60 birds were recorded seen in Connecticut in September in our iNaturalist sample; 3 of the top 50 are at their peak this month. The list is ranked by number of research-grade observations.
Top birds in September

Great Blue Heron

Double-crested Cormorant

Great Egret
Common Yellowthroat

American Herring Gull

Wild Turkey

Northern Cardinal

Red-tailed Hawk

Osprey

Mallard

Mourning Dove

Ruby-throated Hummingbird
All birds seen in Connecticut in September
| # | Species | Scientific name | Family | Obs. | Peak in state |
|---|---|---|---|---|---|
| 1 | Great Blue Heron | Ardea herodias | Herons, Egrets, and Bitterns | 276 | Aug (past peak) |
| 2 | Double-crested Cormorant | Nannopterum auritum | Cormorants and Shags | 260 | Aug (past peak) |
| 3 | Great Egret | Ardea alba | Herons, Egrets, and Bitterns | 208 | Aug (past peak) |
| 4 | Common Yellowthroat | Geothlypis trichas | New World Warblers | 205 | May (past peak) |
| 5 | American Herring Gull | Larus smithsonianus | Gulls, Terns, and Skimmers | 204 | Aug (past peak) |
| 6 | Wild Turkey | Meleagris gallopavo | Pheasants, Grouse, and Allies | 195 | Apr (past peak) |
| 7 | Northern Cardinal | Cardinalis cardinalis | Cardinals and Allies | 178 | Apr (past peak) |
| 8 | Red-tailed Hawk | Buteo jamaicensis | Hawks, Eagles, and Kites | 174 | Mar (past peak) |
| 9 | Osprey | Pandion haliaetus | Ospreys | 172 | Apr (past peak) |
| 10 | Mallard | Anas platyrhynchos | Ducks, Geese, and Swans | 169 | Apr (past peak) |
| 11 | Mourning Dove | Zenaida macroura | Pigeons and Doves | 162 | Apr (past peak) |
| 12 | Ruby-throated Hummingbird | Archilochus colubris | Hummingbirds | 157 | Aug (past peak) |
| 13 | Eastern Phoebe | Sayornis phoebe | Tyrant Flycatchers | 146 | Apr (past peak) |
| 14 | Tufted Titmouse | Baeolophus bicolor | Tits, Chickadees, and Titmice | 138 | Jan (past peak) |
| 15 | Blue Jay | Cyanocitta cristata | Crows, Jays, and Magpies | 133 | Apr (past peak) |
| 16 | Downy Woodpecker | Dryobates pubescens | Woodpeckers | 133 | Jan (past peak) |
| 17 | Black-and-white Warbler | Mniotilta varia | New World Warblers | 131 | May (past peak) |
| 18 | Laughing Gull | Leucophaeus atricilla | Gulls, Terns, and Skimmers | 128 | Aug (past peak) |
| 19 | Red-shouldered Hawk | Buteo lineatus | Hawks, Eagles, and Kites | 127 | Feb (past peak) |
| 20 | Black-capped Chickadee | Poecile atricapillus | Tits, Chickadees, and Titmice | 127 | Jan (past peak) |
| 21 | Ring-billed Gull | Larus delawarensis | Gulls, Terns, and Skimmers | 125 | Jan (past peak) |
| 22 | American Goldfinch | Spinus tristis | Finches, Euphonias, and Allies | 124 | Aug (past peak) |
| 23 | American Redstart | Setophaga ruticilla | New World Warblers | 119 | May (past peak) |
| 24 | House Sparrow | Passer domesticus | Old World Sparrows | 118 | Feb (past peak) |
| 25 | Northern Flicker | Colaptes auratus | Woodpeckers | 115 | Apr (past peak) |
| 26 | Gray Catbird | Dumetella carolinensis | Mockingbirds and Thrashers | 113 | May (past peak) |
| 27 | Canada Goose | Branta canadensis | Ducks, Geese, and Swans | 108 | May (past peak) |
| 28 | Snowy Egret | Egretta thula | Herons, Egrets, and Bitterns | 100 | Aug (past peak) |
| 29 | Chipping Sparrow | Spizella passerina | New World Sparrows | 96 | Apr (past peak) |
| 30 | Cooper's Hawk | Astur cooperii | Hawks, Eagles, and Kites | 96 | Oct (rising) |
| 31 | Song Sparrow | Melospiza melodia | New World Sparrows | 94 | Oct (rising) |
| 32 | Bald Eagle | Haliaeetus leucocephalus | Hawks, Eagles, and Kites | 88 | Apr (past peak) |
| 33 | Northern Mockingbird | Mimus polyglottos | Mockingbirds and Thrashers | 86 | Apr (past peak) |
| 34 | Carolina Wren | Thryothorus ludovicianus | Wrens | 84 | Jan (past peak) |
| 35 | House Finch | Haemorhous mexicanus | Finches, Euphonias, and Allies | 83 | Apr (past peak) |
| 36 | White-breasted Nuthatch | Sitta carolinensis | Nuthatches | 80 | Oct (rising) |
| 37 | Red-eyed Vireo | Vireo olivaceus | Vireos, Shrike-Babblers, and Erpornis | 79 | Sep (peak) |
| 38 | Turkey Vulture | Cathartes aura | New World Vultures | 78 | Apr (past peak) |
| 39 | Green Heron | Butorides virescens | Herons, Egrets, and Bitterns | 77 | Aug (past peak) |
| 40 | Palm Warbler | Setophaga palmarum | New World Warblers | 75 | Oct (rising) |
| 41 | Eastern Bluebird | Sialia sialis | Thrushes | 74 | Apr (past peak) |
| 42 | American Kestrel | Falco sparverius | Falcons and Caracaras | 70 | Sep (peak) |
| 43 | Northern Parula | Setophaga americana | New World Warblers | 69 | May (past peak) |
| 44 | Semipalmated Plover | Charadrius semipalmatus | Plovers and Lapwings | 67 | Aug (past peak) |
| 45 | Yellow-crowned Night Heron | Nyctanassa violacea | Herons, Egrets, and Bitterns | 66 | Aug (past peak) |
| 46 | Red-bellied Woodpecker | Melanerpes carolinus | Woodpeckers | 65 | Jan (past peak) |
| 47 | Barred Owl | Strix varia | Typical Owls | 65 | Jun (past peak) |
| 48 | Belted Kingfisher | Megaceryle alcyon | Kingfishers | 62 | Sep (peak) |
| 49 | Savannah Sparrow | Passerculus sandwichensis | New World Sparrows | 58 | Oct (rising) |
| 50 | American Robin | Turdus migratorius | Thrushes | 58 | Apr (past peak) |