Where can you see Boreal Chickadee AND Prothonotary Warbler in the Greater Toronto Area? The best answer is probably nowhere, but there is only one spot where both species have been reported to eBird, and that spot is what I'd like to write a bit about today.
For birders, a patch is a small area you bird frequently and regularly, and is often your go-to location for a few hours of birding. My patch is a block of natural habitat in Mississauga consisting of Riverwood Park, Erindale Park and the University of Toronto's Mississauga Campus. This area along the Credit River forms the largest and most biodiverse natural area in Mississauga.
This map shows the approximate boundaries of my patch. The three markers represent particularly attractive features - a storm-water pond (blue) which provides some of the only (limited) water habitat in the area, a toboggan hill (yellow) that provides a near-panoramic view of the surroundings, perfect for hawk-watching, and bird feeders (red) that entice a variety of birds to stay the winter.
I lived adjacent to this area for all of high school and still visit regularly when I am in Mississauga. I've submitted 439 eBird checklists between the components of this area, and have probably birded it close to 600 times in total. It's safe to say that I have a fairly good handle on how birds use the area.
Several large bridges pass over the valley. This is Burnhamthorpe Rd, and this bridge does not support any nesting birds, but other bridges have nesting Cliff, Bank and Northern Rough-winged Swallows, Eastern Phoebes, Rock Pigeons, European Starlings and House Sparrows.
I've found exactly 170 species of birds here, which is very good for an area with no significant habitat for waterbirds (I've had only 9 species of waterfowl and 6 species of shorebird). The only locations around Toronto on eBird with a comparable diversity that aren't directly on Lake Ontario or have other major wetland habitats are Bronte Creek Provincial Park in Oakville and Kortright Conservation Area in Vaughan. Still, there is probably more to be found, as this area is rarely birded by anybody besides myself.
I have little doubt that there are more species of birds breeding here than anywhere else in Mississauga. Particularly notable species I've found here on territory include Mourning Warbler, Pine Warbler, Yellow-throated Vireo, Sharp-shinned Hawk, Orchard Oriole, Cliff Swallow, Bank Swallow and Wood Thrush.
Winter is great too, especially due to bird feeders enticing birds to stay and the river valley providing shelter for some of our less hardy birds. Hoary Redpoll, Swamp Sparrow, Common Yellowthroat, Long-eared Owl, Barred Owl, Brown Thrasher, Eastern Bluebird, Bald Eagle and White-winged Crossbill are some of the more interesting birds I've had in midwinter. Song Sparrows, White-throated Sparrows and Winter Wrens, all of which have the bulk of their wintering grounds to the south of here can be reasonably common in winter. I've had as many as 5, 17 and 9 respectively spending the winter (and that's only the ones I actually found).
Long-eared Owl in Erindale Park
Migration is still the time to visit, as with most birding spots. Some of my most notable sightings:
Prothonotary Warbler - male singing on June 6, 2013. There are less than 10 records of this species on eBird from the GTA, and none from the summer. I thought this bird might be on territory, but it was not seen again by anybody, and may have been a very late migrant.
Boreal Chickadee - in the fall of 2010 this species, not normally found any closer than Algonquin Park, made a major incursion into Southern Ontario. My sighting on October 21 was one of the southern-most individuals.
American Bittern - not an incredibly rare bird, but the fact that it was perched in a bush in the middle of a dry field is notable! They are normally denizens of dense marshes.
Golden Eagle - I've had Golden Eagle here twice. On 28 November 2010 I had one fly over. More notably, in mid-May of either 2008 or 2009 (I unfortunately never wrote down the date) I had a juvenile Golden Eagle fly over in Erindale Park. This is not unheard of, but still rather late for this species.
Short-eared Owl - October 7, 2009
Golden-winged Warbler - twice in May
Brewster's Warbler - twice in May
There are still some holes in my patch list that should be fillable, including species like Snow Bunting, Hooded Warbler, Northern Goshawk, Gadwall, Green-winged Teal, Lesser Yellowlegs and Cackling Goose. There is nothing really expected I haven't seen though.
This list may make it seem like an extremely good birding spot, but really it's just the result of birding a moderately good area so frequently. I would highly recommend getting very familiar with one area, it makes for really satisfying birding.