The Bonaparte's Gull (Chroicocephalus philadelphia) is a small, graceful gull that breeds in North America (Canada and western Alaska) wintering south regularly to northern Mexico and the Greater Antilles, with vagrants recorded all the way to western Europe, the Lesser Antilles, southern Central America, including Panama, and northern South America.
My first experience with this species was some years ago at the Niagara river in April, above the famed Niagara Falls. There, dozens of birds were flying and resting above some rocks in the middle of the river (OK, my photo shows exactly zero gulls... but the place is magical).
This gull is less variable than the larger species, needing only one year to acquire the adult plumage. The dark marks in the wings (forming a broken W pattern) and black tail band make this individual a first-winter bird.
As I mentioned above, this species is only a vagrant to Panama, with six previous records. Three of these records were in the 70s and 80s in the Caribbean side of the Panama Canal, while the most recent were from Panama City's waterfront in the Pacific Ocean, with a group of six adults in winter plumage in Panama Viejo back in january 1996 (eBird report) and a first-winter bird at the mouth of the Matasnillo river in december 1998 (report in Xenornis). Then, one was found by Rosabel Miro in Costa del Este last november 23rd and another (probably the same bird?) was found by Itzel Fong in Panama Viejo last december 28th and relocated the next day, when I was able to see it.
In ABA terms, this species would have been a Code 5 (if applicable) right in our front yard! For this and many other reasons is why we chose Bonaparte's Gull as our Bird of the Month!
1. National Geographic Society's Field Guide to the Birds of North America.
2. Ridgely RS, Gwynne JA. Guía de las Aves de Panamá. 1ra edición español 1993.
3. Angehr G, Dean R. The Birds of Panama. A field guide. 1st edition 2010.