Interesting Roger.

I have not kept tabs by numbers on the HL's I observe but I have a few notes to add.

The CHL populations I observe on a regular basis are not in developed areas, far from it. They are also in drier climes than Newberry Park. So I have seen no declines at all and no invasive ant species (I believe due to the drier habitat).
I did walk around in Moorpark and found that almost all of the P. californicus nests were under serious attack by the argentine ants.
So I have a feeling that HL's in moist habitat, with serious development are going to continue to decline, probably to extinction, while the HL's in drier desert habitat without so much pressure from development will continue to thrive.
I don't know what you could do short of getting rid of the people and the ants to stabilize them. I think it's just a fact of life that we will have to accept for these areas.
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