Re: 5MR Circle thoughts

Roger Uzun

For a 5MR circle if you want to keep Sweetwater Reservoir in the mix you lose Hollister st (for the most part), Bird and Butterfly Garden, Sunset ballfields, Dairy Mart Ponds, etc but you still have Nestor and Tesoro.

Is that the idea behind the sweetwater river CBC circle, to include the Reservoir?  If so it might be the best 5 mile radius, but you can't keep Otay and you will lose most of whats south of Nestor / Tesoro.

It seems like somehere in Chula Vista is going to be the best 5 mile spot though.  It's just a matter of how far South and West vs how far North and East you want to go because no single 5MR will give you all you think of in the area.


On Sun, Jan 6, 2019 at 7:47 AM Justyn Stahl <justyn.stahl@...> wrote:
Roger - interesting thought project. The San Diego CBC circle (7.5 mile radius) is centered near the mouth of the Sweetwater River and encompasses many habitat types (including open ocean, good shorebird/duck habitat, Balboa Park and various other migrant hotspots you mention, and stretching all the way east to the Sweetwater Reservoir). With 216 species in a single day last December, a 5MR circle based on that idea would likely be hard to top, but reducing it by 2.5 miles in either direction may require shifting it a bit to maximize diversity.

Greg - I'm not sure the 5MR circles can be adapted to replicate something as rigorous as the San Diego County Bird Atlas squares. [However, it's possible one could extract general eBird data for a similar purpose - but very few people use appropriate breeding codes***.] Being centered on a person's home, there's little choice in the matter of how 5MR circles are placed on the map. Most circles would overlap. And Atlas squares were 3x3 miles (9 square miles), while a 5MR is 78.5 square miles. They do, however, share at least one common theme: intensive scrutiny of a small area, particularly underbirded locations, in an effort to better document species' occurrence (including, but not limited to, rarities).   I do wish I'd lived here when the Atlas work was done (1997-2002) by Phil Unitt and the 400 volunteers from this community. But hopefully someday soon we'll be able to replicate it to assess the changes that have surely taken place locally.

The San Diego County Bird Atlas is an indispensable piece of literature for local birders. It's available to view online ( but I would encourage anyone with an interest in San Diego birds to swing by the Natural History Museum and pick up a copy.

*** This does actually bring up a good point: for those of you eBirding, I encourage you to use appropriate breeding codes throughout the breeding season, which is underway for some species already. Anna's Hummingbirds, for example, begin nesting as early as December. For more info on eBird breeding codes, follow this link:

Justyn Stahl

On Sat, Jan 5, 2019 at 8:49 PM Greg Gillson <greggillson@...> wrote:
Can this be adapted to be used with the old San Diego Bird Atlas squares? And if so, how? It would be nice to have something to compare with and perhaps be useful for future research. 


Greg Gillson
Escondido, California

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