Song and Calls

At the Project:
The number of swallows inspecting your nest boxes is growing as more arrive,
and one thing is certain, for small birds Tree Swallows can make a racket!

You'll be hearing lots of Tree Swallow vocalizations in the weeks to come.  
Now is a good time to start listening carefully, seeing if you can distinguish
specific calls and song, and noting what situations and behaviors seem to
evoke and accompany them.













Concepts:
Each songbird species has its own set of vocalizations.  Numbers can range
from a few up to hundreds or even thousands of different calls and songs in
some species.  Each vocalization is a signal, with a specific purpose, given in
specific circumstances.  Vocalizations and visual displays are the main tools
birds use to communicate with and exert influence over other birds.

Calls and songs have many functions, among them:
  • Species recognition.
  • Sexual recognition.
  • Individual recognition.
  • Assessing individual quality.
  • Impressing potential mates.
  • Establishing and maintaining pair bonds.
  • Establishing and maintaining territory.
  • Establishing and maintaining dominance hierarchies.
  • Attaining extra-pair copulations.
  • Maintaining contact with others.
  • Sounding predator alarms.
  • Mobbing and aggression toward predators.

Ornithologists often distinguish between songs and calls.
Songs:
  • Are usually louder and longer than calls.
  • Are often given from a conspicuous position.
  • Are most often produced by males.
  • Function to repel intruders and defend territory.
  • Also function to attract and stimulate females.
Calls:
  • Are shorter and simpler than songs.
  • Convey specific messages, such as location, danger, hunger, etc.

Every song and call has qualities, including:
  • Sound wave frequency.
  • Volume.
  • Duration.
  • Time between vocalizations.

The possibilities for variation are huge, both among species and among
individuals of each species.  Some vocalizations seem rather simple, others
extremely complex to our ears.  But birds almost certainly hear and interpret
sounds quite differently from us, and we really don't know what aspects of
songs and calls birds key on.











What songs and calls do Tree Swallows make?
Tree Swallows vocalize throughout the year, but since you'll be observing
them during nesting, here are four important calls and one song you're sure to
hear and should be able to distinguish.

PLEASE NOTE: If you click on underlined call or song names below you will
be able to hear audio clips from the Macaulay Library of Natural Sounds
Catalog at the Cornell Laboratory of Ornithology.

Chatter Call:  A loud, rapid, repeating monotone she-she-she-she-sheet.  
This is the most common call you'll hear early in the nesting season as boxes
are being claimed and pairs formed.  Both males and females give it when
other swallows approach their nest site.  Chattering swallows usually appear
excited or agitated, flattening their bodies, fluttering their wings, and aiming
their heads at the other swallow while the call is made (see picture above).  
This combination of postures form a classic territorial defense threat display.  
When given by males to other males it seems to mean "this nest site is mine,
keep away".  When males give it to females it can be mean "this site is mine,
come and see".  Females also give the Chatter Call to repel intruding females.

Gurgle, or Contact Call:  A rather soft and low-pitched 2 to 4 note repetition
of buli-duli-dullit.  The Gurgle varies slightly from swallow to swallow and
probably helps pair members recognize and bond with each other.  Although
it is heard throughout the nesting season, it's especially noticeable during
pairing as males and females become used to each other's presence at the
cavity, and then again later during incubation and brooding of small young
when pair members relieve each other at the nest.  It may act to alert the
other of the first's presence and location.  Adults also Gurgle when they
arrive at the nest with food for their young, which may help stimulate
nestlings to beg.

Alarm Call:  A loud, single or double-noted, shrieking  pee-peeh, often given
with the Chatter Call when other swallows intrude close to nest sites.  It is
also given when potential predators, especially avian predators, are spotted.   
It lets the predator know it's been seen and stimulates other swallows in the
area to join in sounding the alarm.  

Ticking Call:  This rapid tic-tic-tic-tic is associated with mating, and is given
when males swoop down to perched females just prior to copulation.  
Females sometimes give it to perched males, and in this circumstance it
seems to signal her willingness to copulate.  Tree Swallows give a harsher
version of the Ticking Call when they dive on potential predators, as you'll see
when you make nest checks.

Song:  There is one main Tree Swallow song, given mostly but not exclusively
by breeding males.  In contrast to calls, which are rather monotone, the Song
includes notes that sweep up and then down, plus various chirps and gurgles,
all strung together in countless different combinations that vary from bird to
bird.  Song is most commonly heard after pairs are well-established at nest
sites.  Listen for it when nests are being built, and eggs are being laid and
incubated.  Swallows usually sing while perched at the box, although they
sometimes sing in flight.  As with most songbirds, Tree Swallow Song seems
intended to repel intruders of their own species.

As the nesting season at your project advances listen for other, less
frequently given vocalizations, and watch the situations they occur in.
Also, listen for individual differences among your swallows; it seems there's
always one that screams Alarm at every other swallow that passes, or one
that always Ticks and dives on you when you check its nest, or one that
Chatters at an odd pitch or a slower rate.  Part of the fun is realizing these
birds really are individuals and getting to know their personal quirks.










Questions for the next Topic:  Nest Site Claiming.
  • Why don't Tree Swallows spend the winter at your project?
  • Where do they go during winter months?
  • Why are they back here so early in spring?

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