[Merlin?]

yes.

[Common vs. Roseate vs. other tern]

Seems to fit the bill for Roseate--Thin black bill,only two dark outer primaries on slender wings and all white tail.

[Common vs. other tern]

My guess would be common, based on what seems to be a gray body,dark tipped outer primaries and the bill looks to be quite reddish. I am not an expert. 

[Sanderlings?]

 The blackish scapulars with frosty edges and the birds location on the shore has me leaning more towards Least Sandpiper. Wait for the experts.

[Looking to confirm.]

Halifax Nova scotia today. Can you have a look at these please. I think I have a Least and Yellow-bellied Flycatcher and a Swainson's Thrush. Thanks.

[I'm stumped!]

Looks a bit like a Ruby-crowned Kinglet but wait for the experts.

[Who’s feather is this? It’s 10.5 inches. It’s from southern Indiana.]

Welcome to Whatbird. I think Kevin is correct. Turkey Vulture.

[Bird of Prey ID]

Maybe Osprey???

[forgot one]

These are difficult for me but, the slight upturn of the bill in the first picture would suggest Greater Yellowlegs. Wait for more input.

[both semipalm?]

Right you are.

[Swainson's or Hermit Thrush MN]

I didn't think of Gray-cheeked (my bad) and it does seem too rusty colored,but I know you folks are more experienced. As observed by IKLIand, not much of an eye-ring and a complete black upper bill with the lower having a yellowish pink base.

[Swainson's or Hermit Thrush MN]

Because of the lack of buff color on the face and upper breast and the whitish eyering, my vote is Hermit Thrush.

[Warbler]

Adult females and one year male Magnolia show less black in the back,fainter face pattern and less streaking. 

[Grasshopper sparrow?]

A closer look at your bird and a look at Sibley has changed my mind. I now agree with with Grasshopper.

[Grasshopper sparrow?]

That bold white eye-ring and white edged tail feathers has me thinking Vesper Sparrow. Wait for others to respond.

[kingbird?]

I believe you have a Yellow-breasted Chat.

[A couple flycatchers from today…]

my guess  #1 Agree with Western Wood-Pewee

                  #2 Agree with Pacific-slope

                  #3 Western Wood-Pewee (only because it's posture doesn't seem                          as upright as an Olive-sided) Wait for the experts.

[Flycatcher?]

Your bird doesn't seem yellow-green enough to be a Yellow-bellied.  IMO it's white contrasting throat,chest and belly along with steep forehead and large round crown suggests a Least Flycatcher.

[A little help with these]

I agree with your IDs. The strong chestnut cheek patch on the first bird suggests Cape May and the orange legs on the bird in the last photo suggests Blackpoll.

[Shorebirds]

I originally thought #1 was a Lesser and when Aiden suggested Greater, I had a closer look. It seems to be looking slightly away from the camera, which would make the bill appear shorter and it also looks slightly upturned. I now agree with Aiden.

[Least Flycatcher?]

I believe you are correct. Steep forehead,  bold messy eye-ring,  white contrasting throat,chest,belly,   short primary extention, bold wingbars and short tail.

[Foster's or Common Tern?]

In the first picture the flying birds seem to be Forster's, displaying silver-white primary coverts and gray tails with white outer webs.

[Scruffy Indigo Bunting?]

I think you are correct. Indigo Bunting. Maybe immature male (1st spring)

[Assuming House Finch, but so much red/pink]

Purple Finch

[Various Birds]

Yellow-billed Cuckoo, Common Yellowthroat, Swamp Sparrow, House Wren, Gray Catbird, House Wren, House Wren.   I think.