Date: 7/9/18 2:07 pm
From: DAN SCHEIMAN <birddan...>
Subject: Re: A question of mockingbirds
The short answer is that yes, Northern Mockingbirds definitely mimic other birds' sounds, as well as other animal sounds and mechanical sounds. The size of a male's repertoire is a signal to a female of his quality. Females sing too.


The long answer from Birds of North America:


Individuals learn new sounds throughout life. Adults possess extensive vocal repertoires of acoustically distinct sounds called song types (Figure 2 https://download.ams.birds.cornell.edu/api/v1/asset/25002551 ). In a detailed study of the repertoires of two males, Burnett (Burnett 1978 https://birdsna.org/Species-Account/bna/species/normoc/references#REF34467 ) found that spring and fall song repertoires have only 1% of their song types in common. Thus, mockingbirds effectively may have two vocal repertoires. Also, a minimum of 35%–63% of song types in a given spring repertoire occur again the subsequent spring; the rest are new (Derrickson 1985 https://birdsna.org/Species-Account/bna/species/normoc/references#REF16155 , unpubl. data). Finally, spring repertoire size (the total number of distinct song types recorded from an individual as determined from analyses of extensive recordings) increases with age.


Mockingbirds are persistent mimics. Mockingbirds appear to cluster imitations from the same species more often than expected by chance, but this has not been studied in detail.


Mockingbirds have extraordinarily diverse song repertoires consisting of acoustically distinct song types (= song patterns = syllable patterns). These songs are acquired through imitating the calls, songs, and parts of songs of other avian species, vocalizations of non avian species, mechanical sounds, and sounds of other mockingbirds. The proportion of songs imitated is not known and would be extremely difficult to estimate because the entire auditory experience of an individual would need to be known to determine whether a vocalization was acquired through imitation. Geographic variation, although not studied, is likely, given that mockingbirds are relatively sedentary, acquire songs from neighbors, and imitate other species characteristic of the local avifauna.


Males begin to sing sometime during February (as early as late January in southern populations) and continue into August throughout their range. Females rarely sing during the summer, and only when their mates are off the territory (KCD). Males sing during the establishment of fall territories during mid-September through November. Females also sing during this period, but the amplitude is generally lower. Because female song is difficult to sample, no one has estimated the proportion of females that sing during the fall. Females do not sing as much as males during this period. The propensity with which females sing may be greater in northern populations because more birds establish separate winter territories and pairs do not remain together as often as they do farther south. Song by females seems less complex but this has not been studied.


Mockingbirds typically repeat one song type several times before switching to another. Songs are presented in “bouts,” with each bout consisting of repetitions of only one song type. Song types of short duration are repeated more often within a bout than are longer song types (Derrickson 1988 https://birdsna.org/Species-Account/bna/species/normoc/references#REF16157 ). Mockingbirds also vary how often they return to repeat a bout of a particular song type (called “recurrence interval”). Several measures have been developed to describe the presentation of the extensive repertoire: versatility measures (see below), bout length (number of repetitions within a bout), and recurrence interval (number of intervening bouts before a song type is repeated). All measures vary among reproductive stages, behavioral situations, and individuals.


“Total versatility” is the product of song versatility and transition versatility. Singing behavior is most versatile during courtship, declines significantly during incubation, and then slowly increases during subsequent nesting stages (Derrickson 1988 https://birdsna.org/Species-Account/bna/species/normoc/references#REF16157 ). Rare song types occur most commonly during the pre-female and courtship stages, and result in an increase in versatility (Derrickson 1988 https://birdsna.org/Species-Account/bna/species/normoc/references#REF16157 ). Males that sing with the greatest versatility and lowest bout length are the first to attract mates and begin nesting.


The vocal repertoires of individual males have been estimated to be as low as 45 and as high as 203 song types (Wildenthal 1965 https://birdsna.org/Species-Account/bna/species/normoc/references#REF59784 , Howard 1974b https://birdsna.org/Species-Account/bna/species/normoc/references#REF46428 , Merritt 1985 https://birdsna.org/Species-Account/bna/species/normoc/references#REF34473 , Derrickson 1987b https://birdsna.org/Species-Account/bna/species/normoc/references#REF16156 ). Song types appear to be added continuously to the vocal repertoire, suggesting that an individual bird may not have an upper limit to its repertoire.


While both intrasexual (i.e., male-male) and intersexual (male-female) functions have shaped mockingbird singing behavior, it appears that song serves mainly to attract and stimulate females. Unmated males project their song in many different directions, as if broadcasting widely for females, while mated males, although also broadcasting widely, project their song statistically more often into their territory (Breitwisch and Whitesides 1987 https://birdsna.org/Species-Account/bna/species/normoc/references#REF34465 ). The preponderance of nocturnal song (see above) by unmated males also argues for a mate attraction function as does the observation that unmated males sing more than mated males. That song occurs during copulations seems to imply some intersexual function, as does such song's low amplitude, which restricts its propagation into neighboring territories. The amount of singing by mated males varies cyclically with breeding stage (maximum song output during nest building and egg laying; Logan 1983 https://birdsna.org/Species-Account/bna/species/normoc/references#REF46433 , Merritt 1985 https://birdsna.org/Species-Account/bna/species/normoc/references#REF34473 ) and the versatility of song follows a similar pattern (Derrickson 1988 https://birdsna.org/Species-Account/bna/species/normoc/references#REF16157 ). Also, males dramatically increase song output with the experimental removal of their mates (Merritt 1985 https://birdsna.org/Species-Account/bna/species/normoc/references#REF34473 , C. Logan pers. comm., KCD). Logan et al. (Logan et al. 1990 https://birdsna.org/Species-Account/bna/species/normoc/references#REF16174 ) presented experimental evidence that song may stimulate established pairs to renest in the presence of dependent young and thereby regulate the extent of clutch overlap. Repertoire size estimates are highest during courtship and nest building (Derrickson 1987b https://birdsna.org/Species-Account/bna/species/normoc/references#REF16156 ) and males with the largest repertoires tend to attract females earlier and nest earlier (Howard 1974b https://birdsna.org/Species-Account/bna/species/normoc/references#REF46428 , but see above cautions; Derrickson 1987b https://birdsna.org/Species-Account/bna/species/normoc/references#REF16156 ). This finding, too, was based on a detailed study of only four males, a common problem in studying song in a species with such an extensive repertoire. Rare song types occurred frequently during the pre-female and courtship stages and rarely during subsequent nesting stages (Derrickson 1988 https://birdsna.org/Species-Account/bna/species/normoc/references#REF16157 ).


Dan Scheiman

Little Rock, AR

> On July 7, 2018 at 11:59 AM Glenn <000001214b3fcb01-dmarc-request...> wrote:
>
> We have a lot of mockingbirds around our house, as I’m sure just about anybody who lives in Arkansas does. I enjoy listening to their singing. Most of the time their songs do not sound like any other bird I am familiar with, so I assume these are unique mockingbird songs. However, since I haven’t heard every bird in the world, I can’t vouch for that. Occasionally, the mockingbird that has been living in our holly tree for a few years will sound like a Great-crested Flycatcher. And at other times it will sound like birds I’ve heard before, even though I can’t quite place which bird. So my question, do mockingbirds really mock other birds? The way the human mind works is it tries to make sense out of randomness. For instance, we will see a human shape in the shadows, even though it is only bushes. So, is our mind telling us the mockingbird is singing like an Eastern Bluebird because his song is similar for a few short notes? Or is it really singing a bluebird song? Have there been any studies where a mockingbird has been locked up with a Kookaburra, for example, to see if it will start singing like a Kookaburra? Why does a mockingbird sing? I assume it is to attract a mate. Does a female mockingbird get turned on when a male mockingbird sings like a towhee? Or is it just the number of different sounds that get her attention? What is especially interesting to me is our local mockingbird makes sounds that sound like birds that I know have not been in our neighborhood. And I know our mockingbird is not a world traveler, it stays pretty close to our neighborhood as far as I can tell. So it makes more sense to me to think the mockingbird is singing a bunch of random noise songs, some of which sound like other birds, then it does to think they are singing songs of birds they have never heard before. That was probably more than one question.
>
> Glenn Wyatt
> Cabot
>




 
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