BEHAVIOR GENETICS STUDIES WITH BIRDS

By Luis F. Baptista

IFCB 1978

INTRODUCTION
Each animal possesses a genome which endows it with dispositions to respond in a certain range of ways, to a certain range of appropriate stimuli, and thus feeds itself, finds shelter, acquires a mate and contributes to the gene pool (Manning 1972). Gene mutations are continually emerging. As environment changes, genomes may also have to change to adapt to these changes. Thus, individuals possessing dispositions to perform new behavior patterns that enable them to cope with environmental changes will be selected for and leave progeny. The heritability of behavioral traits has been a long debated issue often referred to as the “Nature versus Nurture” controversy. Ethologists have long been aware of the heritability of behavior patterns (nature), whereas many psychologists, preoccupied with learning phenomena (nurture) were slow to be convinced.

That dispositions to perform specific behavior patterns may actually be inherited and thus be subjected to the forces of natural selection, comes from studies of interspecific hybrids, artificial selection of extreme behavior traits, and intraspecific hybrids between selected strains of animals. Data from studies on invertebrates are plentiful (Gould 1974). Data on birds are relatively few. This paper reviews some of the changes brought about during the process of domestication of birds and summarizes studies on behavior of natural and artificial interspecific avian hybrids. These include my own unpublished studies on hybrid Estrildid Finches study of domesticated species can be very instructive as to how natural selection operates on behavior, especially if the ancestral forms are still available for comparison. Both natural and artificial selection (e.g. domestication) operate on mutations resulting in reduction of variation (Frank 1974). The process of speciation requires isolation of gene pools. Domestication is the result of artificial isolation of segments of a gene pool from the wild population (Goodwin 1965, Nicolai 1976).

EFFECTS OF DOMESTICATION

Tameness

Canaries
Birds that lend themselves to domestication must be easily maintained and bred in captivity. Indeed, Goodwin (1965) points out that most domesticated forms are granivorous species (Galliformes, Columbiformes, Psittaciformes, Fringillids and Estrildids), the groups that are easiest to maintain in captivity.

Man must also have selected for individuals that would breed readily in captivity. Throughout the world today, societies exist for the propagation and perpetuation of the many domesticated breeds of canaries (Serinus Canaria). These birds are docile and are often bred in small cages. Nicolas (1960) compared the behavior of domesticated and wild caught canaries. He found that wild birds remained skittish for a long time while held captive and seldom came into breeding condition. Clearly, man must have selected good breeders as ancestors of our domesticated forms. That tameness in domesticated canaries is heritable was demonstrated by Hinde (1956). He presented canaries, Goldfinches (Carduelis carduelis) and hybrid Goldfinch x canaries with stuffed owls. Goldfinches mobbed the owls, but many canaries showed only a passing interest in the models. The latter was interpreted as a by-product of artificial selection for tameness by man. Hybrid Goldfinch x canaries also mobbed the models but less vigorously than pure Goldfinches.

Turkeys
Loepold (1944) studied the heritability of tameness in turkeys (Meleagris gallopavo). Wild turkeys are difficult to keep and breed it captivity, frequently fighting so that game farms usually cross domesticated birds with wild ones and release the hybrids for the hunter’s gun. Leopold noted a lack of alertness and wariness in wild hybrids. Wild birds had an uncanny ability to see the observer before he spotted the birds and would immediately run for cover. hybrids could be approached more closely. If the observer withdraw a few hundred yards at the first sign of alarm from the hybrids, the latter would resume normal activity and permit further observation.

Ducks
Another measure of tameness is the speed at which an animal habituates to a novel stimulus. Desforges and Wood-Gush (1975a) presented wild mallards (Anas platyrhynchos) and domestic Aylesbury Ducks with a model of a stuffed brown Leghorn Hen. The domestic breed habituated faster to the presence of the model. They then replaced their food pellets with colored pellets. Although the latency to respond increased in the Aylesbury, they eventually consumed the pellets. The mallards never ate the colored pellets.

Recognition of Young

Chickens
Heinroth (in Lorenz 1971) noted that females of Burmese Jungle Fowl (Gallus gallus) will only lead chicks with markings on the head typical of the wild form. Chicks of domesticated breeds lacking head markings will be killed. This recognition of species’ specific characteristics in chicks is still found in some domestic breeds (e.g. some gamecock breeds, Phoenix chickens). However, in many domesticated breeds man has apparently selected against the ability to recognize species’ specific characteristics so that even ducklings or goslings may be brooded and led. Indeed, in some breeds (Orpington, Plymouth Rock) even the response to the acoustic character of the releasing mechanism has been selected out so that hens will even try to care for young mammals (Lorenz 1971).

Estrildid Finches
Nestlings of Estrildid Finches have species’ specific colors and markings on their palates and beg with species’ specific head-twisting movements and vocalizations. That these palate markings serve as species’ specific releasers was tested quantitatively by Immelmann, et al (1977). The authors placed nestlings of domesticated strains of Zebra Finches (Poephila guttata) which lacked palate markings with “wild-colored” Zebra Finch nestlings which had five black spots on their palates. Wild-colored nestlings had significantly higher survival rates, had priority to the first feedings of the day and received more food during the later phases of the nestling stage so that they grew at a more rapid rate. Nicolai (1964) performed cross-fostering experiments with various Estrildid species. He noted that these finches would not feed newly-hatched chicks with mouth markings differing from those of their young. If mouth markings of fostered heterospecific nestlings were similar to those of their own, the strangers would be fed for a while and then deserted.

As in some domesticated breeds of chickens, man has bred out the selectivity of response to the species’ specific releasers (mouth markings) of their young in the domesticated Bengalese Finch (Lonchura striata). Guttinger and Nicolai (1973) report that Bengalese Finches in their experiments raised 122 individuals belonging to 15 species in 7 genera (Lagonosticta, Uraeginthus, Ptyilia, Spermestes, Lonchura, Heteromunia, Erythrura) with diverse palate markings. In other cross-fostering experiments, Bengalese have been used to raise the genera Poephila, Euodice, Chloebia and Odontospiza (Immelmann 1969, Baptista 1973a, 1973b). Indeed, Gouldian Finches (Chloebia gouldiae) are frequently raised by Bengalese Finches in Japan and exported to Europe (Nicolai 1967). The list of genera raised by Bengalese is probably incomplete.

Social Behavior

Turkeys
Leopold (1944) found differences in the social behavior of wild turkeys and free-ranging wild x domestic turkey hybrids. Wild turkeys tended to gather in small flocks ranging from 2 to 12 animals (X 2.5 to 6.3 between 1940 and 1943). Even at low densities, hybrid turkeys gathered in large flocks ranging from 7 to 33 birds (X 14.8
to 19.2 between 1940 and 1943). There is a partial segregation of the sexes in wild turkey flocks, i.e. adult males tended to winter separately from adult females and young of the year. This segregation was not found in the hybrid strains.

Pigeons
Edrich and Keeton (1977) performed homing experiments with feral and domestic “homer” pigeons (Columba Livia). Ferals had on the average longer homing times and lower return rates than “homers”. This was partly due to weaker homing drives in the feral pigeons but partly due to a selected change in the social behavior of homers. Feral pigeons tend to be easily “distracted” by other pigeons, tending to join other pigeons flocking in the air or on the ground. Man has apparently selected out this tendency to flock in the homer.

Cockerels
A number of game-cock breeds have been selected for aggression. Fennel (1945) compared the behavior of some game-cock breeds and more docile domestic chickens. He found that game-cocks were able to tolerate more punishment, were shiftier, faster and not as clumsy as “domestic” cocks. He also noted that different breeds utilized different methods of fighting. “Kentucky Dominiques” attack from above by flying at the opponent. “Allen Roundheads” move to within striking distance, then strike forward or toward the enemy on either side.
Cockerels have also been selected for high and low sex drive through three generations (Wood-Gush 1960). Siegel (1965) performed bidirectional selection experiments for completed matings over six generations.

Japanese Quail
Kovach (1974) has reviewed the literature on genetic factors in sexual behavior in this species. Strain differences have been found in the sexual receptivity of females. Another investigator successfully undertook bidirectional selection for high and low mating activities in male quail in one generation. Strain differences were also found in mating frequencies.

Ducks
Desforges and Wood-Gush (1975b) reported selection against aggression in domestic Aylesbury Ducks. Individual distance was smaller for Aylesbury than for mallards during feeding and resting. For example, mallard drakes maintained an individual distance of
45.7 cm from another drake during feeding, whereas the domestic drakes maintained distances of only 30 cm.

Vocalizations

Domestic Chickens
Kruijt (1964) studied the ontogeny of behavior in Burmese Jungle Fowl (Gallus gallus), ancestor of our domestic breeds of chickens. When distressed (hungry, cold or isolated), chicks utter a loud shrill call at the rate of 2 to 3 per second. Kruijt’s spectrograms showed that shrill calls of domestic chicks differed in morphology from those of their wild ancestor.

Konishi (1963) showed that crowing in domestic cocks is genetically determined, developing normally even in birds deafened at the time of hatching. Selection for differences in crow duration in two different breeds was demonstrated by Siegel et al (1964) who studied Athens-Canadian Random breds and White Rock roosters. Crows of White Rocks were significantly longer. They suggested polygenic inheritance in crow duration as evidenced by the fact that variation between individuals was greater than within individuals

Crow duration in the above breeds averaged 1.58 to 2.43 seconds. Masui (in Siegel et al 1964) reported that the Totenko breed of ornamental chickens had crows lasting 15 to 20 seconds, again a result of artificial selection.

Goodwin (1965) noted that males of most of the largest breeds of domestic chickens have crows that are more long-drawn with the last syllable lengthened out, whereas bantams have shorter crows more similar to the ancestral Gallus gallus.

Domestic Ducks
When performing the sexual display known as the grunt-whistle (see Figure 2), mallards utter a clear flute-like whistle. Desforges and Wood-Gush (1976) found that in one of the domestic breeds (the Aylesbury) the whistle has been reduced to a low grunting sound.

Domestic Pigeons
In his treatise on domestic animals, Darwin (1875) pointed out that man has selected for distinct qualities of voice in at least two breeds of pigeons. Levi (1965) describes 13 “voice” breeds known collectively as “Trumpeters). A second voice breed noted by Darwin is known as the “Laugher.”

behaviorgenetics_pict222

Figure 1. Principle components of distress calls of pheasant, chicken, small hybrid (H1) and large hybrid (H2). After McGrath et al. 1972.
behaviorgenetics_pict223
Figure 2.
First row, left to right:
1. Mallard, grunt-whistle
2. Mallard, headup-tailup
3. Mallard, downup
4. Mallard, nod-swim

Second row, left to right:
1. Pintail, grunt-whistle
2. Pintail, headup-tailup
3. Pintail, burp

Third row
Mallard, bridling.

After Lorenz, 1971.

Levi (1965) describes the courtship song of the Thailand Laugher as a “who-a, who-a” followed by 8 or 10 wock-wock, wockwock. The male English Trumpeter begins its courtship song with several coo-coo-roo-coo’s similar to the ancestral Rock Dove, but this is followed by a long series of who-oo-oo-oo-oo-oo, who-oo-oo-oo-oo-oo, etc. (Baptista and Abs 1981). The peculiar sounds used by other breeds are also used in the nest showing ceremony. In this display the male sits in the nest cup, bows rhythmically, flicks the wings up and down rapidly and vocalizes. Another breed, the Altenburg Trumpeter, has a much more rapidly uttered series of vocalizations following the courtship coo. The Altenburg’s trumpeting is also more uniform in rhythm than in the English breed (Baptista and Abs 1981).

Domestic Quail
The Japanese Quail (Coturnix coturnix japonica) was domesticated as a “good song bird” during the Muromachi era, some 600 years ago (Yamashina 1961). In Central Europe, Coturnix Quail were independently selected for qualities of voice. All breeds of Japanese singing quail were lost during World War II, and the European strains were lost because of loss of popularity of the hobby (Howes 1964).

Goodwin (1965) noted that wild Japanese Quail give a call (crow) which sounds like “Quah–kah”. Domesticated birds give a call which sounds like “Quah-grrr”. This was selected for because it suggested to the Japanese the sound of “distant thunder”. During the Tokugawa Period, they were kept in elaborate cages and judged in competitions on quality of song. Moreau and Wayre (1968) compared sound spectrograms of wild Japanese Quail with extant domestic stock. Although calls of wild quail are similar to those of the domestic birds, the latter are “louder” and harsher.

Greater and Lesser Prairie Chickens
The vocalization associated with the “booming” display in a hybrid consisted of six syllables in contrast to the three syllables in both parental species. Duration of the directed display was 1.96 seconds in the greater, 0.60 seconds in the lesser, versus 0.97 seconds in the hybrid (Crawford 1978).

Canary
Along with differences of appearance in the various domesticated canary breeds, man has selected for different qualities of voice/ Marley (1959) studied spectrograms of Roller Canary songs and compared them with songs of their wild ancestors. Roller songs are softer, lower pitched, consist of long repetitive trills with shorter intervals between notes and are simpler in structure than songs of wild canaries. Poulson (1959) also noted that Rollers sing with their bills virtually closed, whereas “common” canaries (= choppers?) sing with their bills open. Common canaries may imitate Roller songs but sing them with bill open. He found also that the soft and low pitched quality of the songs developed in Rollers raised in isolation. Syllable diversity, however, is learned (Poulson 1959, Marler and Waser 1977, Waser and Marley 1977).
Poulson (1959) also compared two social calls of Roller and “common” canaries. Both contact and alarm calls of the Roller Canary are also lower pitched than those of common canaries and exhibited differences in patterns of pitch modulation. Recent studies by Murdinger (1970) indicate that at least some social calls in Carduelid Finches are learned. Thus the relative contributions of nature versus nurture in the development of canary calls remains to be ascertained.

Courtship

Pigeons
As a result of artificial selection by man, various breeds of domestic pigeons exhibit breed specific behavior patterns. The latter appear to be derived from various components of courtship and other social displays of Columba livia.

Pouting
Columba livia inflates its neck with air (pouts) during courtship and during the nest-calling display. Pouting may continue for a while after courtship (Whitman 1919). In the 40 or so extant breeds of pouter pigeons, pouting is exaggerated and occurs at the slightest disturbance, e.g. during aggressive displays against conspecifics or a human intruder. Pouting is, therefore, the hypertrophy of a universal instinct in pigeons to inflate the neck (Whitman 1919, Nicolai 1976).

Wing Lifting
The aerial display of C. livia is territorial and sexual in motivation. In this display the pigeon claps its wings loudly several times, then glides with its wings held slightly above the horizontal, finally gliding with its wings held out horizontally. The Swing Pouter holds it wings almost vertically above its back during the gliding phase so that it quickly loses altitude and must flap its wings to return to a greater height.

Wing Clapping
Two breeds, the Swing Pouter and Rhine Ringbeater, perform exaggerated loud clapping phases during their display flights. This leads to premature fraying of the primaries early in the breeding season. The clapping phase of the flight display is lengthened in the Swing Pouter. Nicolai (1976) once counted as many as 30 claps during the display flight of this breed, whereas it is usually 4 to 6 claps in the ancestral C. Livia. Nicolai crossed these two loud clapping breeds with some of the normally (softer) clapping breeds, and found that loudness was intermediate in the Fl generation.

Rolling
Levi (1965) has cataloged some 22 breeds of roller and tumbler pigeons. These may be further segregated into flying rollers, parlor rollers, flying tumblers and parlor tumblers. Tumblers differ from rollers in that whereas tumblers perform only one or two backward somersaults per series, rollers may perform many, often falling 50 or more feet in the course of rolling. Young individuals of both types fly normally for the first weeks or months but eventually all perform intermittent somersaults. The parlor types eventually lose their ability to fly altogether, rolling or tumbling on the ground.

Nicolai (1976) traced rolling behavior in Birmingham Rollers to the glide phase of the display flight, noting that loss of altitude is a prelude to rolling in young birds. However, Entrikin and Erway (1972) and Kerry Muller (personal communication) report that any attempts to fly initiates rolling or tumbling in the air or on the ground.

Nicolai (1976) crossed rollers with non-rolling breeds and noted that Fl hybrids could perform only incomplete somersaults. A more detailed study of the inheritance of rolling behavior in pigeons was performed by Entrikin and Erway (1972). Crosses between flying rollers and normal breeds produced 38 non-performers and one bird that somersaulted only once or twice. F2’s were split 50-50 into rolling and non-rolling birds. F1’s back-crossed to flying rollers produced about equal numbers of performers and non-performers. Flying rollers crossed with parlor rollers produced about equal numbers of parlor and flying rollers. The authors suggest that rolling behavior is controlled by a single autosomal mutation. However, the penetrance and expressivity of the gene appears to De modified by other genetic factors.

Ringbeating
During its ground courtship bow-cooing display, a domestic pigeon may sometimes jump into the air, clap its wings loudly several times, then drop just behind or beside the female and recommence his bow-coo display. In the extinct English breed called the Finnikin (Goodwin 1965) and the extant German Ringbeater (Nicolai 1976), the clap display is elaborated so that the courting male will fly one to four times in a tight circle over the female with a constant loud clapping of the wings. Nicolai points out that even the female Ringbeater claps louder than other breeds, although not as loudly as the male.

Nicolai isolated an unpaired female Ringbeater for some time, and then placed her in the middle compartment (1.5 x 2.5 x 2.3 m) of a three-compartment enclosure. In one of the other compartments he placed a male Ringbeater and in the other he placed a male of another breed. She was visually isolated from both males by partitions of cloth but could hear both displaying. She was attracted to the clapping display of the male Ringbeater and ignored the other male. The author suggested that a parallel change in the signal receiver also occurred which was genetically fixed with artificial selection.

Ducks
Desforges and Wood-Gush (1976) compared the courtship displays of domesticated Aylesbury Ducks and the wild ancestors, the mallard. As mentioned earlier, the acoustical component in the grunt-whistle display of the Aylesbury has been reduced to a grunt. Following the head-up-tail-up display, mallards turn the back of the head to the female. The last display is absent in the Aylesbury. Moreover, the preliminary shaking preceding the head-up-tail-up display of the mallard was sometimes absent in the Aylesbury.

The down-up display was performed at lower intensity by the Aylesbury. The nod-swim display was less often seen in the female Aylesbury and reduced to an intention movement.

Pair-formation displays were always directed at only one female in the mallard. Aylesburies would direct these same displays (e.g. precopulatory pumping, preen-behind-wing) at several females. Mallards were thus thought to form pairs in captivity, whereas Aylesburies did not.

Behavior of Hybrids

Maintenance Activities

Diving versus Dabbling in Ducks
The different tribes of ducks tend to forage in different ways. Mergansers (Mergini) dive beneath the water’s surface to pursue their prey. Shelducks (Tadorna tadorna) belong to the surface duck tribe (Anatini) which typically feed by (1) “dabbling” on the water’s surface to pick up vegetation and small animals in their bills or (2) “tipping”, wherein half the body is submerged under water, and the hindquarters remain on the surface. Lind and Poulson (1963) studied the feeding behavior of a Goosander (Mergus merganser) x Shelduck hybrid. The latter never dived but dabbled and tipped like its Shelduck parent. However, whereas Shelducks tip with their body 90° with the horizontal, the hybrid tipped at 45°. The authors attributed tipping angle to the body shape of the hybrid.

Scratching versus Digging
Typical of many galliformes, Lady Amherst Pheasants (Chrysolophus amherstiae) feed by scratching the ground with alternate backward movements of the feet. Impeyan Pheasants (Lophophorus impeyanus) dig the soil with the bill when feeding. A hybrid Impeyan x Lady Amherst Pheasant fed by digging with its bill like its male parent (Huxley 1941).

Foraging for Worms
Whitman (1919) observed that whereas many species of pigeons and doves feed occasionally on earthworms, Passenger Pigeons (Ectopistes mi_gratorius) seemed to relish these food items more than did other species. A Passenger Pigeon hatched under Ring Doves (Streptopelia risoria), never having seen an earthworm before, immediately approached the worms when presented with them, handled and ate them. Whitman went on to present one naive Passenger Pigeon x Ring Dove hybrid and two “pure” Ring Doves with some earthworms and soil. Whereas the Ring Doves ignored the earthworms, the hybrid immediately approached the worms and quickly acquired the skill of extracting worms from their burrows and eating them. Whitman suggested that the recognition of earthworms as preferred food was inherited from the Passenger Pigeon parent.

Holding Items with the Foot
A number of avian taxa have independently derived the ability to manipulate food items or nest material with the feet (Clark 1973). Even within the same family or subfamily, species differ in the frequency with which this behavior is exhibited. The European Goldfinch frequently uses its foot, the canary sometimes and the Greenfinch (Carduelis chloris) rarely. Hinde (1956) noted that several Goldfinch x Greenfinch and Goldfinch x canary hybrids often used their feet, whereas Greenfinch x canary hybrids seldom did. Hybrids inherited their holding ability from their Goldfinch parents.

Among Estrildid Finches, Zebra Finches never use their feet to hold items on a perch, whereas African Silverbills (Euodice cantans) regularly do so. Four Silverbill x Zebra Finch hybrids regularly manipulated seeding heads of grass with their feet, indicating inheritance of a dominant trait (Baptista personal observation).

Biting Versus Pulling of Grass
Poulson (1950) observed that Greylag Geese (Anser anser) are equipped with “tooth-like knots” along the sides of their mandibles enabling them to “bite” grass while grazing. Ducks are not so equipped and thus “pull” grass while foraging thereon. A hybrid domestic duck x Greylag Goose bit grass like the goose parent. However, not being equipped with the bill “teeth” of the goose, the hybrid bit grass with the tip of the bill which was equipped with a large nail.

Drinking Behavior
Most finches in the family Estrildidae drink in the manner of chickens, i.e., water is scooped into the bill, and the head is subsequently raised so that the bill is pointing skyward and the water runs down the throat through gravity. Some Australian Finches in the genus Poephila, independently of the doves and pigeons (Columbiformes), drink by dipping the bill in the water and sucking without raising the head. Immelmann (1976 and personal communication) studied drinking behavior in hybrids between Mannikins (Lonchurae) which scoop, and Poephila species which suck. Hybrids sucked in pigeon fashion, but bills were not dipped as deeply into the water as in Poephila species.

Vocalizations

Chickens x Pheasants
McGrath et al (1972) artifically inseminated female Ring-neck Pheasants (Phasianus colchicus) with semen from White-Leghorn Chickens. One year old hybrids were of two size classes: males weighted 1,775 gm and females weighed 875 gm. Adults of both parental types and their hybrids were hand-held with the wings and their distress calls recorded.
Duration and pitch of the principal component (= darkest and most distinct harmonic) of these calls were measured (Figure 1). Duration of hybrid calls was similar to that of the pheasant. Pitch of the hybrids was intermediate between the parental forms. However, the smaller hybrids had higher pitched calls than the larger hybrids. There was little change in frequency in the chicken calls, whereas there was an initial rise and then a fall in pitch in the pheasant calls and those of the hybrids. Harmonic structure of some of the hybrids of both size classes resembled either the pheasant or the chicken.

It was suggested that the inheritance of duration was controlled by one or few genes, whereas principal component (pitch) was polygenic.

Palearctic Quail
Moreau and Wayre (1968) studied the “crows” of European and Japanese “races” (species?) of Coturnix coturnix. The call of the European bird was clear, brief and consisted of sharp notes, whereas Japanese Quail calls were harsh and blurred on the spectrograms and were less far-carrying. Moreover, the rhythm of the European’s call was “dactylic”.
Calls of European x Japanese hybrids approximated the European’s in rhythm but showed a coarsening in the second and third notes that characterized Japanese calls. Calls of Japanese x European hybrids showed nothing approaching the European rhythm and only a limited coarseness. Although more or less intermediate, hybrid calls tended to be more similar to the male parent.

Greater x Lesser Prairie Chickens
Courtship displays of Prairie Chickens (Tympanuchus spp.) consist of drooping of wings, tail-fanning, erection of pinnae, inflation of vocal sacs and the “booming” vocalizations (Crawford 1978). The Greater (T. cupido) tail-shakes prior to vocalizing and tail-fans at the end of the third syllable in its booming vocalizations. In the Lesser (T. pallidicinctus) tail-fanning occurs during the first syllable of the vocalization. A hybrid tail-fanned during the first (as in Lesser) and third (as in Greater) syllables of the vocalizations. The hybrid did not tail-shake and was thus similar to the Lesser.

Duration of the displays in the Greater and Lesser Prairie Chickens was 2.8 versus 0.6 seconds respectively. The hybrid’s display directed at a female (= Epigamic display) lasted 1.22 ± 0.24 seconds. When performed solitarily (= Antaposematic display), the display lasted 1.11 ± 0.29 seconds. Thus directed and undirected displays were intermediate in duration between the two parental types.

Doves
Lade and Thorpe (1964) studied the coos of five species of doves and their hybrids. Species crossed included the Barbary or Ring Dove (Streptopelia risoria), Turtle Dove (S. turtur), Collared Dove (S. decaocto), Necklace Dove (S. chinensisT and Senegal Dove (S. senegalensis).

Cross-fostering experiments failed to change the coos in any way, indicating that dove calls are genetically coded. In the Ring Dove, vocal signals developed normally even in individuals deafened soon after hatching (Konishi and Nottebohm 1969).

Lade and Thorpe (1964) concluded that specific rhythms of the
songs (coos) of doves were coded in the central nervous system. The effect of hybridization on the rhythm varied. In some crosses (e.g. Senegal x Barbary) a complete breakdown of the coding ensued so that only simple monosyllabic coos were produced by the F11 hybrids. Other hybrids (e.g. Barbary x Collared) produced coos which were rhythmically intermediate or resembled one parent. In back-crossed F2 hybrids, disorganization of the rhythm seemed to have disappeared, and the dominant species rhythm appeared in almost normal form.

Whitman (1919) studied the intervals between perch-coos of Zenaidura macroura, Streptopelia risoria and their hybrids. He noted that fifteen seconds usually elapsed between each perch-coo of Zenaidura. A Zenaidura x Streptopelia hybrid called 17 times in 20 seconds, or even once per second, a rhythm similar to the Streptopelia parent.

Carduelid Finches
Syllablic structures in the songs of canaries and Greenfinches are learned. However, Guttinger (1979) has found that rhythmic structure (temporal organization) in Greenfinch song is innate.

Syllables of both Carduelid species are grouped together into units he calls tours. In canaries, groups of tours may be separated into phrases by intervals exceeding 1 – 2 seconds of silence. Thus a histogram of intervals between tours in canary song is bimodal with a break at 1 second. Songs of Greenfinches are not broken up into phrases, and silent intervals between tours are modal in distribution. A Greenfinch raised by canaries learned canary syllables but sang them in a Greenfinch tempo, i.e. with the absence of phrases. A hybrid Greenfinch x Goldfinch likewise learned canary syllables, but temporal organization was Greenfinch-like, i.e. silent units were modal (Guttinger et al, 1978). However, whereas intervals between tours shorter than 0.5 seconds are rare in Greenfinch song, they are frequent in songs of canaries and the hybrid Greenfinch x Goldfinch.

Estrildid Finches
Cross-fostering experiments have shown that social calls of Grass Finches (Poephilae) and Mannikins (Lonchurae) develop normally independently of learning (Guttinger and Nicolai 1973, Zann 1975). Nestlings of the African Mannikins of the Spermestes/Odontospiza group are distinguished from the Asiatic Lonchura on the basis of begging calls. In the former, begging calls are bisyllabic, whereas in the latter they are monosyllabic. Guttinger’s (1970) spectrograms of begging calls of a Spermestes bicolor x Lonchura striata hybrid indicate that they are bisyllabic as in Spermestes.

Harrison (1962) described the contact call of the Bengalese Finch (L. striata) as a dry “tritt”, and that of the African Silver-bill (Euodice cantans) as a thin-shrill “psit”. The call of a hybrid E. cantans x L. striata was described as a nasal, low-pitched “kent”, thus resembling neither parent. Baptista (personal observation) has obtained spectrographic evidence to support Harrison’s description. Besides being lower pitched, contact calls of the hybrid are harmonically rich whereas those of the parental forms are relatively pure-toned, accounting for the audible differences in tonal quality.

Hummingbirds
A number of authors have suggested that the loud sounds produced at the culmination of the nuptial (aerial) dive displays of Calypte hummingbirds are produced by the specialized outermost rectrices. However, recent spectrographic evidence indicates that these sounds are mostly, if not entirely, vocal (Wells et al, 1978, Baptista and Matsin 1980). The dive sound of the Anna (C. Anna) hummer are harmonically rich, those of the Costa (C. Costae) and their hybrid are pure toned. Dive sounds of the Costa are longer in duration and higher pitched than those of Anna. Dive sounds of their hybrid are intermediate in pitch and duration between the two species.

Crowing in Phasianids
Stadie (1967) analyzed the crows of Ring-neck Pheasant x domestic cock hybrids. The crow of Gallus consisted of four indistinct syllables, with the fourth somewhat lengthened and sometimes emphasized. The crow of Phasianus consisted of two distinct “hoarse-sounding” syllables. Stadie found that not all hybrids crowed, and those that crowed rarely did so. As in Phasianus, crows of hybrids were confined to the spring. Crows of hybrids consisted of four syllables as in Gallus, but as in Phasianus syllables were clear-cut and no syllable was emphasized.

Crows of Gallus sonneratii consisted of ±5 syllables (rarely four). There was a pause between the second and third syllable, and the second and fourth syllables were emphasized. Crows of hybrids between G. sonneratii x G. gallus consisted of 3 to 6 syllables. In most cases syllables were monotoned and a little hoarse-sounding and thus unlike either parent. All hybrids sometimes had a long introductory call preceding crowing found in sonneratii but not in gallus.

Courtship

Ducks

Ethologically, ducks (Anatidae) have been the best studied of any avian group (review in Johnsgard 1965). The early studies on the behavior of duck hybrids by Lorenz (1941, 1971), Ramsay (1961) and von de Wall (1963) have been followed by two important studies: namely, those of Sharpe and Johnsgard (1966) and Kaltenhauser (1971).

Kaltenhauser (1971) studied the behavior of fifteen Anas species and their hybrids. These species possess a number of display postures in common (see, e.g. Figure 2) with some species specific variations. Some postures are absent or rare in some species (see discussion in Lorenz 1967:92 on rare behavior in ducks). Some are obligately coupled motor sequences. For example, the male Mandarin Duck (Aix galericulata) has a ritual drinking display which is always followed by sham-preening. During sham-preening he touches the raised wing “flag” on the side immediately facing the female (Lorenz 1971). Kaltenhauser (1971) chose four postures which exhibited “typical intensity” for analysis: grunt-whistle, headup-tailup, downup, and bridling. (Figure 2).

Kaltenhauser found that when two species had a display posture in common, the hybrid would exhibit the posture in an intermediate form. Sometimes a behavior was rare in one species or was present only during behavioral ontogeny, or during contexts other than courtship. Hybrids involving one such parent would exhibit the posture in an intermediate form, but during courtship as in one parent. For example, bridling is performed during courtship and as a postcopulatory display in A. flavirostris. In A. platyrhynchos, bridling is performed only by juneviles during behavioral ontogeny, or as a postcopulatory display in adults. Hybrids between these two species performed an intermediate form of bridling both as courtship and as a postcopulatory display.

Sometimes behaviors that were rare or absent in the parental forms were present in the hybrids. For example, A. acuta x A. spinicauda hybrids performed downup and bridling displays both of which were apparently absent in the parents. A. platyrhyncho x A. strepera backcrossed to A. platyrhynchos performed bridling displays absent in the parental forms as well as Fl hybrids.

The inheritance of coupled sequences was also studied. She found that coupled sequences found in both parents appeared also in Fl hybrids, albeit sometimes rarely (e.g. the grunt-whistle coupled with the headup-tailup in A. acuta x A. castanea, Table 1). If a coupled sequence was absent in one parent, it was also absent in the hybrids (e.g. A. penelope x A. strepera and A. castanea x A. spinicauda). The time intervals between coupled sequences were often longer in hybrids than in their parents. For example, the interval between grunt-whistle – headup-tailup sequences in A. crecca and A. flavirostris ranged from 0.8 – 1.8 sec. (x = 1.3 seconds); in their hybrids, intervals ranged from 1.6 to 2.0 seconds (x-bar = 1.8 seconds). In two cases hybrids showed coupled sequences not found in either parent. Indeed, in A. sibilatrix x A. strepera, two new coupled sequences appeared (Table 1).

Sharpe and Johnsgard (1966) (see also Johnsgard 1967) studied the behavior of hybrids between A. platyrhynchos and A. acuta and correlated these with plumage inheritance. Both mallard and pintail perform grunt-whistle and headup-tailup. However, only the mallard performs the downup, whereas only the pintail performs the burp (Figure 2). Nod-swim is commonly performed by the mallard but is rudimentary in the pintail. In Fl hybrids the downup is lacking and burp and nod-swim appear in reduced form. F2’s exhibited plumage and behavioral variation ranging from almost pure pintail to almost pure mallard-like. In the most mallard-like F2’s, downup and nod-swim are well developed. The most pintail-like F2’s performed well-developed burp displays. Hybrid scores were constructed for plumage and behavior, and a positive correlation was found between inheritance of plumage and behavioral characteristics. The considerable segregation and independent assortment observed suggested to the authors that both plumage and behavior were under fairly simple genetic control, probably involving relatively few genes.

No abnormal coupled sequences were found in F2’s. However, an F3 linked a bridling (postcopulatory) display with a headup-tailup social display.
Lind and Poulson (1963) described the courtship displays of a Goosander x Shelduck hybrid. They found that during the ritualized drinking display, Goosanders normally held their head up 90 degrees with the horizontal, Shelducks held their heads at 45 degree, and the hybrid held its at an angle intermediate between the two parents.

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Doves
Davies (1970) studied bowing displays in Streptopelia doves and their hybrids. These were the same five species studied by Lade and Thorpe (1964) who described their vocalizations. Bowing displays were performed only by males, were directed at either sex, were species specific, and involved an alternate upright and crouched posture which exhibited “typical intensity”. Bowing displays of hybrids also exhibited typical intensity. Some of the components

of the bows were intermediate between the parents, some resembled one parent closely, and others exceeded either parent. For example, the display of Collared x Barbary Dove hybrids (Figure 3) resembled the Barbary parent at the top of the bow in that the head was not held up as high as the Collared parent. However, the hybrid bowed lower than either parent. The exaggerated movements were lost in the F2 generation.
Similar results were obtained when Davies examined frequency of bouts of bowing, e.g. Turtle x Barbary hybrids bowed at a frequency intermediate between the parents, but frequency of bowing in Necklace x Barbary hybrids approximated the Barbary parent.

Hummingbirds
North American Hummingbirds of the genus Calypte exhibit two displays during territoriality or courtship: (1) a static display during which individuals sing from a perch and (2) a dynamic display which involves singing and species specific movements through the air. Selasphorus Hummingbirds only perform dynamic displays. On the Palos Verdes Peninsula of Southern California, three species of hummingbirds, the Anna (Calypte anna), the Costa (C. costae) and the Allen (Selasphorus sasin) breed sympatrically and overlap extensively in breeding season. Occasional hybrids have been found and their displays analyzed (Wells, Bradley and Baptista 1978, Wells and Baptista 1979).

In the dynamic display of the Anna Hummingbird, the male sings while hovering some 25 to 50 meters above the female. He then ascends, continually looking down (bill pointed down). He pauses at the top of the climb and may sing once more, and then dives, swooping out of his dive just over the female and produces a loud chirp sound. In contrast, male Costa Hummingbirds climb up into the air over the female with bill pointed up, never sing, never pause at the top, then dive and produce a loud whistling sound. One male Costa Hummer was observed tracing a large horizontal circle at the top of his climb just prior to diving. Hybrid Anna x Costa hybrids perform the aerial display with the bill pointed down like the Anna parent, climb up into the air in silence like the Costa, then trace a large horizontal circle in the air before diving and making a sharp but short peek sound. These hybrids also possess a static display wherein they sing songs identical to the Anna parent. It is conceivable, however, that songs are learned in hummingbirds (see discussion in Mirsky, 1976).

Allen Hummingbirds begin their aerial display by flying back and forth tracing a pendulum path over the female. At each end of the pendulum, a high-pitched cricket-like chirping is produced at between 7.5 and 12 kHz. After a number of these horizontal arcs, the hummer climbs in silence 75 to 100 feet into the air, describing spirals or undulations all the way to the top. He never pauses at the top but dives immediately. As he breaks his dive over the female, he produces a loud sound which begins with a number of short pip sounds followed by a long whistle. A hybrid Anna x Allen climbed into the air with bill pointed down like the Anna parent, but traced an undulatory path to the top like the Allen. He sometimes paused at the top like the Anna but was silent like the Allen. The hybrid then dived and produced a loud peek sound at the bottom of the dive. The dive sound was spectrographically like the Allen in harmonic structure, but short in duration like the Anna parent. The pendulum display of the Allen Hummingbird was absent in the hybrid. The hybrid also had a static display like its Anna parent, but its song was unlike any hummingbird known.

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Figure 3.
Bowing displays of doves:
a. Collared Dove
b. Barbary Dove
c. Hybrid Collared x Barbary Dove
After Davis, 1970.

Estrildid Finches
Eisner (1958) described the displays of Bengalese Finch (Lonchura striata) x African Silverbill (Euodice cantans) hybrids, and Harrison (1962) described displays of the reciprocal cross. I made observations additional to those of Harrison (1962) on Silverbill x Bengalese crosses, and extended their observation to three other crosses involving Estrildid Finches (Table 2).

Males of both Silverbill species (E. cantans and E. malabarica) perform a precopulatory display holding a grass stem by one end, all of the body feathers sleeked, tail shut and pointed down, and inverted curtsies (a bobbing movement in which the main component is an upward thrust imparted by a straightening of the legs). Sometimes birds perform ritualized nest-building movements while holding the straw as if molding an invisible nest roof (= U-shaped movements). Hybrids from three crosses involving Silverbills as one parent, performed all the components of the straw display (Table 2), but with some of the feather postures of the other parent. For example, when performed at high intensity, Silverbill X Bengalese crosses spread their tail and fluff their belly feathers like the Bengalese parent, but tails are always pointed down like the Silverbill parent. Silverbill x Zebra Finch (Poephila guttata) crosses always ruffle their nape and belly feathers like the Zebra parent. Some Spice Finches (L. punctulata) sometimes perform inverted curtsies during their precopulatory display as do Spice Finch x Bengalese hybrids. Spice and Bengalese Finches bow before singing at strangers or prior to precopulatory displays. When isolated and then presented with a female, two hybrid combinations involving Spice and Bengalese Finches also bow prior to singing.

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Figure 4.
Peering behavior in Lonchura punctulata. The bird at right is peering at the singing male at left. After Morris, 1958.

Some Estrildid Finches also perform a display known as peering when one bird sings and other members of the social flock sleek their feathers and appear to be listening intently at close range (Figure 4). This display may serve to strengthen flock bonds (Immelmann 1965). All crosses involving peering (E. malabarica,
E. cantans, L. punctulata) and non-peering (P. guttata, L. striata) species performed the peering display (Table 2).

Viduine Finches
Payne (1980) studied displays of Village Indigobird (Vidua chalybeata) x Paradise Whydah (V. paradisaea) hybrids in Lonchinvar Park, Zambia. Viduine Finches usually oviposit in nests of specific host Estrildid Finches. The parasite then learns the songs of its host, and later learns the song of its own species. Since the hybrids sang songs of Paradise Whydahs and Melba Finches (their host), Payne suggested that the crosses he studied must have involved the Paradise Whydah as the female.
Paradise Whydahs perform an elaborate aerial display which was absent in Indigo birds and their hybrids. One observation was made of a hybrid performing a courtship display termed a “fast sideways head bent”, given by Paradise Whydahs. Indig obirds seem to sing and display throughout the day, whereas Whydahs and the hybrids sang only during mid-morning and mid-afternoon. Hybrids were also similar to Indigo-birds in that most songs were delivered from one tree rather than from several singing trees as in Whydahs.

Absence of Courtship Displays
A number of authors have reported the absence of displays in some intergeneric hybrids between distantly related species. Asmundson and Lorenz (1955) produced Ring-neck Pheasant x turkey hybrids by artificial insemination. They reported the absence of eggs or semen in the hybrids and never observed courtship. Huxley (1941) kept an impeyan x Lady Amherst Pheasant hybrid with a female Impeyan and reported no trace of sexual interest in the hybrid. Poulson (1950) studied a domestic duck x Greylag Goose hybrid. Despite injections of testosterone, no courtship displays were observed. Poulson interpreted this as an absence of response from the nervous system.

Nest Building in Agapornis Lovebird Hybrids
Nest building behavior in the African Peachface (Agapornis roseiocollis) and Fisher’s (A. [personata] fischeri) Lovebirds (Psittacidae) and their hybrids was studied by Dilger (1962a, 1962b) and his student Buckley (1969). A. fischeri cuts strips of paper about 7 inches long and 3/8 inches wide and carries these with the bill one at a time into the nest box. Sticks, strips of bark or leaves are also utilized in their nest. A. roseicollis cuts strips 3 to 4 inches long, then tucks several pieces under the feathers of the rump and lower back and thus carries them into the nest box (Figure 5).

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Figure 5.
Nest building by Agapornis roseicollis. The female is tucking a cut strip of paper under its rump feathers. After Dilger 1962a.

Hybrids between roseicollis and fischeri cut paper strips that were longer than those of either parent. Strip-cutting is normally practiced by females of both species: occasional males of roseicollis cut strips, and males of fischeri almost never thus perform. Fl hybrid males cut and carry with greater frequency than males of either parental form. Indeed, these males were continually interfering with strip-cutting attempts of the hybrid females; males of the parental forms rarely do.
Hybrids also exhibited various conflict behavior patterns and were rarely successful in completing a tucking sequence. They might perform the proper movements of tucking, but appeared unable to let go of the strips. They might perform frequent intention movements to tuck without completing the act. Sometimes they attempted to reach the rump with the bill by running backwards. Hybrids often grasped the strips other than by either end, thus making tucking difficult. ‘They were often distracted, so that tucking attempts often passed into drinking or displacement activities (e.g. head-scratching). Sometimes inappropriate items, e.g. twigs, were tucked. This behavior, Buckley (1969) pointed out, was understandable since fischeri often incorporated twigs in their nests. Hybrids would sometimes tuck in inappropriate places, e.g. the breast. Examination of movie footage indicated that hybrids lacked the proper act sequence for successful tucking. That is, items were not correctly placed in the rump. indeed, an important component called “tremble-shoving” was lacking in the hybrids.

Dilger (1962a) observed that hybrids would gradually abandon the abortive tucking attempts in favor of carrying in the bill. After three years, tucking became very infrequent and behavior was very much like A. fischeri. However, Buckley (1969) studied a mixed batch of hybrids ranging from six months to four years old and reported that they could not be reliably divided into age groups on the basis of relative tucking and bill-carrying frequencies. There appears, thus, to be individual variation in hybrids in their abilities to learn to bill-carry. All Buckley’s birds showed both rump-tucking and bill-carrying behavior, with bill-carrying as the last resort.

DISCUSSION
In this paper I have brought together some of the literature on the behavior of domesticated birds, showing how man has modified some of these behavior patterns including social behavior, displays and wildness. Some of these behavior patterns are inherited in crosses between strains in the same way as in Fl hybrids between species. Some of these behavior patterns are clearly mal-adaptive and are permitted to survive only because of protection by man. For example, the aberrant flight behavior of the Swing Pouter Pigeon causing him to lose altitude and the clapping behavior which causes premature fraying of the primaries would probably have been selected out long ago by predators had these mutations occurred in the wild (Nicolai 1976). Since courtship behavior patterns may function as species isolating mechanisms, extreme modifications of these behaviors may present an individual from acquiring a mate in the wild, and thus also be eliminated from natural populations.

In the second portion of this paper I have summarized studies on the behavior of artificial and natural avian hybrids involving five different orders: Galliformes, Anseriformes, Columbiformes, Apodiformes and Passeriformes. Since most Fl hybrids are sterile, .few of these studies were carried on to the F2 generation. The studies by Sharpe and Johnsgard (1966) on duck hybrids and Entrikin and Erway (1972) on rolling in domestic pigeon breeds are especially noteworthy, both because of the excellent analyses and sample sizes involved.

Frank (1974) and Payne (1980) have summarized the various trends in the behavior of hybrids which are as follows:
(1) Hybrids may acquire behavior patterns similar to one or both of the parental forms (e.g. foraging behavior patterns) suggesting genetic dominance.
(2) Hybrids may perform behavior patterns intermediate between the two parental forms (e.g. duration and pitch of distress calls of chicken x pheasant hybrids).
(3) Hybrids may perform exaggerated versions of the parental behavior patterns (e.g. amplitude of bow in the Collared x Barbary Dove hybrids).
(4) Behavior patterns rare in the parental forms may be common in the hybrid (e.g. horizontal circle flight of the Anna x Costa Hummingbird hybrid).
(5) Behavior of hybrids may be incomplete (intention movements), e.g. tucking attempts of Agapornis hybrids, or may be otherwise disorganized (e.g. cooing of S. senegalensis x S. risoria hybrids) due to alteration of the genome.
(6) Complex behavior sequences may be reorganized or new combinations of behavior components may arise (e.g. movements and feather-postures of Estrildids are recombined in the hybrids), suggesting segregation and recombination.
(7) Behavior patterns may appear in the hybrid not found in either parent, e.g. Agapornis hybrids tucking in the breast rather than the rump.
(8) Behavior patterns of both parents may fail to appear in the hybrid (e.g. absence of displays in some hybrids). Hinde (1956) has suggested that this is due to the general developmental breakdown of the hybrid.

A number of authors have interpreted some of the behavior of hybrids as a recapitulation of ancestral behavior patterns (Lind and Poulson 1963, Dilger 1962b, Buckley 1969). For example, Dilger and Buckley noted that some primitive Agapornis species as well as the related Blue-crowned Hanging Parrot (Loriculus galgulus) regularly tuck nest material in the breast. Breast-tucking in Agapornis hybrids, found in neither parental form, has been interpreted as an atavistic behavior which has emerged as a result of changes in the genome. Franck (1974) has taken exception to this idea suggesting that the altered genotype has perhaps disrupted the parental behavior pattern resulting in a behavior accidentally resembling the primitive forms.

Rare parental behavior occurring commonly in hybrids have been interpreted as a lowering of thresholds to perform these behavior patterns due to the altered genome (Kaltenhauser 1971). Indeed, Manning (1963) has suggested that many evolutionary changes in behavior are due to altered thresholds to perform these behaviors. Franck (1974) argues against this, pointing out that we have as yet no actual understanding of the action of genes on behavior or a physiological understanding of the changes that can be described as threshold changes.

SUMMARY
Studies on the behavior of domesticated birds were reviewed. During the process of domestication man has selected for certain behavioral, traits including tameness, changes in social behavior, qualities of voice and changes in courtship patterns. Since the ancestral wild forms still exist, comparison of these behaviors in wild and domesticated forms give us some ideas as to how natural selection operates to change dispositions to perform behavior patterns. Certain behavior patterns are inherited in crosses between domestic strains in much the same way as inheritance of behavior in Fl interspecific hybrids.

Studies on the behavior of natural and artificial (laboratory produced) interspecific hybrids were surveyed. Heritable characteristics included maintenance activity patterns, quality of voice, courtship patterns, and nest-building behavior. Since Fl hybrids are usually sterile, few studies continued on to F2 generations. Behavior patterns in hybrids may (1) resemble one parent, (2) be present in intermediate form, (3) resemble neither parent or (4) be absent altogether. Behavior rare in parental forms but common in hybrids have been interpreted as changed thresholds to perform these behavior patterns or recapitulation of ancestral behavioral traits due to altered genomes. Alternate interpretations of these data are discussed.

ACKNOWLEDGMENTS
I thank Kerry Muller and Robert B. Payne for their critical comments on the manuscript. Kerry Muller also called my attention to some literature on behavior of domestic pigeons. Roland Sossinka assisted me with the translation of some of the German literature.

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