Burn Aftermath

by Carl Strang

Mayslake Forest Preserve had much of its acreage burned for management purposes last spring, as described earlier. One result, aided by good amounts of seasonal rains, was a very lush, tall growth of prairie vegetation.

Part of one of Mayslake’s prairies on August 12.

Part of one of Mayslake’s prairies on August 12.

What impact did this have on the prairie insects, in particular the singing insects? I expected the species that lay their eggs in the tops of prairie plants would be impacted the most, but those that lay their eggs in the soil would be relatively unharmed. It was clear, though, that despite the unusual completeness of the burn, small patches of prairie here and there were missed by the fire, as were wetland and woodland edges, and there were portions of the preserve not included in the burn plan. These provided a reservoir from which affected species might spread.

My impression through the season was that the numbers of fall field crickets (a species which lays its eggs in the soil) were down from last year, but the numbers don’t bear this out. Counts on the whole in the various habitats are similar between this year and last. Likewise, the 3 species of common ground crickets are so abundant in all habitats that no quantitative comparison seems necessary.

Greenstriped grasshoppers overwinter as nymphs, and so are more vulnerable. If anything, however, their numbers seemed somewhat larger in all habitats, including burned ones.

Greenstriped grasshopper nymph

Greenstriped grasshopper nymph

Unfortunately, confusion about the species identity of meadow-dwelling tree crickets (described in a post earlier this week) prevented my gathering quantitative data last year. I did record numbers this year, though, and attended their locations through the season. It was clear that the earliest singers in this group were concentrated in unburned areas and around the edges of burned areas, where they might have hatched from eggs in the unburned adjacent habitats. As the season progressed, though, these tree crickets (mainly Forbes’s tree crickets) proved to be very mobile, and spilled into the hearts of the burned areas (where the forage no doubt was richer thanks to the burn, and where there was an advantage to escape the competition). Though numbers overall may have been down a little, there were plenty of these tree crickets to ensure a rapid population recovery.

As for meadow katydids, they all to some extent concentrate in wetlands, which were scorched in places but not thoroughly burned. There again appeared to be plenty of survivors to reproduce and fill the habitat.

Perhaps the most interesting observation relevant to this question this year was a big drop in wasps of the genus Sphex. There were a lot of these last year, crowding into the areas where swamp milkweeds were blooming. The great black wasp and great golden digger specialize in capturing katydids to feed their young, and potentially can influence populations significantly. I saw only a very few of those wasps this year. As they overwinter underground, I doubt the fire had anything to do with their absence. Whatever the cause, their departure further assured a successful reproductive season for the katydids of Mayslake.

Great golden digger

Great golden digger

The upshot of all of this is that the extensive spring burns, while they may have had some minor and spotty effects on singing insect populations (and, by extension, other invertebrates), did not devastate any populations as far as I can tell. This was somewhat surprising, but in retrospect it becomes clear that it would take an extraordinarily complete and extensive burn to have a long-term impact. Refugia within and without the burn area seem likely to carry populations through enough to recover from this disturbance.

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Specialist Predators

by Carl Strang

Yesterday I mentioned one hazard that limits the number of katydids that achieve reproductive maturity. Gwynne referred to another danger, this one a group of wasps that specialize on katydids as food for their young. This caught my attention, as two members of genus Sphex have been abundant at Mayslake Forest Preserve in recent years.

The great black wasp is especially common. I have seen as many as 8 at a time visiting swamp milkweed flowers in the south stream corridor prairie.

The great black wasp is especially common. I have seen as many as 8 at a time visiting swamp milkweed flowers in the south stream corridor prairie.

Less abundant, but a consistent presence, great golden diggers likewise catch katydids to feed their young.

Less abundant, but a consistent presence, great golden diggers likewise catch katydids to feed their young.

Each female wasp needs more than one katydid for each egg she lays in her burrow. That can add up to a significant impact on a katydid community. Being aware of such ecological factors enriches our understanding of the local abundance and distribution of singing insects.

Mayslake Update

by Carl Strang

With the onset of winter, things have slowed at Mayslake Forest Preserve. Bird activity has diminished as the migration season winds down.

This sharp-shinned hawk was one of the later migrants to stop by the preserve.

Winter bird activity hasn’t quite settled into a consistent pattern.

A few blue jays continue to hang around, but they may yet move on if the winter turns frigid.

The weather itself has seemed indecisive. The lakes froze over about a week later than they did last year.

May’s Lake had an inch of ice on December 12.

Then we had renewed warmth, and heavy rains that opened the lakes again.

May’s Lake on December 15.

I look forward to expanding my collection of winter botany photos.

Recently I took some pictures of swamp milkweed.

The big push there will need to wait until there is snow on the ground to provide a contrasting backdrop.

Swamp milkweed in winter resembles some of the other milkweeds, but the pods are narrower and more delicate than common milkweed, but wider than those of butterfly weed. There’s also the habitat association.

Snow also will provide for easier tracking, and I’ll renew my acquaintance with the preserve’s mammal activities.

Some Wetland Plants

by Carl Strang

To this point in the season I have included wetland plants with prairie plants in my accounts of species flowering at Mayslake Forest Preserve. This time I’ll feature them separately. It has been a while since the common cattails flowered.

Cattail b

Their seeds are ripening now. Though elderberry can occur in woodlands, at Mayslake this shrub grows mainly in wetlands.

Elderberry 1b

The pink and white flowers of swamp milkweed are my favorites in genus Asclepias.

Swamp milkweed 2b

Spotted Joe Pye weed is a wetland plant that superficially resembles its woodland relative, purple Joe Pye weed.

Spotted joe-pye weed b

A less conspicuous wetland species is the common water horehound.

Common water horehound b

Most buttercups bloom early in the season. An exception is the bristly buttercup.

Bristly buttercup b

Two of the knotweeds recently began to bloom along the stream: Lady’s thumb

Lady's thumb 2b

and smartweed.

Smartweed 1b

Late summer brings hummingbirds, gradually making their way south. Among the flowers that especially appeal to them, being red and tubular in shape, is the cardinal flower.

Cardinal flower 2b

Finally, here is the first of the late season beggar’s ticks group, the bur marigold.

Bur marigold b

And that brings us up to date.

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