I'd do some research on these two calls and both are categorized as alarm calls but you wouldn't know it by looking at them interacting with one another and neither seemed agitated by my presence as I was there a good five minutes and watched the male preen and the female inhale a couple caterpillars so believe they were more contact calls as the male would call and she'd respond and fly closer to him or vice versa. I did make sure to keep a respectable distance and stay on the path which is something I'm always cognizant of this time of the year so who knows.
I'd also go to Birds of America Online and figured I'd share some of it with you on both calls.
"Chewink Call.. Conventionally transliterated as tow-hee, chewink, joree . Employed by both sexes, juveniles, and adults, and at all seasons. Generally regarded as alarm call, since it occurs in mobbing contexts (i.e., used in presence of ground predators and disturbances near nest), but it occurs in other situations as well."
"Lisp Call. “ Seee -Call” of Stokes and Stokes . Heard in all populations, perhaps second most common call after Chewink Call; uttered by both sexes. It is high-pitched, clear, sibilant, even-pitched (short versions) or down-up slurred (longer versions), duration about 1 s. Tonal quality soft, thin, barely audible beyond few meters distance. Mentioned in literature as wee, tsee-a- wee-e, or seee. Occurs in social context (e.g., within pairs and families, in foraging groups during winter and migration), evidently functions as contact note."
I do have to admit I'm wondering why the female isn't on her nest as I would think it would be around that time. All this rain we've had this month has me very concerned about all of our nesting birds here in the North East.
Take care all.