Western Mosquitofish

Wading a Winter Creek

/ Michael Smith / Leave a comment

On a day when the temperatures reached the upper 70s, under bright sunshine, we took a walk and a wade through a cold creek, ten days into winter (using the December 1st meteorological beginning). It was delightful.

It probably seemed ridiculous to Barbara’s kids when we arrived at the creek bed and found much more water flowing than I had predicted. They followed me upstream a short distance until I reached a broad pool that would require serious wading. I volunteered to go ahead and see how deep it would be, and when it became thigh deep, frigid and numbing, I glanced back toward them. Barbara was gamely ready to give it a shot; Nicholas stood with his infectious grin as if to say, “you gotta be crazy.” Dani looked like she was figuring out how she could quietly slip back to the car. 

“OK, well how about downstream?” I asked, and everyone quickly assented. By the time we got back to our entry point, I could not feel my feet. Above the water was a different story. There could hardly be a more comfortable, sunny day as we made our way downstream over dry limestone rock and water only an inch or two deep. 

Fragments of ammonite (the piece on the right is a cast, not a piece of the ammonite itself)

I talked about finding fossils in this white Cretaceous limestone, including echinoids (like sea urchins), conical snails, and ammonites. The most dramatic fossils are the ammonites with their ribbed, coiled shells resembling today’s nautilus and related to the squid or octopus. I rarely find intact ammonites but it is exciting to find even a portion of one. We soon found a fragment or two, along with some fossil oysters and other bivalves. Nicholas soon found a living modern bivalve, that is, a freshwater clam that a friend identified as a species originally brought here from Asia. 

The water got deeper, and that give me a chance to net up some fish for us to examine. What I netted were mosquitofish, a sort of minnow that often swims in groups searching for something edible on the surface of the water. I showed the others the little ones among the wet leaves in the net and mentioned one of the things that charms me about these fish. While they are basically colorless, when seen in the right light a blue color is evident. It might be a sort of iridescence, though it seems to come from within the fish. I noticed it when I first caught and kept them as a teenager – mosquitofish and I go back a long way – and it is still one of the first things I think of when I see them.

Throughout autumn the leaves fall, spinning and sailing down to the water’s surface where they become saturated and sink to the bottom. Bur oaks, beeches, red oaks and sycamores all contribute to a beautiful collection resting under the clear water. The pale silt from limestone and shale lightly dusts these leaves, making them the creek equivalent of a sepia-toned photo.

We found a place where the creek has cut straight down through sand and shale, forming a sort of wall. Some layers and spots erode more easily, so during floods the current has carved a shallow pocket into the wall, leaving a bench of gravelly soil that we sat on for a while. I wrote notes while Barbara sketched sections of ammonite and leaves. Dani found a comfortable place in the sun. 

As Dani enjoyed the sunshine, the rest of us waded further downstream. Because it was sunny, the cricket frogs were sitting at the water’s edge, waiting to ambush tiny invertebrates to eat. These thumbnail-sized frogs may seek shelter when it’s truly cold and when it’s overcast or raining, but otherwise they are active year-round in our area. In summer they seem impossibly fast, jumping into the water and swimming to some place of concealment almost faster than your eyes can follow. Today their “cold-blooded” metabolisms could not generate that kind of energy. 

A Blanchard’s cricket frog floating in the water

Nicholas caught a couple of cricket frogs by hand, a pretty cool trick in summer but much easier today. When one slipped away and jumped into the creek, it hung in that clear, numbing cold water and floated over the rocks and leaves of the creek bottom. A few minutes later it would be sunning on the creek bank and hoping for a little hunting success.

Further down the creek, Nicholas spotted a small bird getting a drink at the water’s edge. It dipped it’s slender beak into the water a couple of times and soon flew away. I got a good photo but struggled to know this bird’s identity, but with the help if iNaturalist I found that it was a yellow-rumped warbler. The narrow beak, a bit of a white ring around the eye, and the wing bars helped, but there was only a suggestion of a yellow patch on its breast. It turns out that in its winter plumage, there’s not a lot of yellow to be seen, and this bird’s position obscured whatever yellow may have been evident on its rump. 

Yellow-rumped warbler

There were no clouds in the sky, and in shallow riffles the sun and water created the most beautiful patterns of light. Each ripple in the water focused sunlight onto the pale limestone creek bottom in a shimmering, dancing line. Sometimes they moved in the direction of the current and they swirled when the water was disturbed as it passed through troughs and over stones. At times through some trick of the light they seemed to move back against the current. It might be a small and ordinary thing to watch what the bright sunlight creates in clear, moving water, but it was a wonderful gift today.

And then it was time to head back. This creek has been such a treasure over the fifty-plus years that I have visited it, and I look forward to seeing another spring there when the new green growth and spring rains transform it into one more wonderful version of itself. 

Skinks, Turtles and Birds on a Summer Morning

/ Michael Smith / 2 Comments

8/13/20

Two Jims

I knew that having Jim Frisinger join us would be a harbinger of good birding. Jim teaches birding at Southwest Nature Preserve and is the first one we think of when we think about birds at the preserve. And sure enough, even though this morning’s walk was part of a survey of reptiles and amphibians, it turned into a pretty good birding walk as well.

We got started just after 7:00am, meaning that I had to get up before sunrise, but that’s OK, we needed to get there before the day heated up. It is now mid-August, with serious summer heat, and it climbed to 102°F later in the day, with the heat index feeling like 107°F. The survey plan is to walk in one of three habitats, either in the morning, mid-day, or evening, and we rotate among those options. Last week, Jim Domke and I did a mid-day walk, trying to avoid heat exhaustion and clearly demonstrating what Jim figured any idiot would know – the blistering mid-day heat of an August day is not the best time to see wildlife. This morning was much better.

What remained of the smallest middle pond

One of our destinations, the smallest pond at the preserve, was a casualty of summer. The water had completely evaporated, leaving concentric rings – an outer one of drying Water Primrose, surrounding an area of cracked, dry mud, with a bulls-eye center of wet mud. The temperature was 74°F and the humidity a steamy 89%. I walked through some of the vegetation and around the circle of dried mud, scaring up grasshoppers but no Blanchard’s Cricket Frogs. The two Jim’s (Domke and Frisinger) and I talked about where the frogs and turtles would have gone. Maybe the frogs dug under the mud, expecting to estivate during a period of drought. In a pond this small, I said I thought that the turtles may have migrated the short distance to the nearest pond with water. I did notice that several seed pods of Halberd-leaf Rosemallow (see the July 18 entry) had dried and cracked open.

Halberd-leaf Rosemallow

Next, we walked to the north pond, whose water level has dropped but not by much. A group of about six young anglers were fishing, and Jim Domke extracted a promise that they would clean up before leaving. Domke carries a bag in each visit and picks up the litter left by visitors to the preserve. He is an unsung hero for this and deserves appreciation from all of us, because people leave a surprising amount of trash around the preserve. The kids did indeed pick up their stuff!

On the trail a few feet from the water, we saw two Little Brown Skinks. They were roughly two-inch juveniles, little even as Little Brown Skinks go. These lizards did not slow down for photographs, and quickly disappeared into leaf litter and cracks in the mud. And as always, there were Blanchard’s Cricket Frogs hopping around at the water’s edge, and at least one amorous boy was calling, trying to attract females. His episodic “grick-grick-grick” calls were a Call Index of one in frog monitoring jargon, an isolated call not overlapping with other Cricket Frog calls.

Various turtle heads popped up in the water and using binoculars I could see on many of them the tell-tale red patch behind the eye that defines the Red-eared Slider. River Cooters are sometimes seen at the preserve, so it is important to try to observe the head pattern.

At this point the tops of the trees were bright from the rising sun, though the ground was still in shadow. The temperature was 79°F and the relative humidity 76%. Walking back, at the same spot where we saw skinks a few minutes before, we saw a large Little Brown Skink and a couple of juveniles. As before, they spotted us and were in frantic flight back across the trail to the trees by the time we saw them. I tried to capture one of them for a photo, but as soon as I tried to gently pin one down with my hand, it slipped into the cracks in the mud and was gone. These little lizards have very smooth, glossy scales and small legs, so that they shimmy across the ground almost like little snakes.

We wondered why we were seeing skinks in groups, and Jim Domke raised the possibility of a mama herding her babies to safety. I am less quick than I used to be to dismiss such ideas, though I doubt this is what we were seeing here. Researchers are increasingly documenting maternal care among pit-vipers (a group of venomous snakes that are pretty advanced among reptiles, in terms of their evolutionary status). Rattlesnake mothers have been documented to keep their young with her after they are born for a brief time until they shed their skin the first time. They may gather in rookeries to give birth and seem to have some ability to recognize kin. Clearly, some reptiles are capable of much more advanced social behavior than we typically expect. Were we seeing a family group of skinks on the trail? A possibility that seems more likely to me is that as the woodland floor becomes quite dry, these lizards come to the pond’s edge to drink and/or hunt the tiny invertebrates that congregate there. However, there is not much cover at the pond’s edge and when confronted with a predator (or lumbering human observers) they run for the cover of the leaf litter and cracks down into the soil. This is just speculation. My best answer is: “I don’t know.”

Turtle heads in the big pond

Our final destination was the north shore of the biggest pond, where the preserve has the north and west shores and residential housing has the east and south shores. As we arrived, a Great Egret took off with slow, powerful strokes of its snow-white wings. Turtle heads emerged from the water and looked around, a group of eight or so curious reptiles that watched the egret fly off as the humans arrived.

Western Mosquitofish

Along the water’s edge, a group of small fish foraged along the surface and among the submerged stems of Water Primrose. These were surely Western Mosquitofish, though I did not net any to confirm it. Their size, shape, and movements all indicated that they were mosquitofish, those surface-feeding fish that feed voraciously on zooplankton and invertebrates, including mosquito larvae. Females grow much larger and bulkier than males and may have a black spot at the back of the body cavity where the ovaries are located. They are not particularly colorful, though there is a bluish iridescence you can see in the right light.

A glimpse at a Spiny Softshell

Further along the shore, a turtle in the water just offshore caught my eye. It was that round shell and a curious head shape that grabbed my attention, and it did not hang around for a photo. It must have been a softshell! I was sure I’d seen a snorkel nose and a pancake-shaped shell – and then it returned to the surface to breathe, staying just long enough for me to take a quick and rather poor photo. It was fairly small, either immature or a young male (females grow quite a bit larger). There is only one other iNaturalist record of the Spiny Softshell at the preserve, and this was another!

Great Egret
On his way to the concert?

That observation made this a really successful survey walk – what could be better? Well, a really fine bird observation would not make it better, but it would sure round out our walk in a beautiful way. On the walk back, we saw a couple of Great Egrets again, standing in their tall, bright white elegance along the shore. And then, after they had flown, a smaller bird flew in to take the place of the one who had been standing on a log in the water. His crest of feathers suggested a young man with a Mohawk on his way to see Green Day perform Jesus of Suburbia, as he landed on his log and eyed us with suspicion. His Mohawk flattened and he began to look at the water around him, periodically glancing up at us just to make sure he wasn’t going to have any trouble from us. He (or she) was a Green Heron, maybe a young bird whose brown and white streaked chest had not filled in from the sides with the reddish-chestnut brown of an adult.

Green Heron

This heron was surprisingly tolerant of three old guys hanging around, two of them taking photos. While we watched, he hopped down as low as he could get on the log and watched the water intently. We waited – he waited, and then there was a quick stab of his long bill into the water, bringing back a juvenile sunfish. Was there a hint of a self-satisfied smile on that long beak, and a glint in his eye as he looked up at us? Probably not, but his skillfulness was impressive. In fact, the Cornell Lab of Ornithology tells us that these birds sometimes even drop bits of bread or insects on the water to lure a fish in close enough to be caught.

A talented fisherman

The temperature had risen to 84°F and 74% humidity and it was time to leave before it became really hot. This had been a great walk, with the thought-provoking observations of Little Brown Skinks, finding a Spiny Softshell, and then the chance to share a few minutes with the Green Heron. I knew Jim Frisinger would be some kind of good luck charm!