← Methods Validation: arrival dates Run on 1 Oct 2026 · methods 0.2 · weeks 17 Nov 2025 to 27 Sept 2026
Wildlife Network estimates when a species arrives in a region from acoustic detections. This page compares those estimates with an independent source: photographs and recordings submitted by people to iNaturalist, for the same species, the same 5 degree cells and the same weeks. The two sources share no data and have different biases, so agreement between them is meaningful, and disagreement is informative.
Arrivals compared
204
82 species
Median difference
+1 week
Wildlife Network is later
Within 1 week
70%
83% within 2, 91% within 4
Mean absolute error
2.14 weeks
correlation 0.51
What was compared The 300 best sampled arrivals in Wildlife Network between February and mid July 2026, at most six cells per species so that no species dominates. The sample was taken by detection count, not chosen by hand. For each, iNaturalist's weekly count of research grade observations of that species in that cell. The same rule on both sides: the arrival is the first week a species reaches a tenth of its seasonal peak, after at least six weeks below that level, and stays there the following week. 204 of 300 could be compared. In 94 cases iNaturalist had too few observations or showed no clear seasonal arrival, and 2 requests failed. Result 1 Mar 1 Mar 1 May 1 May 1 Jul 1 Jul 1 Sept 1 Sept Common Chiffchaff (50°, 5°): Wildlife Network 9 Mar, iNaturalist 23 Feb, difference 2 weeks American Robin (40°, -75°): Wildlife Network 2 Mar, iNaturalist 2 Feb, difference 4 weeks American Robin (40°, -80°): Wildlife Network 23 Feb, iNaturalist 2 Feb, difference 3 weeks American Robin (40°, -90°): Wildlife Network 16 Feb, iNaturalist 9 Feb, difference 1 weeks Common Grackle (40°, -80°): Wildlife Network 2 Mar, iNaturalist 2 Mar, difference 0 weeks Gray Catbird (40°, -75°): Wildlife Network 27 Apr, iNaturalist 20 Apr, difference 1 weeks Eastern Phoebe (40°, -75°): Wildlife Network 16 Mar, iNaturalist 9 Mar, difference 1 weeks Common Chiffchaff (50°, 0°): Wildlife Network 2 Mar, iNaturalist 2 Mar, difference 0 weeks Broad-tailed Hummingbird (35°, -110°): Wildlife Network 20 Apr, iNaturalist 13 Apr, difference 1 weeks Eurasian Blackcap (50°, 5°): Wildlife Network 30 Mar, iNaturalist 6 Apr, difference -1 weeks Chipping Sparrow (40°, -75°): Wildlife Network 6 Apr, iNaturalist 30 Mar, difference 1 weeks House Wren (40°, -90°): Wildlife Network 20 Apr, iNaturalist 13 Apr, difference 1 weeks Common Grackle (40°, -85°): Wildlife Network 23 Feb, iNaturalist 23 Feb, difference 0 weeks House Wren (40°, -75°): Wildlife Network 20 Apr, iNaturalist 13 Apr, difference 1 weeks House Wren (40°, -80°): Wildlife Network 20 Apr, iNaturalist 13 Apr, difference 1 weeks House Wren (40°, -85°): Wildlife Network 20 Apr, iNaturalist 13 Apr, difference 1 weeks Cedar Waxwing (45°, -125°): Wildlife Network 4 May, iNaturalist 4 May, difference 0 weeks Gray Catbird (35°, -80°): Wildlife Network 20 Apr, iNaturalist 13 Apr, difference 1 weeks House Wren (40°, -95°): Wildlife Network 20 Apr, iNaturalist 13 Apr, difference 1 weeks Common Chiffchaff (50°, 10°): Wildlife Network 16 Mar, iNaturalist 9 Mar, difference 1 weeks Common Swift (50°, 5°): Wildlife Network 18 May, iNaturalist 20 Apr, difference 4 weeks House Wren (35°, -80°): Wildlife Network 13 Apr, iNaturalist 13 Apr, difference 0 weeks Common Grackle (40°, -90°): Wildlife Network 23 Feb, iNaturalist 2 Mar, difference -1 weeks Gray Catbird (40°, -80°): Wildlife Network 27 Apr, iNaturalist 20 Apr, difference 1 weeks Painted Bunting (30°, -100°): Wildlife Network 20 Apr, iNaturalist 20 Apr, difference 0 weeks Ruby-throated Hummingbird (35°, -95°): Wildlife Network 15 Jun, iNaturalist 13 Apr, difference 9 weeks Broad-tailed Hummingbird (40°, -110°): Wildlife Network 20 Apr, iNaturalist 20 Apr, difference 0 weeks Eastern Phoebe (40°, -80°): Wildlife Network 9 Mar, iNaturalist 9 Mar, difference 0 weeks Eastern Wood-Pewee (35°, -80°): Wildlife Network 11 May, iNaturalist 4 May, difference 1 weeks Violet-green Swallow (45°, -125°): Wildlife Network 30 Mar, iNaturalist 2 Mar, difference 4 weeks American Robin (40°, -95°): Wildlife Network 9 Feb, iNaturalist 2 Feb, difference 1 weeks Purple Martin (25°, -100°): Wildlife Network 9 Feb, iNaturalist 2 Mar, difference -3 weeks White-winged Dove (30°, -115°): Wildlife Network 16 Mar, iNaturalist 16 Mar, difference 0 weeks Red-eyed Vireo (40°, -75°): Wildlife Network 11 May, iNaturalist 4 May, difference 1 weeks Chuck-will's-widow (30°, -100°): Wildlife Network 20 Apr, iNaturalist 13 Apr, difference 1 weeks Common Chiffchaff (50°, -5°): Wildlife Network 16 Mar, iNaturalist 2 Mar, difference 2 weeks Black Redstart (50°, 10°): Wildlife Network 16 Mar, iNaturalist 9 Mar, difference 1 weeks Pacific-slope Flycatcher (45°, -125°): Wildlife Network 20 Apr, iNaturalist 6 Apr, difference 2 weeks Eastern Wood-Pewee (40°, -90°): Wildlife Network 18 May, iNaturalist 11 May, difference 1 weeks Eurasian Blackcap (45°, 5°): Wildlife Network 16 Mar, iNaturalist 9 Mar, difference 1 weeks White-crowned Sparrow (45°, -125°): Wildlife Network 16 Mar, iNaturalist 23 Mar, difference -1 weeks Common Chiffchaff (45°, 10°): Wildlife Network 9 Mar, iNaturalist 23 Feb, difference 2 weeks Ruby-throated Hummingbird (30°, -100°): Wildlife Network 6 Jul, iNaturalist 6 Apr, difference 13 weeks Chipping Sparrow (40°, -80°): Wildlife Network 30 Mar, iNaturalist 30 Mar, difference 0 weeks Common Chiffchaff (55°, 10°): Wildlife Network 30 Mar, iNaturalist 16 Mar, difference 2 weeks Violet-green Swallow (35°, -125°): Wildlife Network 16 Mar, iNaturalist 23 Feb, difference 3 weeks Wood Thrush (35°, -80°): Wildlife Network 20 Apr, iNaturalist 20 Apr, difference 0 weeks Chipping Sparrow (40°, -85°): Wildlife Network 30 Mar, iNaturalist 30 Mar, difference 0 weeks Common Grackle (40°, -100°): Wildlife Network 9 Mar, iNaturalist 9 Mar, difference 0 weeks Eurasian Blackcap (50°, 10°): Wildlife Network 6 Apr, iNaturalist 30 Mar, difference 1 weeks Purple Martin (35°, -80°): Wildlife Network 13 Apr, iNaturalist 6 Apr, difference 1 weeks Eastern Wood-Pewee (40°, -80°): Wildlife Network 18 May, iNaturalist 11 May, difference 1 weeks Red-eyed Vireo (40°, -80°): Wildlife Network 11 May, iNaturalist 4 May, difference 1 weeks Wood Thrush (35°, -85°): Wildlife Network 20 Apr, iNaturalist 13 Apr, difference 1 weeks Common Swift (45°, 5°): Wildlife Network 18 May, iNaturalist 30 Mar, difference 7 weeks Eastern Wood-Pewee (40°, -85°): Wildlife Network 18 May, iNaturalist 11 May, difference 1 weeks Eurasian Blackcap (45°, 10°): Wildlife Network 30 Mar, iNaturalist 16 Mar, difference 2 weeks Common Swift (50°, 0°): Wildlife Network 18 May, iNaturalist 20 Apr, difference 4 weeks Chimney Swift (35°, -80°): Wildlife Network 13 Apr, iNaturalist 6 Apr, difference 1 weeks Common Grackle (45°, -80°): Wildlife Network 9 Mar, iNaturalist 23 Mar, difference -2 weeks Chimney Swift (40°, -75°): Wildlife Network 4 May, iNaturalist 20 Apr, difference 2 weeks Pacific-slope Flycatcher (35°, -125°): Wildlife Network 16 Mar, iNaturalist 16 Mar, difference 0 weeks Spotted Flycatcher (50°, 5°): Wildlife Network 27 Apr, iNaturalist 27 Apr, difference 0 weeks Great Crested Flycatcher (35°, -80°): Wildlife Network 20 Apr, iNaturalist 13 Apr, difference 1 weeks Common Swift (50°, 10°): Wildlife Network 18 May, iNaturalist 20 Apr, difference 4 weeks Ruby-throated Hummingbird (30°, -85°): Wildlife Network 6 Jul, iNaturalist 23 Mar, difference 15 weeks Wood Thrush (40°, -75°): Wildlife Network 27 Apr, iNaturalist 20 Apr, difference 1 weeks Eastern Wood-Pewee (35°, -90°): Wildlife Network 4 May, iNaturalist 27 Apr, difference 1 weeks Purple Martin (45°, -100°): Wildlife Network 20 Apr, iNaturalist 27 Apr, difference -1 weeks Ruby-throated Hummingbird (35°, -85°): Wildlife Network 13 Jul, iNaturalist 13 Apr, difference 13 weeks Ruby-throated Hummingbird (35°, -80°): Wildlife Network 6 Jul, iNaturalist 13 Apr, difference 12 weeks Red-winged Blackbird (40°, -75°): Wildlife Network 23 Feb, iNaturalist 2 Mar, difference -1 weeks Chuck-will's-widow (30°, -85°): Wildlife Network 30 Mar, iNaturalist 23 Mar, difference 1 weeks Eastern Phoebe (45°, -95°): Wildlife Network 6 Apr, iNaturalist 30 Mar, difference 1 weeks American Robin (45°, -95°): Wildlife Network 2 Mar, iNaturalist 9 Mar, difference -1 weeks Pine Warbler (40°, -75°): Wildlife Network 30 Mar, iNaturalist 16 Mar, difference 2 weeks Eastern Wood-Pewee (40°, -75°): Wildlife Network 18 May, iNaturalist 11 May, difference 1 weeks Black Redstart (50°, 5°): Wildlife Network 9 Mar, iNaturalist 23 Feb, difference 2 weeks Purple Martin (35°, -90°): Wildlife Network 6 Apr, iNaturalist 23 Feb, difference 6 weeks European Pied Flycatcher (55°, 15°): Wildlife Network 27 Apr, iNaturalist 27 Apr, difference 0 weeks Painted Bunting (25°, -100°): Wildlife Network 20 Apr, iNaturalist 13 Apr, difference 1 weeks Eurasian Blackcap (50°, 0°): Wildlife Network 23 Mar, iNaturalist 23 Mar, difference 0 weeks Red-winged Blackbird (40°, -80°): Wildlife Network 2 Mar, iNaturalist 2 Mar, difference 0 weeks Purple Martin (25°, -85°): Wildlife Network 16 Feb, iNaturalist 19 Jan, difference 4 weeks Osprey (40°, -75°): Wildlife Network 23 Mar, iNaturalist 16 Mar, difference 1 weeks Common Nightingale (40°, 0°): Wildlife Network 6 Apr, iNaturalist 6 Apr, difference 0 weeks Osprey (35°, -80°): Wildlife Network 9 Mar, iNaturalist 2 Mar, difference 1 weeks Ruby-throated Hummingbird (30°, -95°): Wildlife Network 6 Jul, iNaturalist 23 Mar, difference 15 weeks Hooded Oriole (30°, -120°): Wildlife Network 9 Mar, iNaturalist 9 Mar, difference 0 weeks Chimney Swift (40°, -80°): Wildlife Network 27 Apr, iNaturalist 20 Apr, difference 1 weeks Common Redstart (50°, 10°): Wildlife Network 13 Apr, iNaturalist 16 Mar, difference 4 weeks White-eyed Vireo (30°, -100°): Wildlife Network 9 Mar, iNaturalist 9 Mar, difference 0 weeks Wood Thrush (35°, -90°): Wildlife Network 13 Apr, iNaturalist 6 Apr, difference 1 weeks Violet-green Swallow (40°, -125°): Wildlife Network 9 Mar, iNaturalist 2 Mar, difference 1 weeks Black Redstart (45°, 15°): Wildlife Network 9 Mar, iNaturalist 9 Mar, difference 0 weeks Wood Thrush (40°, -80°): Wildlife Network 27 Apr, iNaturalist 20 Apr, difference 1 weeks Tennessee Warbler (40°, -95°): Wildlife Network 11 May, iNaturalist 11 May, difference 0 weeks Great Crested Flycatcher (30°, -85°): Wildlife Network 6 Apr, iNaturalist 13 Apr, difference -1 weeks Rufous Hummingbird (45°, -125°): Wildlife Network 9 Mar, iNaturalist 9 Mar, difference 0 weeks Cordilleran Flycatcher (35°, -110°): Wildlife Network 18 May, iNaturalist 18 May, difference 0 weeks Common Nightingale (50°, 10°): Wildlife Network 20 Apr, iNaturalist 13 Apr, difference 1 weeks Purple Martin (25°, -95°): Wildlife Network 16 Feb, iNaturalist 16 Feb, difference 0 weeks Common Redstart (55°, 10°): Wildlife Network 20 Apr, iNaturalist 13 Apr, difference 1 weeks Rufous Hummingbird (35°, -110°): Wildlife Network 6 Jul, iNaturalist 29 Jun, difference 1 weeks Striated Pardalote (-30°, 150°): Wildlife Network 16 Feb, iNaturalist 12 Jan, difference 5 weeks Swainson's Thrush (45°, -125°): Wildlife Network 11 May, iNaturalist 11 May, difference 0 weeks Chimney Swift (40°, -85°): Wildlife Network 4 May, iNaturalist 4 May, difference 0 weeks Barn Swallow (50°, 5°): Wildlife Network 20 Apr, iNaturalist 6 Apr, difference 2 weeks Brown-headed Cowbird (40°, -90°): Wildlife Network 2 Mar, iNaturalist 23 Mar, difference -3 weeks Chipping Sparrow (40°, -90°): Wildlife Network 30 Mar, iNaturalist 6 Apr, difference -1 weeks Brown Thrasher (30°, -85°): Wildlife Network 9 Feb, iNaturalist 14 Sept, difference -31 weeks Common House-Martin (50°, 5°): Wildlife Network 18 May, iNaturalist 20 Apr, difference 4 weeks Red-winged Blackbird (40°, -85°): Wildlife Network 23 Feb, iNaturalist 23 Feb, difference 0 weeks Eastern Kingbird (40°, -75°): Wildlife Network 4 May, iNaturalist 27 Apr, difference 1 weeks Chimney Swift (40°, -90°): Wildlife Network 27 Apr, iNaturalist 20 Apr, difference 1 weeks Indigo Bunting (35°, -80°): Wildlife Network 4 May, iNaturalist 20 Apr, difference 2 weeks Brown-headed Cowbird (40°, -80°): Wildlife Network 2 Mar, iNaturalist 16 Mar, difference -2 weeks Black-headed Grosbeak (45°, -125°): Wildlife Network 27 Apr, iNaturalist 27 Apr, difference 0 weeks Tennessee Warbler (40°, -90°): Wildlife Network 4 May, iNaturalist 4 May, difference 0 weeks Barn Swallow (50°, 10°): Wildlife Network 27 Apr, iNaturalist 6 Apr, difference 3 weeks Indigo Bunting (30°, -90°): Wildlife Network 20 Apr, iNaturalist 6 Apr, difference 2 weeks European Bee-eater (40°, -5°): Wildlife Network 20 Apr, iNaturalist 6 Apr, difference 2 weeks Western Tanager (45°, -125°): Wildlife Network 27 Apr, iNaturalist 27 Apr, difference 0 weeks White Wagtail (50°, 5°): Wildlife Network 23 Feb, iNaturalist 2 Mar, difference -1 weeks House Sparrow (35°, -75°): Wildlife Network 13 Apr, iNaturalist 6 Apr, difference 1 weeks Red-eyed Vireo (35°, -80°): Wildlife Network 20 Apr, iNaturalist 20 Apr, difference 0 weeks Rufous Hummingbird (30°, -120°): Wildlife Network 22 Jun, iNaturalist 16 Feb, difference 18 weeks Blue-gray Gnatcatcher (35°, -80°): Wildlife Network 23 Mar, iNaturalist 30 Mar, difference -1 weeks Wood Thrush (30°, -85°): Wildlife Network 13 Apr, iNaturalist 13 Apr, difference 0 weeks Red-winged Blackbird (40°, -90°): Wildlife Network 16 Feb, iNaturalist 23 Feb, difference -1 weeks Chimney Swift (30°, -85°): Wildlife Network 6 Apr, iNaturalist 20 Apr, difference -2 weeks Eastern Kingbird (35°, -80°): Wildlife Network 20 Apr, iNaturalist 2 Mar, difference 7 weeks Least Flycatcher (40°, -75°): Wildlife Network 11 May, iNaturalist 4 May, difference 1 weeks Summer Tanager (30°, -100°): Wildlife Network 6 Apr, iNaturalist 6 Apr, difference 0 weeks Brown-headed Cowbird (40°, -85°): Wildlife Network 9 Mar, iNaturalist 23 Mar, difference -2 weeks Northern Parula (25°, -85°): Wildlife Network 2 Mar, iNaturalist 9 Feb, difference 3 weeks European Serin (50°, 10°): Wildlife Network 23 Mar, iNaturalist 23 Mar, difference 0 weeks European Pied Flycatcher (55°, 10°): Wildlife Network 20 Apr, iNaturalist 20 Apr, difference 0 weeks Mourning Dove (40°, -100°): Wildlife Network 2 Mar, iNaturalist 9 Mar, difference -1 weeks Veery (40°, -75°): Wildlife Network 4 May, iNaturalist 27 Apr, difference 1 weeks Great Crested Flycatcher (40°, -75°): Wildlife Network 4 May, iNaturalist 27 Apr, difference 1 weeks Canada Goose (45°, -95°): Wildlife Network 9 Feb, iNaturalist 2 Mar, difference -3 weeks Red-eyed Vireo (45°, -75°): Wildlife Network 25 May, iNaturalist 18 May, difference 1 weeks White-throated Sparrow (45°, -95°): Wildlife Network 13 Apr, iNaturalist 13 Apr, difference 0 weeks White-throated Sparrow (40°, -95°): Wildlife Network 13 Apr, iNaturalist 13 Apr, difference 0 weeks Indigo Bunting (35°, -85°): Wildlife Network 27 Apr, iNaturalist 20 Apr, difference 1 weeks Common Swift (45°, 10°): Wildlife Network 18 May, iNaturalist 6 Apr, difference 6 weeks Ovenbird (40°, -75°): Wildlife Network 4 May, iNaturalist 27 Apr, difference 1 weeks Indigo Bunting (35°, -90°): Wildlife Network 20 Apr, iNaturalist 13 Apr, difference 1 weeks Indigo Bunting (35°, -95°): Wildlife Network 27 Apr, iNaturalist 20 Apr, difference 1 weeks Brown-headed Cowbird (40°, -75°): Wildlife Network 23 Feb, iNaturalist 9 Mar, difference -2 weeks Fish Crow (35°, -95°): Wildlife Network 23 Feb, iNaturalist 9 Feb, difference 2 weeks Gray Catbird (40°, -95°): Wildlife Network 27 Apr, iNaturalist 4 May, difference -1 weeks Rose-breasted Grosbeak (40°, -90°): Wildlife Network 27 Apr, iNaturalist 20 Apr, difference 1 weeks Blue-gray Gnatcatcher (30°, -100°): Wildlife Network 9 Mar, iNaturalist 9 Mar, difference 0 weeks Evening Grosbeak (45°, -90°): Wildlife Network 9 Mar, iNaturalist 23 Mar, difference -2 weeks Summer Tanager (35°, -80°): Wildlife Network 20 Apr, iNaturalist 20 Apr, difference 0 weeks Warbling Vireo (40°, -75°): Wildlife Network 27 Apr, iNaturalist 20 Apr, difference 1 weeks Gray Catbird (40°, -85°): Wildlife Network 4 May, iNaturalist 27 Apr, difference 1 weeks Say's Phoebe (35°, -110°): Wildlife Network 2 Mar, iNaturalist 2 Mar, difference 0 weeks Red-eyed Vireo (45°, -90°): Wildlife Network 25 May, iNaturalist 18 May, difference 1 weeks Chuck-will's-widow (30°, -80°): Wildlife Network 13 Apr, iNaturalist 13 Apr, difference 0 weeks Gray Catbird (40°, -90°): Wildlife Network 4 May, iNaturalist 27 Apr, difference 1 weeks Indigo Bunting (40°, -75°): Wildlife Network 11 May, iNaturalist 4 May, difference 1 weeks Laughing Gull (35°, -80°): Wildlife Network 30 Mar, iNaturalist 16 Mar, difference 2 weeks Red-eyed Vireo (40°, -90°): Wildlife Network 18 May, iNaturalist 4 May, difference 2 weeks Hermit Thrush (40°, -75°): Wildlife Network 13 Apr, iNaturalist 30 Mar, difference 2 weeks Say's Phoebe (35°, -105°): Wildlife Network 16 Mar, iNaturalist 2 Mar, difference 2 weeks American Crow (50°, -115°): Wildlife Network 23 Mar, iNaturalist 23 Mar, difference 0 weeks Summer Tanager (30°, -85°): Wildlife Network 13 Apr, iNaturalist 13 Apr, difference 0 weeks American Redstart (40°, -75°): Wildlife Network 4 May, iNaturalist 4 May, difference 0 weeks Summer Tanager (35°, -95°): Wildlife Network 20 Apr, iNaturalist 5 Jan, difference 15 weeks Eastern Towhee (40°, -75°): Wildlife Network 6 Apr, iNaturalist 6 Apr, difference 0 weeks Great Crested Flycatcher (30°, -90°): Wildlife Network 30 Mar, iNaturalist 30 Mar, difference 0 weeks Pine Siskin (45°, -65°): Wildlife Network 2 Mar, iNaturalist 5 Jan, difference 8 weeks Acadian Flycatcher (35°, -80°): Wildlife Network 4 May, iNaturalist 4 May, difference 0 weeks Eurasian Siskin (55°, 15°): Wildlife Network 2 Mar, iNaturalist 10 Aug, difference -23 weeks Killdeer (40°, -85°): Wildlife Network 2 Mar, iNaturalist 2 Mar, difference 0 weeks European Serin (45°, 10°): Wildlife Network 16 Mar, iNaturalist 5 Jan, difference 10 weeks Eurasian Skylark (55°, 10°): Wildlife Network 9 Mar, iNaturalist 23 Feb, difference 2 weeks Yellow-throated Warbler (30°, -85°): Wildlife Network 16 Feb, iNaturalist 31 Aug, difference -28 weeks Summer Tanager (35°, -90°): Wildlife Network 20 Apr, iNaturalist 20 Apr, difference 0 weeks Eastern Towhee (40°, -80°): Wildlife Network 23 Mar, iNaturalist 16 Mar, difference 1 weeks European Pied Flycatcher (50°, 5°): Wildlife Network 13 Apr, iNaturalist 13 Apr, difference 0 weeks Willow Warbler (50°, 5°): Wildlife Network 6 Apr, iNaturalist 6 Apr, difference 0 weeks Barn Swallow (45°, -125°): Wildlife Network 6 Apr, iNaturalist 30 Mar, difference 1 weeks Eastern Kingbird (40°, -90°): Wildlife Network 11 May, iNaturalist 27 Apr, difference 2 weeks Red-winged Blackbird (45°, -95°): Wildlife Network 16 Mar, iNaturalist 9 Mar, difference 1 weeks Laughing Gull (40°, -75°): Wildlife Network 6 Apr, iNaturalist 30 Mar, difference 1 weeks Garden Warbler (50°, 5°): Wildlife Network 20 Apr, iNaturalist 20 Apr, difference 0 weeks Common Nighthawk (45°, -125°): Wildlife Network 25 May, iNaturalist 1 Jun, difference -1 weeks Yellow-throated Warbler (35°, -80°): Wildlife Network 23 Mar, iNaturalist 16 Mar, difference 1 weeks Tennessee Warbler (35°, -90°): Wildlife Network 20 Apr, iNaturalist 20 Apr, difference 0 weeks Summer Tanager (30°, -90°): Wildlife Network 13 Apr, iNaturalist 13 Apr, difference 0 weeks White-crowned Sparrow (40°, -90°): Wildlife Network 27 Apr, iNaturalist 20 Apr, difference 1 weeks Common Loon (45°, -95°): Wildlife Network 30 Mar, iNaturalist 23 Mar, difference 1 weeks Brown-headed Cowbird (35°, -95°): Wildlife Network 16 Feb, iNaturalist 9 Mar, difference -3 weeks American Goldfinch (50°, -110°): Wildlife Network 18 May, iNaturalist 11 May, difference 1 weeks Least Flycatcher (45°, -95°): Wildlife Network 11 May, iNaturalist 4 May, difference 1 weeks Rose-breasted Grosbeak (40°, -85°): Wildlife Network 27 Apr, iNaturalist 27 Apr, difference 0 weeks Tennessee Warbler (45°, -95°): Wildlife Network 11 May, iNaturalist 4 May, difference 1 weeks Black-and-white Warbler (40°, -75°): Wildlife Network 27 Apr, iNaturalist 20 Apr, difference 1 weeks Warbling Vireo (40°, -90°): Wildlife Network 27 Apr, iNaturalist 20 Apr, difference 1 weeks Black-headed Grosbeak (35°, -125°): Wildlife Network 13 Apr, iNaturalist 30 Mar, difference 2 weeks Arrival week, iNaturalist observers Arrival week, Wildlife Network Each dot is one species in one cell. Dots on the dashed line agree exactly; above it, Wildlife Network is later. Hover a dot for the species. 3 arrivals 3 ≤−6 0 arrivals -5 0 arrivals -4 4 arrivals 4 -3 6 arrivals 6 -2 14 arrivals 14 -1 57 arrivals 57 0 72 arrivals 72 +1 21 arrivals 21 +2 4 arrivals 4 +3 8 arrivals 8 +4 1 arrivals 1 +5 2 arrivals 2 +6 2 arrivals 2 +7 10 arrivals 10 ≥8 Wildlife Network minus iNaturalist, weeks Most arrivals agree to the week or are one week later in Wildlife Network. Reading it honestly For most species the acoustic arrival date is usable to within about a week. 70 percent of arrivals agree within one week and 83 percent within two.There is a consistent lag of about one week. A species has to be heard often enough to reach a tenth of its peak, while a single photograph is enough for a person. Early scouts are seen before they are heard in numbers.The overall correlation is only 0.51 because 18 arrivals (9 percent) miss by more than four weeks. Without them the correlation is 0.94. They are not random, and fall into two groups described below.Weeks are coarse. Both series are weekly, so a difference of one week can be a difference of one day across a week boundary.iNaturalist is not the truth either. It reflects when and where people go outdoors with a camera. It is independent, which is what makes the comparison useful.Where it fails Species that are quiet when they arrive Ruby-throated Hummingbird is 9 to 15 weeks late in all six cells tested: Wildlife Network puts its arrival in June and July, while people photograph it from late March. Hummingbirds make little sound in spring and a great deal around feeders in late summer, so a threshold set relative to the peak is crossed far too late. Rufous Hummingbird shows the same miss in one of its three cells and agrees within a week in the other two. Expect this for any species whose calling changes strongly through the season.
Residents that start singing Brown Thrasher and Yellow-throated Warbler on the Gulf coast are present all year. Their "arrival" in February is the start of the singing season. For a resident species, the acoustic onset marks behaviour, not movement. The site labels this limit wherever arrival dates are shown.
Species Cell Wildlife Network iNaturalist Weeks Brown Thrasher 30°, -85° 9 Feb 14 Sept -31 Yellow-throated Warbler 30°, -85° 16 Feb 31 Aug -28 Eurasian Siskin 55°, 15° 2 Mar 10 Aug -23 Rufous Hummingbird 30°, -120° 22 Jun 16 Feb +18 Ruby-throated Hummingbird 30°, -85° 6 Jul 23 Mar +15 Ruby-throated Hummingbird 30°, -95° 6 Jul 23 Mar +15 Summer Tanager 35°, -95° 20 Apr 5 Jan +15 Ruby-throated Hummingbird 30°, -100° 6 Jul 6 Apr +13 Ruby-throated Hummingbird 35°, -85° 13 Jul 13 Apr +13 Ruby-throated Hummingbird 35°, -80° 6 Jul 13 Apr +12 European Serin 45°, 10° 16 Mar 5 Jan +10 Ruby-throated Hummingbird 35°, -95° 15 Jun 13 Apr +9
The twelve largest disagreements.
What this does not show It covers one spring, mostly in North America and Europe, where both sources have data. It tests arrival timing only. Range centres, surges and the relative frequency index are not validated here. It is not a comparison with eBird or BirdCast. Their arrival and migration products are not available without an access agreement. That comparison is the next step. It has not been reviewed by an ornithologist. If you are one, corrections are welcome. Reproduce it The comparison is one script, scripts/validate.mts , and every pair is in src/data/validation.json . Arrival dates for any species can be downloaded as CSV from /api/v1/arrivals?species=Hirundo rustica&format=csv.