According to Wisconsin herbarium curator Gary Fewless, “Phenology is the study of the timing of natural events. Common examples include the date that migrating birds return, the first flower dates for plants and the date on which a lake freezes in the autumn or opens in the spring.”

I invite you to send me your local records that do not conform to those of the past. The following dates, derived from the Buffalo Ornithological Society’s “Seasonal Checklist of the Birds: The Niagara Frontier Region,” indicate when new arrivals should become “fairly common” in appropriate areas:

Feb. 21-28: tundra swan and Northern pintail.

March 1-10: American wigeon, left, American black duck and red-winged blackbird.

March 11-20: wood duck, gadwall, Northern shoveler, green-winged teal, lesser scaup, white-winged scoter, horned grebe, Northern harrier, red-shouldered hawk, American coot, killdeer, American woodcock, Eastern bluebird, American robin, Eastern meadowlark, rusty blackbird, common grackle and brown-headed cowbird.

March 21-31: snow goose, left, ring-necked duck, hooded merganser, pied-billed grebe, great blue heron, black-crowned night heron, turkey vulture, sharp-shinned hawk, Cooper’s hawk, common snipe, tree swallow, brown creeper, golden-crowned kinglet and song sparrow.

April 1-10: blue-winged teal, left, ruddy duck, common loon, American bittern, osprey, Eastern phoebe, winter wren and white-throated sparrow.

April 11-20: double-crested cormorant, left, broad-winged hawk, greater yellowlegs, lesser yellowlegs, spotted sandpiper, yellow-bellied sapsucker, Northern flicker, purple martin, Northern rough-winged swallow, barn swallow, ruby-crowned kinglet, brown thrasher, yellow-rumped warbler, Eastern towhee, chipping sparrow, field sparrow, savannah sparrow and swamp sparrow.

April 21-31: great egret, left, green heron, common moorhen, Caspian tern, common tern, belted kingfisher, red-headed woodpecker, bank swallow, red-breasted nuthatch, house wren, blue-gray gnatcatcher, hermit thrush, American pipit, yellow warbler, pine warbler, black-and-white warbler, Northern waterthrush, Louisiana waterthrush, fox sparrow, white-throated sparrow and purple finch.

May 1-10: Virginia rail, left, sora, chimney swift, ruby-throated hummingbird, least flycatcher, great-crested flycatcher, Eastern kingbird, yellow-throated vireo, warbling vireo, cliff swallow, wood thrush, gray catbird, Nashville warbler, chestnut-sided warbler, magnolia warbler, black-throated blue warbler, black-throated green warbler, palm warbler, cerulean warbler, ovenbird, hooded warbler and Baltimore oriole.

May 11-20: least bittern, left, semi-palmated plover, whimbrel, sanderling, least sandpiper, dunlin, Eastern wood-pewee, blue-headed vireo, red-eyed vireo, marsh wren, veery, Swainson’s thrush, blue-winged warbler, Tennessee warbler, blackburnian warbler, bay-breasted warbler, American redstart, mourning warbler, common yellowthroat, Canada warbler, scarlet tanager, rose-breasted grosbeak, indigo bunting and bobolink.

May 21-31: semi-palmated sandpiper, left, black-billed cuckoo, yellow-billed cuckoo, alder flycatcher, willow flycatcher and blackpoll warbler.

Here are the dates at which overwintering species become uncommon:

March 10-20: horned lark, left.

March 21-31: canvasback, Northern shrike and snow bunting.

April 11-20: redhead, left, rough-legged hawk and American tree sparrow.

April 21-30: greater scaup, bufflehead, common goldeneye and common merganser.

May 11-20: long-tailed duck, above, and red-breasted merganser.

And finally, here are birds that may be found here all year long: Canada goose, mallard, red-tailed hawk, American kestrel, ring-necked pheasant, ruffed grouse, wild turkey, bald eagle, Bonaparte’s gull, ring-billed gull, herring gull, great black-backed gull, rock dove, mourning dove, Eastern screech owl, great horned owl, red-bellied woodpecker, downy woodpecker, hairy woodpecker, pileated woodpecker, blue jay, American crow, black-capped chickadee, tufted titmouse, white-breasted nuthatch, Carolina wren, Northern mockingbird, European starling, cedar waxwing, dark-eyed junco, Northern cardinal, house finch, American goldfinch and house sparrow.

Compare your observations, and let me know when they differ.