At the Project:
Nesting is over.  Your project is empty. The swallows have all left, but you still have
things to do like box cleaning, data treatment, finalizing records, reporting results,
etc.  And as you work you may find yourself wondering where your swallows are and
what's next in their lives?  Hint: after nesting is completed Tree Swallows become
very social!   The photo below by Ken Schneider shows part of a much larger flock.





















Concepts:
What should you do with the old nests?
  • Old nests should be removed from the boxes.
  • Wear disposable gloves if you can.  Used nests can be messy.
  • Remove nests from boxes, put them in a trash bag, seal and dispose.
  • Exception: if there has been a major blowfly infestation, take the bag of nests
    elsewhere, empty them on the ground and leave them.  This allows tiny wasps
    that parasitize blowflies to mature inside blowfly pupae that remain in the
    nest.  Big parasites often have little parasites of their own!

Box Care:
  • If you are concerned about vandalism you may want to take your boxes and
    poles down.
  • Remove boxes and poles if land owners need to mow the field.
  • Once removed boxes can be hosed and scrubbed.  Wearing gloves, rinse boxes
    with a dilute bleach solution, then rinse again with water.
  • Store boxes and poles out of the elements.  They'll last longer.

Where have the swallows gone and what are they doing?
  • Your swallows are trying to keep themselves alive so they'll have a chance to
    reproduce next year.  That's really what a songbird's life is all about outside
    the breeding season.
  • Most Tree Swallows move to large wetlands soon after nesting.  
  • Now they become very social, forming flocks of tens of thousands to hundreds
    of thousands, flocks so large they are easily picked up on weather station
    radar and can pose danger for aircraft.  Flocks numbering in the millions have
    been reported from coastal areas on migration and on wintering grounds.
  • It's thought that advantages to flocking include more eyes to spot predators
    and more eyes to discover food.
  • By day the swallow flocks rise up from the marshes and spread out searching
    for food.  Photo below by Butterfly Psyche.







  • Their food is usually insects, but unlike other swallows Tree Swallows eat small
    berries, fruit and seeds.  Bird guides state they resort to these in bad
    weather, but in truth they consume preferred vegetable food whenever they
    find it.  Here in upstate NY we've often watched flocks eating berries of red-
    osier dogwood and arrowwood viburnun on hot August days.  The swallows
    grasp individual berries in their mouths, pluck them with a twisting motion of
    their heads, and gulp them down whole.  The chart below shows how their
    percent of plant food varies over the year.















  • Tree Swallows are especially fond of bayberries and waxmyrtle berries, and
    they possess special enzymes that allow them to digest these berries' waxy
    outer coatings.  (Below left: bayberries in winter;  center: hundreds of
    swallows descending on bayberry bushes in New York in summer;  right: 28
    bayberry seeds dissected from a single road-killed swallow's digestive tract).








  • When not foraging they sun themselves and preen.








  • In evenings the swallow flocks return to marshes to roost, usually in cattails or
    reeds growing out of the water.  This is a time of increased danger because
    predators are attracted such large concentrations of potential prey.  The
    photo below was taken by Jo-Anna Ghadban at Newburyport, Mass.
















  • As if not wanting to be the first to come in, thousands of swallows swirl about
    high feet overhead as dusk falls.  Then, often forming a funnel cloud, wave
    after wave of swallows dashes down into the marsh with a roar of wings.  Click
    this link to watch Brett Slattery's YouTube video of Tree Swallows funnelling.  
    You'll be amazed!
  • Tree Swallows going to roost can be one of nature's truly awesome sights, and
    one you can see in person!  If you're in southern New England in September
    and October consider taking one of Connecticut River Expedition's "Swallow
    Spectacle" cruises, where you can witness hundreds of thousands of Tree
    Swallows converging at sunset on their overnight roosts in Connecticut
    coastal marshes.












  • Eventually the gatherings of Tree Swallows begin the gradual migration south
    to their wintering grounds in Florida, the U.S. Gulf Coast, Mexico, Central
    America, and the larger Caribbean islands.  
  • They travel during the daylight hours, feeding as they go.  Each night the
    flocks converge on marshes for their overnight roosts.  
  • Tree Swallow migration south progresses at a rather leisurely pace step-wise
    down along a series of vital traditional foraging and roosting sites, especially
    along the seacoasts and major river corridors.  
  • Once on the wintering grounds the Tree Swallow population becomes even
    more concentrated.  The vast majority rely on wetlands in southern Florida,
    coastal Louisiana, and a few areas of Mexico.  Obviously, the continued
    availability and integrity of these areas of wintering habitat is important for
    the future of the species.
  • On both the southward migration and the especially during the winter months
    waxmyrtle berries and bayberries are crucial food resources.  Click this link to
    view Jill Kusba's YouTube video of a flock of thousands of Tree Swallows
    feeding on waxmyrtle berries in Florida.
  • However, not all Tree Swallows winter in the deep south.  Each year a few
    hardy ones risk toughing it out in coastal wetlands as far north as New England
    and Atlantic Canada in the east, and up the Pacific coast to Washington State
    in the west, and occasionally some survive to spring.  As you might expect
    their ability to endure this far north depends largely on bayberries and
    waxmyrtle berries.

Why do many songbird species migrate away from their nesting grounds?
  • Food supply is the main force driving songbird migration.
  • Breeding is usually timed to coincide with maximum availability of food for
    nestlings.
  • But once breeding is over and summer passes into fall, and winter nears, there
    are fewer daylight hours for food searching, and the colder temperatures
    require much more energy for survival.
  • Most insect eating birds would starve if they tried to winter on their nesting
    grounds.  In cold weather most potentially available insects become dormant
    and don't fly.  Plus most northern insect species pass winters as eggs, non-
    flying larvae, or hibernating adults, unavailable for most songbirds.
  • So, many songbird species must migrate south to winter in warm areas, but
    they don't wait for winter to migrate.  They move well before winter, while
    food to fuel their movement is still abundant along their migration routes.
  • These songbird migrants aren't driven by immediate hunger.  They must
    migrate in order to avoid future food shortages.

Is Tree Swallow migration north similar to their migration south?
  • As the daylight hours lengthen in late winter and temperatures moderate
    once again, internal hormonal changes stimulate movement of Tree Swallows
    back toward their nesting grounds.
  • However, migration north is different.  For one thing many of the swallows
    that began the move south last year have perished.  And instead of autumn's
    great flocks, surviving Tree Swallows head north early in spring as individuals
    and small groups, older swallows migrating first, followed a few weeks later by
    second-year birds.
  • And rather than a slow step-wise progression from roost to roost, northern
    migrants fan out across the continent rapidly until they reach their nesting
    grounds.
  • Migrating north as early as Tree Swallows do can be dangerous.  Flying insect
    food and even berries may be scarce or absent, and death from starvation and
    hypothermia is a very real risk.  Marty Burke's photo below shows a flock in
    Ontario halted by cold, snowy weather during the first part of April.  Note
    how the swallows have huddled together trying to conserve body heat, and
    compare this behavior with the "normal" individual distance maintained by the
    unstressed swallows on power lines in a previous photo.


















Will your swallows come back?
  • As we've discussed migration and wintering have their own sets of dangers,
    and it's inevitable that some, perhaps many, of your birds will die.
  • However, others, both adults who nested and young that fledged from your
    boxes, will make the journey south and winter successfully.
  • And with luck many of these survivors and others that travel with them will
    return north to spend another nesting season with you at your project.     























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After Nesting
Learn About Birds at Tree Swallow Nest Box Projects