General Discussion : What is considered a healthy population density?

I have conducted a general Spring driving survey of the local Kestrel population this March and have identified 34 individuals, 17 males and 17 females with 8 noted as pairs perched together. I have limited my survey to the northern section of the county consisting of about 125 miles of rural, zig-zaging backroads. Many of the sightings come in successive clusters over a distance of a mile or two in some of the better habitat.

At what levels or densities is a Kestral population considered “healthy?” Is there a quantification of individuals per square mile of habitat that is indicative of declining, stable or improving population levels?

By the way, I'm having trouble getting the data submission apps past my firewall on my computer, so I have yet to post these observations. It's a work in progress at the moment.