More Mayslake Insects

by Carl Strang

As we progress into the warm season, more and more insects jump, fly or climb into view. Most of the recent photographic subjects at Mayslake Forest Preserve have been moths or butterflies.

Monarch butterflies have received a lot of attention lately. Here a nearly mature caterpillar nibbles at a common milkweed flower.

Monarch butterflies have received a lot of attention lately. Here a nearly mature caterpillar nibbles at a common milkweed flower.

The beauty of moths is more subtle. This one is called the confused eusarca, a member of the inchworm family.

The beauty of moths is more subtle. This one is called the confused eusarca, a member of the inchworm family.

The prairies and meadows have produced dozens of tiger moths in the genus Haploa. These all seem to belong to two species.

I identify this one as a reversed haploa. A dark line extends from the midpoint of the leading edge of the forewing to the back corner of the wing.

I identify this one as a reversed haploa. A dark line extends from the midpoint of the leading edge of the forewing to the back corner of the wing.

This one appears to be a LeConte’s haploa. Here the dominant line goes out from the tip of the wing.

This one appears to be a LeConte’s haploa. Here the dominant line goes out from the tip of the wing.

Each species is represented by an array of confusing variations on these themes.

It hasn’t been just about moths. Here a Batyle suturalis longhorn beetle visits an ox-eye daisy.

It hasn’t been just about moths. Here a Batyle suturalis longhorn beetle visits an ox-eye daisy.

The most dramatic recent insect observation was this Laphria robber fly, with its prey, a honeybee. Laphria are bumblebee mimics.

The most dramatic recent insect observation was this Laphria robber fly, with its prey, a honeybee. Laphria are bumblebee mimics.

Literature Review: Some Finer Points of Species Interactions

by Carl Strang

This week’s literature focus is on three papers that looked at complex interactions among species.

Ben-Ari M, Inbar M (2013) When Herbivores Eat Predators: Predatory Insects Effectively Avoid Incidental Ingestion by Mammalian Herbivores. PLoS ONE 8(2): e56748. doi:10.1371/journal.pone.0056748 They found that lady beetle adults and larvae of three species responded to the humidity and warmth of mammalian breath by dropping to the ground beneath their aphid plants. The adults dropped instead of flying.

A colony of aphids occupies a goldenrod top. If a deer were to munch that top the aphids would add some protein, but ladybugs preying on the colony might get away.

A colony of aphids occupies a goldenrod top. If a deer were to munch that top the aphids would add some protein, but ladybugs preying on the colony might get away.

Mouillot D, Bellwood DR, Baraloto C, Chave J, Galzin R, et al. (2013) Rare Species Support Vulnerable Functions in High-Diversity Ecosystems. PLoS Biol 11(5): e1001569. doi:10.1371/journal.pbio.1001569 They looked at tropical fish, alpine plants and tropical trees, considering rarity vs. ecosystem function. Rare species often fill ecological roles that are not covered by common species, and so their loss could cause significant ecological damage.

Dunne JA, Lafferty KD, Dobson AP, Hechinger RF, Kuris AM, et al. (2013) Parasites Affect Food Web Structure Primarily through Increased Diversity and Complexity. PLoS Biol 11(6): e1001579. doi:10.1371/journal.pbio.1001579 They compared food web structure with and without parasites, and found that for the most part the parasites’ influence was an increase in community diversity and complexity rather than adding new features to web structure. The exceptions were the incidental consumption of parasites with their hosts by predators, and the odd connections that result when some parasites have more than one host during their life cycle.

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.

Lessons from Travels: Alaska Predators

by Carl Strang

My thesis research back in the early 1970’s focused on glaucous gulls as predators.

Glaucous gulls, like the other gull species, have a very broad diet.

Glaucous gulls, like the other gull species, have a very broad diet.

My host, the U.S. Fish & Wildlife Service, was especially interested in the gulls as predators of goose eggs and goslings.

Goose egg probably consumed by a glaucous gull.

Goose egg probably consumed by a glaucous gull.

I found that coastal gulls were mainly after seafood. They were opportunists that took advantage of exposed nests and broods, but birds were not their main target. In fact, geese often nested within the gull nesting colonies.

A gull stands at its nest while a brant makes clear that they aren’t buddies even if they share a nest pond.

A gull stands at its nest while a brant makes clear that they aren’t buddies even if they share a nest pond.

Inland gulls were more focused on terrestrial prey, but they were widely scattered pairs and so their impact was limited. I spent many hours watching predator activity.

This observation tower built by Pete Mickelson, a previous researcher on the inland site, was one of several observation posts. A raven used the storage box, which was open on one side, as its overnight roost.

This observation tower built by Pete Mickelson, a previous researcher on the inland site, was one of several observation posts. A raven used the storage box, which was open on one side, as its overnight roost.

Even that far north, the number of species of both predators and prey was impressive, and as I watched the predators working the landscape I sensed the turns of the ecological dance they were performing in the summer. Here are some of the major players on the predator side, in addition to the glaucous gulls, in western Alaska.

Parasitic jaegers had a strong interest in shorebirds and waterfowl as prey.

Parasitic jaegers had a strong interest in shorebirds and waterfowl as prey.

The smaller long-tailed jaegers focused more on small rodents, but also fed on the smaller birds.

The smaller long-tailed jaegers focused more on small rodents, but also fed on the smaller birds.

Red foxes could prey on adults of the smaller geese, but ducks, eggs, goslings and rodents were more important to them.

Red foxes could prey on adults of the smaller geese, but ducks, eggs, goslings and rodents were more important to them.

Arctic foxes reminded me of little puppy dogs. I remember them systematically removing and caching goose eggs in the tundra for later consumption.

Arctic foxes reminded me of little puppy dogs. I remember them systematically removing and caching goose eggs in the tundra for later consumption.

The mew gull, a species much smaller than the glaucous gull, seldom showed interest in avian prey, focusing on invertebrates and small fish.

The mew gull, a species much smaller than the glaucous gull, seldom showed interest in avian prey, focusing on invertebrates and small fish.

The lesson was to attend to the predators in any landscape, and it informs me to this day.

Mourning Dove Post Mortem

by Carl Strang

Last week I found a pile of feathers beside the trail at Mayslake Forest Preserve.

The distinctive tail feathers indicated that the prey was a mourning dove.

The distinctive tail feathers indicated that the prey was a mourning dove.

At first I was inclined to think the predator was mammalian. A raptor plucking its dinner from an elevated perch would scatter the feathers more widely. The feathers were pulled cleanly, however, and without the tooth marks and salivary gumming up of barbs that might accompany a mammal’s work. Furthermore, there was no blood and there were no bones.

One of the quill feathers showed a distinct cut or crease across the barbs.

One of the quill feathers showed a distinct cut or crease across the barbs.

That kind of mark could have been made by the edge of a raptor’s bill, biting the feather to pull it out. I compared the crease to a great horned owl skull, and the match was perfect, furthermore pointing precisely to a less visible mark made closer to the feather’s attachment point by the other bill edge. The location of the feather pile was well within the woods, and not far from a favorite daytime roost of the local owls. It appears that after removing a bunch of feathers, the owl carried its meal to a more secure, elevated location.

Lessons from Travels: Adak Eagles

by Carl Strang

One side study in my Ph.D. thesis work with glaucous gulls in Alaska was an exploration of apparent hybridization with another gull species. I’ll get into that another time. For now, the point is that it gave me the opportunity to spend some time on Adak Island in the middle of the Aleutian chain, where I studied glaucous-winged gulls. I was hosted by the naval base there, which was a legacy of WWII. One of the unusual sights in early spring on Adak was a concentration of bald eagles.

In summer the eagles scattered around the Adak coast, but in winter they congregated at the naval base.

What drew them? The dump.

Here an immature eagle picks at a bit of garbage.

At the time, bald eagles in most of the continent still were at a low point thanks to metabolites of DDT which interfered with eggshell production, and so it was truly novel to see so many in one place. Now that the eagles have recovered, we find concentrations of them along rivers in Illinois in winter, where they feed mainly on fish. The ones on Adak were not exclusively garbage-eaters, however. One day I watched a young eagle as it flushed a flock of roosting gulls (likewise concentrated by the dump), chasing one down in mid-air and killing it.

It brought its prey to shore, where it was joined by an adult.

The adult chased the youngster off its catch, and ate the gull. As I will elaborate tomorrow, the naval base since has closed, and the eagles no doubt are making do without those easy winter pickings.

Literature Review: Earliest Animal Life

by Carl Strang

Yesterday’s post featured reef communities of today and the distant past. Today I want to stay in those early times when multicellular animals first entered the fossil record. The first paper was published about a year ago in Science.

Erwin, Douglas H., et al. 2011. The Cambrian conundrum: early divergence and later ecological success in the early history of animals. Science 334:1091-1097.

They used a variety of improved molecular clock, fossil, developmental and ecological data to look at animal diversification which seemed to appear full blown in the Cambrian Period at the beginning of the Paleozoic Era. They concluded “that the major animal clades diverged many tens of millions of years before their first appearance in the fossil record,” with basic developmental toolkits appearing in the Cryogenian Period of the Proterozoic Eon (before that eon’s final, Ediacaran Period). The researchers place the split between sponges and other animals in the mid-Cryogenian about 750 million years ago (mya), with Cnidaria (the group that today includes corals, sea anemones and jellyfish) appearing around 700mya, Chordates around the beginning of the Ediacaran, arthropods around the beginning of the Cambrian, and vertebrates in the late Cambrian. Only some of the well-known fossil Ediacaran organisms can be tentatively tied to the animals of today: some possible sponges, mollusks and placozoa. Otherwise, there are only some suggestive trace fossils (e.g., burrows) from the Ediacaran Period that point to metazoan animals. Erwin’s group attributes the apparent “Cambrian explosion” to the evolution of predation, which applied selective pressure resulting in protective shells and other structures that were better preserved in the fossil record.

Barnacles, arthropods that protect themselves with shells.

Another paper, published earlier this year, added another dimension to the story.

Shanan E. Peters, Robert R. Gaines. Formation of the ‘Great Unconformity’ as a trigger for the Cambrian explosion. Nature, 2012; 484 (7394): 363 DOI: 10.1038/nature10969

As reported in a ScienceDaily article. This study focused on the largest gap in the geologic record worldwide, dividing the Proterozoic Eon from the Cambrian Period which opened the Paleozoic Era, and tied that unconformity to a hypothesis about the sudden appearance of diverse life forms and skeletal features. They suggest that the erosion of preCambrian rock that produced the unconformity had the effect of adding concentrations of dissolved minerals to the sea. The resulting altered chemistry of their environment posed a challenge to living forms. The first production of biominerals thus was to remove those substances from organisms’ tissues. Having evolved that capability, animals then had the foundation for evolution of various uses of those minerals in shells and other skeletal formations, teeth, etc.

Thus the geological processes that grew the early continents, and lifted them above the sea, altered the chemistry of that sea. There were no land plants to resist the erosion. The marine animals, in addressing the challenge posed by the increased mineral content, found ways to create hard parts which in some were useful tools for predation, and in others were armor to resist that predation. The visible result of this biological arms race was the “Cambrian explosion,” in which multicellular life forms suddenly began to appear as fossils. But now evidence exists that points to those animals’ ancestors having diversified much much earlier.

Dragonfly Notes

by Carl Strang

Today I want to share some observations of dragonflies from last week. It was, as you know, stinking hot all week, reaching 100F on Thursday and Friday. In the late morning on Friday, with the temperature in the mid-90’s, I was taking an early lunchtime walk along the May’s Lake shore. I noticed that the black saddlebags all were flying in an unusual position.

All had this peculiar abdomen dip, which they held as they flew.

It was reminiscent of the obelisk posture, shown by a perched dragonfly pointing its abdomen up at the sun. This is thought to reduce overheating in the insect’s body. I wonder if the saddlebags, in that extreme heat, likewise were reducing the size of their abdomens’ exposure profile. They were among the largest dragonflies I saw that day, which further might increase their danger of overheating.

Earlier in the week I was walking through one of Mayslake Forest Preserve’s prairies when I saw a common pondhawk carrying a relatively large prey to a perch.

It had caught a smaller dragonfly, a female eastern amberwing.

Female and immature male pondhawks have such perfect grass-green camouflage that they are practically invisible when perched in prairies and meadows. They are sit-and-wait predators, zooming out to catch passing insects. This predation on another dragonfly is not so rare. I once saw one catch a calico pennant, a dragonfly larger than the amberwing.

Lessons from Travels: Kookaburras

by Carl Strang

In northeast Illinois we have one kind of kingfisher. The belted kingfisher belongs to a large and diverse group of birds, however, and especially in the tropics one can find several species in the same area, usually forming a guild with a range of body sizes. Most kingfishers dive into the water to catch fish. In Australia live some species that are quite different.

Laughing kookaburra

The laughing kookaburra is a kingfisher high on the list of birds that visiting biologists and birders want to see. I also hoped to get a good recording of their famous odd, laughing choruses. In that second goal I was frustrated. At least in the season I was there, they were not very vocal. They had dawn choruses, and I enjoyed hearing them, but I was never close enough to get a good recording. On rare occasions when one called during the day, it finished before I could get out the digital recorder and microphone.

Once I watched a laughing kookaburra hunting. It was perched and looking down, like any other kingfisher, but beneath it was not water, but rather a brush tangle. I saw it dive into the brush and return to its perch a couple of times, but it was not successful. They reportedly eat insects and small reptiles.

It turns out there are two species of kookaburras, and I saw the second a few times as I explored the north central region of Australia.

Blue-winged kookaburra

The blue-winged kookaburra is a little smaller than the laughing, and appears to be more a species of moist forest areas. Its voice has a similar quality, but it calls in a different, less distinctive pattern.

Experiencing the diversity of related forms in other parts of the world is valuable in breaking down conceptual walls and assumptions. Kingfishers can hunt on land. So, what does the kookaburras’ job in northeast Illinois? We have few reptiles and large insects, so a kookaburra probably could not succeed. Generalists like crows, and raptors including hawks, owls and falcons (all of which also have Australian relatives), cover the tiny bit of ecological ground that a kookaburra would take in our part of the world.

Red-tailed Hawk Species Dossier

by Carl Strang

I have heard reports that red-tailed hawks are starting to carry sticks, and March is the month when they begin to nest in DuPage County, so today I am sharing my species dossier on that raptor. As usual, the rule is that the dossier is limited to what I have observed personally rather than second-hand reports or through the literature.

Hawk, Red-tailed

Red-tailed hawk

This hawk is common in the eastern U.S. They nest in treetops in woodlots, sometimes on utility poles, and forage over nearby fields, soaring, or perching on trees or poles. Unless winter weather is severe, they remain all year round.

28MR87. Hawk carried a snake by the head, body dangling beneath, to treetop.

16JA88. McDowell. A great horned owl flew to a tree on the west bank of the river, just north of where trees thin to a thread of willows, and where a housing development comes down to the river. There’s a top-blown tree nearby, also several large oaks. Then crows began raising a ruckus nearby in another direction, as though pestering a great horned owl. From that direction a red-tailed hawk soared, but they paid it no heed. It circled an adjacent riparian strip, but when the owl finally broke and flew with a flock of 10 crows in pursuit, the hawk fell in between, and also began to chase the owl. Once it got above the owl and swooped at it, brushing the owl’s back with its feet, but about then the crows caught up and chased both raptors down toward where I had seen the first owl perched, now out of my sight.

1MY88. Call a wheezing “preeyarrrr.”

7FE89. A red-tail “visited” Willowbrook’s outdoor animal exhibit. The captive red-tails called, caged crows gave short, uninflected (flat) caws with somewhat sharp beginnings but open ends. These were fairly rapid, but not chattering, and not clearly strung together.

Soaring red-tails usually seem to be patrolling territory rather than hunting.

12JA92. Hidden Lake Forest Preserve. A soaring red-tail gave the k-yer call, over woods. Moments later a second passed over, going in the same direction. Is that call given only when another hawk is in sight?

2DE95. West DuPage Woods. A red-tail called frequently. After 10 minutes I saw a second one, also flying. It seems likely that if one calls, another is in its view.

27JA97. Morning. Snow fairly deep. A red-tail flew over the College of DuPage parking lot with something in its talons, pursued by half a dozen crows. The hawk perched on a flat-topped, wooden light pole, and began plucking its prey while crows sporadically left nearby perches and swooped at it. After 10-15 minutes the hawk flew away, and I checked the feathers, which were scattered in singles and small clumps over a 20×30-foot area: mourning dove. The crow calls resembled the ones they use in owl mobbing, but there were fewer birds and the mobbing was less sustained.

Red-tail fledgling at Mayslake, July 2011.

9DE99. Crows pursued a red-tailed hawk in the northeast part of Willowbrook preserve.

18JL00. Willowbrook. In the early afternoon, a Cooper’s hawk soared low above the marsh and areas east and west of it, while 3 red‑tails soared high. One of the visiting red‑tails called once, but the Cooper’s, which has been resident all summer, called repeatedly.

22AU04. Canadian side of Lake Superior. On a driving journey around the lake I passed through an area where there had been a big fire, and saw there both the first kestrel and the first red-tail of the trip, showing them to be associated with relatively early successional, extensive areas in this part of the northern forest.

20NO09. Mayslake. A pair of adult red-tails circled the west end of the savanna calling frequently, and a third call was coming from within the canopy. Eventually one of the adults flushed out a young red-tail, perched in one of the oaks, and it flew low out of the savanna and south across the lake. This could be the same bird that was perched near the dog parking lot yesterday. Clearly this was a defense of winter territory by the pair. It was not clear whether the young bird called, or whether that was mimicry by a blue jay that was nearby. Last winter a pair of adult red-tails stayed around Mayslake the entire season. They seemed to be investigating nesting possibilities, but ultimately vanished for the summer.

The 2010 red-tail nest at Mayslake

16MR10. A red-tail pair is building a nest at Mayslake, in the stream corridor woods adjacent to the parking lot marsh. They carried small sticks in their beaks while flying. (This pair fledged one youngster from this nest, and it stayed around the mansion grounds area for some weeks in the summer, calling loudly and frequently. In 2011 they did not nest on the preserve; their 2010 nest was used by the great horned owl pair. Apparently they nested nearby, however, as a fledgling came onto the preserve occasionally in the summer, and displayed the same loud calling behavior. The pair has been present on the preserve through February of this year, and I will be watching for nesting activity.)

The noisy fledgling from 2010

19JA11. Mayslake. A red-tail flushed from one of the trees near the chapel was carrying a dead gray squirrel and accompanied by its mate. They flew toward the S stream corridor.

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