Julie Craves

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Nuthatches: A Different Perspective

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Tuesday, February 7th, 2012

I find that the appeal of nuthatches lie in the fact that they do things a bit differently than most other birds: they hunt in the “wrong” direction. They scramble headfirst down a tree trunk with more grace and agility than a woodpecker hitches upwards.

White-breasted Nuthatch, adult male © James M. Wedge/VIREO

Nuthatches don’t forage upside-down to be contrary, of course. They’ve just found a way to exploit resources that might be overlooked by woodpeckers, creepers, and other bark-gleaning species that use a more conventional approach. Of the two dozen plus species of nuthatches in the world, four are found in North America: White-breasted Nuthatch, Red-breasted Nuthatch, Brown-headed Nuthatch, and Pygmy Nuthatch.

Red-breasted Nuthatch, adult male © Claude Nadeau/VIREO

The topsy-turvy lifestyle isn’t the only thing that makes nuthatches engaging and unique. Brown-headed Nuthatches are known to use twigs to pry insects out of crevices; few of our other songbirds are known to use tools. Red-breasted Nuthatches use pine resin to spackle the edges of their nest holes, which is thought to help deter predators. White-breasted Nuthatches sometimes wipe blister beetles around their nest entrances for the same reason – these beetles exude an acidic substance. Clever!

Brown-headed Nuthatch, adult © Brian E. Small/VIREO

Nuthatches aren’t creative vocalists. All have some variation of a nasal, two-noted, “yank-yank” call. Naturalist John Burroughs described the more muted courtship calls of the White-breasted Nuthatch “like the voice of children, plaintive but contented, a soft interrogation in the ear of the sylvan gods.” Lofty admiration for such modest birds.

Pygmy, adult © Brian E. Small/VIREO

As an ornithologist, I have seen and worked with many birds in my lifetime. Of all the exotic and interesting birds I’ve seen, the familiar nuthatches remain my favorites. They simply appeal to the determined, if not rugged, individualist in me.

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My Year in Nature Part 2: Bugs and Plant Edition

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Tuesday, January 10th, 2012
Racket-tailed Emeralds

Racket-tailed Emeralds by Julie Craves

In my quest to have a more pleasant look back at 2011 than I was receiving from the news, I reviewed the surprise discoveries I made in the natural world this year. Since I am an ornithologist, many high points have to do with birds. But like anybody who spends a lot of time in the field, I find other taxa are often in the spotlight.

For instance, for the last decade my husband and I have been compiling a list of county dragonflies and damselflies for our urban southeastern Michigan home county. In the past year, we decided we had likely discovered all the species likely to regularly occur here, having added nearly 50 species to the list. I started writing up a paper. Yet right at summer’s start, we stumbled upon a thriving population of Racket-tailed Emeralds (Dorocordulia libera), many busy working on the next generation, like the pair in the photo. This is a species previously represented in the county only by a literature record from the 1870s. A month later, we were amazed to find a Dragonhunter (Hagenius brevistylus), a new county record and the largest dragonfly in the U.S. – not easily overlooked. Both of these species were in places we had searched many times over the years.

Dragonhunter

Dragonhunter © Sidney W. Dunkle

A bit more prosaic was my discovery of a population of Florida Lettuce (Lactuca floridana) along the trails at work on my urban university campus. This is a state-threatened plant in Michigan. I have walked by the plants I found thousands of times before. Although similar to other Lactucas and sort of non-descript (okay, ugly) when not in bloom, woodland lettuce is tall and easy to see. Was this a very recently established population, or had I somehow missed them on my countless walks?

Florida Lettuce

Florida Lettuce © Jessie M. Harris

Common Checkered-Skipper (Pyrgus communis) reaches its northern range limit in southern Michigan. Over the years they’d occasionally been seen locally and seemed to be becoming more common, but my searches had been fruitless. Happily, 2011 was my year to add this species to my state butterfly list with one in a neighboring county. Shortly thereafter, I got to add it to my home county list…and hometown list…and yard list. I walked outside with my morning cup of coffee to find one right in the front garden.

Common Checkered-skipper

Common Checkered-skipper, Female © Rick Cech

My 2012 bring us all the excellent experience of new discoveries in familiar places!

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My Year in Nature Part 1: Bird Edition

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Wednesday, January 4th, 2012

Barred Owl © Glenn Bartley/VIREO

Year-end wrap-ups are often filled with dreadful news events, odes to the recent dead, and other things you’d just as soon not have to be reminded of. I decided to take a look back and focus on some of my favorite moments of natural history discovery in 2011. I’ll start with my top bird surprises.

I have been a bird bander for over 20 years. Mostly it involves the routine, though important banding of many individuals of common species. One of these is the American Goldfinch; I’ve banded over 5,000 of them. In May I received a report that a goldfinch I’d banded here in southeast Michigan in October 2010 was captured and released by another bander in a rural area in Ontario, about 175 miles northeast of here. That itself was quite interesting. What was more astonishing, though, was in 2008, this same bander at the same place had captured a Blue Jay I had banded here a few months previously! What are the odds of that?

Earlier in the season, my surprise banded bird was, in contrast, a very rare species banded by someone else. In March, a Ross’s Goose was located in a local retention pond, the first record of this species for my town of Dearborn, Michigan and only about the sixth county record. That was cool. Better yet, the goose was banded. I reported the band number to the Bird Banding Lab of the U.S. Geological Survey and discovered this goose had been banded in 2006 north of the Arctic Circle at McTavish Point, Nunavut – 1900 miles from Dearborn. Most goose reports are of birds shot by hunters, making this sighting even more unique.

A final surprise was a call I received this fall from a church adjacent to our university natural area, where my study site is located. They told me a large owl had fallen through a vent and was trapped in their basement. That seemed unlikely to me, and while I can’t possibly respond to all the rescue calls I receive from the public, this time I decided to head over to the church. Indeed, the unfortunate bird was an owl – a Barred Owl, the first record for Dearborn since a single sighting in 1976! The young owl was in good health, and I was able to band and release it within the hour.

Years ago I might have written about my amazing experiences with new birds in Nicaragua and Honduras, two places I visited this year. There’s no denying I loved seeing many remarkable species. These days, however, it seems I appreciate discoveries closer to home even more.

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Witches brooms

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Thursday, December 15th, 2011
Northern Hackberry

Northern Hackberry

Halloween has passed, but with the last of the leaves now fallen from the trees, witches brooms are visible everywhere.

Witches brooms, botanically speaking, are deformities in woody plants which cause an abnormally high number of shoots to sprout from one location. These dense tangles of stems and twigs look like a bird or squirrel nest, or, if one has sufficient imagination the end of a broom.

Witches brooms have multiple causes, none that involve sorcery. Viruses, fungi, and insects, either through their own damage or via introducing micro-organisms are all frequent culprits. Brooms may occur nearly anywhere on a tree, and a single tree might have one broom or many. Witches brooms afflict dozens of plant species, but here in the Midwest I most often see witches brooms on hackberry trees (Celtis occidentalis) and honeysuckle shrubs (Lonicera spp.).

Witches brooms are so common on hackberry that I have had people tell me they’ve thought the weird twig clumps were a normal characteristic of the tree. Despite this ubiquity, the precise cause on this species is not known. Examination of hackberry brooms reveals that most of the time a particular tiny mite and/or a specific powdery mildew fungus are present. Even hackberry trees with multiple brooms remain healthy, so no harm done.

On the other hand, the cause of brooms on honeysuckle shrubs is known: a non-native aphid, Hyadaphis tataricae. Honeysuckle brooms typically occur at the tips of branches, and if the infestation is bad enough, there is the potential to slowly kill the shrub. Since most shrub honeysuckles in North America are also non-native and often invasive, this might not be considered a bad thing. However, many invasive, non-native honeysuckles are resistant to the aphid, and the aphid could attack native honeysuckles. Witches brooms won’t solve our honeysuckle infestations. We may need a little eye of newt for that.

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Be a Sport

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Friday, November 4th, 2011
White Hackberry

White Hackberry

Plants with variegated leaves are usually found in gardens. But spend enough time in the field, and you might run across some unusual examples in the wild.

In the forest at work, there is a Common Hackberry about ten feet tall, and several limbs have beautiful leaves that are mostly white with green speckles. When I first noticed the tree a few years ago it was a few feet shorter and all the limbs had white leaves. The tree seems to be growing a little bit slower than other hackberries, perhaps handicapped by the diminished amount of chlorophyll fueling its growth. Nonetheless, it is persisting.

Variegated Garlic Mustard

Variegated Garlic Mustard

In an open area in the same forest, I once found a single Garlic Mustard plant with some very attractive variegated leaves. Garlic Mustard is biennial, so I knew this plant would be back in the coming years. I did check to see if any more came up in the same area after that, but I’ve never encountered another Garlic Mustard plant like the first. Just as well. I would hate to see unsuspecting visitors collecting and planting seeds of non-native and outrageously invasive species.

While sometimes due to a virus, intercell mutation, or “jumping genes”, variegation in plants usually occurs due to a cell mutation in one of the three layers in the plant’s bud, or meristem. If the mutation prevents the normal production of green chlorophyll, the cells arising from that layer will be white, or sometimes yellow or some other color if other leaf pigments show through. Plants with variegated leaves are often known as “chimeras” or “sports.” They are valued in the nursery trade, of course. Finding them in nature is even more invaluable!

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Shades of Blue

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Tuesday, October 11th, 2011

When you think of fall wildflowers, goldenrods and asters immediately come to mind. Even as those fade in the fields, I set out to look for my favorite late season wildflowers, Fringed Gentians. As noted by the poet William Cullen Bryant in 1832,

Thou waitest late and com’st alone,
When woods are bare and birds are flown,
And frosts and shortening days portend
The aged year is near his end.

-William Cullen Bryant, To the Fringed Gentian

To find Fringed Gentians, you have to go out on the brightest late autumn days, as the flowers only open in direct sun. They grow in damp, open habitats, usually in poor sandy or calcareous soils. This kind of habitat isn’t very common in my urban southeastern Michigan county. While many gentians are perennial, Fringed Gentians are biennial. When I find a spot that has them, the open aspect of the landscape often becomes shaded through rapid succession, handicapping seed germination. The ephemeral nature of their populations just makes discovering these gentians all the more special.

And I admit to being a sucker for the cerulean blue of the flowers that match the crisp October skies under which they bloom. Nearly 20 years ago, I lost one of my brothers on one of these fragile fall days, and often the sight of colorful leaves glowing in a sun hanging low in the sky leaves me feeling pretty bereft. Somehow, finding these rare azure beauties chases away my other blues, reminding me that seasons change, and life moves on.

 

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Frass Baskets

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Tuesday, August 30th, 2011

My research centers around urban ecosystems and invasive species. Typically, this means birds and non-native fruit, but I’ve done a fair amount of insect work and am always on the lookout for intriguing, exotic urban bugs. A few years ago, at a meeting of the Michigan Entomological Society, I saw a presentation about a moth introduced to North America around 2002. It’s been estimated that nearly 100 species of moths have been introduced on this continent from Great Britain alone. This particular moth, the Greenish-Yellow Sitochroa Moth, Sitochroa palealis, is also native to Great Britain, and its range extends to eastern Russia and south into North Africa; there are also records from the Far East.

Although my mind went a little numb listening to the details of the adult moth’s genitalia structure, I perked up when I heard that the larvae have a distinctive lifestyle. They feed on the flowers and seed heads of plants in the Umbelliferae (Apiaceae) family. In North America, the dominant host is Daucus carota, Queen Anne’s Lace, one of the most familiar non-native wildflowers in the U.S. This feeding habit accounts for the insect’s other common name, the Carrot Seed Moth.

The presenter at the meeting told us to look for larvae of Sitochroa palealis in the cup-shaped seed heads of Queen Anne’s Lace, as the moth was established in Michigan, as well as Illinois, Indiana, and Wisconsin. I spent the next two years peering into hundreds of seed heads, to no avail.

Eventually, my interest in finding the caterpillars waned, although I still looked at Queen Anne’s Lace seed heads out of force of habit. Last summer, I was walking through an old brownfield site along the Detroit River when I noticed a pile of frass – insect poop – in a seed head. I peeked inside, and there it was: a fat, speckled Sitochroa palealis larva. In fact, nearly every nearby Queen Anne’s Lace seed head acted as a basket of frass produced by a resident caterpillar. Often the caterpillar was hidden, but the frass was very conspicuous.

I never noticed any Sitochroa palealis adults at that site, but within a month I did photograph a rather boring-looking diurnal moth nectaring on Culver’s Root in my garden. It turned out to be the Carrot Seed Moth. It was quite fresh, and while I didn’t find any larvae in the neighborhood Queen Anne’s Lace, I now know what to look for.

And you do, too. In late summer, look for frass-holding Queen Anne’s Lace seed heads in the upper Midwest. In addition to the four states mentioned above, I’ve seen photos from Iowa, Pennsylvania, and Ontario. The Carrot Seed Moth could be coming to an old field near you!

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Robber Flies

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Thursday, August 18th, 2011

The insect family Asilidae is known as the robber flies: an ordinary name that is nonetheless evocative. Are robber flies masked? Stealthy? Whom or what do they rob?

Worldwide, there about 7,000 species in over 500 genera. The name infers some sort of piratic behavior, but robber flies don’t steal prey from other creatures — they hunt for themselves, and very well. Their usual modus operandi is to take up a position on a twig, leaf, or stone (each type tends to have a preference) and fly out to grab a passing insect. When prey is captured, a robber fly stabs its victim, injects it with a neurotoxin which immobilizes it, followed by enzymes that liquify the prey’s innards, which are then slurped up by the fly.

Most robber flies have a distinctive pointy-faced, large-eyed look that reminds me of the old Spy vs. Spy comics from Mad Magazine. Some are very large – up to 4 centimeters – and have been known to attack hummingbirds, or bite rough human handlers.

Robber flies of the genus Diogmites are called hanging thieves. They often consume their victims while hanging by one or a few of their very long legs, while holding their prey with those legs not so engaged.
Flies of many families mimic bees or wasps, better to fool their prey if they hunt in the open. Lots of robber flies are master mimics, particularly those in the genera Laphria and Mallophora, which are very credible and sometimes beautiful imitators of bumblebees or hornets.

Larvae usually live in soil or decaying wood, mostly feeding on the eggs or larvae of other insects, and overwinter as pupae.
You really don’t sneak up on robber flies, with their excellent eyesight. But many are pretty tolerant so long as you don’t make any fast moves. I’ve even had them ride around on my insect net handle. So next time you encounter one of these predatory flies, feel free to steal a look.

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That’s Mitey Interesting!

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Wednesday, August 3rd, 2011

A couple of years ago, my husband and I set out to see how many species of wasps and bees we could document with photos in our small urban yard. We’re up to nearly 90, which covers all the conspicuous and easy-to-ID stuff. One of the challenges has been to differentiate among all the black and yellow wasps. The yellowjackets and other hornets aren’t too bad, but there are many species of potter and mason wasps in the family Eumeninae that are very similar except for the number or arrangement of yellow spots or stripes on a black body.

A series of good photos from multiple angles often cinches the ID. Occasionally we have to resort to netting an individual, chilling it, and looking at some features under a microscope while consulting detailed keys.

That is how I discovered a remarkable structure found on some bees and wasps, especially the Eumeninae: the acarinarium.

Acarinaria are special structures on the body of bees and wasps that function exclusively to harbor mites. They may be a hollow chamber, a hairless area that is easy for mites to cling to, or a series of pits along the edge of an abdominal segment. In my photo of the potter wasp above, the mites are carried on the thorax.

The mites on the wasp are benign – they are in a non-feeding phase while on board. If the mites are on a male wasp, they transfer to the female when the wasps mate. Potter and mason wasps are not social wasps; each female constructs a separate nest made of mud, in the ground, in wood, or some other cavity. As the female provisions her nest, the mites disembark. There they continue to develop, and once the immature wasp pupates, the adult mites feed on the young wasp. Amazingly, this apparently does not harm the wasp. A new generation of mites hitches a ride out of the nest on the wasp when it emerges.

Evolving modified body parts to accommodate mites makes sense so long as the mites are beneficial. It’s presumed that the mites perform a service in the nest prior to them feeding on the wasp, such as combating fungi, predators, or parasites that might damage wasp eggs or young. Each genus of wasp is associated with a particular genus of mite, so this relationship is very specialized. Yet the precise mechanism of this mutualism is still poorly understood.

Now, do we start a mite list for the yard?

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The Smallest Dragonfly

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Thursday, July 7th, 2011


I know that for an ornithologist, I write a lot about insects. My bird research requires lots of long-term data gathering. On the other hand, the work I have done with insects, especially dragonflies and damselflies, provides frequent episodes of instant gratification. I’m currently working on a paper documenting the dragonflies and damselflies of my urban southeastern Michigan county. Over the last ten years, my husband Darrin and I have discovered nearly three dozen new species for the county, including five state records. Pretty satisfying!

Darrin and I make good partners in this regard. He likes going after the bigger, showy species. His nom de plume on our dragonfly blog, Urban Dragon Hunters, is Stylurus. This is a genus of hanging clubtails, fast flying and high perching dragonflies mostly found along big rivers. I, on the other hand, often spend time “thinking small” and searching for less conspicuous species. This usually means delicate damselflies, but can also include small dragons. Thus, my handle at Urban Dragon Hunters is Nannothemis, the genus of the smallest dragonfly in North America, the Elfin Skimmer (Nannothemis bella).

These little odes are less than an inch long and are found flitting just inches above the ground through vegetation in sphagnum bogs and similar habitats. They are perfect miniatures of their larger relatives in the family Libellulidae, which includes familiar robust species found on nearly any summer pond, such as Twelve-spotted Skimmer or Common Whitetail.

Male and female Elfin Skimmers are highly dimorphic. Some people believe the coloration of the female is meant to mimic a wasp. Males are dull gray, acquiring a bluish appearance as they mature.

Despite their diminutive size, they share their family’s territorial and feisty manner. Elfin Skimmers are the tiny masters of their little domains, where boggy puddles are their oceans, bulrushes are like redwoods, and mosquitoes dare not enter, since they represent entire meals.

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