Ian Stewart

These are the opening words of the poem ‘To a mouse’, written by the legendary haggis-eating Scottish poet Robert Burns in 1785 (which also contains the famous line oft-paraphrased as ‘The best-laid schemes of mice and men go often askew’). Although this is an apt description of mice it is also used to refer to all manner of small, obscure and reclusive animals and feather mites fit perfectly into this category.

Most people have never heard of feather mites which is hardly surprising. They are tiny brown arthropods which spend most of their lives flattened along the vanes of bird wing feathers where they were assumed to scavenge on feather debris and oily secretions and perhaps even rasp away at the feathers themselves. However, a remarkable study published last summer (Doña et al. 2018) examined the contents of mites’ stomachs using high-power microscopy and DNA analysis and found that their main food was fungi, and perhaps also bacteria and oil produced from the birds’ preen gland. Whether this means feather mites harm their hosts or are simply commensal remains to be seen.

Birds are assumed to acquire feather mites through physical contact with their parents while they are still in the nest, although they could also pick up mites from bumping into other birds at feeders or sharing the same dust bathing sites. Mites are quite easy to see if you are holding open a bird’s wing although with the naked eye they just look like a cluster of small dots (shown below).

We gained a whole new appreciation for these creatures when Shannon Modla of the University of Delaware kindly photographed some Gray Catbird feather mites under a light microscope. The magnified views show that they are long and thin with two pairs of legs at the front of their body and two pairs at the back (image below). The darker mites on the left and below are probably older mites with a hardened exoskeleton while the paler one on the right is probably a younger mite that has just molted.

Shannon was then able to view them under a powerful electron microscope and got some incredible images of their head as well as an egg (below).

To try to gain some insights into the biology of these enigmatic creatures we have been scoring the number of feather mites present on birds handled during the Delaware Nature Society’s Bird Banding project. Our simple questions were which bird species are most likely to have mites and whether the number of birds with mites varies according to the time of year.

Our first finding was that feather mites are quite common. We examined 448 birds belonging to 48 species and found that almost half of them (203 birds from 37 species) had mites on at least one of their wing feathers. We also found the proportion of birds with mites varies a lot between species. Over 75% of the Slate-colored Juncos, House Finches and Downy Woodpeckers that we examined had feather mites yet fewer than 15% of Ruby-crowned Kinglets, Common Yellowthroats or House Wrens had them. We also found that the proportion of birds with mites stayed quite consistent across the year with a noticeable peak in May.

This year we will be gathering more data on mites from the birds we band and then try to figure out why some birds are more likely to have mites than others, and why some have lots of mites while others have very few. Is it related to their body size perhaps, or how social they are, or maybe whether their beak is small and pointed enough to preen away the mites? So watch this space for updates on this new and fascinating DNS research project!

DNS has plenty of birding opportunities coming up soon, so sign up and enjoy the outdoors!

The Great Backyard Bird Count ~ Coverdale Farm Preserve

The Great Backyard Bird Coount: Kent County Tour ~ Abbott’s Mill Nature Center

Owls and Other Winter Raptors ~ Ashland Nature Center

 

By Joe Sebastiani, Ashland Nature Center Manager

Delaware Nature Society graduated fourteen “Certified Naturalists” in December, awarding those who successfully completed the year-long Naturalist Certification Series and the associated field journal.  In the past 12 years, over 300 people have taken this class which focuses on gaining a foundation for the study of nature in Delaware.

The Naturalist Certification class visits Teardrop Pond in Blackbird State forest with Jim White, Herpetologist and Delaware Nature Society Director of Land and Biodiversity.

Our graduates this year include: Jen Smyth, Suzanne Blair, Noreen Cambell, Brooke Cherry, Ted Gatanis, Lana Glass, Bea Kaplan, Laurie Linton, Emily Magnani, Christen Majewicz, Diane McGovern, Katie Pollock, Kayla Krenitsky, and Tere Schubert.  Delaware Nature Society congratulates them on their attendance and devotion to completing the field journal!

The first field trip of the year was to Coverdale Farm Preserve to study local mammals.  Register for the 2019 class, which begins on March 21st!  Photo by Noreen Campbell.

Students attend lectures and field trips revolving around 8 topics which include the study of: Mammals, Terrestrial Ecosystems, Reptiles and Amphibians, Birds, Wildflowers, Insects, Trees and Shrubs, and Aquatic Ecosystems.

The 2019 Naturalist Certification Series is ready for registration!  Here is a flyer to review about the class or send to your friends.  If you are a school teacher, by completing the class, you qualify for 60-hours of inservice credit.

A student in the Naturalist Series holds a Northern Pine Snake in the Herpetology lecture. Photo by Jim White

In one year, you will gain experience with tracking mammals, wade into a wetland at night in search of frogs, learn how to compare the ecology of different forests, evaluate stream ecological health, identify trees, shrubs, and wildflowers, understand various insect orders and their role in the environment, and band birds with an ornithologist.  In the process, you’ll make new friends who are interested in the outdoors, botany, wildlife, and the environment.  We hope you can join us for the 2019 Naturalist Certification Series.

In the meantime, here are some “Naturalist Quotes” for you to ponder and enjoy…

“We are all meant to be naturalists, each in his own degree, and it is inexcusable to live in a world so full of the marvels of plant and animal life and to care for none of these things.” ~ Charlotte Mason

“Since we humans have the better brain, isn’t it our responsibility to protect our fellow creatures from, oddly enough, ourselves?” ~ Joy Adamson

“Happy indeed is the naturalist: to him the seasons come round like old friends; to him the birds sing: as he walks along, the flowers stretch out from the hedges, or look up from the ground, and as each year fades away, he looks back on a fresh store of happy memories.” ~ John Lubbock

“Even the lifelong traveler knows but an infinitesimal portion of the Earth’s surface. Those who have written best about the land and its wild inhabitants…have often been stay-at-home naturalists…concentrating their attention and affection on a relatively small area.” ~ Edwin Way Teale

“The clearest way into the Universe is through a forest wilderness.” ~ John Muir

“Delight itself, however, is a weak term to express the feelings of a naturalist.” ~ Charles Darwin

By Jim White: Senior Fellow for Land and Biodiversity

It’s not every day that a new species of animal is found in Delaware. In fact, it is very rare indeed. However, in the summer or 2015 Adam Mitchel, a PhD candidate at the University of Delaware did just that. While collecting insects in a meadow at the Ashland Nature Center for his PhD research project on the effects of invasive alien plants on native insects, Adam found several insect specimens that he could not identify.  After examining them under a microscope in his lab he could only identify them as insects belonging to the Insect Order Thysanoptera commonly called Thrips (both the singular and plural of the noun has an (s). The Order Thysanoptera are minute insects with reduced wings, most species being around 1mm long. All but a few use sucking mouth parts to feed on the stems of plants. Several species are considered pest as they can damage crops and other plants. However, the vast majority of the 6,000 or so species are not pests to humans and are valuable members of the food chain.

This species of Thrips, new to science, was discovered at the Ashland Nature Center by entomologist Adam Mitchel. It has no English common name, but scientifically it is called Konothrips polychaeta.  Photo courtesy of Dr. Mitchel, from Goldarazena et al. (2017).

These tiny insects are not often studied unless they are considered pests and information on the many non-pest species is limited. Lucky for Adam, a professor from Belgium, Dr. Arturo Goldarazena…an authority on Thrips, was visiting the University of Delaware. Adam approached Dr. Goldarazena and asked if he would look at some of the Thrips specimens that he collected.  It did not take long for the professor to realize that he had never seen some of the specimens and declared that Adam might have discovered a new species. Adam agreed to give Dr. Goldarazena the specimens to study back in Belgium.  After an exhausting investigation the new species was described and published in Goldarazena et al. (2017). Its official scientific name is Konothrips polychaeta which loosely translates to “hairy tenacious woodworms”.  At this time, there is no common English name for this new species of Thrips. However, I propose to call it Mitchell’s Thrips.

Andropogon virginicus is the host plant for the newly discovered Thrips. Is the new species found wherever this plant exists??? Photo courtesy of Dr. Mitchel, from Goldarazena et al. (2017).

Finding a new species of animal or plant is a dream for biologists – finding them right under our noses in places like Ashland is even more exciting. Adam found the new species inside the flowers of the broom-sedge, Andropogon virginicus but he believes that Konothrips polychaeta probably feeds and breeds on other grasses and sedges that are abundant in the meadows and marshes at the Ashland Nature Center and beyond. These meadow and marsh habitats have been restored and maintained at several of Delaware Nature Society sites as part of the land and biodiversity management program. The program is dedicated to the conservation and preservation of native species and their habitats.

Dr. Adam Mitchel is a native Delawarean and discovered the new species of Thrips while he was a PhD candidate at the University of Delaware. Photo courtesy of Dr. Mitchel.

Dr. Adam Mitchel is a native Delawarean. He attended St. Marks High School and received his undergraduate degrees at the University of Delaware in Wildlife Conservation, Entomology, Plant Protection, Agriculture and Natural Resources (quad majored), and earned his master’s degree in Fish and Wildlife Management at Montana State University. Adam returned home to University of Delaware to obtain a PHD in Entomology and Wildlife Ecology (concentration: Entomology) at the time of the discovery of the Thrips. Adam is now employed as an Assistant Professor of Entomology at Tarleton State University in Texas.

Reference:

Goldarazena A, Mitchell AB and T. Hance (2017) Konothrips polychaeta sp.n. from Delaware, North America, with a key to the three species of this genus. Zootaxa 4341: 445-450.

Ian Stewart

Happy New Year everyone! If you’re looking for an interesting New Year’s Resolution to get you outdoors, why not seek out and learn about a different tree every month? This is exactly the time of year to spot one of Delaware’s most distinctive trees – the Osage orange.

The Osage orange (Maclura pomifera) is a small to medium-sized deciduous tree native to the Midwest that was originally restricted to a relatively small stretch of Arkansas, Oklahoma and Texas. It is not related to oranges but is in the Mulberry family. The name refers to the bright orange color of its wood and the Osage Nation, a midwestern Native American tribe who used the wood for making bows and apparently supplied early settlers with young plants.

The exposed orange roots of a fallen Osage

Although their original range was small, Osage oranges are now found throughout the lower 48 states after lines of them were planted to provide windbreaks in flat open landscapes such as farmland and isolated homesteads. Lines of Osages were also planted throughout the rest of the country to act as natural thorny fencerows for housing livestock and to delineate driveways and land borders, which is why you most often find Delaware Osages arranged in rows on either side of old country roads. Coverdale Farm Preserve’s famous ‘Avenue of the Osages’ contains no fewer than 72 of these striking trees which were probably planted over a hundred years ago.

Coverdale Farm’s famous ‘Avenue of the Osages’, with fallen fruit in foreground

Gnarly, orange-tinged bark of an Osage

The easiest time of year to identify Osage oranges is in the middle of winter as the bare trees now reveal their distinctive gnarled orange-tinged bark made up of many twisted strips. Some trees still bear their large green fruit, commonly known as ‘monkey brains’, although most of these have now fallen to the ground. Be careful – if they fall on a sidewalk or road they become a slippery hazard to pedestrians and motorists alike!

Osage orange fruit with knobbled surface

Interior of an Osage fruit with some seeds

Osages occur as either male or female trees but only the female trees produce the softball-sized fruit which contains several small seeds within its gooey white flesh. Although the fruit is edible almost all animals ignore it as it is tough, unpalatable and exudes latex, so the clusters of monkey brains simply remain where they fall until they decay. Squirrels do eat the seeds however, which may be why you see so few young trees mixed in with the old ones.

Interestingly, almost every Osage I see has a poison ivy vine growing up its trunk, perhaps because the vine finds it easy to grip onto the furrowed bark. Next time you are a passenger in a car being driven along a country lane, try to spot some rows of Osage oranges. If you spot some it might make you resolve to learn about our local trees in 2019!

This Osage was cut down at Coverdale and has about 90 growth rings, suggesting it was at least 90 years old. The poison ivy vine seen in cross-section on the left of the trunk had 19 growth rings so it had been attached for many years.