60 birds were recorded seen in Illinois in December in our iNaturalist sample; 0 of the top 50 are at their peak this month. The list is ranked by number of research-grade observations.
Top birds in December

Northern Cardinal

Dark-eyed Junco
Canada Goose
Downy Woodpecker

Red-tailed Hawk

House Sparrow

American Tree Sparrow

Mallard
Red-bellied Woodpecker

Red-breasted Merganser

Black-capped Chickadee

Cooper's Hawk
All birds seen in Illinois in December
| # | Species | Scientific name | Family | Obs. | Peak in state |
|---|---|---|---|---|---|
| 1 | Northern Cardinal | Cardinalis cardinalis | Cardinals and Allies | 869 | Apr (past peak) |
| 2 | Dark-eyed Junco | Junco hyemalis | New World Sparrows | 847 | Jan (past peak) |
| 3 | Canada Goose | Branta canadensis | Ducks, Geese, and Swans | 708 | Apr (past peak) |
| 4 | Downy Woodpecker | Dryobates pubescens | Woodpeckers | 659 | Apr (past peak) |
| 5 | Red-tailed Hawk | Buteo jamaicensis | Hawks, Eagles, and Kites | 608 | Feb (past peak) |
| 6 | House Sparrow | Passer domesticus | Old World Sparrows | 594 | Apr (past peak) |
| 7 | American Tree Sparrow | Spizelloides arborea | New World Sparrows | 517 | Jan (past peak) |
| 8 | Mallard | Anas platyrhynchos | Ducks, Geese, and Swans | 483 | Apr (past peak) |
| 9 | Red-bellied Woodpecker | Melanerpes carolinus | Woodpeckers | 466 | Apr (past peak) |
| 10 | Red-breasted Merganser | Mergus serrator | Ducks, Geese, and Swans | 449 | Mar (past peak) |
| 11 | Black-capped Chickadee | Poecile atricapillus | Tits, Chickadees, and Titmice | 443 | Apr (past peak) |
| 12 | Cooper's Hawk | Astur cooperii | Hawks, Eagles, and Kites | 401 | Sep (past peak) |
| 13 | American Herring Gull | Larus smithsonianus | Gulls, Terns, and Skimmers | 399 | Feb (past peak) |
| 14 | Bald Eagle | Haliaeetus leucocephalus | Hawks, Eagles, and Kites | 397 | Feb (past peak) |
| 15 | House Finch | Haemorhous mexicanus | Finches, Euphonias, and Allies | 396 | Apr (past peak) |
| 16 | Common Goldeneye | Bucephala clangula | Ducks, Geese, and Swans | 394 | Jan (past peak) |
| 17 | American Goldfinch | Spinus tristis | Finches, Euphonias, and Allies | 387 | Aug (past peak) |
| 18 | White-breasted Nuthatch | Sitta carolinensis | Nuthatches | 363 | Mar (past peak) |
| 19 | Mourning Dove | Zenaida macroura | Pigeons and Doves | 322 | Apr (past peak) |
| 20 | Ring-billed Gull | Larus delawarensis | Gulls, Terns, and Skimmers | 303 | Mar (past peak) |
| 21 | American Robin | Turdus migratorius | Thrushes | 295 | Apr (past peak) |
| 22 | Blue Jay | Cyanocitta cristata | Crows, Jays, and Magpies | 273 | May (past peak) |
| 23 | American Crow | Corvus brachyrhynchos | Crows, Jays, and Magpies | 232 | Apr (past peak) |
| 24 | European Starling | Sturnus vulgaris | Starlings | 204 | Apr (past peak) |
| 25 | Great Blue Heron | Ardea herodias | Herons, Egrets, and Bitterns | 198 | Aug (past peak) |
| 26 | Hooded Merganser | Lophodytes cucullatus | Ducks, Geese, and Swans | 196 | Mar (past peak) |
| 27 | American Kestrel | Falco sparverius | Falcons and Caracaras | 171 | Mar (past peak) |
| 28 | Bufflehead | Bucephala albeola | Ducks, Geese, and Swans | 166 | Mar (past peak) |
| 29 | Greater Scaup | Aythya marila | Ducks, Geese, and Swans | 146 | Feb (past peak) |
| 30 | Common Merganser | Mergus merganser | Ducks, Geese, and Swans | 141 | Feb (past peak) |
| 31 | White-throated Sparrow | Zonotrichia albicollis | New World Sparrows | 139 | Apr (past peak) |
| 32 | Tufted Titmouse | Baeolophus bicolor | Tits, Chickadees, and Titmice | 128 | Apr (past peak) |
| 33 | Eastern Bluebird | Sialia sialis | Thrushes | 122 | May (past peak) |
| 34 | Red-breasted Nuthatch | Sitta canadensis | Nuthatches | 122 | Sep (past peak) |
| 35 | Red-shouldered Hawk | Buteo lineatus | Hawks, Eagles, and Kites | 114 | Sep (past peak) |
| 36 | Trumpeter Swan | Cygnus buccinator | Ducks, Geese, and Swans | 113 | Jan (past peak) |
| 37 | Great Horned Owl | Bubo virginianus | Typical Owls | 112 | Apr (past peak) |
| 38 | Hairy Woodpecker | Leuconotopicus villosus | Woodpeckers | 110 | Apr (past peak) |
| 39 | Redpoll | Acanthis flammea | Finches, Euphonias, and Allies | 107 | Feb (past peak) |
| 40 | Gadwall | Mareca strepera | Ducks, Geese, and Swans | 107 | Mar (past peak) |
| 41 | American Coot | Fulica americana | Rails, Gallinules, and Coots | 106 | Apr (past peak) |
| 42 | Redhead | Aythya americana | Ducks, Geese, and Swans | 103 | Feb (past peak) |
| 43 | Northern Flicker | Colaptes auratus | Woodpeckers | 101 | Apr (past peak) |
| 44 | White-crowned Sparrow | Zonotrichia leucophrys | New World Sparrows | 99 | May (past peak) |
| 45 | Belted Kingfisher | Megaceryle alcyon | Kingfishers | 98 | Apr (past peak) |
| 46 | Snow Goose | Anser caerulescens | Ducks, Geese, and Swans | 92 | Mar (past peak) |
| 47 | Mute Swan | Cygnus olor | Ducks, Geese, and Swans | 91 | Apr (past peak) |
| 48 | Red-headed Woodpecker | Melanerpes erythrocephalus | Woodpeckers | 83 | May (past peak) |
| 49 | Sandhill Crane | Antigone canadensis | Cranes | 83 | Mar (past peak) |
| 50 | Song Sparrow | Melospiza melodia | New World Sparrows | 82 | Apr (past peak) |