I've gone through some of the known vagrant traps along the Great Lakes (biased towards Ontario) and pulled out some specific examples to discuss:
Birder concentration/ human influence:
red lines - a long "run" for birds until they hit Duluth (large catch-area)
Sample: Glaucous-winged Gull, Snowy Plover, Vermillion Flycatcher, Black-headed Grosbeak, Burrowing Owl, Fork-tailed Flycatcher
The skinny: Duluth is a heavily populated and birded area right at the end of Lake Superior. With a long run of shoreline to catch (or trap) birds, it has turned up an impressive list. Populated areas also attract a variety of birds due to man-made influcenecs like landfills (Glaucous-winged Gull), parks to concentrate bird migrants/vagrants and even things like sewage lagoons.
Chicago Waterfront, IL:
Red X - development helps concentrate birds at remaining habitat on waterfront.
Sample: Ross's Gull, "Olympic" Gull, Grace's Warbler, Large-billed Tern, Black-tailed Gull, Brewer's Sparrow, Reddish Egret, Rock Wren, Vermillion Fly, Groove-billed Ani
The Skinny: similar to Duluth, the Chicago waterfront boasts an impressive list of mega's. Many rarities are found because they're attracted to humans (Gulls) or have been super-concentrated in the few remaining natural areas along the lakeshore, and are easier to find (Grace's Warb). It also doesn't help that the number of birders in the area is also very high.
Red: points funnel birds to a concentration point (tip) and attract birds flying in off the water
Sample: Black Swift, Mottled Duck, Neotropic Cormorant, Lesser Nighthawk, Gray Flycatcher, Plumbeous Vireo, Cassin's Finch
The Skinny: Point Pelee is world famous for its birds, and is a mecca for rarities. Thousands of observers go over this location with a fine toothed comb and have turned up an impressive list (mainly in spring). Being located at the very bottom of the Great Lakes, the "catch area" for this location is much larger than the map suggests.
Sample: Inca Dove, Short-tailed Hawk, Virginia's Warbler, Lucy's Warbler, Least Tern, Brewer's Sparrow, McCown's Longspur
The Skinny: Whitefish is another point with a huge catch area. Prevailing SW winds blow directly down to the tip of the point, which has probably helped turn up some of these real CMF's. It also has a huge run to catch vagrant waterbirds passing the point (or coming ashore).
Manitou Island, MI:
Sample: Say's Phoebe, Scissor-tailed Flycatcher, Snowy Egret, Smith's Longspur, Black Vulture
The Skinny: Islands are a haven for birds who find themselves out over water, and don't want to be there. I can only assume that Islands are great for rarities, because rarities are likely very lost to begin with and maybe end up out over water more frequently than our local birds. Manitou has a huge draw area from the waters of Superior, and probably also benefits from being at the end of a major peninsula. Part of the problem with Islands, is they're much harder for birders to get to - which is the case here.
(Green lines for Pelee Island).
Sample: Western Wood-Pewee, Wood Stork, Garganey, Crested Caracara, Burrowing Owl, White Ibis
The Skinny: being surrounded by water is one thing, but Pelee Island also benefits from having small (natural) points on 4 corners. Point Pelee and Pelee Island seem to share a unique relationship as being a bit of a "bridge" for passerines to cross during their nocturnal migration. This is often visible on nexrad radar, and being right smack in the middle of the bridge could have added to this impressive list of birds.
Sample: Lesser Sand-Plover, Sulphur-bellied Flycatcher, Sandwitch Tern, American Oystercatcher, Snowy Plover, Wilson's Plover
The skinny: part of the "wild card" aspect to vagrant hotspots is habitat. On the above map, Presqu'ile doesn't really stand out compared to the plethora of points and bays of Prince Edward County. Yet there is a story here that maps don't show - habitat! Presqu'ile is blessed with great habitat for waterbirds, shorebirds and has lush woods for landbirds. Prince Edward County is a Red Cedar/Juniper savannah wasteland sort of habitat (the circle), with hard rocky shorelines and limited beaches. Presqu'ile has enough of a geographic impact on the lake to allow it's spectacular habitats attract a very impressive list of birds .
(At the same time, the "question mark" on the map is Prince Edward Point Bird Observatory, which still gets an impressive list of rarities in its own right).
Sample: Brewer's Sparrow, Violet-Green Swallow, Sulphur-bellied Flycatcher, Virginia's Warbler, Sprague's Pipit, Yellow-billed Loon
The skinny: This one is obviously a point, but I think also has the right habitat... I've heard that high elevation areas attract birds (heard this in Bermuda), and Sleeping Giant itself is pretty big. Then there is a nice low level area right at the tip for them to settle down into.
Sample: Yellow-nosed Albatross, Razorbill, Great Cormorant, Tufted Duck, Eurasian collared Dove, Northern Wheatear, Vermillion Flycatcher
The skinny: Wolfe Island is a large Island in Lake Ontario, known for concentrations of raptors and waterfowl. A short ferry ride from Kingston (free), which runs almost every hour of the day, makes getting here very easy. Once you're there, you can drive hundreds of km's of roads to dramatically increase the area you can search.
Clark's Nutcracker, Smith's Longspur, possible Barid's Sparrow & Black-headed Grosbeak
The skinny: only 3 birders have ever been here, yet some impressive records exist. It is fairly obvious that this location would be a mecca for rare birds. But there is a massive problem - it is very hard to get to. As noted above, it doesn't even appear on most maps! Once you're there, all searching is done on foot. Not that it's a terrible thing, but sometimes can really help keep you motivated with a change of scenery.
Sample: Black-capped Petrel, Band-rumped Storm-Petrel, White Ibis, Wood Stork, Smew, Prairie Falcon, Snowy Plover, American Oystercatcher, Ross's Gull, Sandwich Tern, White-winged Tern, Thick-billed Murre, Common Ground-Dove, Boreal Owl, Black Swift, Western Wood-Pewee, Black-capped Vireo, Carolina Chickadee, Fieldfare, Varied Bunting, Great-tailed Grackle (2), Hooded Oriole (2), Gray-crowned Rosy-Finch, Cassin's Finch
A look in detail at each of the categories listed above:
Human influence: Is a big part of the history for Long Point - the "point" itself has been protected for a looong time, which is a good thing. At the same time, the mainland has enough human influence to also make it appealing to birders. Access to various locations has allowed a number of good birds to be found, not to mention deliberately man made areas (see: Smew at the fish hatchery).
Point: No denying this point, sticking out close to 30km into the lake. It funnels birds, and rarities, to the end, such as their Black Swift.
Island: Now here's where you need to bear with me, but I feel that Long Point also draws on the "island effect". Check the black marks/arrows I added to the map. As far as mega-rare passerines are concerned (like the Black-capped Vireo or Varied Bunting), returning to the "mainland" from the tip or Breakwater isn't all that easy --- there is huge expanses of marsh that they probably do NOT want to cross. It really isolates them... It's the best of both worlds, since "point attraction" birds like a Swallow-tailed Kite, don't mind crossing over the marsh.
Natural Habitat: You can't deny Long Point has the right habitat. There is so much, that huge amounts go unchecked on a yearly basis. Just imagine what has been out there! But the entire construct, of the "island and point" effect, along with ample marsh, woodland, beach, shorebird habitat, etc etc make Long Point get an A+ here.
Accessibility: Thankfully due to the banding operations and research, a number of CMF's have been found at places that are really hard for birders to visit (eg,/ the TIP... ) It is partially really unfortunate that it is like this, but what can you do ? I wrote this piece and awarded Long Point the "best vagrant spot" award.. Not the "best chance for you to get there and find vagrants" award!