Photo of the Week – August 27, 2015

My wife, whom I love deeply.

Kim Helzer collecting aquatic invertebrates in wetland at sunset. Helzer Prairie, Stockham, Nebraska.

Kim Helzer collecting aquatic invertebrates in the Helzer family prairie/wetland.

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Saving Pollinators One Thistle at a Time

Pollinator populations are in trouble for a lot of reasons.  Loss and degradation of habitat, pesticides, and diseases are all major contributors.  However, at least in the Central United States, much of the pollinator decline can be tied to spiny pink/purple-flowered plants and the way humans react to them.

Tall thistle, a native annual wildflower, is a big favorite among pollinator insects.

Tall thistle, a native annual wildflower, is a big favorite among pollinator insects.  However, it is seen by many people as a weed that needs to be eliminated from the earth.

On the face of it, thistles seem like they’d be pretty well-liked.  Thistle seeds are a major food source for birds and other wildlife, as well as for a variety of invertebrates. The abundant nectar and pollen found in thistle flowers make them one of the most popular plants among both pollinator and non-pollinator invertebrates.  As if that wasn’t enough, most thistles have large and/or abundant blossoms, which you’d think would make them very attractive to people.  Sure, they’ve got spines, but so do cacti, yucca, and many other plants gardeners love to landscape with.  So why do we hate thistles so much?

The cultural dislike of thistles is not at all a new phenomenon; references to the unpopularity of thistles can be found at least as far back as the Book of Genesis in the Bible.  There, thistles are mentioned when God curses Adam after he eats the forbidden fruit. Genesis 3:17-18 – “Cursed is the ground because of you… Both thorns and thistles it shall grow for you…”  Clearly, if God includes thistles as part of His curse on all humanity, they are not a crowd favorite.

Regardless of why thistles are so widely disliked, our contempt for them causes serious problems for pollinators.  This happens in two ways: 1) direct destruction of an important floral resource for pollinators, and 2) major side effects associated with #1.

Because thistles are so important to pollinators, our compulsion to destroy them is a major problem.  Sure, some thistle species are invasive and can cause enough ecological damage that their control is warranted.  Most thistle species, however, are targeted for destruction purely because they are thistles.  Many of those are native wildflower species and are not at all aggressive or problematic.  Regardless, there are few places where thistles are tolerated, let alone encouraged.  The result is the loss of a big source of food for many pollinators.

Musk thistles and regal fritillaries (before we chopped them because they are designated as noxious weeds and we are legally obligated to eradicate them.) The Nature Conservancy's Platte River Prairies, Nebraska.

Musk thistles and regal fritillaries.  Musk thistles are designated as noxious weeds and we are legally obligated to eradicate them.) The Nature Conservancy’s Platte River Prairies, Nebraska.

While the loss of thistles themselves is a big problem for pollinators, the methods we use to eliminate them can have much bigger impacts.  If we were content to dig thistles out of the ground one by one, things wouldn’t be so bad.  Of course, that’s not always feasible – some perennial species such as Canada thistle are rhizomatous and can’t be killed by digging.  Herbicide use is the other available option.  Spot spraying individual plants or clumps can be relatively innocuous, but only if the person spraying is judicious and selective about what they spray.

However, working thistles one by one takes a lot of time, and just because we hate thistles doesn’t mean we want to spend a lot of time getting rid of them.  Broadcast herbicide spraying, by airplane or boom sprayer, can kill lots of thistles in very short order.  It’s a great way to get rid of all those unsightly pink flowers in one fell swoop…at least for that season.  Unfortunately, broadcast spraying also kills a wide array of other wildflowers, and most of those never recover (the ones that do are the ones we tend to like least – like ragweeds).

The grand irony is that because broadcast spraying kills so many non-target plant species, the spaces left open by those dead wildflowers are usually colonized by thistles.  Thus, while broadcast spraying is quick, it tends to perpetuate thistle populations by destroying their competitors.  (Also, most large thistle populations are there because of chronic overgrazing or some other major disturbance that weakens perennial vegetation and creates space for thistles to grow.  Broadcast spraying doesn’t address those underlying issues.)  Oh, and by the way, killing off all the wildflowers in a pasture or roadside also wipes out the pollinators that depend upon them for food.

Our cultural dislike of thistles leads us to kill off as many as we can each year.  Since thistles are a major food source for pollinators, that’s grave news for pollinator conservation.  Our desire for more “efficient” ways to kill thistles has led to even worse news, however – the loss of plant diversity across millions of acres.  Since plant diversity sustains pollinators by providing varied and consistent food through the season, losing that diversity at a large scale is devastating.  We can rebuild some of what we’ve lost through restoration, and we can save what’s left, but only if we change the way we think about thistles.  We’d better hurry; pollinator declines are not slowing down.

I think we need a thistle fan club.  Who’s with me??  Let’s do this thing.  I’ve come up with a basic logo and tag line (below) to get us started.  Click here to get an easily printable version you can hang on your office door or tape to your car window.  It’ll be a great conversation starter!  In fact, let’s have fun with this.  If you feel like it, take a picture of how you displayed the logo and put it on your favorite social media with the hashtag #thistlehelp.  Not a social media person?  Feel free to email me a photo – maybe I’ll collect some of them and use them in a future post.  If you email me, please keep the file size below 1 mb…   Use this email address: chelzer(at)tnc.org.

The bees and butterflies of the world are depending on you.  This is going to sweep the nation, you’ll see!

ThistleFanClub

 

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The Gluttonous Crab Spider

The following post was written by Evan Barrientos, of our two Hubbard Fellows for this year.  Evan is a talented writer and photographer, and if you enjoy this post, I encourage you to check out his personal blog as well.  …For the record, I did not in any way encourage Evan to photograph or write about crab spiders.  This is despite my well-known affinity for them and my personal inability to walk past one without taking its portrait.

Over this summer I’ve tried to focus on photographing the prairies with a wide angle in order to show what the landscape looks like, but sometimes it’s just impossible to resist delving into the tiny details and dramas of prairie microfauna. One morning in June I was admiring the spiderwort flowers when I stopped to photograph a crab spider (Thomisidae sp.) sucking the juices out of a hoverfly (Syrphidae sp.) that she had caught.

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If you’ve been reading this blog for a while, you’ll know that many crab spiders hide on flowers and ambush insects as they stop for a drink of nectar (similar to ambush bugs). Some crab spiders can even change their color to yellow or white in order to match the flower they are on, but this spider didn’t seem to need that trick. To my great surprise, a second hoverfly was brave, hungry, or stupid enough to land on the same flower while I was taking photos. Maybe it thought the spider would be content with the hoverfly already in her fangs. It was wrong.

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The spider quickly honed in on the intrepid visitor, even though her fangs were already more than full. What she planned to do with the second hoverfly, I don’t really know, but  watch what happened when the clueless hoverfly strayed a little too close:

 

Apparently, this hoverfly liked adrenaline, because it continued to gorge itself on delicious spiderwort nectar for a few more moments and eventually flew off to safety. Thinking the spectacle had ended, I started to pack up my camera gear, but before I could, another fly landed on the flower!

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As you can see from the photo sequence, the spider was once again too slow to catch the visitor. I watched her for a little longer, but eventually left to photograph a bird singing nearby. I came back a few minutes later to check on the spider and found yet another surprise.

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In the five minutes I was away, the crab spider had finished eating the first hoverfly and caught another one. I don’t know if spiderworts are irresistible to flies, or if hoverflies are terrible at spotting white crab spiders on purple flowers, but this spider sure was lucky that morning!

Encounters like this remind me how important it is to pause every once in a while and notice the little details. When I do this I’m often amazed by how much is going on around me and how much I would have missed it if I hadn’t stopped. Wide-angle views certainly have their place too, but to fall in love with prairies you really need to stick your nose in them at times.

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Photo of the Week – August 21, 2015

How could you look at this spider and not think it’s cute?

Jumping spider. Helzer yard. Aurora, Nebraska.

This beautiful jumping spider was in my background last weekend.  I cajoled it onto a piece of cypress mulch and took its portrait.  The crazy green color in the background is the underside of a maple leaf I put beneath the wood chip.  Doesn’t it look like a cute little teddy bear?  (Or an Ewok?)

Unfortunately, many people will look at this photo and recoil.  I’ve gotten so used to handling and admiring spiders and other invertebrates that I forget most of the human population is much less comfortable with them.  I wish I could help; spiders (and other “creepy” invertebrates) are incredibly important, but it’s hard to have a conservation discussion about them when the person you’re talking to is covering their face in disgust and fear.

I get that many people have a very strong visceral reaction to spiders (and/or snakes), and I’m not trying to minimize or mock that.  In fact, I can relate.  My own initial reaction to seeing a snake in the wild is usually to take a quick step backward.  However, I’ve spent enough time getting comfortable with snakes that after that first backward step, my next move is usually to try to catch them to get a better look.  Experience helped me conquer my discomfort and turn it into admiration.  I think the same would help most people deal with snakes, spiders and others, but getting the majority of the public that kind of direct exposure and experience seems unlikely.

Here’s a compromise.  We don’t need everyone in the world to love spiders and snakes to the point where they try to cuddle every one they find.  Instead, it’d be great if people could just understand that spiders and snakes are critically important components of complex ecological systems rather than nasty creatures to stomp on or chop with shovels.

I don’t expect anyone to transform from spider hater to spider cuddler just because I say spiders are cute and ecologically valuable.  However, maybe I can nudge the ball in the right direction by pointing out some mythology about the danger of spiders.  Let’s start with this:  Almost no one reading this blog post will ever encounter a spider that will pose any danger to their health.  Seriously.  The vast majority of spiders can’t even bite you – their little fangs can’t penetrate your skin.  With very few exceptions reported “spider bites” turn out to be something else.  SPIDERS DON’T WANT TO HURT YOU.  I’ve handled countless spiders of many many varieties and have never had one act aggressively toward me, let alone try to bite me.

I’m not going to tell you there are no dangerous spiders.  There are a few species that can cause you harm, but the chances of running into one of them are pretty slim, especially in Nebraska and most other midwestern U.S states.  Really slim.  And if you do happen to encounter one, they’re not going to jump up and bite you on the throat.  I promise.  Also, they are not going to lay their eggs inside you so that your face (or other body part) swells up until it eventually bursts and thousands of tiny spiders come out.  Not going to happen.  That’s a particularly vivid, but completely false urban legend.

Spiders are just tiny creatures trying to survive in a dangerous world.  Just like you, though possibly cuter – I don’t know, I haven’t met all of you.  Maybe you don’t want to pick spiders up and play with them.  That’s cool.  But  maybe you don’t have to kill every spider you see because you figure it’s either them or you.  It’s not.  They’re just trying to find something to eat and avoid being eaten themselves.  Ignore them.  Or catch them in a cup and take them to a safe place.  Or, if you’re feeling really crazy, pick them up, put them on a wood chip and take pictures of their adorable little faces.

Here are two more links that talk about spider bites and other myths, in case you’re interested:

http://www.burkemuseum.org/spidermyth/

http://arthropodecology.com/2012/02/15/spiders-do-not-bite/

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Killer Thistles

Two years ago, I posted some photos of ants and other insects that had died on the sticky lower portion of thistle flowers.  At the time, I speculated about whether or not the sticky bracts below the thistle blossoms were an adaptation to prevent ants from reaching the flowers and “stealing” nectar.  Since ants aren’t fuzzy and don’t dependably go from flower to flower like bees do, they probably don’t provide many (any?) benefits to the flower in return for the nectar they take.

Dead ant stuck to bottom of wavy-leaf thistle flower. Helzer family prairie near Stockham, Nebraska.

Dead ant stuck to bottom of wavy-leaf thistle flower. Helzer family prairie near Stockham, Nebraska.

After that post, a friend sent me a journal article detailing a study (see citation below) in the 1980’s that looked at this same phenomenon, trying to figure out what benefit the thistle might get from having sticky bracts.  They used Liquid Paper to coat the bracts and make them non-sticky and then measured seed predation between coated and non-coated plants.  Overall, their results were fairly inconclusive, though they did see higher seed predation by insects on non-coated flowers in one of their sites.  The mystery remains!

One interesting part of the study was that of the 331 insects they found trapped on the bracts of Flodman’s thistle at Frenchman’s Bluff in Minnesota, 96% were ants.  (Given that result, I’m not sure why they focused on seed predation – I don’t think ants feed much on thistle seeds?)  I have been trying to keep track of what insect species I see stuck to thistle bracts during the last few years, and while ants do make up the majority of dead insects found there, a number of other species show up as well.

Dead ant stuck to bottom of wavy-leaf thistle flower. Helzer family prairie near Stockham, Nebraska.

The ant on the left appears to have completely lost his head over sticky thistles.

All the photos on this page were taken on the same morning last month.  I was walking around our family prairie and looking at the wavy-leaf and Flodman’s thistles (Cirsium undulatum and C. flodmanii) to see what was feeding on them, as well as what insects had become fatally stuck.  As usual, the majority of dead insects were ants, but there were several bees and even a little cicada as well.  More interesting, I also tried to pay attention to insects that seemed to move across the sticky flower bracts without getting stuck.  Crab spiders and stink bugs were two that seemed to have no trouble.  Spiders, at least some of them, have a special coating on their fuzzy feet that help keep them from sticking to their own webs – does that help them not stick to thistle bracts?  Maybe?  What about stink bugs?

Dead bee on bottom of wavy-leaf thistle flower. Helzer family prairie near Stockham, Nebraska.

This bee probably chose a nice sheltered place to spend the night without knowing it’d be the last choice it ever made.

Dead bee on bottom of wavy-leaf thistle flower. Helzer family prairie near Stockham, Nebraska.

This bee had been stuck for a while.

Dead beetle on wavy-leaf thistle flower. Helzer family prairie near Stockham, Nebraska.

This tiny beetle was another victim of the killer thistles.

Sphinx moth on wavy-leaf thistle flower. Helzer family prairie near Stockham, Nebraska.

Sphinx moths and many other pollinators feed on the tops of on wavy-leaf thistle flower. It’s the underside that’s dangerous.  If you look closely at the bottom of the thistle flower, you can see a couple wings…

Dead cicada on bottom of wavy-leaf thistle flower. Helzer family prairie near Stockham, Nebraska.

…and those wings belong to this poor dead cicada.

Stink bug on wavy-leaf thistle flower. Helzer family prairie near Stockham, Nebraska.

Stink bugs and crab spiders are among the insects that are apparently unaffected by the sticky thistle bracts.  This stink bug was moving around the flower with no apparent problems.

These are the kinds of mysteries that make walking through prairies fun.  Maybe someday we’ll figure out the secret of thistles’ “bracteal exudate”, but in the meantime, it’s just one of many prairie interactions we can marvel at.

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Journal Citation:

Bracteal Exudates in Two Cirsium Species as Possible Deterrents to Insect Consumers of SeedsAuthor(s): Mary F. Willson, Pamela K. Anderson and P. A. ThomasSource: American Midland Naturalist, Vol. 110, No. 1 (Jul., 1983), pp. 212-214Published

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Photo of the Week – August 13, 2015

Nebraska has 108 species of grasshoppers.  They come in a wide variety of sizes, shapes, and colors, and generally speaking, the further west you go in the state, the more species you can find.  While on a short trip to the Nebraska Sandhills last week, I was fortunate to see two of the most beautiful of Nebraska’s grasshopper species.

Lubber grasshopper. Valentine National Wildlife Refuge, Nebraska.

Plains lubber grasshopper (Brachystola magna). Valentine National Wildlife Refuge, Nebraska.

I saw several plains lubber grasshoppers (aka homesteaders) in the prairie.  These huge flightless grasshoppers are about the size of mice (more than two inches long, and very thick).  They feed primarily on wildflowers, including sunflowers and hoary vervain (Verbena stricta).  According to Grasshoppers of Nebraska, they are not crop pests but in years when their population soars, they can present a hazard to drivers because their bodies can make roads slick.  Think of that!

Lubber grasshopper. Cherry county ranch of Jim VanWinkle, Nebraska.

Here is a plains lubber on its favorite (according to some sources) food – an annual sunflower (Helianthus petiolaris).  Cherry County, Nebraska.

I also enjoyed the chance to see a painted grasshopper (Dactylotum bicolor), a species I first noticed last year on a trip to western Kansas.  This gorgeous creature might be the easiest grasshopper in Nebraska to identify – as far as I know, there isn’t anything else in the state that looks remotely like it.  Like the lubber, the painted grasshopper eats primarily wildflowers, particularly false boneset (Brickellia eupatorioides).  It likes habitat with lots of exposed soil, which is convenient for those of us trying to find and photograph them.

Painted grasshopper at the Valentine National Wildlife Refuge. Nebraska.

A painted grasshopper at the Valentine National Wildlife Refuge. Nebraska.  The colors and patterns on this species make it impossible to confuse with others.

Grasshoppers, and katydids, which look like grasshoppers but have much longer antennae, are a fascinating group of insects.  They have interesting and complex communication strategies and each species has its own set of dietary preferences – some are specialists on just a few plant species and others are generalists.  Only a very few are considered to be pest species, and most of those are simply native species that have adapted well to the abundant food humans provide in the form of monoculture row crops.

Perhaps most of all, the sheer abundance and biomass of grasshoppers make them ecologically important in grasslands.  If you collected all the grasshoppers from a prairie, their biomass would equal that of the bison or cattle in the same prairie.  As such, they are a major food source for many other species, including many birds, and major herbivores that influence plant communities in complex ways.

Grasshoppers are also very visually appealing if you take the time to look closely at them.  The plains lubber and painted grasshopper are particularly pretty, but every grasshopper species has its own beautiful combination of colors and patterns.  Go out and find your favorite today!

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August 21 Field Day – Agenda

We’ve completed the full agenda for our next Platte River Prairies Field Day on August 21.  We’ll have a wide range of topics and sessions to choose from; it should be a fantastic day.

See the full agenda, descriptions of sessions, and directions to the site here.

See you on the 21st!

Our Platte River Prairies are beautiful and full of life right now.  Field Days are a great time to learn more about what's living in those prairies as well as the management and restoration strategies we use to keep them vibrant and healthy.

Our Platte River Prairies are beautiful and full of life right now. Field Days are a great time to learn more about what’s living in those prairies as well as the management and restoration strategies we’re experimenting with to keep them vibrant and healthy.

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Double flowered sunflowers

When you look at a sunflower, you’re really looking at a composite of tiny flowers, or florets.  The same is true for asters, daisies, and other members of the composite family of plants.  The colorful “petals” of a sunflower are actually a series of tiny florets, called ray flowers, and the seed-producing dark center is made up of lots of disk flowers.  Together, they join together and function as one large flower that attracts pollinators and produces seed.

Stiff sunflower.  The Nature Conservancy's Platte River Prairies, Nebraska.

This sunflower has two kinds of flowers – ray flowers that look like yellow petals, and small disk flowers in the center.

This is how sunflowers are “supposed” to look.  However, you will occasionally find a sunflower that looks more like a chysanthemum, with yellow ray flowers across most or all of the face of the flower head.  Botanically speaking, this is called “double flowering”.  Horticulturists find and breed double flowering varieties of sunflowers and other composites, and you can find them at many nurseries and other plant stores.

Maximilian sunflower.  TNC Bluestem Prairie, Minnesota.

A double flowered Maximilian sunflower (Helianthus maximiliani) at The Nature Conservancy’s Bluestem Prairie in Minnesota.  Most of the disk flowers have been replaced by ray flowers.

When we were in Minnesota a few weeks ago, we saw a fair number of double flowered Maximilian sunflowers at The Nature Conservancy’s Bluestem Prairie.  I don’t remember seeing so many examples in one prairie before, but maybe I just haven’t paid close attention.  The abundance of them made me curious to learn more, so I did a quick internet search when we got back to Nebraska, and emailed a few botanist friends for more information.  The best information I found was related to a 2012 PLos Genetics journal article in which scientists described their discovery of the particular mutation that causes double flowering to occur.  You can read descriptions of the research here and here.

Maximilian sunflower.  TNC Bluestem Prairie, Minnesota.

Extra “petals” can be awfully pretty.

You might think of genetic mutation as something bad, but mutations are actually very common and mostly benign (and don’t affect form or function).  Now and then, a mutation can cause serious problems for an organism, but other times it can generate variations in a DNA sequence that turn out to be advantageous.  Double flowering seems to be somewhere in the middle.  On one hand, producing fewer disk flowers means the plant has fewer opportunities for pollination and seed production.  On the other hand, extra ray flowers could make a plant more attractive to insect pollinators and increase visitation.  In the case of the Maximilian sunflowers at Bluestem Prairie, the mutation doesn’t seem too disastrous, at least based on the number of plants we saw that have the trait.

I’m glad – it sure is pretty.

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Next Platte River Prairies Field Day – August 21

On Friday August 21, we’ll be hosting our next Field Day on the Platte River Prairies.  The agenda is nearly set – we’re just waiting for final confirmation from a few presenters before putting out the official agenda.  We’ll have sessions on plant identification, prairie restoration and management, birds, ethnobotany, pollinators, dragonflies, invertebrate ecology, and more.

Fish sampling demonstration at Derr Wetland during TNC Platte River Prairies Field Day.

Field Day participants look at stream fish at our June 2015 Platte River Prairies Field Day.

Please plan to join us between 9am and 4pm (come and go as you like.)  There is no cost or registration required, but bring your own lunch.  We’ll have some light snacks and water/lemonade for you.  Directions to the site can be found here.

I’ll post the final agenda when it’s ready to go.

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Photo of the Week – August 6, 2015

There are many benefits of being a morning person.  For example, I see a lot of sunrises – even in the summer when the sun comes up well before most people are awake.

Last weekend, I got up early and drove out to our Platte River Prairies to catch the sunrise.

I’m sure glad I did.

Sunrise in sand prairie.  TNC Platte River Prairies, Nebraska.

Stiff sunflowers (Helianthus pauciflorus) greeting the sunrise in sand prairie. TNC Platte River Prairies, Nebraska.

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