[EBB Sightings] Coyote Hill and Tree Swallows

I have a question for anyone on this list who frequents Coyote Hills Reg Park; Especially anyone who was a regular there during Nov & Dec.  

Today, Bob Lewis and the Albany Adult School field trip saw an estiamted 35 Tree Swallows at Coyote Hiills.  Bob says the birds were perched on and inspecting nestboxes,  acting like they could be recent arrivals.

Are these birds that have overwintered, or are these 'Spring' arrivals?  What were typical numbers of Tree Swallows like this winter season until now? 

Thanks,

     Rusty Scalf