- Ross's Gull (adult). Rockingham County, New Hampshire. 01 December 2018.
- Seen off-shore on a pelagic trip.
- Slaty-backed Gull (adult). Nipissing County, Ontario. 01 December 2018.
- Continuing from November.
- Mew Gull (adult). Kings County, NY. 03 December 2018
- Lesser Black-backed Gull (adult). Contra Costa County, California. 06 December 2018.
- First County Record.
- Slaty-backed Gull (adult). Brant County, Ontario. 11 December 2018.
- Bonaparte's Gull (1st cycle). Hawaii County, Hawaii. 12 December 2018.
- Black-legged Kittiwake (juvenile). Monroe County, Florida. 12 December 2018.
- Slaty-backed Gull (adult). Brant County, Ontario. 12 December 2018.
- A second adult discovered with the bird from the previous day.
- Laughing Gull (1st cycle). Del Norte County, California. 12 December 2018.
- Bonaparte's Gull (adult). Valdez-Cordova County, Alaska. 14 December 2018.
- Slaty-backed Gull (adult). Larimer County, Colorado. 14 December 2018.
- 3rd State Record. First County Record.
- Slaty-backed Gull (adult). Wayne County, Michigan. 15 December 2018.
- California Gull (adult). Bay County, Michigan. 22 December 2018.
- First County Record.
- Slaty-backed Gull (3rd cycle). San Mateo County, California. 23 December 2018.
- Black-headed Gull (adult). San Bernardino County, California. 23 December 2018.
- First County Record.
- Black-legged Kittiwake (juvenile). Maricopa County, Arizona. 25 December 2018.
- Thayer's Gull (adult). North Hampton County, Virginia. 26 December 2018.
- Heermann's Gull (adult). Valley County, Montana. 29 December 2018.
- FIRST STATE RECORD.
Miscellaneous:
- A first for the Great Lakes region were 2 Slaty-backed Gulls discovered feeding at the same site in Brantford, Ontario. Both birds were adults. 12 December 2018. Photograph comparisons show both birds are different than the Nipissing County individual continuing into December from November, making it 3 adult Slaty-backed Gulls in Ontario at once.
