Ferruginous hawks ghost through the trees in the morning fog

Last Friday night about two inches of snow fell in the Rexburg area, so after cleaning my driveway I headed out Saturday morning to the Mud Lake area to look for some wildlife to photograph. As I hit Sage Junction I was greeted by some very thick fog, not a good omen for photographs. I had visited the area several times during the past week watching from 20 to 34 Ferruginous hawks roosting in a grove of trees south of Idaho Highway 33 near the road that leads to the South Boat Ramp on the lake.

As I got to the area, I could barely see eight hawks in one of the flocked trees, but the fog was too thick to see the other trees. After about 45 minutes of waiting, I could see other hawks roosting in the other trees and I was able to count 28 hawks in them. The thick fog had covered everything, but the hawks, with a coating of white frost.

For years I have inaccurately called these thick frost crystals, “hoar ice crystals,” but with more detailed study, I have found that they are “rime ice crystals.” Thick freezing fog creates large clusters of rime crystals while hoar crystals forms on cold, clear windless nights with low humidity when water vapor comes from within items. Hoar crystals are needle-like instead of clusters.

As the sun burns off the fog, two ferruginous hawks can be seen surrounded by rime ice crystals. | Bill Schiess, EastIdahoNews.com

As the sun started burning off the thick fog, the hawks started leaving the protection of the trees, heading southeast of the town of Mud Lake to the agriculture lands. It was time for them to capture brunch as the fog-laden air delayed their hunting for a couple of hours.

I followed them, finding them perched on power poles, bushes and irrigation pivots, watching for some hapless rodents for them to munch on. The ferruginous were not the only birds in the ag lands helping farmers rid their lands of crop-eating rodents. I found prairie falcons, kestrels, marlins, rough-legged hawks, red-tailed hawks, northern harriers and even four great-blue herons joining in on the hunt.

A prairie falcon had killed a Horned lark as it fed with others in some grain stubble, but it did not take long for a rough-legged to try to steal the songbird. After some aerial maneuvers, the falcon quickly found a bush to hide in to finish its meal. It was not hard to locate raptors who had successfully captured a meal as magpies, crows or ravens would standby to clean up the pieces left by the raptor.

A small flock of horned larks eat ice crystals for a drink. | Bill Schiess, EastIdahoNews.com

As I drove through the ag fields studying about 100 raptors, I found it a little difficult to identify some of the darker ones. Ferruginous, red-tailed and rough-legged vary in color from light to dark morphs with some almost totally black. So, if I miss identify any of the raptors in photos, please let me know.

Back to the frost crystals, they lasted most of the day and I even found flocks of ravens and Eurasian-collared doves hiding groves of flocked trees. I also watched as Horned larks pecked at the crystals to get a drink.

An Eurasian collared dove hides in a tree covered with rime ice crystals. | Bill Schiess, EastIdahoNews.com

As to the pocket of trees where the Ferruginous hawks spend the night, they have been congregating there for the last three weeks. They must find those trees offering them some protection from the elements – or, there is a house under the trees, where a domestic cat lives. I watched one hawk make several dives toward the cat only to return to the same branch. A few times I have also located rough-legged hawks with the ferruginous.

WARNING!!!!!!! Ririe Reservoir has attempted to freeze over during the last two weeks. In the process there are pockets that did not freeze until Thursday and Friday nights. Friday it snowed and covered the thin ice, insulating the ice from becoming solid. Be careful or wait until some bitter cold comes to build the ice safer.

A prairie falcon is chased by a rough-legged hawk as it tries to steal a horned lark that the falcon captured.| Bill Schiess, EastIdahoNews.com A Ferruginous hawk leaves the tree to hunt for some food. | Bill Schiess, EastIdahoNews.com