Yngve Espmark

Sexual response of female yellowhammers to differences in regional song dialects and repertoire sizes

Female yellowhammers, Emberiza citrinella, a common Eurasian songbird, were tested in the laboratory for their sexual response to male songs from two different dialects and to three different repertoire sizes (one–three). In the first experiment, the females responded with significantly more copulation solicitation displays when played their home dialect from Norway than when played a dialect from Denmark. These two dialects also occur in adjacent populations. This result is consistent with the hypothesis that females mate assortatively with males of their own dialect in natural populations. Previous work on yellowhammers suggested an adaptive explanation for assortative mating. In the second experiment, the females responded with significantly more copulation solicitation displays when played a repertoire of two or three song types than when played a single song type. This result is consistent with the hypothesis that sexual selection has been involved in the evolution of enhanced repertoire size in songbirds.

Singing activity and song pattern of the Redwing Turdus iliacus during the breeding season

During spring in 1982 and 1983, 28 male Redwings Turdus iliacus were observed at Songli in Central Norway, from the time of arrival until most had completed reproduction. Function of song was studied by recording changes in singing rate and song structure throughout the breeding season. The singing rate of breeding males decreased significantly when egg-laying started, indicating that song might function in mate attraction and mate retention. Singing rate of individual males correlated positively with the number of simultaneously singing males, which suggests that the song may also function in competition between males. The seasonal variation of the introductory section of the song was negligible, whereas the terminating section became shorter after egg-laying or was omitted altogether.

Development and Habituation of Cardiac and Behavioral Responses in Young Red Deer Calves (Cervus elaphus) Exposed to Alarm Stimuli

Heart rate was recorded by radiotelemetry in six red deer calves ranging in age from 6 h to 7 days. A few hours after birth the mean heart rate of undisturbed resting calves was 170 beats/min (BPM). During the first week of life the rate declined to 155 BPM. The calves responded by bradycardia, startle responses, and heart blocks to three kinds of alarm stimuli; the intensity and rate of the responses varied with stimulus type and age of the calves. At about one week of age the calves displayed flight responses when disturbed by human approach. Calves with low birth weights retained the freezing response significantly longer than calves with higher birth weights. The onset of the flight response was more dependent on the calfs physical development than on its age. Habituation to repeated stimulations, shown by weakening of the bradycardia response, less frequent startle responses and heart blocks, and shorter recovery time, was recorded for all types of stimuli. The tendency for older calves to display weaker cardiac responses than neonatal calves was probably due to maturation rather than habituation. The results are discussed from an adaptive and evolutionary viewpoint.

VARIATIONS IN THE SONG OF THE PIED FLYCATCHER WITHIN AND BETWEEN BREEDING SEASONS

ABSTRACT The main objectives of this study were to provide a thorough description of the advertising song in the male pied flycatcher Ficedula hypoleuca and examine the complexity of the song and its variability within and between breeding seasons by qualitative and quantitative analyses of its structure. Songs were recorded from 117 males in central Norway in one or more of the three stages of the breeding season: before pairing, during nest building, and in the laying/brooding stage. Eight males were recorded both before and after pairing, and 13 males were recorded in two consecutive years. Spectrographic analyses were based on 25 consecutive song strophes per male. When the males became mated their song changed in a number of ways: in addition to reduced singing activity, the number of figures and figure types in the song strophe became fewer at the same time as the song strophe became shorter. There was also a tendency towards increasing song versatility and decreasing repertoire size. Individual mal...

Lying down as a means of reducing fly harassment in red deer (Cervus elaphus)

SummaryResting time in red deer (Cervus elaphus) was shown to be more than twice as long on days when harassment by head flies (Hydrotaea irritans) was considered severe compared with days when fly harassment was estimated as low. Avoidance reactions in the deer decreased as soon as the deer reclined and became stabilized at a level corresponding to approximately 50% of the initial response frequency. The present observations do not give any clear indications as to whether it is the head flies per se or climatic factors that are the primary cause of reduced locomotory behaviour in the deer. It is concluded, however, that due to a causal relationship between the appearance of flies and certain types of weather, and because lying down has a relieving effect, inactivity may be an important part of the strategy used by red deer to cope with head fly harassment.

Song conformity and continuity in song dialects of Redwings Turdus iliacus and some ecological correlates

This study is based on the assumption that song sharing in neighbouring Redwings is advantageous in terms of genetic fitness. By calculating dispersal and immigration rates we also wanted to gain information about the timing of song learning and the causal background for the maintenance of local song dialects in this species. We recorded and analysed the song patterns of 304 Redwing males during three or four consecutive years in six populations in central Norway and Sweden. Data on breeding success, dispersal and immigration were collected for three of the populations. Although some males had two song types, most had only one. The frequency of two-type singers in the different areas did not correlate with the density of singing or breeding birds, nor with the extent of song sharing between birds, which differed considerably between areas. Song sharing did not correlate with the density of singing or breeding birds, but was positively correlated with breeding success. To explain this relationship we suggest that differences in age structure, onset of breeding in spring and nest predation are important. Sparsely populated areas and areas with high breeding success had a more stable song pattern from one year to the next than areas with higher density and lower breeding success, respectively. Colour-banding indicated that on average 17% of adults returned to the area in which they nested previously, whereas less than 1% of nestlings returned to the natal area. Thus, we suggest that the local nestling population contributed very little to the same breeding population in the following year, and that the longterm maintenance of a local dialect may be explained by the young males copying the song of the older males of the area in which they settle to breed in their first spring.

Sibling recognition in the rook (Corvus frugilegus)

In this study we tested whether rook siblings were able to recognize each other vocally when 2-2 1 2 months-old and, if so, whether this recognition still persisted about 10 months later. Twelve rook nestlings were hand-reared. Vocal recognition by the young birds (aged 2-2 1 2 months) was tested. The birds responded significantly more frequently to the call of a sibling than to the call of a non-sibling. This indicates that audible cues are at least important for sibling recognition. The individual rooks were thereafter visually isolated, in 12 individual cages, for a further 10 months. The birds were then put together in an aviary and their social relationships studied. Siblings were significantly less aggressive towards each other than towards non-siblings and siblings remained close together significantly more often than non-siblings. The significance of sibling recognition is discussed.

Behavioural lateralisation in reindeer

Reindeer (Rangifer tarandus) kept in corrals or otherwise forced to clump typically start milling in response to stressing events. This behaviour is generally considered to have an antipredator effect. An inquiry on herd behaviour, to which 35 Norwegian reindeer husbandry districts responded, showed that 32 experienced that corralled rein¬deer consistently circled leftwards, whereas the remaining three reported consistently rightward circling. Regular monitoring of a reindeer herd in central Norway over a two-year period (1993-94), and experimental studies on a fraction of the same herd, revealed the following traits. Free-ranging reindeer showed no right- or left-turning preference during grazing or browsing, but when the reindeer were driven into corrals or forced to clump in the open they invariably rotated leftwards. The circling of corralled reindeer was triggered at an average group size of 20 to 25 animals, apparently independently of the age and sex of the animals. When they dug craters in the snow to reach food, the reindeer used their left foreleg significantly more often than their right. In 23 out of 35 reindeer, the right hemisphere of the brain was heavier than the left. However, in the sample as a whole, the weights of the left and right hemispheres did not differ significantly. Lateralised behaviour in reindeer is thought to be determined by natural and stress induced asymmetries in brain structure and hormonal activity. In addition, learning is probably important for passing on the behaviour between herd members and generations. Differences in lateralised behaviour between nearby herds are thought to be related primarily to different exposure to stress and learning, whereas genetical and environmental fac¬tors (e.g. diet), age structure and sex ratio are probably more important for explaining differences between distant pop¬ulations.

SONG QUALITY DOES NOT INDICATE MALE PARENTAL ABILITIES IN THE PIED FLYCATCHER FICEDULA HYPOLEUCA

Summary Femalepied e ycatchers Ficedula hypoleuca prefer to mate with males having complex songs, but the benee ts of this preference are not known. One potential benee t might be that males with complex songs are of higher quality and thus contribute more to the feeding of the brood than males with simple songs. We tested this by recording the feeding rate of males in two different populations in Norway. Neither the feeding rate nor the male ¢s contribution to the feeding relative to his mate correlated signie cantly with song complexity (27 and 21 males studied, respectively). However, male feeding rate may beine uenced by femalefeeding effort. Therefore, we also recorded body mass change of 13-day-old nestlings of 30 males during a period of eight hours of enforced female absence. The males were matched in pairs according to brood size and, if necessary, nestlings were exchanged between broods to reduce initial differences in body mass. Both males in each pair were treated on the same day. The change in brood mass did not differ signie cantly between males with complex and simple songs, and the latter males did not lose more body mass than the former males during female absence. Thus, we conclude that female pied e ycatchers mated with males having large song repertoires do not seem to benee t in terms of increased feeding effort from their mates. 2) Helge Rinden is unfortunately not with us any longer. He had a tragic accident in the nature

INDIVIDUAL AND LOCAL VARIATIONS IN THE SONG OF THE SNOW BUNTING (PLECTROPHENAX NIVALIS) ON SPITSBERGEN

ABSTRACT Variations in song pattern within and between individuals as well as between areas were investigated by analysing the song of 11 and 13 snow bunting Plectrophenax nivalis males at Longyearbyen and Ny Aalesund, respectively, on Spitsbergen (Svalbard). Individually, each of the males, except one, had only one song type, and the number of figure types ranged between 3 and 11. The relative variability (CV) was below 16% for all the variables analysed in the song strophe (number of figures and figure types, figure diversity, duration, maximum, minimum and range of frequency). The males differed significantly in all the variables analysed, and when the two study areas were compared with regard to these variables, no differences were found except for longer song strophes and a tendency towards less song versatility in Ny Aalesund. Furthermore, more than 90% of the 125 identified figure types were specific to the areas, although the majority of them (70%) were specific to particular males. Most of the ma...