Behavior & MigrationDifferences between Bluebirds and Other Small Cavity Nesters

Differences between Bluebirds and Other Small Cavity Nesters

If You’re Used to Bluebirds, You May Be Suprised to find….

Some differences in behavior and nests
between Bluebirds and Other Small Cavity Nesters

Differ from Bluebirds in this regard
More Info
Ash-throated Flycatcher
  • Nest gets filthy
  • Adult may “explode” out of the nestbox when monitor approaches
  • Very tolerant of monitoring
  • Female builds nest and incubates
  • Nest does not have layers (e.g., like chickadee)
  • Both parents remove fecal sacs right up to fledging (unless widowed/too busy)
  • Male often perches on box
  • Incubation may begin on last or next to last egg
Differences between bluebird species
Carolina Wren
  • Often nests in weird places, not often in a box
  • May use snakeskin in nest
  • Male may build dummy nests
Black-capped Chickadee
  • Very secretive during nestbuilding and egg laying. Does not perch on box roof
  • Pull a “blanket” of fur/hair over eggs when leaving nests
  • Eggs are very fragile
  • Have a hard time defending nest – see competition
  • Unlikely to return to the site of a failed nesting
  • Can excavate their own hole
  • May prefer boxes with some sawdust/wood chips in the bottom that they can then ‘excavate’
  • Generally only have one brood, often laying 6-8 eggs
  • Often remove unhatched eggs
  • Do not migrate
  • In CT, I seldom see blow fly larvae in nests, but BNA reports 71% of nests infested in TN.
Carolina Chickadee
  • Can excavate their own hole
  • May start excavation or nestbuilding in several locations before chosing one
  • Do not seem to prefer boxes with sawdust in them (which they can “excavate “
  • Pull a “blanket” of fur/hair over eggs when leaving nests
Carolina Chickadee
Downy Woodpecker
  • Not known to use nestboxes for nesting, but will roost in a box
  • Excavate a new cavity for each nest
  • Both male and female develop a brood patch, both incubate, only males incubate at night
  • Males are primarily responsible for removing fecal sacs. Nestlings may only defecate after being fed 3-4 times.
  • Incubation time is short (12 days), but they don’t fledge for 20-25 days after hatching
Downy Woodpecker
Great Crested Flycatcher
  • Very secretive during nesting
  • May prefer nest sites very high up (up to 70 ft. off ground)
  • Both male and female build nest
  • May use snakeskin in nest
  • Female may hiss and strike (snake-like) when the nestbox is opened during incubation
  • Tend to nest in same site every year (high nest site fidelity)
  • One brood per year
  • Young fledge in 13-15 days
  • After fledging, young may only stay in area 3-4 days
House Finch
  • Fecal sacs accumulate on rim of nest
  • Do not migrate?
House Sparrow
  • Can build a (bulky) nest very quickly (a couple of days)
  • Tend to use trash (cigarette butts etc.) and many feathers in nest cup.
  • Nests very close to others of its species
  • Do not tolerate sparrow spooker, avoid boxes with fishing line on them, may not prefer Gilberston nestbox.
  • Male also incubates
  • Do not migrate
  • Frequently attack nests (eggs, young adults) of other species
House Wren
  • Male builds dummy nests
  • Entirely removes prior nests and nests of other birds
  • Frequently remove nests, eggs and very young nestlings from nests of other species
  • Seem to prefer a box under/on a tree
  • May prefer a box with a chalet roof?
  • May remain in box (up near roof) even after tapping/calling during monitoring
  • During laying may cover eggs with feathers/fur
  • Lay 5-10 eggs (typically 7-8)
  • Pygmy may use snake skin in nest
  • WBNU nestlings do not fledge until up to 24 days
  • Do not migrate?
Prothonotary Warbler
  • May nest in weird locations, generally over or near running water
  • May be sensitive to human disturbance around the nest site
  • Young can swim
  • Uses green vegetation in nest
  • Can build nest in 1-3 days
  • Fecal sacs pile up, fouling nest
  • Incubation begins with the next or next to last (penultimate) egg
  • Both sexes develop an incubation patch
  • 15-33% of nests are parasitized by other starlings
  • Seem to prefer a box mounted on a tree or under tree canopy
  • Secretive during nestbuilding and egg laying, do not perch on box
  • May use snake skin in nest
  • May hiss like a snake and strike wall during monitoring
  • May abandon nest if disturbed, especially during construction
  • JUTIs tumble to ground when fledging, fledge all at once.
  • Do not migrate?
  • Fewer blow flies?

Tree Swallow

  • Will nest within 25+ of another pair of Tree Swallows (colonial)
  • Take a really long time (2-4 weeks) to build a nest, with lots of (typically white) feathers recurved over eggs, feathers may introduce lots of mites into nest
  • Egg laying often in synch (within 7-10 days) with neighboring Tree Swallows.
  • Usually only have one brood
  • Often do not remove unhatched eggs
  • Stop removing fecal sacs about a week before fledging so nest gets filthy (may also have a lot of mites)
  • Tend to dive bomb monitors more
  • Adults may refuse to budge when nestbox is monitored
  • Often have head poking out of hole during incubation and brooding
  • Older young may “hog” the hole to get more food
  • Usually stay in box 18-22 days
  • Young can feed themselves as soon as they fledge
  • Young may occasionally go back in box to be fed by own parents/others
Violet-green Swallow
  • May nest in colonies of up to 25 pairs.
  • Eggs may hatch over 2-5 days.
  • Young dependent on parents after leaving nest for unknown period.
  • Parents stop removing fecal sacs after eyes open.
  • Fledging may occur over a period of days, young may return to the nest over the next few days?
Violet-green Swallow


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the thing that makes the bluebirding hobby so intriging is that you CANNOT answer questions simply True or False all of the time. MOST of the time you cannot even answer a question with four multiple choice answers. We should all enjoy these debates or exchanges of opinions and be willing to experiment and contribute to the knowledge we all seek.
– Keith Kridler, Bluebird_L, 2007


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