Tachycineta bicolor
Silhouette: Andy Wilson · PhyloPic
In 3 days ~10%
The tree swallow (Tachycineta bicolor) is a migratory bird of the family Hirundinidae. Found in the Americas, the tree swallow was first described in 1807 by French ornithologist Louis Vieillot as Hirundo bicolor. It has since been moved to its current genus, Tachycineta, within which its phylogenetic placement is debated. The tree swallow has glossy blue-green upperparts, with the exception of the blackish wings and tail, and white underparts. The bill is black, the eyes dark brown, and the legs and feet pale brown. The female is generally duller than the male, and the first-year female has mostly brown upperparts, with some blue feathers. Juveniles have brown upperparts, and gray-brown-washed breasts. The tree swallow breeds in the US and Canada. It winters along southern US coasts south, along the Gulf Coast, to Panama and the northwestern coast of South America, and in the West Indies.
The tree swallow nests either in isolated pairs or loose groups, in both natural and artificial cavities. Breeding can start as soon as early May, although this date is occurring earlier because of climate change, and it can end as late as July. This bird is generally socially monogamous (although about 8% of males are polygynous), with high levels of extra-pair paternity. This can benefit the male, but since the female controls copulation, the lack of resolution on how this behavior benefits females makes the high level of extra-pair paternity puzzling. The female incubates the clutch of two to eight (but usually four to seven) pure white eggs for around 14 to 15 days. The chicks hatch slightly asynchronously, allowing the female to prioritize which chicks to feed in times of food shortage. They generally fledge about 18 to 22 days after hatching. The tree swallow is sometimes considered a model organism, due to the large amount of research done on it.
An aerial insectivore, the tree swallow forages both alone and in groups, eating mostly insects, in addition to mollusks, spiders, and fruit. The nestlings, like the adult, primarily eat insects, fed to it by both sexes. This swallow is vulnerable to parasites, but, when on nestlings, these do little damage. The effect of disease can become stronger as a tree swallow gets older, as some parts of the immune system decline with age. Acquired T cell-mediated immunity, for example, decreases with age, whereas both innate and acquired humoral immunity do not. Because of its large range and stable population, the tree swallow is considered to be least concern by the International Union for Conservation of Nature. Wikipedia →
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Anchorage | 🇺🇸 United States | |
| 2 | Montreal | 🇨🇦 Canada | |
| 3 | Sacramento | 🇺🇸 United States | |
| 4 | Calgary | 🇨🇦 Canada | |
| 5 | Chicago | 🇺🇸 United States | |
| 6 | Toronto | 🇨🇦 Canada | |
| 7 | Vancouver | 🇨🇦 Canada | |
| 8 | Boston | 🇺🇸 United States | |
| 9 | Los Angeles | 🇺🇸 United States | |
| 10 | Philadelphia | 🇺🇸 United States |
Rare
Under 5% of wildlife watchers report a Tree Swallow sighting in Grand Canyon National Park on a given day, based on 52 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 104th most-seen of the 194 birds we can rate there. Over three days the chance rises to about 10%, if each day is a fresh chance.
Any time of year
In every month with enough records, under 5% of wildlife watchers report a Tree Swallow in Grand Canyon National Park on a given day, so our monthly data shows no clear season.
Between 9 am and noon
Across all the parks we cover, that three-hour window holds the most Tree Swallow sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
41st of 56
Of the 56 parks where we can rate Tree Swallow sightings, Grand Canyon National Park ranks 41st at under 5%. The best odds are in Point Pelee National Park (Canada, about 70%), Katmai National Park (United States, about 40%) and Kluane National Park (Canada, about 30%). All parks ranked.
GBIF citizen-science records
It is estimated from how often the Tree Swallow is recorded against all the birds logged in Grand Canyon National Park (52 verified sightings from 2019 to 2026), 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.
