Concluding the Search

by Carl Strang

This year’s great horned owl nest search was the most intimidating I have done. There are 344 acres in the area I monitor, the portion of St. James Farm Forest Preserve that is north of Butterfield Road. A large portion of that acreage is forested, and it’s an old forest with many large trees that might harbor an owl nest. Furthermore, despite excellent restoration of the forest, a significant portion still has a difficult-to-negotiate understory dense with thorny barberries and roses mixed with way-blocking honeysuckles. Over a two-week period I went through the preserve, noting locations of candidate tree cavities and open tree tops.

One of the many possible nest cavities, large enough to hold an incubating owl that might not be visible from the ground.

One of the many possible nest cavities, large enough to hold an incubating owl that might not be visible from the ground.

Another candidate cavity. The weather often was gloomy, the limited light reducing photo quality and making it difficult to see if anything was inside.

Another candidate cavity. The weather often was gloomy, the limited light reducing photo quality and making it difficult to see if anything was inside.

There also were many old trees that had lost their tops.

There also were many old trees that had lost their tops.

Another example of a topped tree that could host a nest.

Another example of a topped tree that could host a nest.

After that initial survey, I decided to dig out my clunky old GPS unit and determine the latitude-longitude locations of all the candidate trees, while also mapping the survey routes I follow in routine monitoring work.

Here is the resulting map. I created a grid, the finest lines separated by one second of latitude or longitude. The blue dots and white lines mark my survey routes. The red dots are locations of trees that might harbor a great horned owl nest.

Here is the resulting map. I created a grid, the finest lines separated by one second of latitude or longitude. The blue dots and white lines mark my survey routes. The red dots are locations of trees that might harbor a great horned owl nest.

I was a little embarrassed by my failure to re-find 3 candidates from the descriptions in my notes. I ended up with 23 trees, and that turned out to be enough, as I saw this in one of them:

Sometimes a single feather tuft is all you get. In this case I could see part of the top of the head, too.

Sometimes a single feather tuft is all you get. In this case I could see part of the top of the head, too.

I realized that I was fortunate that this was a sunny day, and the additional ambient light made the difference. Now I look forward to following the progress of this nest. The eggs should have hatched by now.

 

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