This list of birds of Pennsylvania includes species documented in the U.S. state of Pennsylvania and accepted by the Pennsylvania Ornithological Records Committee (PORC). As of May 2021, there were 439 species on the official list. Of them, 80 are classified as accidental, 59 are classed as casual, six have been introduced to North America, two are known to be extinct and another might be, and two have been extirpated. An additional nine species are classed as provisional and are also classed as accidental. This list is presented in the taxonomic sequence of the Check-list of North and Middle American Birds, 7th edition through the 62nd Supplement, published by the American Ornithological Society (AOS). Common and scientific names are also those of the Check-list, except that the common names of families are from the Clements taxonomy because the AOS list does not include them. Unless otherwise noted, all species listed below are considered to occur regularly in Pennsylvania as permanent residents, summer or winter visitors, or migrants. These tags are used to annotate some species: (A) Accidental – "generally fewer than five modern records" per the PORC (C) Casual – "casual or increasing vagrant" per the PORC (P) Provisional – Species accepted by the PORC with only sight records (I) Introduced – Species established in North America as a result of human action (X) Extinct – Recent species that no longer exist (Ex) Extirpated – Species which no longer occur in Pennsylvania but are found elsewhere Ducks, geese, and waterfowl Order: AnseriformesFamily: Anatidae Anatidae includes the ducks and most duck-like waterfowl, such as geese and swans. These birds are adapted to an aquatic existence with webbed feet, bills which are flattened to a greater or lesser extent, and feathers that are excellent at shedding water due to special oils. Black-bellied whistling-duck, Dendrocygna autumnalis (A) Snow goose, Anser caerulescens Ross's goose, Anser rossii Greater white-fronted goose, Anser albifrons Tundra bean-goose, Anser serrirostris (A) Pink-footed goose, Anser autumnalis (C) Brant, Branta bernicla Barnacle goose, Branta leucopsis (C) Cackling goose, Branta hutchinsii Canada goose, Branta canadensis Mute swan, Cygnus olor (I) Trumpeter swan, Cygnus buccinator Tundra swan, Cygnus columbianus Common shelduck, Tadorna tadorna (A) Wood duck, Aix sponsa Blue-winged teal, Spatula discors Cinnamon teal, Spatula cyanoptera (A) Northern shoveler, Spatula clypeata Gadwall, Mareca strepera Eurasian wigeon, Mareca penelope American wigeon, Mareca americana Mallard, Anas platyrhynchos American black duck, Anas rubripes Northern pintail, Anas