In general note the overall coloration and finch/sparrow bill. The Black upper parts and rufous sides are key marks. Also, note the white markings on the wings. You are looking at a male Eastern Towhee, formerly, Rufous-sided Towhee.
Royal Tern (in flight) & Forster's Tern (smaller birds)
Always a challenge to identify terns can be confusing. In the photo note the size difference. The tern in flight is larger with a orange slender bill, white crown and pale under wing. This is a winter plumage adult Royal Tern. The smaller terns, both have a distinctive ear patch which is a field mark of Forster's Tern. Have a look at your Eastern Sibley Guide or the "New" National Geo. "Birds of Eastern N.A.".