Song and Song learning

Robert J. Cooper

WILD 5200/7200

Southern Africa Field Ornithology

Figure 10-4 – The syrinx and associated sound-producing morphology

Figure 10-5 – In schematic form (don’t worry about detail)

Song & Communication• Song

– Only males sing – functions include mate attraction, territory defense

– Both sexes give calls – functions include mate-to-mate communication, flock cohesion, parent-offspring communication, predator mobbing

Songs versus Calls

Songs Calls

Given by males (usually) Given by both sexesFunctions: mate attraction, Variety of functions territorial defenseLong and complex Short and simpleUnder hormonal control NotUsually restricted to Given year-round breeding season

Song & Communication

• Song– Only males sing – functions include mate

attraction, territory defense– Both sexes give calls – functions include mate-

to-mate communication, flock cohesion, parent-offspring communication, predator mobbing

– An important part of bird surveys and birding is song identification

– Breeding Bird Survey

Using song in bird surveying

Eastern Meadowlark

Song Learning

There is a diversity of degrees of avian song learning, ranging from no evidence of learning at all (innate, or under genetic control) to learning new songs or parts of songs throughout life.

Song learning (learned vs innate behavior):

• Some birds exhibit no evidence of song learning (brood parasites, doves)

• Others exhibit limited learning from the bird they are most closely associated with, usually the father (WCSP, INBU)

• Others are capable of learning songs of other birds but normally do not do so in nature (e.g., NA warblers)

                                                         

Hooded Warbler

White-crowned Sparrow

IndigoBunting

Song & CommunicationSong learning (learned vs

innate behavior)• Others learn throughout life and

regularly mimic songs of other birds (e.g., mockingbirds, lyrebird) – why?

• Others learn throughout life from their mate (duetting –strengthens pair bond) – many wrens, antshrikes, etc.

Song learning in the White-crowned Sparrow

Characterized by critical periods, memory templates and eventual irreversibility of song patterns

• First critical period coincides when adult males are singing and young are about to fledge (10-20 days old).

• During this time a memory template is formed (i.e., young birds remember what they are supposed to sound like).

• Second critical period corresponds to a time when they are beginning to practice singing (~150 days).

• They must be able to hear themselves sing to make use of their auditory template, attempting to match their song to it.

• Eventually they are able to match their song to the template, and by ~200 days the song is crystallized (unchanged forever after).

• Non-auditory memory is involved too,

matching internal sensory information

about muscle and air movements used

to produce particular notes.

Avian Social Interactions:Territoriality and Flocking

WILD 4060/6060Field Ornithology

Territory and Home Range

Territory – any fixed area defended continuously for some period of time.

Home range – an area used by an animal in the course of its normal daily activities.

Considered roughly the same thing for birds.

Territories are usually established for the purpose of defending a limited resource. Also, for breeding territories, a nest and mate are usually contained within the territory, and will be vigorously defended.

The result is that the population size is regulated and resources are not over-consumed.

Types of Territories

Most songbirds (and their allies; e.g. cuckoos, hummingbirds, etc.), woodpeckers, raptors, and kingfishers, have an all-purpose territory, in which they find all their food, build a nest and raise young.

Many waterbirds, especially colonial nesters, defend a small area around the nest, but will tolerate other individuals near them when they feed away from the colony, and often form flocks. Even in flocks, though, each bird will defend a small area around itself.

Other oddities exist. Oropendola nests

Territory-size Regulation in Black-shouldered Kites (Elanus caeruleus)*

• BSKI occupy coastal grassland in northern California, where they feed almost entirely on Microtus californicus.

• M. californicus exhibit a 12-month population cycle, in which their density fluctuates from only a few to about 1000/ha.

• Other raptors, including BSKI, migrated there in fall, left in spring

• Dunk (1991) measured BSKI territory

sizes year-round• Found that territory size was related to

both food and # of competitors –

proximate versus ultimate factors.

* Now known as White-tailed Kite

Key players in the Arcata grassland ecosystem

Keystone prey item – California vole (Microtus californicus)

Kite’s exact position could be measured when they perched or

hovered

Even wading birds ate voles

Intraspecific encounters were often violent

And so were interspecific encounters

The inverse relationship between food abundance and territory size in known as the Food Value Theory (Stenger 1958).

Does it hold for the majority of species that obtain food in a 3-dimensional area?• Yes: Marshall and Cooper showed

that Red-eyed Vireos’ territory volume was inversely related to caterpillar density.• Also holds for fish.

Does it hold for migratory species, which must assess a territory’s future food value when they arrive in the spring?• Yes: Ovenbirds have been shown to use structural cues (litter depth) to assess habitat and adjust territories.• Also holds for REVI, whose

territories were inversely related to foliage density.• Known as Structural Cues

Hypothesis

From Marshall and Cooper (2004). Ecology.

Figure 14-5

Figure 14-3 – Economics of territoriality

Opportunistic flocks formed for food acquisition still have individuals that defend territories – Ant-following birds

Flocks moving in unison can confuse predators