Saturday 21 April 2012

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

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
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

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
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
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

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

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
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

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.


  1. Terrific list and thanks for taking the time and making the effort to put it together.

  2. Hey Mike, I've noticed a few species that you're missing: European Starling, Blackburnian Warbler, Worm-eating Warbler, House Finch (perhaps too erratic, but there's a noticeable peak in early may on the graph)

  3. Thanks Reuven! The Blackburnian was definitely an oversight so I have added it in. Worm-eating Warbler and House Finch (and to a lesser extent European Starling) I had purposely excluded because when you start looking at the daily frequencies the pattern isn't very clear. However, I have added them in anyways!

  4. Any birds known for setting up nest in a backyard BBQ?... Has a yellow beak, black feathers and orange legs... the nest is the size of my BBQ...

    1. Hi Stephen, most likely a European Starling. You can google lots of photos of this!

  5. I know someone who keeps an arrival date list for Timmins. It will be interesting to compare your list with hers. We are probably a week or 2 behind southern Ontario.