Looking at the fire-fighting helicopter data made me wonder what other helicopters fly around our area. I didn't know if there was an identifier that the FAA uses to distinguish planes from helicopters, but when I looked at the FAA site I noticed that they had a database field that designated whether the aircraft was for government use or not. I skimmed through the list of aircraft registered in Alameda and found the following gov planes: two sheriff's cesnas (N10CX and N5525U), three Oakland police helicopters (N220PD, N330PD, and N510PD), and two helicopters registered to the East-Bay Regional Park District (N708PD and N996PD). I didn't know the EBRPD had helicopters, but thinking about it it's not surprising. EBRPD manages parks all over the bay area, many of which are far off into the hills. Their operations page talks about how they use the helicopters to support police tasks, fight fires (they have their own water buckets), and do rescue work (I've thought about this on some of the long bike rides I've done with the kids back into Morgan Territory).
Looking through my flight data I found that the EBRPD helicopters are sent out periodically to check on the different parks. The fires from the lightning strikes the other week have been awful though, so it looks like the EBRPD helicopters have been doing more flights over the areas. The below track from September 5th shows how they go out to Chabot, Morgan Territory, Diablo, Sunol, the Pleasanton Ridge, and Brushy Peak.
Looking through the data some more I spotted a few of the Oakland Police Department helicopters. So far, these usually seem to fly out from Oakland to check things out along the interstate, but sometimes they seem to be circling some activity like the below (maybe something was happening at the Oakland Zoo?). One of the interesting things about all this is that while they broadcast their location over ADSB, aggregate sites like FlightRadar don't report the PD helicopter positions (I think plane owners can request that their tracks not be reported on these sites). The data is out there, you just have to know how to get it.