Across much of the Midwest and Great Plains of North America, the blooming of eastern pasqueflower is a pleasing indicator that a new growing season has begun. For photographers like me, it also helps break a long fast from showy wildflowers that typically runs from late October through early April each year.
Pasqueflower at The Nature Conservancy’s Niobrara Valley Preserve this week.
Pasqueflower isn’t always the first plant to bloom in a prairie, but it’s right there, and there aren’t many other early spring blossoms with more curb appeal. Actually, saying “it’s right there” is misleading because pasqueflower is not actually present in most of Nebraska’s prairies. Its range extends across the state (or the northern 2/3 of the state, at least) but it’s found very sporadically within that range.
Most of the prairies I know best don’t have pasqueflower, but there’s a really nice population at the Niobrara Valley Preserve. Since first discovering it there nine or ten years ago, I’ve tried hard to find an excuse to travel to NVP each April and then find another excuse to climb the ridge to check on the flowers. This year, the excuse was that the Hubbard Fellows and I were asked to drive up to NVP to help with some prescribed fires. I was happy to oblige!
Because it’s one of the first blossoms available, pasqueflower attracts a lot of invertebrates looking for a meal. A rich diversity of flies visit pasqueflowers at the Niobrara Valley Preserve, along with some of the earliest of the native bees. This year, I didn’t spend a lot of time trying to photograph those little pollinators, but I did manage to capture a shot of one tiny fly before it flew off.
A tiny fly on the tip of a pasqueflower petal.
Flies and bees are great, but the pasqueflower-related insect I really look forward to each year is the oil beetle (Meloe sp.). The very first time I photographed pasqueflower at the Niobrara Valley Preserve, I spotted some of these big bulbous beetles crawling around. I was immediately intrigued, and later found out what they were. That led to some investigation into what was known about their lives and that led to one of my favorite insect ecology stories ever.
As a result, I was excited when Noelle (one of our two Hubbard Fellows this year) found a little cluster of oil beetles when we visited the pasqueflowers this week. I’d told the Fellows about the little creatures as we got close to the flower patch and had asked them to keep an eye out for them. I then proceeded to walk right past the group of beetles Noelle spotted after immediately after I passed them. So much for my reputation as someone with a good eye for finding small creatures.
Oil beetle feeding on pasqueflower petals.
I’ve posted pasqueflower and/or oil beetle photos quite a few times on this blog now. In fact, probably six times, since that’s the number of times I’ve had a successful trip to NVP during the pasqueflower blooming season since I first discovered them. I don’t always find oil beetles on the flowers, but I find them more often than I don’t. It’s also the only time and place I’ve ever seen oil beetles.
Each year, I think I say the same thing, which is that I’ve found no evidence that oil beetles focus particularly on pasqueflowers as a food source, at least relative to other options. So why don’t I see them elsewhere? Despite this year’s failure, I really am pretty good at spotting insects, and oil beetles are pretty large and obvious. It’s odd that I’ve never seen oil beetles in other prairies or on other plant species.
2025 Hubbard Fellows Noelle Schumann (left) and Kojo Baidoo (right) enjoying the show.
The fellows and I enjoyed some quality time with the flowers and beetles on Tuesday morning, before heading back south toward home. Much of that time was spent with heads close to flowers, watching the slow, methodical munching of petals. It was peacefully mesmerizing.
In fact, here’s a short video to show you what I mean. (If the video doesn’t work for you, click on the title of this post to open it online and make the link active.)
If you’re tired of seeing pasqueflower and oil beetle photos here each spring, I guess I apologize for putting you through that particular trauma. On the other hand, no one is forcing you to be here.
For those of you who haven’t left, here are two more!
Oil beetles working to ensure there will be a new generation for me to enjoy next year.Look at the amazing little crook in the antennae of this male.
I’d love to hear if other people see oil beetles on pasqueflower as predictably as I do. I think I’ve only heard from one other person who has seen that. I’ve found no references to an oil beetle/pasqueflower interaction online, but that doesn’t mean it doesn’t exist. Help!
If you live near a pasqueflower population, I hope you get a chance to see them this spring. Even without the oil beetles, they’re sure a great way to kick off the spring.
Habitat heterogeneity is a fun jargon term within the fields of ecology and land stewardship. It’s a good one to know if you’re at a party trying to impress an ecologist. Although, to be honest, if you’re trying to impress an ecologist, going to a party is probably not the best way to start. You’d be better off meeting them “accidentally” on a hiking trail and bending down to closely examine a set of tracks or a fly feeding on a flower. Ecologists are impressed when people notice things in nature.
Regardless of whether you’re trying to impress an ecologist, habitat heterogeneity is an important concept. Most commonly, it is used to describe the variety of habitat conditions available in a particular location. It’s generally good to have numerous habitat types represented across a site that each provide something a little different in terms of food or shelter for animals or growing conditions for plants. That kind of variety supports the habitat needs of a broad diversity of species.
This prairie has at least four different habitat types available, including variation in the height and density of vegetation, as well as what species of plants are blooming.
It’s not hard to imagine why lots of different habitat conditions would lead to a high number of species thriving in a prairie. However, if you really want to impress an ecologist, you’ll also consider the time elements, not just the spatial elements of habitat heterogeneity. In other words, it’s not just important to vary the kinds of available habitat across space, it’s also important for each of those habitat patches to change through time.
Good farmers and gardeners know the value of rotating crops. Rotation can help soil productivity because each crop uses soil resources differently. Shifting the location of crops from year to year also helps reduce impacts from diseases and insect herbivores that can build up over time when their favorite food source is available year after year.
Many of the same concepts apply very well to prairie and other natural land stewardship work. When habitat conditions remain static in a given location, bad things can happen to the inhabitants of that patch. Disease organisms (pathogens), parasites, and herbivores can build up high populations. Predators can learn to be very effective at finding and catching prey. Within plant communities, the plants best adapted to the current conditions will thrive at the expense of others. If those conditions don’t change, the plants less adapted to those will struggle to survive.
Here are two specific examples to illustrate why variation through time matters so much:
Years ago, a wildlife refuge manager told me about a situation he’d encountered early in his career. He was charged with managing wetlands for ducks. Ducks like nesting in dense vegetation, so he was told to make sure all the wetlands in his site had thick cover around them to maximize the number of duck nests. After a few years of this, though, he realized that nesting success was actually very low, even though he was providing the habitat ducks supposedly wanted.
What he thinks happened is this: The consistent dense vegetation allowed the vole population around wetlands to grow. That higher population attracted predators like bull snakes to feed on the voles. Unfortunately, those predators also enjoyed eating duck eggs, which worked out poorly for those ducks.
Bull snakes are just one of many predators that like feeding on both voles and duck eggs.
Regardless of whether the manager’s hypothesis was right or not, when he started varying the habitat structure from year to year, nesting success went up. He managed the site so that each year, some of his wetlands were surrounded by dense cover and others weren’t. Every nesting season, he’d change which wetlands had thick vegetation around them. Even though there was less overall nesting cover each year, ducks did better because nests suffered from lower rates of predation.
The second example comes from my own experience. Canada milkvetch (Astragalus canadensis) can be frustrating to harvest seeds from because the pods are often empty by the time we get to them. Those empty pods are easily identified because of the exit holes left by larvae of a small weevil (Tychius liljebladi) that feed on the seeds and then burrow out of the pod when they’re done. After leaving, the larvae dig into the soil beneath the plant, where they overwinter. The next summer, they emerge as adults and will lay eggs on the flowers in mid-summer to continue their life cycle.
Holes left by weevil larvae usually indicate there’s no point picking seed from a particular patch of Canada milkvetch plants.
I’ve seen populations of Canada milkvetch go many years in a row without ever producing seeds because of the recurrence of those weevils. That’s not good for the longevity of a population. However, we’ve found that if we can break that annual pattern, we can get a year of strong seed production, which is good for both us and the plants. The easiest way to break the cycle is to prevent the plants from flowering for a year. If the weevils emerge from the soil and don’t see flowers to lay eggs on, they’ll fly off in search of flowers elsewhere.
The following year, when Canada milkvetch blooms again, a few weevils might travel from other places to breed on the flowers, but there aren’t high numbers of them popping out of the soil right beneath the plants. Usually, that results in low rates of seed predation. Even delaying flowering by a few weeks can help. In years where milkvetch plants are mowed or grazed in a way that makes them bloom later in the season, they tend to produce lots of seed because the weevils were done breeding by the time the flowers appeared.
Following the crop rotation model, the best way to vary habitat conditions through time is to create a kind of ‘shifting mosaic’ of habitat patches across a site. The ‘mosaic’ part of that phrase represents the variety of available habitats. Those can include patches with tall, thatchy vegetation as well as others with short plants and exposed bare ground – and still other patches where that tall and short structure is intermixed. It’s also helpful to have patches differ in the plant species that are blooming or otherwise thriving. That might include some patches where annual plants are temporarily flourishing instead of the usually dominant perennials. Having all those patches arrayed near each other allows animals to move between them to look for food, escape predators, seek out shade or sunlight, and anything else they need.
The ‘shifting’ aspect of the mosaic, though, is also crucial. Each habitat type should appear in a different place each year, or on some similar time scale. That can be created by simply mowing or burning different patches within a site at varying times of the year. You might end up with a patch that was burned in the early spring, another that was mowed in mid-summer, and another that hasn’t been mowed or burned for a while. That idled patch could then be burned the following year and the previous year’s burned patch could be mowed sometime during the growing season. Or whatever. Basically, you want to shake things up each year so you’re applying management in different places over time and always providing a good mix of habitat options.
Grazing can be used the same way, except that there’s a lot more flexibility in how it’s applied. Patch-burn grazing is a terrific way to combine fire and grazing to create heterogeneity across time and space. I’ve written about the ‘open gate rotational grazing’ approach we’ve been experimenting with. That’s another potential option. In both those examples, each part of a prairie is grazed for a full season or more and then allowed to rest for a couple years. The grazing and rest cycles are staggered across the site so there are always patches in each stage of that cycle available for the plants and animals that thrive best in those conditions.
Patch-burn grazing is just one of many ways to create a shifting mosaic of habitats. Here, cattle are grazing a recently burned patch while mostly ignoring an adjacent unburned patch. Not shown in the photo are other nearby areas with more patchy habitat structure. Each of those provides different cover, foraging opportunities, and growing conditions for animals and/or plants.
Those grazing approaches, though, are only a couple examples among an infinite array of choices. You can vary the stocking rate, timing, and duration of grazing to achieve lots of different results. You can combine grazing with fire and/or mowing to create even more variation. There’s lots of room for creativity, but more importantly, to observe, learn, and adapt over time.
Regardless of the stewardship options available to you, the key is to look for ways to provide a good variety of habitat options for animals and growing conditions for plants. More to the point of this post, it’s important to make sure those habitat options shift around in location to help prevent anyone from winning too consistently at the cost of others.
Or, if you’re still trying to impress that ecologist, you might say that you’re trying to foster both spatial and temporal heterogeneity. If that doesn’t work, you might try talking about how fascinating parasitoid-host relationships are. That always gets me going.
The Prairie Ecologist 