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Birdaday Field Notes

Species profile

Blue Jay: identification, calls, food, nesting and migration

The Blue Jay is the loud, crested bird that grabs peanuts and flies off with them. The Cornell Lab of Ornithology notes its intelligence and tight family bonds, and credits its taste for acorns with helping spread oaks after the last glacial period. A shorter profile sits on common backyard birds.

Quick facts

Fact Blue Jay
Scientific name Cyanocitta cristata, family Corvidae: crows, jays and magpies (Cornell). Named Corvus cristatus by Linnaeus in 1758 (Wikipedia)
Length 9.8–11.8 in (Cornell); 9–12 in (Audubon)
Weight 2.5–3.5 oz (Cornell, Audubon)
Wingspan 13.4–16.9 in (Cornell); 13–17 in (Audubon)
Range Southern Canada through the eastern and central US to Florida and northeastern Texas, west to the Rocky Mountain foothills (Wikipedia); expanding northwest (Audubon)
Population About 17 million (Partners in Flight, via Cornell; Audubon). Down about 0.6% a year, roughly 27% in total, 1966–2019 (Cornell)
Status Low Concern (Cornell); Least Concern (IUCN, via Audubon)
Oldest known At least 26 years 11 months, banded in Newfoundland and Labrador (Cornell)
Provincial bird of Prince Edward Island, Canada (Wikipedia)

How to identify a Blue Jay

Cornell describes a large crested songbird with a broad, rounded tail, bigger than an American Robin and smaller than an American Crow. The sexes look alike; the male is slightly larger (Audubon).

Blue Jay perched on a weathered branch, seen from the side: blue crest held low, white face edged by a black necklace, blue wing with black bars and white spots, pale gray underparts Blue Jay on a thin bare branch, seen from the front: blue crest, white face and throat ringed by a black necklace, pale gray breast fading to white, white tail tips showing below the branch
Two Blue Jays, as identified by the photographers. Left: the blue wing with black barring and white wing marks, crest held low. Right: the black necklace around a white face and throat, and grayish underparts fading to a white belly (Cornell).
Photos: Stephanie Gibeault (left) and Patrice Bouchard (right) on Unsplash
Blue Jay field marksA simplified side view of a generic Blue Jay perched on a branch, facing left, with seven numbered field marks: crest, black necklace, white face and throat, white wingbar, black barring on wings and tail, white tail corners, and grayish to white underparts. To the right, two feather shapes show that an intact feather looks blue while a crushed one loses its blue. 1 2 3 4 5 6 7 8 9
  1. Crest: lowered when calm, raised when aggressive (Cornell).
  2. Black necklace. The black bridle varies between birds and may help jays recognize each other (Cornell).
  3. White face and throat (Cornell).
  4. Bold white wingbar (Cornell, Audubon).
  5. Black barring on wings and tail (Cornell).
  6. Large white tail corners, conspicuous in flight (Cornell).
  7. Underparts: grayish breast and flanks fading to a white belly (Cornell).
  8. Intact feather: blue from light scattering off its structure (Cornell).
  9. Crushed feather: the blue disappears; the pigment is brown melanin (Cornell, Wikipedia).
Drawn for Birdaday Field Notes as a generic jay shape, not copied from any field-guide plate. Field marks follow the Cornell Lab's All About Birds ID page and the Audubon field guide, cited below. Colors approximate. Not to scale.

Behavior clues. Jays are usually found by their calls but often cross open areas silently. A jay holds a nut in its feet and pecks it open (Cornell). More on behavior as an ID key: bird identification basics.

Look-alikes

Audubon notes that other blue jays lack the Blue Jay's white wing and tail pattern, and that bluebirds and buntings are much smaller. Cornell lists these jays as similar:

Species Where How it differs (Cornell)
Steller's Jay Western evergreen forests, also campgrounds and backyards Charcoal-black head and crest; looks very dark, with no white underparts
California Scrub-Jay West Coast, Washington to Baja California No crest; blue and gray above, pale below, partial blue necklace
Florida Scrub-Jay Central Florida only, in oak scrub No crest; whitish forehead, pale gray back and belly

Where their ranges overlap, Blue Jays may hybridize with Steller's Jays (Wikipedia).

Calls and the hawk imitation

Food: acorns, insects and the nest-raider question

Blue Jays are omnivores. About 22% of their year-round stomach contents were insects, nearly all the rest acorns, nuts, fruits and grains (Cornell). Audubon puts plant matter at up to 75% of the diet, more in winter.

Acorn caching. A jay can carry 5 acorns at once: 2–3 in its throat pouch, 1 in its mouth and 1 at the bill tip. In one study, six radio-tagged jays each cached 3,000–5,000 acorns in a single autumn (Cornell).

Do Blue Jays eat other birds' eggs? Sometimes: Audubon lists eggs and baby birds among their foods. But Cornell reports that one feeding study found eggs or nestlings in only 1% of jays, and just 6 of 530 stomachs held traces. NestWatch lists jays among nest predators and asks nest monitors to check that jays, crows and cats aren't following them.

At your feeder What the sources say
Peanuts A favorite (Cornell). Jays may grab several and fly off to hide them (FeederWatch). In the shell, "a special treat for jays" (Cornell seed guide). No salted or coated peanuts (FeederWatch)
Sunflower seeds A favorite (Cornell)
Suet A favorite (Cornell). See suet recipes and heat limits
Peanut hearts Jays are likely takers; offer in a small hopper or on a platform, discard if moldy (FeederWatch)
Corn Eaten by jays, among other birds (Cornell seed guide)

Cornell says Blue Jays prefer tray or hopper feeders on a post to hanging feeders. They don't always win there: at Florida feeders, Red-headed Woodpeckers, Common Grackles and gray squirrels often outcompete them. Compare bird feeder types and what to feed backyard birds.

Nesting

Blue Jays often mate for life. Both sexes build; the male gathers more and the female builds more (Cornell). The nest is an open cup in a tree, not a cavity, so Blue Jays aren't on our birdhouse dimensions table. Jays may abandon a nest after spotting a predator nearby (Cornell). Sources differ, so both are shown:

Stage Cornell Lab Audubon field guide
Nest height Usually 10–25 ft, in a crotch or thick outer branches Usually 8–30 ft, sometimes 5–50 ft
Materials Twigs, grass, sometimes mud; lined with rootlets Twigs, grass, weeds, bark strips, moss; rootlet lining, often with paper, rags or string
Clutch 2–7 eggs Usually 4–5, sometimes 3–7
Eggs Bluish or light brown with brownish spots; 1.0–1.3 in long Greenish or buff, sometimes pale blue, spotted brown and gray
Incubation 17–18 days, female only About 16–18 days, by both parents, mostly the female
Nestling period 17–21 days Young leave 17–21 days after hatching
Broods per year 1 Not stated
Blue Jay nesting timeline in daysA timeline from day 0 to day 100 with six rows: incubation of 17 to 18 days by Cornell's figure; incubation of about 16 to 18 days by Audubon's figure; the female brooding the young for the first 8 to 12 days after hatching; the nestling period of 17 to 21 days; young wandering near the nest 1 to 3 days before fledging; and parents feeding the young for at least a month, sometimes two. Solid bars show the shortest stated time and pale bars the longest. 020406080100 days 1 2 3 4 5 6
  1. Incubation, Cornell: 17–18 days, female only; the male feeds her.
  2. Incubation, Audubon: about 16–18 days, by both parents, mostly the female.
  3. Brooding: the female broods the young for 8–12 days while the male brings food (Cornell).
  4. Nestling period: 17–21 days (Cornell, Audubon).
  5. Wandering: 1–3 days before fledging, young may wander up to 15 ft from the nest (Cornell).
  6. After fledging: young stay with their parents and are fed for at least a month, sometimes two (Cornell).
Drawn for Birdaday Field Notes from the Cornell Lab (All About Birds) and Audubon figures cited below. Day 0 is the start of incubation; the dashed red line marks hatching, drawn at day 18 (the upper Cornell figure). Solid bars show the shortest stated time and pale bars the longest, so this is a schematic, not one real nest.

Migration: some go, many stay

Cornell calls the Blue Jay the only New World jay that migrates north and south. Thousands move along the Great Lakes and Atlantic coasts, yet some jays winter in every part of the range. Probably under 20% migrate, and some individuals migrate one winter and stay north the next (Cornell). Audubon adds that they migrate by day and don't go south of the United States; Wikipedia describes flocks of 5 to 250 birds.

A source disagreement. Cornell's overview says young jays are more likely to migrate than adults; its life-history page says banding shows no age difference between migrants and residents.

For your Bird-a-Day streak

In most of its range the Blue Jay is present all year (Audubon), and it's easy to log by ear. Like the American Robin and Northern Cardinal, it makes a good reserve bird. See the Bird-a-Day challenge guide and the species planner.

Blue Jay-friendly yard checklist

Sources