(April 23, 2018) The results for the 2017 Biological Effectiveness Monitoring Program on Conservancy preserves are in. Here, a focus on the Swainson’s hawk.
view an enlarged image of a Swainson's hawk

In 2016, there were 43 successful nests and 63 fledged. In 2017, there were 49 successful nests, and 68 fledged. The upward trend is great, of course. But we want to know why.

We see cycles in the Swainson’s hawk favorite prey, microtus (meadow mice). And those show an ebb and flow of population variances.

But now, looking at the graphs, we are starting to see trends based on annual rainfall. I am not sure the academic biologists agree. But it appears that Swainson’s hawk numbers decline in drought years and rise in a wet years.

Maybe the answer is as simple as rain providing the essential resource for greater prey populations. More data is needed, and this will take time. Now, however, we’re watching this one closely.

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