Two robins (Turdus migratorius) hopped through the yard this week – spring is on its way. The sound of lawn mowers now drift through the air, confirming the avian prediction. Shockingly, these two very distinct signs of warming weather are actually related, according to a backyard research study conducted in 1979.
L.A. Eiserer conducted a series of scientific (well, somewhat) studies examining the impacts of lawn mowing on robin-hunting behaviors. Robins spend more time foraging when grass is short, especially just after it has been mowed.
So is it the mowing or the height of the grass that impacts robin behavior? Eiserer mowed his lawn to two different heights, 2.5 and 4.5 inches. (I wonder if his neighbors complained.) The robins spent 10x as much time in the shorter patch. Apparently, the birds eat different foods when exposed to different heights of grasses. In short grass, robins go for worms; in longer grass, they pluck small insects off the blades. The short-grassed hunting grounds may just be more efficient for finding a heartier meal.
But that doesn’t discount the act of mowing. Observations over the same time of day show the birds prefer hunting in a freshly mowed yard rather than the day after. No difference in grass height, but perhaps the act of mowing disturbs invertebrates, allowing for a more successful hunt.
Overall, I miss the days when a researcher could sit on a suburban porch and time how long a couple of robins spend looking for food. As I struggle to teach my students how to think like scientists, reading a study like this makes me long for the good old days.
Eiserer, L.A. 1980. Effects of Grass Length and Mowing on Foraging Behavior of the American Robin. The Auk. 97(3) 576-580.
Cicada by E. Overbaugh
As a college professor, like all teachers, I relish my students’ successes. Today, I’m a whole jar-full of relish. My students’ work is posted all over a Scientific American blog, Symbiartic. Yay!
Please visit Symbiartic to see lots more student illustrations – and don’t forget to share with all your friends!
See that Tall Bluebell (Campanulastrum americanum) flower? Is it red or is it blue?
Believe it or not, it’s kind of both!
The color pigment in plants that makes red is called anthocyanin. The pigment normally reflects red light waves. But if you raise the pH and add a couple metal atoms to anthocyanin, it changes the light waves reflected – and poof – blue!
Turns out, blue is a pretty rare color in nature. Dr. David Lee wrote a whole book about how colors in nature come to be, including the fairly complex steps to making blue in “Nature’s Palette: The Science of Plant Color”.
If you’d like to check out the color pigments in the flowers around your home, visit Scientific American for an easy, do-it-yourself pigment experiment.
Red-Spotted Newts (Notophthalmus viridescens) are the coolest animals on the planet. I should know – I worked with over 10,000 of them for two years.
Newts have four different life stages – egg, larva, eft, adult. The eft stage is most unusual since it’s completely terrestrial (for up to 7+ years!) AND incredibly poisonous (you have to eat it though). People used to think that efts were born from fire. The red color may have contributed to this folktale, but it may also be their emergence from logs thrown on the fire. Newt skin secretions can protect them from flame for a short time. It’s the reason many firefighter companies have a newt in their logo. Asbestos was once called “salamander wool”.
I researched the Red-Spotted Newt for my Master’s Degree (and fell in love with them – hence, the name of this blog). Every week, I trapped newts and recorded their spot patterns to identify each one individually. Since Red-Spotted Newts are fairly common, I trapped, identified, and released over 10,000. The scientific relevance of this work turned out to be … well… lame. Reports indicated that this population was very unusual. Turns out (sigh) it wasn’t. But I did learn a couple random things that no one else has reported.
- Newts can freeze solid and survive. I know because I left one out too long while I was checking traps and it was a little newt-popsicle when I returned. I took it back to the lab to use as a dissection specimen, but thankfully she’d recovered.
- While most experts call Red-Spotted Newts aquatic as adults, I think my study population was terrestrial with a brief aquatic period for reproduction. Even in permanent pools of water, newts leave in the fall. Only a few females overwinter in the ponds.
Dragonflies hover, swoop and twirl but never walk. They use their legs to trap their insect prey in a tiny six-barred prison before devouring them head-first. When guarding its territory along the water’s edge, this Blue Dasher (Pachydiplax longipennis) grasps a reed or blade of grass and waves his blue abdomen as a warning for other males. Females, in general, aren’t blue at all; they’re black with yellow lines running down their bodies While the name “dragonfly” may be confusing, other names – “snake doctor” or “devil’s darning needle”, for instance – are equally perplexing. No, dragonflies do not treat ailing snakes (or bring them back to life) and the insects don’t sew up any parts of you (although my Grandmother convinced me not to lie with the threat that dragonflies would sew my lips shut if I did). And in case you were wondering about that species name, it means “long wings”… not what you were thinking.
What’s the #1 killer of Roly Polies (Armadillidium vulgare)? I’ll give you a few hints… it’s not hungry birds, shoes, or tiny heart attacks.
The irony is that Roly Polies are crustaceans (not bugs, millipedes, lice or small organic tanks). Their closest relatives include shrimp and lobster.
Roly Polies like moisture – they retreat to damp areas and burrow underground in case of drought. They roll up as a defense against dehydration (and when you poke them). Ah, the wonders of evolution on land. All this protection against desiccation, but no ability to survive in water.
So now that you know Roly Polies are crustaceans, don’t try to rescue them by putting them back in the sea. We’re about 300 million years too late for that!
SOURCE :Population Characteristics of the Terrestrial Isopod Armadillidium Vulgare in California Grassland by Oscar H. Paris and Frank A. Pitelka
Ecology Vol. 43, No. 2 (Apr., 1962) , pp. 229-248
Stable URL: http://www.jstor.org/stable/1931979