Chroicocephalus philadelphia
Silhouette: Michael Scroggie · PhyloPic
In 3 days ~10%
Bonaparte's gull (Chroicocephalus philadelphia) is a gull found mainly in northern North America. At 28 to 38 cm (11 to 15 in) in length, it is one of the smallest species of gull. Its plumage is mainly white with grey upperparts. During breeding season, Bonaparte's gull gains a slaty-black hood. The sexes are similar in appearance.
When George Ord first described Bonaparte's gull in 1815, he gave it the scientific name Sterna philadelphia, and the English name 'Banded-tail Tern'; the description clearly identifies it as a bird in first-winter plumage, while "The slender and tern-like form of the bill probably induced Mr. Ord to put it in Sterna". Most later taxonomists assigned it to the genus Larus, a longtime catch-all for most of the gull species. However, in 1858, George Newbold Lawrence moved the species to the genus Chroicocephalus, and some taxonomists followed suit. Subsequent molecular DNA studies have shown that this species fits neatly into a clade with other Chroicocephalus "hooded" gulls, and that it is in a close-to-basal position in that grouping. Based on these studies, the American Ornithologists' Union, which had previously assigned the... Wikipedia →
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Anchorage | 🇺🇸 United States | |
| 2 | Dallas | 🇺🇸 United States | |
| 3 | San Diego | 🇺🇸 United States | |
| 4 | Seattle | 🇺🇸 United States | |
| 5 | Los Angeles | 🇺🇸 United States | |
| 6 | Miami | 🇺🇸 United States | |
| 7 | Orlando | 🇺🇸 United States | |
| 8 | Vancouver | 🇨🇦 Canada | |
| 9 | Montreal | 🇨🇦 Canada | |
| 10 | San Francisco | 🇺🇸 United States |
| # | Zoo / Centre | Country | |
|---|---|---|---|
| 1 | Ralph Perkins II Wildlife Center and Woods Garden | 🇺🇸 United States |
Rare
Under 5% of wildlife watchers report a Bonaparte's Gull sighting in San Francisco on a given day, based on 1,681 verified sightings from GBIF citizen-science data. It is the 177th most-seen of the 375 birds we can rate there. Over three days the chance rises to about 10%, if each day is a fresh chance.
November
In that month about 10% of wildlife watchers report a Bonaparte's Gull in San Francisco on a given day, against under 5% in December to October, the lowest months.
Between 2 and 5 pm
Across all the parks we cover, that three-hour window holds the most Bonaparte's Gull sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
10th of 29
Of the 29 cities where we can rate Bonaparte's Gull sightings, San Francisco ranks 10th at under 5%. The best odds are in Anchorage (United States, about 30%), Dallas (United States, under 5%) and San Diego (United States, under 5%).
Same family: Laridae
The closest relatives of the Bonaparte's Gull that you can see in San Francisco (family Laridae, Gulls, Terns, and Skimmers) are California Gull (about 40%), Western Gull (about 30%) and Ring-billed Gull (about 20%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Bonaparte's Gull is recorded against all the birds logged in San Francisco (1,681 verified sightings), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
