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Songs and Calls
Only a few species of birds have no voice–storks, pelicans, and some vultures. Most birds
produce some sort of vocal sound. The Passeriformes (perching birds,songbirds) are noted for
their singing ability. Many birds are restricted to vocal sounds rather than songs or calls.

Check out Bird-Songs.net

And notice this cool gadget at BirdWeather PUC.

1 second of 1 minute, 0
00:37

Call– a brief sound of simple acoustic structure- a peep, cheep, squawk,


chatter, etc.
Song – a relatively long, often melodious, series of notes usually associated
with some aspect of courtship.

The vocal organ of birds is composed of membranes located at the


junction of the bronchi and called the syrinx. When a bird sings, air from
the lungs is forced through the syrinx and air passing over the membranes
causes a sound. Either one of the two membranes, or both, may be used in
singing. Since two different sounds may be produced, the variation in both
loudness and frequency is enormous.

The songbirds have the greatest number of muscles in the syrinx (4-9
pairs) while most other bird groups have only one pair. In general, the
complexity of the syringial muscles is related to the complexity of the songs
a bird can produce. But there are exceptions such as the American Crow,
which has seven pairs of syringial muscles but a limited voice. Parrots on
the other hand, can mimic the human voice and only have three pairs of
syringial muscles.

Function of Song

Bird songs are basically related to reproductive activities in one way or


another. Calls may be related to reproductive or self-maintenance activities.
Some specific functions of song:

1. Proclaim sex/induce another bird to reveal its sex. There is a correlation


between the complexity of the song and dull plumage and little or no sexual
dimorphism. The duller the plumage and/or the more the sexes look alike,
the more complex the song (e.g. Song Sparrows)
2. Attract a mate. True for many species.
3. Establish a territory. Often, males arrive on the breeding grounds before
the females (e.g. Red-winged and Yellow-headed Blackbirds); singing
establishes the territory and maintains it later.
4. Stimulate and synchronize courtship behavior. Indicates readiness to
breed by both sexes.
5. Maintain pair bond. A female Song Sparrow will come off the nest and
sing back to her mate.
6. Signal changes in domestic duties. May trade feeding or incubation
duties, signaled by song.
7. Identify individual to young. Most precocial birds can recognize their
own young – waterfowl and penguins, e.g. Experiments with Mallards
indicate that communication between the female and young begins before
hatching.
8. “Species” identification. A song or call may be given to identify a bird of
the same species or population.
9. Hold flock together. Calls, usually, but often songs, are used to
coordinate the movement of a flock; e.g. Pygmy Nuthatch, Mountain
Chickadee.
10. Intimidate enemies. May be use to scare predators.
11. To perfect song through practice. Often, complex songs are learned
through imitation and practice.
12. “Because they enjoy it“. Probably not

Basically a bird’s song is a very specific type of communication. If a


predatory bird is perched conspicuously in a tree small birds will often
make themselves known by a behavior called mobbing; they set up a chorus
of calls around the predator to point it out and perhaps chase it away. But if
the predator is flying overhead, the small birds race to the nearest bush or
tree and utter their calls from there.

The calls may be very different. In the case of Chaffinches (below), they
mob a predator with low pitched sounds described as ‘chink’ calls. But
when they are in cover, the birds give a high-pitched thin note called a
‘seeet’ call which causes the birds to seek cover. The difference is that the
chink note is easy to locate because of its low frequencies that differ in
phase while the seeet call is composed of high frequencies which don’t allow
it to be located because it is composed of high frequencies with little phase

difference.

Many birds have warning calls that are species-specific. Crows give a
warning call that will frighten away only other crows – this call has been
recorded and used to scare other crows from cornfields.

Starlings roost in trees in cities and can be pests; they can also be driven
away by species-specific calls – Robins and Grackles in the same flock are
not affected. But in other cases, such as that of the Herring Gull, their alarm
call will also scare away the Great Black-backed and the Laughing Gulls.

Parent birds can call to their young to make them ‘freeze’ in the
presence of a predator, swim, peck at food, etc. Young birds can vocalize in
such a way as to stimulate a parent to feed them, etc.

Song is typically the function of the male, but there are many exceptions.
The female Mockingbird, Cardinal, and Black-headed Grosbeaks have
songs as complex as the males’. In the phalaropes, where sexual
dimorphism and courtship roles are reversed, the female only sings. And if
females hold individual territories in the winter, they may sing then even
though they don’t sing during the breeding season.

Song Variation

Each bird species exhibits a more or less characteristic song, but the
song varies by age, sex, geographic location, and time of year.

Populations of the same species of birds having different songs


are song races; each variation in a song is a dialect. The white-crowned
Sparrow is well-known for having many song races and dialects.
Geographic variation in song is very common. But within different
populations of the same species, the song is more stereotyped (less
variable) when there are other species present with similar songs. But when
no other species with similar songs are present, there is more variation in
the song within a population of one species. More variation is not only
allowed, but it helps the recognition of single individuals.

Ecology of Song

Males of many bird species use a singing post to call their mate or
establish territory from – tree. post, wire, etc. Other birds the live in
grasslands like the Horned Lark or Bobolink have a flight song. Birds living
in dense vegetation such as in rainforests or thick reed beds have loud
voices since vegetation absorbs sound as well as obstructs vision. So birds
have evolved calls and songs at least partly in response to the structure of
the habitat in which the call is given. Weather also has an influence on bird
song. Both cool and hot weather decrease the amount of singing, as do rain
and wind.

A few species such as the Red-eyed Vireo sing more or less all day.
But most birds sing more vigorously in the early morning and evening
when there is less light. Some species sing at night, such as the
Mockingbird and Nightingale. The amount of light (photoperiod) rather
than the time of day determines the beginning and end of singing.
Cloudiness in the morning, for instance, will delay singing. Different bird
species react to different amounts of sunlight. So some species in a
particular area will begin to sing before others chime in (Dawn Chorus).
The dawn chorus may begin at different times each day, depending on the
amount of light, but the bird species will begin singing in the same order.

Most birds show a seasonal variation in some that is mainly correlated


with breeding activities and hormone production. The richest, fullest song
generally comes in the spring when birds are establishing territories and
courting (unmated males sing more). After egg-laying commences, the
birds sing less so as not to attract predators.

If a male bird renests or its mate is killed, it resumes full singing. In the
fall after the breeding season, the bird stops unless it holds a winter
territory.

For most species, hormones, stimulated by photoperiod, probably play


a dominant role in determining the time of year a bird sings. The injection
of male hormones into male birds in mid-winter will start them singing.
(Used to do this to Canaries in pet shops – even females injected with
hormones will start them singing.)
Inheritance and Learning of Song

Generally, calls are genetic while songs are partly inherited and partly
learned. Many studies have been done of song development; the classic one
is the one done in England on the Chaffinch. The full song of the male
Chaffinch performs the function of keeping other males from its territory
and attracting females. This song is described as: ‘chip-chip-chip, tell-tell-
tell, cherry-erry-erry, tissy-chee-wee-oo’

When a young Chaffinch is taken from the nest and reared separately
out of hearing of all Chaffinch song, its song development is greatly
restricted. The bird eventually produces a song of about the normal length
(2-3 seconds), but it fails to divide the first part of the song into phrases as
a normally-reared Chaffinch does; or it does not end the song with the
normal elaborate flourish. This simple, restricted song of the isolated bird
represents the genetic basis of the Chaffinch’s song.

There is a short, critical six-week period at about eleven months of age


during which the Chaffinch develops its final, refined song pattern. Once
this critical learning period is over, the song is fixed for life, no matter how
much a bird is exposed to other songs, it will continue to sing the final song
pattern developed during this six weeks.

So what’s happening? In the wild, young Chaffinches learn some details


of song from their parents or from other adults in the first few weeks of life.
At this stage a young bird absorbs the general pattern of the song. But not
until the critical learning period the following spring does the bird develop
the fine details of the song. This is the time the young wild Chaffinch first
sings in competition with other Chaffinches (for females, territory) and it
learns the details of the song from its more mature neighbors. This, of
course, leads to a bit of individual variation in song, although the general
pattern is characteristic of the species. So song is an integration of both
genetic and learned components and calls are entirely genetic.

Song Mimicry

A large number of birds exhibit varying degrees of vocal mimicry and


imitate call notes of songs of other species. The Starling frequently mimics
the Killdeer or nighthawk. Scrub and Blue Jays can imitate a Red-tailed
Hawk.

The Mockingbird (and others in the family- Catbird, Brown Thrasher)


are well known for imitating other bird’s calls. But there is no evidence to
indicate that these calls are an attempt to communicate with the other
species. They may, in fact, only be a human interpretation as birds hear
songs much differently that we do. A Bullfinch in England was taught to
whistle the English National Anthem. A lyrebird in Australia learned to
whistle the noon whistle at a factory.

Parrots, mynahs, crows, and magpies apparently only mimic in


captivity. And their imitation of a human voice is very different acoustically
than the real human voice.

Evolution of Song

Birds evolved from voiceless reptiles. What is the evolutionary


advantage of song for it to have developed to the extent it has?

1. Alarm notes to frighten predators.


2. Finding each other in dense vegetation.
3. As mobility increased with flight, the need for long-distance
communication did also.
4. As a way of keeping a group together- for protection and during
migration.

Non-vocal Sounds

The Passerines have the most well-developed songs and calls, but
other birds with less vocal abilities have developed other sounds. Kiwis
stamp their feed when annoyed. Boat-billed Herons, Storks, and
Albatrosses rattle or clap their bills. Woodpeckers drum. The Ruffed Grouse
drums with its wings. The nighthawk and hummingbirds often make
sounds with their wings or tails. A number of birds make whistling sounds
as they fly through the air- may or may not serve a purpose.
More on songs from PBS. Some links:

Songs –
American Bird Patuxent
Sounds Wildlife Res.
Center

Some songs of Florida Bird


New York birds Songs
8 thoughts on “Songs and Calls”
1. Pingback: Why Do Birds Sing in the Morning? | ERA OBServer

1.
DR. ROGER LEDERER
AUGUST 10, 2016 AT 6:51 AM
Birds respond to the amount of light. A little amount of morning light gets
some birds to sing, then more light gets more birds to sing, and so on. This is
called the dawn chorus. Mockingbirds need very little light to stimulate them so
they even sing with moonlight. Why the morning? There’s no point in a bird
singing in the dark if it can’t see potential predators or competitors or mates.

Reply

2.
ANDREAS SEYFANG
FEBRUARY 19, 2017 AT 10:30 AM
Why there is much more bird song activity and variety in Europe than in North America? I
grew up in Germany and now live in the US (both Oregon/temperate climate and
Florida/subtropical climate) and noticed the remarkably fewer and less melodious song
activity compared with Central and Mediterranean Europe (e.g., like nightingale, European
robin, warblers, thrushes etc.).

Reply

1.
ULF ELMAN
MARCH 30, 2020 AT 2:21 AM
Andreas,

I saw the last interview ever made with Aleksandr Solzjenitsyn, one made after
his return to Russia. He said that what he missed the most during his years in
exile in North America was the dawn chorus, and he claimed the dawn chorus in
Europe was far louder than what he experienced during his exile.

Of course, Aleksandr was a young man, presumably with perfect hearing, during
his youth in Russia, and may possibly have suffered from reduced hearing
during his years in North America. This could explain his view, which then would
be incorrect.

Your comment in this forum is the only other reference to this phenomenon I’ve
encountered. Is it really so? If so, have you found an explanation?
Reply
3. Pingback: Why Do Birds Sing in the Morning? - The Popular Videos
4. Pingback: Avian Vocalists – Ornithology
5. Pingback: January’s reading – Unlocking Words
6. Pingback: Avian Vocalists – Ornithology – Pawsomeconnection

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The Nervous System and Senses

Vulturine Guineafowl

A bird’s brain is similar to that of mammal’s but there are difference in the acuity of the senses,
especially sight. In addition, the cerebrum, the “thinking ” part of the brain is not as well
developed because birds are more instinctive than learners. But their cerebellum, the center of
mechanical coordination, is well developed for flight.

SIGHT
Birds are highly visual animals; they have to be to be able to fly. The importance of birds’ eyes is
implied by their size – they are the largest relative to the body of all animals. Some hawks and
owls have eyes as large as human eyes. The eyes of the ostrich, at 50 mm in diameter are the
largest of any land vertebrate. In some owls, the eyes comprise up to 1/3 of the total weight of
the head. In the Starling, the eyes comprise 15% of the head weight; in humans it is only about
1%. In most aspects, the avian eye structure resembles that of mammals.

The eyes of a bird are able to adjust to the light about 2x as well as that of a 20 year old human.
The lens is very flexible in most birds and can change shape readily – birds need to focus near
and far and change rapidly. The entire eye also varies in shape form flat to round to tubular
(hawks and owl); the shape is maintained by a ring of overlapping bony plates.

The retina is the sensitive layer of the eye that absorbs the incoming light, senses it, integrates
the information in it, and sends this information to the brain. The entire retina is thicker than that
of mammals and the rods and cones are more abundant. Cones are for color and rods are for
black and white and dim light. The distribution and density and proportion of rods to cones
varies with the species of bird. Diurnal birds have retinas dominated by cones while nocturnal
birds have mostly rods. Many hawks and owls have more sensory cells in the upper half of the
eye that receives more light when the birds look down.Color vision varies among birds; some, but
not all, see color. Hummingbirds, like insects, can see ultraviolet light.

Any part of the retina that has a denser concentration of receptor cells
perceives sharper images. One such area of densely packed cells is called
a fovea. Not only are the cells denser in that area but the pit shape serves to
refract the light so that a larger image is formed. Humans have a fovea;
when you focus directly on an object the image falls on the fovea- that’s why
peripheral vision is weak. Overlapping of the visual fields of the two eyes
produces binocular vision and depth perception. Most birds have a one-
fovea eye that functions similarly to ours, but many birds are bifoveal. One
fovea birds have the fovea located near the place where the optic nerve
enters the eye- a central fovea. In the birds with two foveas, especially those
that need to be good judges of speed and distance, the second fovea is
located in the temporal region of the eye. This is typical of birds of open
country- hawks, eagles, terns, parrots, swallows, doves. This additional
temporal fovea broadens the width of sharp focus and helps to judge speed
and distance; e.g.’ hawks, terns, parrots, swifts, and hummingbirds. A few
birds even have a third fovea – a few terns and swallows. A few other
species of birds have only one poorly developed fovea – owls and
sandpipers and thus bob their head to gain perspective.

There has been a lot of debate regarding the acuteness of avian vision.
It appears that it is better than human vision but perhaps not significantly
so. A vulture sees about as sharply as humans but a chicken appears to see
about 1/25th as well as humans and the hawks and songbirds see about
21/2 times as sharply. But with a double fovea, birds can keep track of a
moving object easier than can a human. Pigeons, e.g., can detect movement
as slow as 15 degrees per hour.

The density of receptor cells in the retina also allows birds to see in very
dim light. Barn Owls can see an object at 2 meters with an illumination
of .00000073 foot candles. This is equivalent to a person seeing an object
by the light of a match a mile away.

The nictitating membrane (third eyelid) is used for blinking; eyelids


are used only for sleeping. It is covered with brushlike processes inside so
that the cornea is swept with tears every time the membrane moves over
the eye. In diving birds this membrane serves as a contact lens. In owls,
unlike other birds, it is opaque. In the Black-billed Magpie, this third eyelid
has an orange spot that is displayed during courtship or aggressive
behaviors. It is also found in some amphibians, reptiles, and some
mammals. In some diving birds such as loons and grebes and ducks and
auks the nictitating membrane has a clear center which acts as a contact
lens under water.

HEARING

Birds’ ears are divided into three parts -external , middle, and inner.

In terrestrial vertebrates the organ of hearing probably first evolved as


an organ of equilibrium and later as one for hearing. In reptiles and birds a
single bone transmits sound vibrations from the eardrum to the cochlea
while in mammals, we have the malleus, incus, and stapes.

In most birds, specialized feathers surround the ear opening (except


ostriches, vultures, and some galliformes) to minimize air turbulence. The
shape of the outer ear varies; the shape of the ear openings also differ. The
most extensive variations of the ear are found among the owls- many
species have evolved very large ear flaps which look almost like human ears.
In several owls the ears are bilaterally asymmetrical (unique among
vertebrates) to helplocalize sound.

Owls can detect prey in total darkness with an error of only 1 horizontal
0

and vertical. Owls can also change the position of their auricular feathers
and to some extent the shape of their ear. The heart-shaped face of the owl
helps collect sound and direct it to the ears.

The cochlea transmits vibrations to the auditory nerve. There seems to


be a correlation between the length and complexity of the cochlea and
complexity of the song of that species.
Rhea

The frequency range of sound waves a single bird species can receive is
narrower than that of mammals. Birds are less sensitive to the high and low
ends of their range than mammals, but in the middle frequencies it is
similar. However, birds are about 10x as sensitive to rapid fluctuations in
pitch and intensity than humans. Birds can distinguish between frequencies
that differ by 1% or less and they can distinguish between sounds separated
in time by only .6 to 2.5 milliseconds.
A few birds use echolocation, like bats. The Oilbird and the Cave
Swiftlet of southeast Asia are examples. They use echolocation to navigate
but not to catch prey. Recent evidence indicates, however, that penguins
can locate prey via echolocation.

OLFACTION

Both Darwin and Audubon showed that vultures did not find carcasses
if they were covered. Audubon painted a picture of a dead sheep and
vultures tried to eat it. There is also an anecdote about Black Vultures
attacking and eating a spraying skunk. And migrating vultures have been
disoriented by releasing smells into the air.

Birds have been tested for their ability to smell by training them to
discriminate between odorless and odorous air; e.g. pigeons were trained to
peck at a disc when they smelled an odor. Vultures can smell carrion
because carrion emits the gas ethyl mercaptan; some enterprising engineers
put ethyl mercaptan in a gas line to detect leaks and found them when they
saw vultures circling over a part of the gas line.

Albatrosses, skuas, and petrels in the Antarctic seem to be able to


detect meat, fat, or blood spread on the sea’s surface. Leach’s Petrel do
some navigating by olfactory clues – they can find their nests at night by
flying from downwind into the wind coming from the colony and find their
own nesting material even if moved to a different burrow.

Evidence indicates that African Honeyguides can locate beehives by


the odor of the wax. Homing pigeons may also use olfactory clues for
navigation; birds with experimentally plugged nostrils took longer to find
their way home. The flightless Kiwi is nocturnal and feeds on food hidden
in the soil. Its vision is poor and it is the only bird with nostrils at the end of
the beak and sniffs while foraging.

In general, olfactory senses of birds are poor, but there are exceptions
and we might just think they are poor because we don’t have evidence.

TASTE

Taste buds, concentrated on the posterior part of the tongue and


pharynx floor, are similar to mammalian ones. The total number of taste
buds is less, though.
Sweet– Many birds show little interest in sugar/sweet taste except for
parrots, hummingbirds, and other nectar and fruit feeders. Hummingbirds
can distinguish different kinds of sugars and their concentrations. Seed
eaters show no preference for sweet or sour.

Salt – For most birds there is a variety of salt discrimination levels. For sea
birds tolerance for salt water is high; they can excrete excess salt through
their nasal glands although they will drink fresh water in preference to salt
water if given the choice.

Sour– Birds have a wide range of tolerance for sour.

Bitter– Again, a variety of responses. The classic study was done by Brower
in 1969. Many species of milkweeds contain cardiac glycosides. If the
milkweed is eaten by an animal the heart rate drops but the beat is
stronger; a large enough dose is fatal. But 1/2 the fatal dose causes vomiting
so an animal will throw up before it absorbs a lethal dose. Many animals
learn, then, not to eat milkweeds. Some insects, however, can eat the plants
with no apparent side effects. One is the caterpillar of the Monarch
Butterfly. Brower raised Monarchs in captivity; some on milkweed and
some on cabbage, which has no cardiac glycosides. The cabbage-raised
butterflies were fed to Blue Jays and they ate them with no ill effects. Then
the birds were offered the monarchs raised on milkweed; 12 minutes later
the Blue Jays became violently ill, vomited, but recovered in 1/2 hour. Then
the Blue Jays would reject all Monarchs introduced into the cages, no
matter how they were raised. If starved, the Blue Jays would capture and
pick at the butterflies to taste them first.

The point of this is that birds can taste bitter and will learn to associate
bitter with plants or animals and avoid them. Both the predator and prey
benefit as the prey doesn’t get eaten and the predator doesn’t get sick and
waste time eating them.

TOUCH

A bird’s skin possess sensory nerve endings, as in mammals, that


detect heat, cold, pressure, and pain. Many are also associated with
filoplumes. The tip of the bill of ducks and geese, the tongues of
woodpeckers, and the bill tips of many altricial birds have concentrated
nerve endings. In many shorebirds there are pits with sensory cells along
the bill that are very sensitive to pressure – for finding prey. Woodstorks,
for instance, can fish in turbid water and close their beak on live fish in .019
seconds after initial contact (takes us .040 seconds to blink our eyes).
Similar sensory cells are also found at the base of flight feathers and it is
likely that they play an important sensory role in flight.

CENTRAL NERVOUS SYSTEM

The central nervous system (brain and spinal cord) is arranged and
works similarly to that of mammals. Its job is to integrate sensory impulses
from the environment, to stored learned information, and to coordinate
voluntary and involuntary functions and movements.

In the brain, the optic lobes are large and the olfactory lobes small,
correlating with their senses.

The cerebral hemispheres in birds are large and well-developed, as in


mammals, but the center of complex behavior in the cerebrum is different
in the two groups. The brain of a mammal is dominated by the top layer of
the cerebral hemispheres (cerebral cortex) which have a high capacity for
learning. The bird brain is dominated by the middle of the cerebral
hemisphere which lacks learning capacity. So mammals, in general, learn
behavior and bird behavior tends to be instinctive and stereotyped. Birds’
brains are also particularly sensitive to control by hormones; implanting a
pellet of testosterone in a dove elicits courtship, copulation, and aggressive
behavior. Experimentally, large sections of the cerebral cortex have been
removed with little effect on the birds’ behavior.

The cerebellum, the center for motor control, is well-developed in birds


as is logical with their ability to fly and the related need for agility.
9 thoughts on “The Nervous System and Senses”

1.
GRETTA
DECEMBER 15, 2016 AT 11:56 AM
hello, I am a 5th grader at stem academy in fond du lac Wisconsin, I am curantly doing a
project on hawks, because I have a sharp shinned hawk, living very near me. I would like
to know more about the CENTRAL NERVOUS SYSTEM so that I can meet my standard. If
you could reply to this I would very much love that. I do not have a web site, so I put in
my email!!!!

Reply

1.
DR. ROGER LEDERER
DECEMBER 20, 2016 AT 3:26 AM
You can read about the central nervous system in an anatomy or ornithology
book. It is too much for me to try and explain it here.

Reply

2.
KNAAL
MAY 27, 2018 AT 4:38 PM
i heard that humans can only use half of their true muscle strength because our brains
limit how much strength we can use. Do the brains of birds also limit their strength in the
same way?

Reply

1.
DR. ROGER LEDERER
MAY 29, 2018 AT 3:43 PM
I have never heard of either humans or birds brains controlling muscle strength
but it makes some sense. But bird brains are much more about muscle control
and coordination than humans are. Could make a difference.

Reply

3.
SHAFAQ AFROZ
NOVEMBER 28, 2019 AT 11:14 PM
Hey,
I was exactly searching for the working of the nervous system of animals, and your article
is worth reading.
thank you.

Reply
4. Pingback: Can Birds See at Night? Everything You Need to Know - Bird Watching Pro

5.
JACK LOGAN
SEPTEMBER 9, 2021 AT 1:14 PM
Can birds lose their sight too just like humans?

Reply

1.
DR. ROGER LEDERER
SEPTEMBER 9, 2021 AT 1:59 PM
Yes, disease or accident. A fatal flaw.

Reply

6.
PAT
FEBRUARY 14, 2024 AT 7:12 AM
Things about birds we always wondered!
Excellent web site!

Reply
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Territoriality of Birds
A home range is anywhere a bird happens to wander – basically anywhere in its appropriate
habitat. A territory is a defended area within that home range and is is typical of songbirds but it
is also found in a number of other orders of birds. A territory may be held by one bird, a pair, or a
flock. It may be held for all or only part of a year. It may be very large such as those held by
eagles and provide all the resources the bird needs or only a part and be very small such as
nesting territories of cliff-nesting birds such as kittiwakes. It may be vigorously defended or
loosely guarded. Depending on the abundance of the resources, a territory might be closely held
one year and not at all the next. Typically, territories are defended against others of the same
species but may also be defended against other species.

Northern Mockingbird Display

What are the kinds of territories?

1. All-purpose – breeding season: mating, nesting,


feeding (songbirds)

2. Mating and nesting – Red-winged Blackbirds,


Tree Swallows

3. Mating – Sage Grouse

4. Nesting – colonial waterbirds

5. Non-breeding (feeding) – Robins in winter

6. Group – various reasons – Acorn Woodpecker

7. Roosting – mixed flocks such as Starlings,


Blackbirds

Territories are defended because the territory contains resources that


are in short supply and it costs energy to defend. In 1964 Brown developed
a model of territoriality that says when resources are in short supply and
the greater the population size the greater the competition for resources.
And the more resources needed, the greater the effect the population size
has. A lot of competition requires a lot of aggressiveness to obtain the
resources. But if it costs too much – economic defensibility- then territories
are not held.
Territoriality requires visual and vocal displays and movement. The
individual exposes itself to aggression from other birds and predators. For
such behavior to evolve, survival and reproductive success must be
improved. This increased success results from the more or less exclusive
use of an area for the individual and its mate or mates. Benefits come from
improved exploitation of resources, lowered diseases and predation rates.

For example, Brewer’s Blackbird nests are preyed upon more


frequently when the nests are closer together – territories serve to spread
them apart. In the case of colonial nesters, however, such as egrets,
swallows, and many seabirds, the individual territories are very small but
the colony itself is large and serves to deter predators.

Purposes of Territories:

1. Provides nest sites – holes (nuthatches, bluebirds, wrens); posts or tree


snags (Osprey); cliff ledges (sea birds, Peregrine Falcon). Here the nest
sites are chose and the territory established around it.

2. Pair formation facilitation – the male can advertise for and attract a
female with a quality territory and perhaps nest. Yellow-headed Blackbirds
and Red-winged Blackbirds.

3. Reduce disease and predation – this is probably an effect of territoriality


rather than a reason for it.

4. Reduction of aggression. Once territories are established, birds know


their relationship to one another and territory maintenance is established
and there needs to be little competition for resources.

5. Stability of resources – since resources are in a territory, they are


predictable.

6. Population control – again, an effect rather than a cause of territoriality.


The most successful birds breed but not everyone does – rather than
everybody depleting resources. (There are floater and immature males on
the fringes waiting to breed.)
Rrsearchers studied the growth of nestling Pied Flycatchers and found
that under favorable conditions both high and low density breeding
populations did well, but when the weather was bad and/or the food scarce,
the low density populations had better success in raising young. Stenger
(1958) found a direct correlation between food supply and territory size; the
more food available, the smaller the territory and the more there were. The
size of the territory, then, is generally determined by population size and
resource availability. But there are lots of modifications to this general rule.

Kendeigh’s House Wren studies showed that increased population size


results in decreased territory size, up to a point.

# of Pairs Area of Territory(hectares)

7 .32

8 .17

25 .14

42 .12 (minimum compressibility)

The size of territories varies with the individual, the species, and
the environmental conditions. Most territories tend to be more or less
circular but the shape varies. Stream bank feeders such as the kingfisher
have linear territories. Birds that feed on animal food have larger territories
than those that feed on plant food. So there are maximum and minimum
sizes of territories, the maximum size being controlled by defensibility and
the minimum by density of resources.
The amount of aggressiveness in defense of the territory also varies. It
may be more advantageous to strongly defend a high quality territory than
weakly defend a poor one.

There has been, in recent years, evidence for facultative territoriality.


Townsend Solitaires hold territories or not depending upon: juniper berry
crop density, accessibility, and competitor populations. (Lederer)

So far we have been talking about intraspecific territoriality among the


same species, which is most common. There is some interspecific
competition between different species as well, however. As a rule, birds of
one species will tolerate birds of other species in their territories and chase
out only conspecifics. A Bald Eagle and a Great Horned Owl, e.g. nested in
the same tree in Florida only one meter apart. Swallows often nest in eagle
and hawk nests. Birds often chase other birds out of their territories if they
are potential competitors or predators. Oystercatchers, e.g. will chase gulls,
ravens, and crows from their territories.

The influence of territoriality on populations may be great and some


individuals may be forced into suboptimal habitats where they are unable
to breed. Territoriality may thus cause an increase in the mortality of adults
and/or young or a decreased success rate of hatching/fledging. A Finnish
study of the Willow Warbler which prefers spruce-birch forests showed that
in years of low abundance of this species, almost all pairs of breeding
warblers were found in the spruce-birch forest. In times of high abundance,
the warblers were found in other habitats also, but their highest density was
in spruce-birch. Thus population densities are much higher in sub-optimal
habitats in high-abundance years. In high abundance years, the territory
numbers increased only slightly and sizes become slightly smaller so more
would fit in optimal habitats. So territoriality forced birds into suboptimal
but adequate habitats.

Since the number of territories in a given year may reach its maximum
in peak years, there may be “extra” individuals -floaters- without territories.
In 1951 Hensley and Cope shot all the male warblers of an eastern spruce-
fir forest and found that they were almost all immediately replaced.
Replacement is usually, but not always, restricted to males.

Territories obviously affect the social system of birds. The male Fiery-
throated Hummingbird of Costa Rica and Panama holds a territory; the
female is attracted to the flowers in that territory, but feeds on different
flowers than the male. The female selects the territories on the basis of the
best food source (rather than the attractiveness of the male). Thus the male
that is most aggressive is selected for by evolution.
The Marsh Wren is polygamous, the male mating with 1, 2 or 3
females. The sex ratio is 1: 1, so some males go without mates. Again, the
females select the males on the basis of the quality of the territory – food
and nest sites. The females will share a male rather than choosing an
unmated male if the former male has a better territory than the unmated
male in a marginal one.

There seems to be a hormonal basis for territoriality;


testosterone.Experiments were done with hormonal implants of
testosterone by Wingfield of the U. of Wash. on Song Sparrows. Birds were
implanted with testosterone tablets to keep their testosterone levels up;
these birds were more aggressive and held larger territories. But high
testosterone levels are incompatible with parental care, so fledging success
went down.

Why do some birds repeatedly fly into windows, glass doors, and
automobile mirrors?
When birds establish territories in the spring, they do so by chasing out
intruders. The birds they are most concerned about are those of their own
species because birds of the same species compete for the same resources –
nest sites, food, mates, etc. Once the territory is established, it is
maintained by singing and chasing intruders, often very vigorously. Any
objects such as windows and glass doors and auto mirrors which reflect the
bird’s image give the territorial bird the impression that there is another
bird in their territory. And since it is usually the male that establishes and
defends territories, other males are the greatest threat, and, of course, a
male sees another male in the window or mirror.
It seems that they do not quickly learn the other bird is a reflection and will
repeatedly fly against the door, window or mirror, occasionally injuring
themselves. They will eventually stop, either because they finally learned
the image is no threat or it is not necessary to continue to defend a territory
as the young have left the nest. What can you do? The answer is simple but
may not be easy to accomplish: eliminate the reflection.
16 thoughts on “Territoriality of Birds”

1.
RYOH MUROFUSHI
NOVEMBER 18, 2018 AT 8:47 PM
Hello, I am curious to find out who coined the terms for the different territories. If I
wanted to read more about the topic, who should I study?
Reply

1.
DR. ROGER LEDERER
NOVEMBER 19, 2018 AT 1:41 PM
Every ornithology textbook has good information on territories. Search google
for Avian territories and for more scientific information search google scholar
for research papers. I believe Margaret Nice created the first categories of
territories about 1947.

Reply

2.
RYOH MUROFUSHI
NOVEMBER 19, 2018 AT 9:24 PM
Thank you, Dr. Lederer. I have searched the net since posting the comment and have
found material by Nice and Brown which I would love to read but these online journals
today are very expensive. To think, Nice and Brown most likely wrote the material to be
shared by everyone and now some company is reaping the benefits of someone else’s
work. Thanks for your help. The search Continues.

Reply

3.
RYOH MUROFUSHI
DECEMBER 18, 2018 AT 5:45 PM
Is there a site where I can find or read the following two research papers?
Nice, M. M. 1941. The role of territory in bird life. Am. Midl. Nat. 26:441–487.
Nice, M. M. 1943. Studies in the life history of the Song Sparrow. II. The behavior of the
Song Sparrow and other passerine birds. Trans. Linn. Soc. N.Y. 6:1–328.

I am trying to find published studies on territories of birds and the only place I can find
anything written about them is on this site and Wikipedia. Wikipedia clearly defines 6
territories as this site does but where did these ideologies come from?

Reply

4.
RYOH MUROFUSHI
DECEMBER 18, 2018 AT 6:13 PM
My apologies I decided to leave two comments to explain my problem.
On this site, it states that 1. is the All-purpose territory which Wikipedia calls Type A. This
territory is called Type A also by Wilson 1975 and Mayr 1935. The problem occurs in the
slight differences between Type C and Type D. This site states that 3. is for mating and 4.
is for nesting. Which I assume 4. includes the nest and the small area surrounding the
nest. Wikipedia reverses these territories and says Type C is used for nesting, including
the surrounding area and Type D which is used for mating and pairing. Mayr 1935
supports this sites views on territory and Wilson 1975 supports Wikipedia. Or I should say
Wikipedia supports Wilson.

My question is why is there a slight difference between authors? I would write more but I
am afraid of taking up too much time. Mayr and Wilson have differences in other
territories.

Reply

1.
DR. ROGER LEDERER
DECEMBER 19, 2018 AT 8:55 AM
Hi Ryoh. The explanation lies in the fact that the authors try to define territories
in a few simple categories when in reality, all territories differ by a little in one
way or another. I’m sure you can find differences between different species of
gulls, for example. So there is some difference in the interpretation of the
various authors. Wikipedia, in my opinion, is a pretty good source of
ornithological information but if you want to dig into the subject matter in
detail, go to Google Scholar and search for scientific papers. I’m sure you can
find considerable information on the topic. For example: Changes in the size of
avian breeding territories in relation to the nesting cycle by Anders PapeMøller
and Sizes of Feeding Territories among Birds by Thomas W. Schoener. And a lot
more.

Reply

1.
RYOH MUROFUSHI
JANUARY 21, 2019 AT 6:52 PM
I see! Said the blind man. I should say of course. Slight differences
occur in many of the raptors I research. So many tiny details which
separate species are in turn the tiny details which cause the
differentiation in territories. Once again, I appreciate your time and the
valuable insight. Thank you.

Reply
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13.
ZAISH
JANUARY 27, 2024 AT 2:20 AM
Yeah! Finally I got it.
Basically I was in search to the answer of question Why do some birds repeatedly fly into
windows, glass doors, and automobile mirrors?
Which i found here. Really a comprehensive answer I found. Thank you for sharing this
helpful information.

Reply
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About Us

Accurate information about wild birds from a professional ornithologist. He has published 30

research papers and eleven books, among them: Amazing Birds, Birds of New England, Bird

Finder, Pacific Coast Bird Finder, Latin for Bird Lovers, Beaks, Bones, and Bird Songs, and The Art of

the Bird : Ornithological History Through Forty Artists. He has also consulted and has spoken on

ornithology across the world.

Email the Ornithologist

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