Polar Bear Shower for Robins

Last 48 hours our night time lows were 7 F and 6 F respectively; highs were 23 F each day. I went to the Woods to see how the life there managed in the cold.

The west pond was frozen over. The previous week of freezing temperatures the northern half had remained open. The east pond was frozen except for a small area half meter square below the big cottonwood tree. The reflectance from the lower bole of the tree provided enough heat to melt the ice there.

Elsewhere water was mostly frozen except ten meters below the Elm bridge. There, in a stretch of 4 meters of open running water, there were 30-40 robins busy bathing themselves.. quite a sight in the freezing temperature, with a very cold night ahead, the birds were dipping their heads into the water, flapping their wings and splashing water over their backs energetically. What is the adaptive value of this? Is managing ectoparasites, mites, lice etc.. that important.. or are the birds that impervious to the cold?

Above the Robins and the eastern wash there was a hawk (red shouldered?) calling and a jay (or a mockingbird) scolding. Along the south boundary a crow was calling. Nearby a small woodpecker (hairy?) worked at the top of a tree drumming.

Wandering through the Woods I encountered the herd of white-tail deer twice, on the north side of the dune at the beaver dam and subsequently in the denser undergrowth between the East and West Pond. I counted four of the five I sometimes see. Could be I missed one as they were running way. They ran off up the escarpment into the denser juniper woods. I wonder if they shelter on the down slope below the ridge and warm themselves with the southern exposure.

I heard one dog bark in the woods east of the west pond but did not see it.

The cold weather had drooped the honeysuckle leaves but the Ligustrum leaves were fully expanded and did not look to be suffering. What physiology protects privet against winter cold?

The flow from the eastern wash south of the Elm bridge had spilled over across the lower area of willow, ash, polygonum and tall dead ragweed stems. In the sandy shallow channels there, water had frozen ice sheets and produced a space that would shelter small animals or plants beneath from the colder night temperatures.

Where do the animals go when ambient temperature approaches zero F? Salamanders, bugs, frogs.. what strategies and hideaways do they have for the deep cold? I found a pentatomid (Brochymena?) under a loose piece of bark I pulled from a dead elm tree. It had situated itself on the south side of the tree where it would be warmed as much as possible by the winter sun. Under a slab of cottonwood bark there was another cluster of 40-50 collembola and a few inches away 3 young wood roaches. There were also the galleries of some unknown bark beetle species with a linear egg laying gallery and radiating individual larval galleries. The entire pattern maybe two inches across.

The Woods on a winter day like this seem particularly open. I wandered through the southeast quarter. Scattered large diameter cottonwoods there rise above a crowded understory of younger green ash teenagers. The ash have all recruited likely since livestock were removed, while the cottonwoods were established decades earlier. Along the south boundary of this section three or four largish cottonwoods 30-50 cm DBH have fallen to the north. What event set up the establishment of this generation of trees? I need to determine their age.. maybe 50-60 years? Determining age of trees might be a good independent research project. I could cut disks from the base of recent fallen trees and students could determine the age and construct a picture of stand dynamics, recruitment, succession, longevity, disturbance, species turnover.. mapped to the different areas of the Woods.