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Pair of female Northern
Cardinals (Cardinalis
cardinalis) rumbling
CHAPTER 11: AVIAN
SOCIAL BEHAVIOR
Friday
March 20 th
going out
for an
extended
lab time, no
lecture
SOCIAL BEHAVIOR
 This chapter focuses
more on non-breeding
social interactions
Flocking species and
acquisition of status in
flocks
Foraging or roosting spots
Territoriality
Defending resources from
others
A female Eastern Bluebird (Sialia
sialis) attacking a female House
Sparrow (Passer domesticus) over a
nest box
 Interactions with
other species entirely
Food, territory, other
resources
SOCIAL BEHAVIOR
Individual spacing and
‘personal space’ important
SOCIAL BEHAVIOR
 Territoriality
 Defending a fixed area for your personal use
Can be temporary or longer term
 Contains resources that you use exclusively
Food, nest sites, roosting sites, safe areas from predators
 May defend from just your own species, may defend
from others as well
 Neighbors and floaters – the threat differs in many ways
 Breeding territories, wintering territories, general purpose
territories
 Defense or announcement of ownership by songs,
calls, or displays
SOCIAL BEHAVIOR
Territory
distribution of
Northern Cardinals
(Cardinalis
cardinalis) at
Aullwood Audubon
Center, Dayton, OH
Typical
song
posture of
a male
cardinal
SOCIAL BEHAVIOR
 Benefits to territory
defense
Assuring a limited
resource is available
 Costs to territory
defense
Must expend energy to
keep your resource safe
Chasing, fighting,
displaying
Golden-winged Sunbird (Nectarinia reichenowi)
 Payoff, protecting the
energy source means
energy to pay back
expense
SOCIAL BEHAVIOR
Defending a territory from
competitors, and defending
the optimal size territory, is
only feasible when the costs of
doing so (energy, potential
injury) are outweighed by the
benefits (food, safety)
When costs are too great
territory is either abandoned
(become non-territorial) or
allowed to shrink (give up
some until defense is feasible)
SOCIAL BEHAVIOR
Territory size required varies with
species and with resource being used
Larger species typically need more
than smaller species (general space)
Predators need more area than
herbivores (energy dynamics)
Quality of the resource on the
territory can also determine size
Archilochus colubris
SOCIAL BEHAVIOR
Acorn Woodpecker (Melanerpes formicivorus) granaries are a valuable resource, strongly
defended by a group.
SOCIAL BEHAVIOR
 Floaters and neighbors are always looking to take
territory
 A territory owner has precedence over an intruder
 Owner knows the value and knows the lay of the land
 Experimentally remove an owner and usurpers fight to remain
based on how long they’ve occupied territory
 Neighbors will take some of what’s yours if that is
allowed
 Long-term territoriality, boundaries are established
 ‘Dear Enemy’ – ‘I know you and what you can do, you cannot steal from
me’
 ‘Nasty Neighbor’ – ‘I know you and what you can do and what you have, I
can take it from you as you’re weak’
SOCIAL BEHAVIOR
 Within flocking species
dominance status can
be important
 Better access
 Better access
 Better access
mates
 Better access
territories
to food
to safety
to future
to future
 There are costs
associated with this
 Some species, dominants
have high corticosterone
levels
Red Junglefowl (Gallus gallus) females
establish ‘pecking orders’ among their
flocks for access to food and mates
SOCIAL BEHAVIOR
 Social interactions can be what keeps order in groups and
what keeps your resources yours, but
 Energy it takes to fight
 Costs due to injury – can be very expensive (death the most
expensive)
 There must be other ways to communicate besides just
jumping right to the attack!
SOCIAL BEHAVIOR
Physical appearance, ornamentation, can be used to
quickly identify who is likely to be dominant and who isn’t.
Ornament expression typically co-varies with age, quality,
sex, or steroid hormones in such a way as to reliably
indicate who is who.
Harris's Sparrow, Zonotrichia querula
“Stud”
Not so much a
‘Stud’
SOCIAL BEHAVIOR
 Experimental
modification of
ornaments and status
 Harris’s Sparrows
Only with implant of T could
non-studs dyed to look like
studs succeed
 House Sparrows
Birds dyed to look dominant
succeeded for a bit, then
were tested
 Northern Cardinals
A pale cardinal held his own even
if he was super red originally
Alteration of red didn’t
change flock status,
something other being used?
SOCIAL BEHAVIOR
Ocellated Antbird
(Phaenostictus
mcleannani)
Bicolored Antbird
(Gymnopithys leucaspis)
Benefits of dominance within flocks, either of a single
species or mixed species, that you get the best food. Not
just ornaments but sheer physical size can be important
Spotted Antbird
(Hylophylax naevioides)
SOCIAL BEHAVIOR
Large Ocellated Antbirds (~50g)
take precedent at the center of
Army Ant swarms, here is the best
insect foraging opportunities
White-plumed Antbird (Pithys albifrons)
SOCIAL BEHAVIOR
 Aggressive (agonistic) behavior
 A physical interaction is going to ensue, one will win and one will not
 If ornaments that co-vary with status not enough, fights may
ensue
 Typically birds of similar status within flocks, or of similar
ornamentation
 Often a stereotypical set of behaviors or postures to show
intent
 Threat, displacement, attack/chase
 Bird that isn’t winning or isn’t escalating has appeasement display
SOCIAL BEHAVIOR
Don’t be fooled by group selection
arguments, avoiding this is good for
both the loser and the winner.
This is what displays are trying to
circumvent, here two male Yellow
Warblers (Dendroica petechia) really
battle it out
SOCIAL BEHAVIOR
Peeved and ready to
do something about it
Not ready to rumble,
trying to diffuse the
situation
Steller's Jay (Cyanocitta stelleri)
SOCIAL BEHAVIOR
Ultimate attack stance in Northern
Cardinals (Cardinalis cardinalis)
SOCIAL BEHAVIOR
 Surprisingly some
aspects of courtship
have aggressive
components
 Some suggest females
incite males to fight to
pick the best
 Males may need to
overcome gut reaction to a
conspecific
 A male could be
mistakenly be trying to
defend against an
intruding female
 Mate has disappeared very
recently
SOCIAL BEHAVIOR
 Aggressive behavior
makes one think of
males, and males
have been focused on
 Females are
aggressive too
 Status in a flock/group
 Territory boundaries
 Access to males
 Defense of nesting
resources
SOCIAL BEHAVIOR
 Flocks – groups of birds, can be small (6 or so) can be huge
(millions of individuals)
 Can be all the same species, can be comprised of multiple
species – more later
 This has costs and benefits
 Benefits
 Safety in numbers, ease in finding food (work of off producers), more time
devoted to foraging
 Costs
 Someone takes your food (scrounger), constant fighting for dominance,
increased disease transmission, food might not be super -abundant
SOCIAL BEHAVIOR
Red-billed Quelea
(Quelea quelea)
flocks are enormous;
promotes safety, and
can manipulate the
scrounger/producer
system
SOCIAL BEHAVIOR
Young Common Ravens
(Corvus corax) use flocks
for information sharing and
to gang up for resource
acquisition
SOCIAL BEHAVIOR
Being in a flock
can help you
avoid predation
(dilution effect,
confusion effect,
and more eyes
on the look-out)
Predator
SOCIAL BEHAVIOR
European (Common?) Starlings (Sturnus vulgarus) alter their behavior when they
cannot easily see others, shows the benefits of associating in flock
SOCIAL BEHAVIOR
Multiple factors go into decisions concerning flock size, if dynamics around the flock
change the optimal inclusion of more or less individuals will alter as well. Notice the
cost of fighting with others over access to resources.
SOCIAL BEHAVIOR
 Mixed species flocks – lots of species moving together
 Why do this?
 Some cases, the resource you’re after forces you together – antbird
species following army ants
 Rare or territorial species may not have enough of their own around,
joining with others a must (safety, better foraging)
 Surprisingly social signals are interpretable across species
groups
 Appearance and behaviors associated with dominance cross species
boundaries
 Often habitual associations lead to similar appearances
SOCIAL BEHAVIOR
 Some cases individuals live or associate in super groups
 Colony nesters – enormous groups nesting near each other
 ~13% of species do this, primarily seabirds
 Shortage of safe nesting spots, everyone congregates where it’s
best/safest
 Communal roosting
 Large groups offer safety – intimidating to predators and many eyes
on the watch
 Large groups offer information – ‘Who ate well today, perhaps I’ll
follow them tomorrow’
 So many together, if sheltered, may reduce energy demands for
thermoregulation
 May be easier to find a mate in the group
 But, energy spent on aggressive interactions over dominance and
individual spacing; disease transmission
SOCIAL BEHAVIOR
Royal Tern (Thalasseus maximus) nesting
colony, just area around body ‘secured’
SOCIAL BEHAVIOR
Not really a communal roost here,
but crowding can have detrimental
impacts.
Here, birds on the bottom of the
piles have been known to suffocate
and if one individual is sick,
everyone is going to get it.