking of mockingbirds, both they and their close relatives, Brown Thrashers, are pretty vocal and active this time of year.  Unlike the mockingbirds, the thrashers aren’t singing right now (in the southeastern part of their range, they typically sing from March to May—and, in case you’re wondering, the females apparently do not sing), but they make their loud chak! calls on a regular basis as they forage in the dense thickets.  

 

Northern Mockingbird

Brown Thrasher

Both of these species, along with bluebirds, woodpeckers, and many others, will remain in this area through the winter.  Certain other birds, such as the Rose-breasted Grosbeak, show up here for only a very short time.  It’s the transitory nature of the season that can make it so simultaneously frustrating and exciting!

Lepidopterans

As much as I initially resisted the idea, the most appropriate topic for me to choose for this post is insect life.  I know—I wrote about bugs around the same time last year.  But the cyclical patterns in nature have ensured that, once again, late summer has been filled with insects—a boon for the birds, who are presumably filling themselves up in preparation for migration.  Maybe the bird migration will provide material for a few more posts this year.  We’ll see.

I don’t mean to depreciate insects, though.  To be fair, if you’re at all interested in observing birds, chances are that, sooner or later, you will find yourself paying attention to insects.  For example, the presence of tent caterpillars in an area generally prompts me to keep a look out for Yellow-billed Cuckoos, since they are one of the major predators of these rather pestilential and unsightly critters.  (Most other animals can’t deal with all of the hairs on the caterpillars.)

A tent caterpillar shelter

In a more general way, insect ecology is pretty strongly tied to patterns of behavior in birds, to the point that some bird species are declining as a result of many insect species emerging earlier in the season than they used to do.  As it turns out, warmer springtime temperatures caused by human-driven climate change can alter the timing of the life cycles of insects, and quite a number of avian species have a hard time adapting quickly to those changes.  This can be particularly damaging to nesting birds, since many of them rely on new insect broods as a food source for their young.  Fat, juicy, protein-rich caterpillars tend to be especially tempting to nesting birds, and, fortunately, it seems that there are good numbers of them in the neighborhood where I live, along with the adult forms: moths and butterflies, Order Lepidoptera.

Although nonnative plants—which tend to attract very few native insects—dot this landscape, there are still enough native species to appeal to a wide variety of bugs.  Large silkmoths, such as this promethea silkmoth that I found in late July, generally utilize hardwood trees—or, at least, their larval forms do.  Adult silkmoths have only vestigial mouthparts and are unable to feed.  The caterpillars hatch, eat leaves (which, for the promethea silkmoth, may include those of sassafras, tulip-tree, spicebush, or ash) for several months, pupate, emerge as moths sometime in the following summer, breed, and die.  I sometimes find it interesting that I ever manage to see the adult giant silkmoths at all, given how brief their existences are.  Promethea silkmoths are odd in that the males are diurnal, their activity overlapping with that of the nocturnal females only during the early evening.  The moth in my photo was a female, as the pinkish tinge of its wings indicates.  Male promethea silkmoths have very dark wings, apparently in mimicry of the toxic pipevine swallowtail butterfly.

Female promethea silkmoth

As an aside, I actually seldom see pipevine swallowtails in the neighborhood (probably because of a lack of pipevine), but I do frequently find another lepidopteran that mimics them: the red-spotted purple!  Red-spotted purple butterflies are far more closely related to another famous mimic, the viceroy (which resembles the monarch butterfly), than they are to swallowtails.  Apparently, red-spotted purple caterpillars feed mainly on black cherry, willow, and birch, all of which are pretty common in this region.

Red-spotted purple butterfly

Here’s another silkmoth—a male io moth.  The nocturnal io moth, like the promethea moth, is strongly sexually dimorphic.  Female io moths are larger and browner than the canary-colored males.  Although you can’t tell in this photo, the underwings of io moths have enormous owl-eye markings.  This species uses a wide variety of host plants, including cherries, maples, willows, poplars, and elms. 

Male io moth

What about moths other than silkmoths?  Well, one of the most conspicuous species around here is the catalpa sphinx.  The larvae, catalpa worms, feed voraciously on their host plants—no prizes for guessing what THOSE are.  

Catalpa sphinx larvae, or catalpa worms

You might have noticed that catalpa worms look somewhat similar to tomato and tobacco hornworms, with their fleshy, green bodies and spiny “horns.”  They’re all in the same family: tomato and tobacco hornworms turn into five-spotted hawk moths and Carolina sphinx moths, respectively.  The adult catalpa sphinx displays subtler patterning than some other sphinx and hawk moths, but it’s still an attractive animal.

Catalpa sphinx caterpillars strip the trees nearly bare in an astonishingly short amount of time.  This photo was taken on July 27:

Less than a week later, the catalpa tree looked like this:

August 2, 2018

The sphinx larvae clung to the veins of the leaves; they had eaten practically everything else.

The “worms” are gone now, having pupated underground.  It’s possible that they may emerge as adults to lay eggs before the summer is over, but it’s been long enough now that I suspect they will stay dormant until next year, as later broods typically do.  Update: Actually, as it turned out, there was one more brood after the one in August. 

By August 15, the tree was well on the way to recovery -- new leaves were present.

Unlike most species of sphinx moths, bagworm moth larvae remain above the ground to pupate.  You may never have noticed adult bagworm moths, but you’ve probably seen their shaggy cocoons (i.e., their “bags”) hanging from the branches of trees.  Below is a photo of an evergreen bagworm pupa on an eastern red cedar tree.  In my opinion, the life cycle of the bagworm moth is more than a little bit disturbing.  Females pupate but never develop wings, instead remaining in their cocoons as caterpillar-like adults.  They emit pheromones to attract the relatively normal-looking, winged males for mating, and then, after breeding, they die in their cocoons.  The larvae hatch inside the females’ dead bodies and work their way out during the spring and summer. 

Bagworm

Tent caterpillars, so named because they create massive shelters out of their own silk, represent yet another interesting group of lepidopterans: the snout or lappet moths.  As I mentioned earlier, tent caterpillars are frequently viewed as pests.  After all, the larvae form enormous colonies and eat several times a day.  Tree defoliation inevitably occurs, but, to be fair, the caterpillars seldom cause permanent damage.  Given that eastern tent caterpillar moths produce only one brood a year, and that the adults—the moth phase—live for only a short time, I think that we should strive to keep things in perspective.  At any rate, if having tent caterpillars around means that I will see plenty of Yellow-billed Cuckoos, then I can live with that.  As you can see in the pictures below, tent caterpillar colonies have sprung up all over the place this year.

Of course, this is by no means meant to be a comprehensive essay on southeastern lepidopterans!  Far too many species exist for me to even begin to do justice to them, and I mainly just learn about and research them as I encounter them.  If you haven’t given them much attention before, though, maybe you’ll feel inspired to seek some out this year or next.