I just re-read in Lusk's Basic Pond Management this morning (it's standard "reading room" material for me first thing in the A.M.) that RES (normally) spawn before BG. IIRC the CW also states that they like slightly deeper beds.

However, variations in water temp with oddball weather (much more common in small ponds, of course), calender alignment with moon cycles, and the innate perversity of the universe sometimes conspire so that RES and BG are on the beds at the same time. Local water cloudiness issues, limited (premium) spawning bed locations, and I'm sure other factors may cause the two species' beds to be intermingled.

"Live like you'll die tomorrow, but manage your grass like you'll live forever."
-S. M. Stirling
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