This is the season of flying fluffy seeds. Asters, thistles, blazing stars, milkweeds, and other late season flowers are sending their seeds into the air, a few of which might actually land in a place where they can germinate. Each of those seeds is attached to a filamentous structure, variously called a pappus or coma, depending upon the species of plant. Those fluffy structures catch the wind and allow the seed to travel many miles, in some cases – though most land within a few meters of their origin.
Seeds that can float on the air are a nice adaptation for plants, but they are also attractive photographic subjects. Over the last week, I’ve photographed the seeds of common milkweed (Asclepias syriaca), dotted gayfeather (Liatris punctata) and tall thistle (Cirsium altissimum) in some local prairies. Here are a few of those photos for your Friday enjoyment.
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.
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.
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?
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.
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
As much as I enjoy looking at prairie flowers, I enjoy them even more when there’s a crab spider lying in wait among their petals. I must have more than a hundred photos of crab spiders on flowers, but when the lighting is good and I see those long hairy legs and cute little face… I just can’t help myself!
Do you suppose I need some kind of intervention?
“Hi, my name is Chris Helzer and I really like crab spiders.” (Hi Chris…)
“It’s been three weeks since I last photographed a crab spider…” (Applause)
The sun finally reappeared this week after what seemed like a month of absence. I figured the best way to celebrate the end of dreariness was a couple of prairie hikes. I started by wandering along a creek at our Platte River Prairies to see what the resident beaver family had been up to. Green sunfish slipped in and out of hiding places in the deep pools behind beaver dams, but little else was moving in the water. Later, the sound of frantic chirping turned my head in time to watch a sharp-shinned hawk just miss its prey. I couldn’t tell what kind of bird the hawk was chasing because it didn’t stop flying until it was out of sight. I also caught a quick glimpse of a small mouse scooting through the thatch, spotted a perched eagle in a far off tree and flushed a small flock of mallards from an backwater wetland. Not a bad way to spend an afternoon!
Later in the day, I stopped at our family prairie and roamed around until the sun went down. As the sun dropped, its warm light illuminated the golden brown prairie and I managed to take a few photographs – something I’ve not done much of lately. Here are a few of those photos.
Happy Holidays, and best wishes for your New Year!
As you might remember, my Photo of the Week last week was an image of a fledgling meadowlark I’d found in mid-September. At the time, I’d talked about how surprised I was to see such a young bird so late in the season. Well, last Friday, Eliza Perry, one of our Hubbard Fellows, called me to say she’d just found a nest full of tiny birds – did I want to come take a look? Of course I did.
I’m pretty sure what Eliza found was an American goldfinch nest. The bills and markings on the birds look right, and we spotted an adult goldfinch nearby. However, the best supporting evidence was that the nest was located in a thistle plant (a native thistle species, by the way) and had thistle down in the nest cup. There is a strong tie between American goldfinches and thistles. Unlike most other bird species which feed their young on insects, goldfinches instead feed them regurgitated seeds – especially those of thistle plants. In fact, they often delay their nesting until those thistle seeds have ripened. Here is a link to photographer/naturalist Stan Tekiela’s post on this topic, if you’re interested in learning more about the topic.
These birds are even further behind the meadowlark in their development, and it’s already getting pretty cold overnight, so the nestlings’ chances for survival might seem slim. Of course, the difference between the meadowlark and the goldfinches is that the goldfinches have adults around to help them. Both have a challenging fall and winter ahead of them, but nothing others of their species haven’t dealt with countless times before, I guess.
Thanks to Anne Stine, our other Hubbard Fellow, who graciously helped hold equipment for me as we photographed the nest. Because of the very bright early afternoon sun, I had Anne hold a diffuser near the nest to reduce the harshness of the sunlight while I held a small flash unit to better illuminate the birds. We worked quickly and got out of the way so the parents could resume their feeding duties.