Urban Red Tailed Hawks

Rather than having 15 separate posts on the red tailed hawk nest in our backyard, I have put a photo log here for those who are interested. The parent birds arrived in February and March.


The nest itself is in the damaged crown of a blue spruce. They began building it in 2016, but didn’t use it last year. This year, in March and April they added to it and began sitting by about the first of May.DSC02537


Continue reading “Urban Red Tailed Hawks”

Williams Alumni at The Nature Place

What a great week at The Nature Place near Florissant, Colorado. Thanks to all the Williams alumni for being interesting people engaged in studies of geology and natural history. See the post below this one for an update on our rabbit bot fly. But first, here are a few photos. Remember the anicia checkerspot?Anicia checkerspot

And, of course, the blue columbine from above the snowfields on Horseshoe Mountain.Blue columbine

And the 50+ elk across the stream below the cirque.Elk at Horseshoe Mtn

And Parry’s primrose, one of the most photographed flowers in the tundra.Parry' Primrose

And meanwhile, back at the lodge, Caripeta aequaliaria, the red girdle moth, hiding under the eaves.Snowia montanaria

And this little mountain bluebird juvenile on Wilkerson Pass.W bluebird juv

Thanks for a great week! See you all in 2019? If I’m not in a wheelchair.


The Female Rabbit Bot Fly

What th—? A Rabbit Bot Fly? Really??

Bot Fly, Cuterebra, family Oestridae, probably a rabbit bot

Today on Shelf Road in Fremont Co., Sam Peck, a veteran Blackhawk helicopter pilot and one of the Nature Place Staff, brought me the most amazing insect I’ve seen in years. Mystified at what it might be, I posted it on Arthropods Colorado Facebook group. Within an hour or two, I had about thirty comments, among which was an identification to genus and family: Alejandro Estrada identified it as a bot fly, genus Cuterebra, family Oestridae. Eric Eaton, entomology generalist who knows almost everything with six legs, further identified it as a rabbit bot, based in part on the red in the eyes. OMG. Then Prof. Boettner from UMass went still further, calling it Cuterebra lepusculi, and female based on the wide gap between the eyes. He verified that only the females have the red eye spots, and said that they fade with time in museum specimens. Unbelievable. They attack mainly cottontail rabbits. Other commenters noted how cute it is, but still others found this revolting, as bot flies are parasites that lay eggs under your skin, where the larvae hatch and cause an inflamed canker that eventually ruptures to allow the hideous (but cute) parasite to fly away. Although this particular specimen was not capable of flight, Prof Boettner assures me that once this thing sits for 24 hours or so, it will fly like its house is on fire, and will lay eggs in rabbit burrows.

Prof. Boettner’s last email on this subject states, “Hi Sam. Say hi to the Williams College gang for me. I should mention that although bots have short lives, females can lay over a thousand eggs in that short 10 day lifespan. And they only need one male and female egg to survive to keep the population stable. Amazing every rabbit isn’t infested. But they waste a lot laid in runways that never get in a host. That is a beauty that you found. One of the larger bots in the world. There is one in New Mexico that has yours beat in size. C. mirabilis. Nearly 2 inch long females! It uses black tailed jackrabbits as a host. And the male of that species has never been seen. So lots of mystery in the bot world.” He is doing DNA studies, and expressed the hope that I might have taken the specimen. Darn. So, maybe Sam Peck will go back up there and find me another one.

Bot Fly, Cuterebra, family Oestridae, probably a rabbit bot

Some viewers thought it might be a sculpture, a model. But it’s the real thing. After that, this moth larva seemed almost pedestrian.DSC03592

Short-short stories with Phil

Many years ago my brother Phil and I wrote stories together. It was a game. I’d write an introductory sentence, and he’d follow it with something. The art was to try to throw the other guy a curve while still maintaining a sense of direction in the “plot.” I found these two stories in my archives. My parts are in standard face, Phil’s are in italics. You should try this sometime.

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Cricket Thermometer

Years ago, when I was a kid, I heard about a Frank Lutz study in which snowy tree crickets could be used as a thermometer by counting their chirping rate, which, because they are poikilotherms, varies with the ambient temperature. At the time I thought that was interesting, but a little irrelevant, since I had a thermometer. But we don’t always have a thermometer when we’re, say, camping, so a few years ago I had my Biology class make a thermometer by going outside, recording the temperature, and counting the chirps per minute of our local crickets. I don’t know the cricket species, but it is a common one in late summer when school starts. Here are their data, compiled to show a good polynomial fit. The linear equation, upper left, is also a good fit at r = 0.96.


Most Abundant Butterflies: Bear Creek Canyon

Here are graphs showing the 18 most abundant species of butterflies in each summer month or half-month. These are based on 23 years of observations of tens of thousands of butterflies. The y-axis shows the numbers of butterflies noted per hour of observation time. This is a historic record, and I understand that many readers will not know the scientific names of these butterflies, but I am illustrating the three most common above each graph. Nymphalis antiopa, the mourning cloak, hibernates as an adult and flies on the warmest days in February. Celastrina lucia is the tiny spring blue that sometimes congregates at mud spots. Its taxonomy is still uncertain. It is the most common butterfly in the canyon from April through early June. In July, its numbers fall off and it is replaced by a series of brush-footed butterflies that are of medium size and generally orange and black in color. Limenitis weidemeyeri is a large black butterfly with bold white bands across the wings. In July, the silver spots (Speyeria) and a couple of skippers (Poanes and Euphyes) become common.Screen Shot 2017-05-23 at 10.51.50 PM


This amounts to about 26 butterflies per hour.

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Early May

This amounts to about 43 butterflies per hour.

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Late May

This amounts to about 60 butterflies per hour, but over half of them are the little Spring Azure Blue.

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Early June

This amounts to about 58 butterflies per hour.

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Now we’re at about 72 butterflies per hour. Quite a jump from June.

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And all the way up to 76 per hour…

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Late July

Then, rather suddenly, back to about 44 butterflies per hour. Clearly, July is butterfly month in the Colorado foothills.

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Or about 55 butterflies per hour.

By September, numbers drop to about 20 butterflies per hour in random habitats. But from late September through October and into November, butterflies can be found in large numbers on rabbitbush, Chrysothamnus nauseosus. On these bushes, I have found 145 butterflies and over 200 day-flying moths in less than a half hour. That’s an average of about 290 butterflies per hour!