Guide to spring arrival dates in Ontario

*: I originally posted this in April 2012 using 1900 to 2011 data. I have since updated everything to include up to the end of 2013.*

I've wanted to put something like this together for a while now but it wasn't until I read the "Changing Seasons" piece in Volume 65 Number 3 of North American Birds that I had a good way to do it.  So what is it?  Following this short introduction you'll find a list of 198 of Ontario's fairly common birds and the dates you can reasonably expect to find them returning.

Background: in the article I mentioned above, Marshall Iliff, Brian Sullivan, and Chris Wood (AKA eBird HQ) proposed that we should start using 20% of the peak arrival frequency for a given species to indicate the day that a species arrives on a broad front (I'll refer to this day from here on out as the "mass arrival date".  The eBird team showed that this is really a good measure of arrivals since it is largely independent of outliers (exceptionally early individual birds), independent of sampling effort (since it is based on percentages of checklists, not raw number of checklists), and adjusted for species' rarity. Email me if you want a scanned copy of the article.


Methods: I went through the eBird frequency graphs (for all data years 1900-2013) for each species reported in Ontario. Frequency is a common statistic eBird calculates - it is the percentage of checklists reported for a given date/location which have a positive observation for a given species.  I didn't include species that are very rare in Ontario during spring migration, species which don't show an appreciable widespread seasonally predictable change in frequency (i.e. resident and irruptive species), or species which are more frequently encountered during the winter season and just decrease through spring migration (i.e. they don't show a spring migration spike in frequency).  That left me with 201 species.  For each of the 201 spring migrants I collected the date and value (frequency) of the spring migration peak and then calculated what the mass arrival date frequency would be and what date the average mass arrival date in Ontario is (Figure 1).  For species which overwinter in parts of Ontario I corrected for the "winter frequency" by calculating the mass arrival date as:

M = 0.2 X (P - W) + W

Where:
M = mass arrival date
P = peak arrival date
W = winter frequency

Results: Well, first of all to most of you this information won't be new, but I think it is interesting to put some hard numbers to things.  Keep in mind when looking at the results that these results show the average date that the species arrives on a relatively widespread front across Ontario.  So, the actual date will obviously be earlier along Lake Erie but later in Thunder Bay - interpret accordingly.  Before the final results, here's a neat figure showing the number of species arriving en masse per week during the course of spring migration.

OK, here are the results, now get out there and find some spring migrants and be sure to report your findings to eBird so we can compare how advanced (or not) this year has been!

02 Feb -	Horned Lark
05 Feb -	American Crow
20 Feb -	Redhead
26 Feb -	Gadwall
	Northern Pintail
	Canvasback
	Bufflehead European Starling
28 Feb -	Tundra Swan
	American Wigeon
02 March -	Snow Goose
	Canada Goose
	Ring-billed Gull
03 March -	Mallard
	Lesser Scaup
	Red-breasted Merganser
	American Coot
04 March -	Cackling Goose
	Hooded Merganser
	Red-winged Blackbird House Finch*
07 March -	Red-necked Grebe
	Common Grackle
08 March -	Ring-necked Duck
09 March -	Horned Grebe
	Sandhill Crane
10 March -	Ross's Goose
	Eurasian Wigeon
	Northern Shoveler
	Green-winged Teal
	Killdeer
	American Robin
11 March -	Red-shouldered Hawk
	Little Gull
12 March -	American Woodcock
13 March -	Merlin
14 March -	Turkey Vulture
	Northern Harrier
	Song Sparrow
16 March -	Eastern Bluebird
17 March -	Pied-billed Grebe
18 March -	Wood Duck
	Golden-crowned Kinglet
	Eastern Meadowlark
	Brown-headed Cowbird
20 March -	Red-throated Loon
21 March -	Great Blue Heron
	Rusty Blackbird
22 March -	American Kestrel
25 March -	Northern Flicker
	Eastern Phoebe
	Brown Creeper
	Winter Wren
	Fox Sparrow
27 March -	Blue-winged Teal
28 March -	Pectoral Sandpiper
	Belted Kingfisher
30 March -	Dark-eyed Junco
31 March -	Wilson's Snipe
01 April -	Bonaparte's Gull
02 April -	Double-crested Cormorant
	Tree Swallow
03 April -	Great Egret
	Yellow-bellied Sapsucker
	Field Sparrow
	Vesper Sparrow
04 April -	Osprey
06 April -	Common Loon
	Sharp-shinned Hawk
	Greater Yellowlegs
07 April -	Cooper's Hawk
	Hermit Thrush
08 April -	Lesser Yellowlegs
	Purple Finch
09 April -	Caspian Tern
10 April -	Black-crowned Night-Heron
13 April -	Louisiana Waterthrush
	Pine Warbler
	Swamp Sparrow
14 April -	American Bittern
	Forster's Tern
	Ruby-crowned Kinglet
	Eastern Towhee
	Savannah Sparrow
15 April -	Surf Scoter
	Barn Swallow
	Chipping Sparrow
	American Goldfinch
16 April -	Broad-winged Hawk
	Brown Thrasher
	Yellow-rumped Warbler
	White-throated Sparrow
17 April -	American White Pelican
	Northern Rough-winged Swallow
18 April -	Virginia Rail
19 April -	Purple Martin
20 April -	Cliff Swallow
21 April -	Yellow-throated Warbler* Worm-eating Warbler*
22 April -	Black Scoter
	Upland Sandpiper
23 April -	Willet
24 April -	Green Heron
	Sora
	Spotted Sandpiper
	Common Tern
	Bank Swallow
25 April -	Long-billed Dowitcher
	Blue Jay
26 April -	Solitary Sandpiper
	Blue-headed Vireo
	Blue-gray Gnatcatcher
	Palm Warbler
27 April -	Wilson's Phalarope
	White-eyed Vireo
	House Wren
	Marsh Wren
	Northern Waterthrush
28 April -	Sedge Wren
	Grasshopper Sparrow
30 April -	Common Gallinule
	Dunlin
	Chimney Swift
	Red-headed Woodpecker
	American Pipit
	Black-and-white Warbler
	Nashville Warbler
	Kentucky Warbler
	Black-throated Green Warbler
01 May -	Eastern Whip-poor-will
	Warbling Vireo
	Wood Thrush
	Gray Catbird
	Ovenbird
	Blue-winged Warbler
	Orange-crowned Warbler
	Hooded Warbler
	Lincoln's Sparrow
	White-crowned Sparrow
	Rose-breasted Grosbeak
02 May -	Ruby-throated Hummingbird
	Least Flycatcher
	Eastern Kingbird
	Yellow-throated Vireo
	Veery
	Golden-winged Warbler
	Prairie Warbler Blackburnian Warbler
	Orchad Oriole
	Baltimore Oriole
03 May -	Great Crested Flycatcher
	Prothonotary Warbler
	Common Yellowthroat
	Northern Parula
	Black-throated Blue Warbler
	Yellow-breasted Chat
	Clay-colored Sparrow
	Scarlet Tanager
	Indigo Bunting
	Bobolink
04 May -	Black-bellied Plover
	Semipalmated Plover
	Least Sandpiper
	Swainson's Thrush
	Cerulean Warbler
	Magnolia Warbler
05 May -	Cape May Warbler
06 May -	Least Bittern
	American Golden-plover
	Short-billed Dowitcher
	Black Tern
	Gray-cheeked Thrush
	American Redstart
	Kirtland's Warbler
	Summer Tanager
07 May -	Common Nighthawk
	Tennessee Warbler
08 May -	Ruddy Turnstone
	Sanderling
	Black-billed Cuckoo
	Philadelphia Vireo
	Red-eyed Vireo
	Connecticut Warbler
	Bay-breasted Warbler
	Canada Warbler
	Wilson's Warbler
09 May -	Semipalmated Sandpiper
	Cedar Waxwing
10 May -	Yellow-billed Cuckoo
	Eastern Wood-pewee
	Acadian Flycatcher
	Blackpoll Warbler
11 May -	Brant
12 May -	Olive-sided Flycatcher
	Willow Flycatcher
	Mourning Warbler
13 May -	Yellow-bellied Flycatcher
15 May -	White-rumped Sandpiper
17 May -	Red-necked Phalarope
18 May -	Whimbrel
20 May -	Red Knot
	Alder Flycatcher

*these species are barely calculable due to a pretty weak peak

Anyways, I hope you find this information interesting/helpful.  Please let me know of any errors you see.  It will only get better as more eBird data comes in.

Last updated March 1, 2014.