60 birds were recorded seen in Connecticut in May in our iNaturalist sample; 20 of the top 50 are at their peak this month. The list is ranked by number of research-grade observations.
Top birds in May

American Robin
Gray Catbird
Red-winged Blackbird

Baltimore Oriole
Canada Goose

House Sparrow

Tree Swallow

Northern Yellow Warbler

Northern Cardinal

Osprey

Mallard

Song Sparrow
All birds seen in Connecticut in May
| # | Species | Scientific name | Family | Obs. | Peak in state |
|---|---|---|---|---|---|
| 1 | American Robin | Turdus migratorius | Thrushes | 641 | Apr (past peak) |
| 2 | Gray Catbird | Dumetella carolinensis | Mockingbirds and Thrashers | 586 | May (peak) |
| 3 | Red-winged Blackbird | Agelaius phoeniceus | New World Blackbirds and Orioles | 446 | May (peak) |
| 4 | Baltimore Oriole | Icterus galbula | New World Blackbirds and Orioles | 443 | May (peak) |
| 5 | Canada Goose | Branta canadensis | Ducks, Geese, and Swans | 426 | May (peak) |
| 6 | House Sparrow | Passer domesticus | Old World Sparrows | 354 | Feb (past peak) |
| 7 | Tree Swallow | Tachycineta bicolor | Swallows and Martins | 336 | May (peak) |
| 8 | Northern Yellow Warbler | Setophaga aestiva | New World Warblers | 322 | May (peak) |
| 9 | Northern Cardinal | Cardinalis cardinalis | Cardinals and Allies | 321 | Apr (past peak) |
| 10 | Osprey | Pandion haliaetus | Ospreys | 283 | Apr (past peak) |
| 11 | Mallard | Anas platyrhynchos | Ducks, Geese, and Swans | 273 | Apr (past peak) |
| 12 | Song Sparrow | Melospiza melodia | New World Sparrows | 270 | Oct (rising) |
| 13 | Mourning Dove | Zenaida macroura | Pigeons and Doves | 249 | Apr (past peak) |
| 14 | Great Blue Heron | Ardea herodias | Herons, Egrets, and Bitterns | 243 | Aug (rising) |
| 15 | Eastern Bluebird | Sialia sialis | Thrushes | 235 | Apr (past peak) |
| 16 | Rose-breasted Grosbeak | Pheucticus ludovicianus | Cardinals and Allies | 234 | May (peak) |
| 17 | Common Yellowthroat | Geothlypis trichas | New World Warblers | 225 | May (peak) |
| 18 | Wild Turkey | Meleagris gallopavo | Pheasants, Grouse, and Allies | 224 | Apr (past peak) |
| 19 | Common Grackle | Quiscalus quiscula | New World Blackbirds and Orioles | 219 | Apr (past peak) |
| 20 | Chipping Sparrow | Spizella passerina | New World Sparrows | 216 | Apr (past peak) |
| 21 | Black-and-white Warbler | Mniotilta varia | New World Warblers | 203 | May (peak) |
| 22 | Great Egret | Ardea alba | Herons, Egrets, and Bitterns | 201 | Aug (rising) |
| 23 | Blue Jay | Cyanocitta cristata | Crows, Jays, and Magpies | 196 | Apr (past peak) |
| 24 | American Goldfinch | Spinus tristis | Finches, Euphonias, and Allies | 188 | Aug (rising) |
| 25 | Scarlet Tanager | Piranga olivacea | Cardinals and Allies | 182 | May (peak) |
| 26 | Brown-headed Cowbird | Molothrus ater | New World Blackbirds and Orioles | 180 | Apr (past peak) |
| 27 | American Redstart | Setophaga ruticilla | New World Warblers | 179 | May (peak) |
| 28 | Double-crested Cormorant | Nannopterum auritum | Cormorants and Shags | 175 | Aug (rising) |
| 29 | Wood Thrush | Hylocichla mustelina | Thrushes | 174 | May (peak) |
| 30 | Ovenbird | Seiurus aurocapilla | New World Warblers | 172 | May (peak) |
| 31 | Eastern Phoebe | Sayornis phoebe | Tyrant Flycatchers | 171 | Apr (past peak) |
| 32 | Red-bellied Woodpecker | Melanerpes carolinus | Woodpeckers | 161 | Jan (past peak) |
| 33 | Veery | Catharus fuscescens | Thrushes | 158 | May (peak) |
| 34 | House Finch | Haemorhous mexicanus | Finches, Euphonias, and Allies | 154 | Apr (past peak) |
| 35 | Ruby-throated Hummingbird | Archilochus colubris | Hummingbirds | 152 | Aug (rising) |
| 36 | Brant | Branta bernicla | Ducks, Geese, and Swans | 148 | Apr (past peak) |
| 37 | European Starling | Sturnus vulgaris | Starlings | 145 | Apr (past peak) |
| 38 | Red-tailed Hawk | Buteo jamaicensis | Hawks, Eagles, and Kites | 143 | Mar (past peak) |
| 39 | Pileated Woodpecker | Dryocopus pileatus | Woodpeckers | 143 | Apr (past peak) |
| 40 | Barred Owl | Strix varia | Typical Owls | 140 | Jun (rising) |
| 41 | Killdeer | Charadrius vociferus | Plovers and Lapwings | 138 | May (peak) |
| 42 | Barn Swallow | Hirundo rustica | Swallows and Martins | 135 | May (peak) |
| 43 | Tufted Titmouse | Baeolophus bicolor | Tits, Chickadees, and Titmice | 133 | Jan (past peak) |
| 44 | Northern Mockingbird | Mimus polyglottos | Mockingbirds and Thrashers | 130 | Apr (past peak) |
| 45 | Eastern Kingbird | Tyrannus tyrannus | Tyrant Flycatchers | 129 | May (peak) |
| 46 | Great Crested Flycatcher | Myiarchus crinitus | Tyrant Flycatchers | 128 | May (peak) |
| 47 | American Herring Gull | Larus smithsonianus | Gulls, Terns, and Skimmers | 127 | Aug (rising) |
| 48 | Northern House Wren | Troglodytes aedon | Wrens | 122 | May (peak) |
| 49 | Eastern Towhee | Pipilo erythrophthalmus | New World Sparrows | 122 | May (peak) |
| 50 | Turkey Vulture | Cathartes aura | New World Vultures | 120 | Apr (past peak) |