Beginning of June in Eberwhite Woods

New Species Appearing in EWW

Virginia waterleaf, common black snakeroot, crown-tipped coral fungus (photos by Jenny Jacobs)

Attack of the Gypsy Moths!!!

Interestingly, the female adult moths are white and flightless, while the males are brown and fly to females by following her scent (called a pheromone) that she releases to attract them. The adults are nocturnal, which means they are active at night. After mating, the female will release an egg mass of approximately 75-1000 eggs often on a tree trunk or other hard surface. When walking through Eberwhite Woods, one may occasionally find egg masses on tree trunks. The egg masses are covered by peach colored hairs, taken from the female adult's abdomen, and the hairs help protect the eggs from predators, parasites and winter conditions. The adult moths die after reproducing and the eggs survive over winter where the life cycle resumes the following spring.

The first major outbreak in Michigan was in 1986 and there have been subsequent population booms since, resulting in major defoliation and die-off events in various forested locations. Fortunately, it is thought that the intensity of these gypsy moth booms has decreased over time since the first outbreak. Many of the dead oak trees on the ground in EWW were killed by gypsy moths in 1999, and elementary students from the Eberwhite Woods forestry club counted 76 dead oaks - here is a link to an article about this die-off. There have been various attempts to control gypsy moth caterpillars and one soil-borne fungus from Japan was discovered to kill gypsy moth caterpillars. This fungal pathogen was released in Michigan in 1991 and began to naturally control gypsy moth caterpillars after a few years. This fungus did a good job of keeping gypsy moth populations in check until droughts occurred in 2007 and 2012. And we are likely observing many gypsy moth caterpillars again this spring because of the droughts that occurred in Michigan in 2016 and 2017. Hopefully, with the nice spring rains of 2018, the fungus will thrive and the gypsy moth caterpillars will not.

Right now, in Eberwhite Woods and the surrounding forest of Eberwhite Elementary, many hairy caterpillars can be observed dangling on silk lines from trees, feeding on leaves in trees, crawling on the ground, crawling on buildings near a forest, or even crawling on you! The caterpillars are pretty, but they are unfortunately an unwanted pest as they are caterpillars of the gypsy moth, Lymantria dispar, one of the most destructive pests of northeastern hardwood forests. The caterpillars feed on over 500 species of trees, shrubs and plants, and are considered one of the most destructive pests in the world!

In the Eberwhite Woods area, we are observing young caterpillars dispersing to look for food, after hatching from their egg masses. Some dangle on silken ropes to catch the wind and disperse to new leaves. Once they find a good feeding area, they will eat voraciously and grow rapidly, molting a number of times over the summer to accommodate their increasing size. When the caterpillars are young, they primarily feed on leaves during the day. They then switch their behavior to feed at night and climb lower down a tree or plant to shelter during the day. After molting 5-6 times, usually in mid-June through early July, they will find a protected area and pupate for 1-2 weeks, then emerge as adults.

Gypsy moths are native to Europe and Asia and were brought to the US in the mid-1800’s. They are now found in New England, west to Michigan and south to Virginia. They are also found on the west coast from California to British Columbia. They were originally brought to New England by a French scientist who wanted to breed a silk-spinning caterpillar that was more disease resistant than the domesticated silkworm. The caterpillars escaped into his Massachusetts backyard and have been wreaking havoc on eastern plants and trees ever since. The genus name, Lymantria, means “destroyer” – a good name for this little beast.

Gypsy moths are in the family, Lymantriidae, part of the insect order, Lepidoptera that includes butterflies and moths. The gypsy moths belong to a large group of “tussock moths”, so named because their larval stage (caterpillar stage) has hairy projections or bristles on their bodies. In many species of tussock moths, these hairs and bristles can irritate the skin and leave a rash on some people. Thus, it is best to avoid handling these caterpillars! Many species in this group go through boom and bust population cycles over time which means that during a boom year, the caterpillars can cause massive defoliation in a given area.

gypsy moth (GM) egg masses (stock), GM caterpillar (Jenny Jacobs), female GM with eggs (stock), jumping spider eating GM (Jenny Jacobs)

References

https://www.massaudubon.org/learn/nature-wildlife/insects-arachnids/nuisance-moths/gypsy-moths

https://en.wikipedia.org/wiki/Lymantria_dispar_dispar

http://msue.anr.msu.edu/news/growing_populations_of_gypsy_moth_caterpillars_raise_concern_for_landscapes

Bird Update

The migrants have headed north - the last warbler in the woods was spotted May 25. There are a number of exciting summer birds in the woods now - the indigo bunting and scarlet tanager are still around and easy to spot. For a tougher bird exploration, go look and listen for the yellow-billed cuckoo and the Acadian flycatcher.


Two yellow-billed cuckoos (YBCU) have been hanging out near the Zion meadow and two in Fritz Park. YBCU are listed as in "steep decline" - it would be great if any pairs successfully nest in Eberwhite Woods - a nice reminder of the importance of preserving urban forests. As an aside, YBCU like to feed on gypsy moths, so it is possible that the large number of gypsy moth caterpillars we are seeing this year in EWW are attracting more YBCU to EWW (in addition to the 4 in the woods, an Eberwhite neighbor has 2 more in her backyard).

Here are tips on how to find them from the Cornell Lab or Ornithology (as an anecdote, I have only ever spotted them early in the morning). 
Yellow-billed Cuckoos are fairly easy to hear but hard to spot. In summer, start by looking in areas of deciduous forest for infestations of tent caterpillars, as well as outbreaks of cicadas or other large arthropods. Listen for the species’ distinctive, knocking call, which can be given at any time, night or day. Later in summer, listen more for their dove-like cooing, as they give their knocking call much less frequently. The species is virtually silent by day during migration, so watch for their distinctive long, slim shape and rapid and fluid wingbeats as they cross over open patches below treetop level on their way from one woodlot to another. In fall, areas with fall webworm infestations often support Yellow-billed Cuckoos.

One of Eberwhite's YBCU photo by Karen Coupland

Another species to be on the lookout for is the Acadian flycatcher - they have been spotted recently in EWW. Eberwhite Woods was home to a nesting pair of these last summer to the delight of Ann Arbor's bird community as southeastern Michigan is on the northern edge of their breeding range.  Breeding "on the edge of their range" is important for the health of the overall population as it enhances the fitness of those individuals because they are in a more challenging environment.

Why do Acadian flycatchers like Eberwhite Woods? They are ravine specialists, meaning they like water and steep slopes. The ponds and steep topography in the woods attract the Acadian flycatcher here. Again, like with the YBCU, another great example of the importance of small pockets of preserved natural spaces.

Acadian flycatcher and its range map (notice scarce breeding in SE Michigan) - photos from Cornell Lab of Ornithology

And lastly, the black-capped chickadees have fledged. A pair nested in the nesting box installed by Eberwhite's Science Olympiad birding group. A big thank you to momma chickadee for allowing a large number of Eberwhite students to watch the progress of her nest. Most classes on EWW walks got to see the chickadee eggs and chicks up close. Looking forward to seeing who takes over the box now that these guys are gone!

5 eggs were eventually laid; momma chickadee incubating her eggs; just hatched!; ready to fledge