ADVANCED LEC 11 ORNITHOLOGY University of Rio Grande Donald P. Althoff, Ph.D. Sound Production & Song – Part II Reference Chapter 8

Central Nervous System Neural pathways of the bird brain that control ____ _________ and ______________ have been mapped in detail Two primary pathways connected a) nuclei of the brain—anterior forebrain pathway b) syrinx – a motor pathway regulates song production

Gill Fig 8-9, p228 Sagittal section through the brain of a songbird showing two main pathways that impact song production and development ANTERIOR POSTERIOR HVC = high vocal center RA = robust archopallial nXllts = intercollicular nuclei-tracheosyringeal motor neurons, etc. LMAN = forebrain DLM = midbrain FIELD L = auditory region Learning & recognition

Left vs. Right Hemisphere _____ hemisphere of forebrain controls bird song— specifically ___________________ in vocal repertoires Right hemisphere of forebrain controls function of the left hemisphere only if the left hemisphere is damaged.

Brain “Space” Amount controlling song varies by species, family, order, etc. General rule: the _______ the repertoires, the greater the _______________ of brain tissue. a) noted in male canaries b) noted in marsh wrens—within populations California marsh wrens have 3x more songs than NY –subsequently have 40% larger volume of song-control nuclei * genetically-controlled & related to competition: more competition for females in California!

Song Nuclei ____ of song nuclei can vary with the season (more in breeding season and non-breeding) Sex hormones can influence size—the male sex hormone ________________ increases the length and branching complexity of dendrites (i.e., receptor branches) of some neurons Exposure of sex hormone estradiol at early age enlarges the sizes of the nuclei of the song centers

Learning to Sing Not all birds have the ability _______ songs. For many species the vocalizations are inherited. a) if bird raised in acoustical isolation—can still produce that species’ vocalizations (including song) b) if bird deafened—can still sing that species’ songs c) this includes chickens, doves, flycatchers and some passerines Most songbirds, parrots, and hummingbirds can “learn” songs.

SEASONAL Species AGE-LIMITED LEARNER OPEN-ENDED LEARNER

Learning to Sing: fixed repertoires ___________________—store info early, but use later. Usually last less than a year. ___________________—long period (< 8 months) in which syllables are learning during early critical period…without practice or rehearsal ___________________—practice period. Equivalent to infant human babbling. Practice without communication ___________________—next practice period which young bird transforms “plastic” song into real song. Syllables are perfected and organized into correct patterns

Learning to Sing…con’t Involves…. a) ___________ b) ___________ Can involve invented and improvised elements as well as imitated Comparing studies of “isolated” individuals vs. those exposed to live tutors (i.e., in the wild), young birds do better when exposed to _____ tutors Learning from tutors: a) sample the repertories of 3-4 neighbors b) preserve the identity of the song tutor c) learn with priority the song types shared among tutors COLLECTIVELY: leads to formation of __________ _________.

Vocal Mimicry ~ _____ of the ___________ worldwide practice vocal mimicry Most of those that mimic are “__________________” They expand their vocal repertoire by imitating calls/songs of __________ species Northern mockingbird record mimics: 150 songs…includes calls of ________________

Songs and Mates The greater the repertoire for the male, the more the female is attracted…thus, has _______________ when it comes to breeding/mating Territorial songs signal potential rivals that the resident is prepared to _______ his exclusive use of that space Experiments show that if a territorial male Great Tit is removed, another male will take over in 10 days or less…unless the territorial song is broadcast from loudspeakers. Females “________” a males fitness—initially—by his song…that leads to courtship…and ultimately pair formation. She can respond with precopulatory trills or copulatory postures.

Songs and Mates…con’t _______: pair recognition that mains pair bond. Bouts of overlapping vocalizations that are synchronzied—to the human ear this might sound as a “single” bird singing. At least 222 species (representing 44 families) are known to sing duets. Most of these species are tropical birds. The duets serve to: a) _______________________________ b) _______________________________ Tropical Boubou Rufous hornero

In Summary… Birds can produce sound via their beak, their feet, their tail & wings, and their “voice box” The vocal “technical intricacy” of birds produced from the _______—a sound-producing organ located at the junction of the two bronchi and the trachea Birds use vocalizations to mediate social interactions over ______________________________________. Physical characteristics of vocalizations affect their _________________ and _____________________ _________________ through the environment Vocalizations can convey information about _______, _____________________________, and _________ ______________.

In Summary…con’t Vocal mimicry is one way a species can _________ the size of their vocal repertiores Avian vocalizations may be _______, ________, or invented. Four stages of song learning: 1) early critical learning period, 2) long silent period, 3 & 4) two practice periods that include subsong production and song crystallization. Formulation of song ________ in local cultures/pop n consequence of song learning. Song repertiores enhance the male’s ____________ to females…and his ability to ___________ with neighboring or rival males