Calls of Nestling Chaffinches Fringilla coelebs: The Use of Two Sound Sources

To investigate the early development of vocalizations in chaffinches Fringilla coelebs a series of daily observations was made on a single nest from a few days prior to hatching until the last chick fledged. Sonograms were made of over 300 calls recorded from nestlings between the ages of 2 and 13 days. The development of the structurally complex vocalizations of older nestlings from the simpler calls of younger chicks is described and the ontogeny of the independent use of two sound sources is discussed.     

Mechanisms of song differentiation in introduced populations of Chaffinches Fringilla coelebs in New Zealand

Chaffinches Fringilla coelebs were introduced to New Zealand from Great Britain over 100 years ago, and since then their songs have diverged from British ones in both syllable structure and basic organization of syllable sequences. The New Zealand populations seem to be unique in that their songs have undergone differentiation of trill segments by progressive elaboration of syllable morphology and hp ascending and descending changes of pitch. Published sonagrams of British song types have significantly more trill phrases and significantly fewer syllables in the end phrase than do Yew Zealand ones. Many New Zealand song types have much elaborated end phrases and concomitantly simpler trill segments, with songs quite commonly having only one trill phrase. This reversal of complexity between the trill and end phrase in New Zealand seems to have been derived by progressive reduction of the ultimate trill phrase to one syllable, and by recombination of end phrase syllables from different song types into one compound end phrase. The significance of the increased complexity in the end phrases of many song types may relate to the sound transmission properties of dense pine forests in New Zealand, in which Chaffinches are ubiquitous. Elaborate end phrases degrade much less from reverberation in pine forests because individual syllables have more dispersed temporal patterning.
Recombination of syllables to form new song types is a major mechanism of song differentiation in New Zealand. Although whole song copying is the predominant mode of replication, very few song types in a locality sample are composed of a unique set of syllables. Rather, song types in an area are interconnected by different combinations of shared syllables, suggesting that the incorporation of some local syllables in a bird's repertoire is sufficient to signal its status as a member of a neighbourhood and also allows the evolution of broadcast complexity.     

The Influence of Fat Stores on Magnetic Orientation in Day-migrating Chaffinch,Fringilla coelebs

Earlier experimental studies have demonstrated the ability of day-migrating birds to perform migration under overcast skies, thereby indicating use of cues other than solar. The orientation behaviour of the chaffinch, a diurnal migrant, was investigated in orientation cage experiments during the autumn migration period. The aim of our experiments was to examine the relationship between different orientation cues and the influence of body condition on directional choices. We obtained the following results: 1. Chaffinches displayed a bimodal distribution of headings along a SW-NE axis when tested in the local geomagnetic field (controls); 2. When the geomagnetic field was experimentally deflected 90° counterclockwise, the chaffinches responded by changing their preferred axial orientation to SE-NW; and 3. The predictive power of stored fat reserves became evident when both the control and experimental samples were subdivided into fat and lean individuals. The majority of fat controls orientated towards a seasonally appropriate SW direction, whereas lean controls chose mean directions towards the NE. Experimentals followed the same pattern, but with the expected deflection, i.e. fat birds selected SE headings and lean individuals chose a NW mean direction.     

Variation in Song Rate during the Breeding Cycle of the Chaffinch,Fringilla coelebs

The variation in song rate during the breeding season was studied in two individually marked chaffinch Fringilla coelebs populations. We gathered data to investigate especially the recently presented mate-guarding hypothesis. The active singing has been supposed to function as a form of mate guarding during the female's fertile period by announcing the high status of the male and preventing extra-pair copulations by neighbouring males. There was no clear dawn chorus in the chaffinch, i.e. a peak in the song rate before sunrise. Male chaffinches continued to sing after mating, but the song rate dropped significantly. In contrast to the mate-guarding hypothesis the song rate was lower during the fertile period of the female than during pre-mating and incubation. Thus, the males do not announce the fertility status of their mates or their own quality and status by active singing. The song does not function as a form of mate guarding in the chaffinch. One function of the song of the chaffinch is mate attraction: singing activity was highest before pair formation in early spring and decreased after mating but increased again if the male lost his mate later in the breeding season.     

Evolution of the chaffinch, Fringilla coelebs, on the Atlantic Islands

Chaflinches have differentiated within the last million years on the Canary Islands and the Azores. All island populations differ more from mainland relatives than from each other. The characteristics of island birds are large body size, short wings, long legs and beaks, and blue dorsal colour. Beak depth and width have increased on the Azores but not on the Canaries. As a consequence the Azores chaffinch has evolved more in the direction of the Canary Island F. teydea than have Canary Island chaflinches. Character displacement may have occurred on the Canaries. Most of the evolutionary shifts are not predicted from a knowledge of clinal variation on the mainland. Populations have differentiated more on the Canaries than on die Azores, but are less variable regardless of whether ecologically restricted (by teydea) or not. Similarly, within the Azores archipelago the most differentiated populations are die least variable. On the Azores, but not on the Canaries, differentiation increases with isolation, whereas wimin-population variation decreases with isolation and increases with elevation. A model for diese patterns is proposed in terms of gene flow between populations, which reduces differentiation but enhances variation, and directional selection and random genetic processes which have the opposite effects.     

Noise, predation risk compensation and vigilance in the chaffinch Fringilla coelebs

Background noise should in theory hinder detection of auditory cues associated with approaching danger. We tested whether foraging chaffinches Fringilla coelebs responded to background noise by increasing vigilance, and examined whether this was explained by predation risk compensation or by a novel stimulus hypothesis. The former predicts that only inter-scan interval should be modified in the presence of background noise, not vigilance levels generally. This is because noise hampers auditory cue detection and increases perceived predation risk primarily when in the head-down position, and also because previous tests have shown that only interscan interval is correlated with predator detection ability in this system. Chaffinches only modified interscan interval supporting this hypothesis. At the same time they made significantly fewer pecks when feeding during the background noise treatment and so the increased vigilance led to a reduction in intake rate, suggesting that compensating for the increased predation risk could indirectly lead to a fitness cost. Finally, the novel stimulus hypothesis predicts that chaffinches should habituate to the noise, which did not occur within a trial or over 5 subsequent trials. We conclude that auditory cues may be an important component of the trade-off between vigilance and feeding, and discuss possible implications for anti-predation theory and ecological processes.     

Interspecific reciprocity explains mobbing behaviour of the breeding chaffinches,Fringilla coelebs

When prey animals discover a predator close by, they mob it while uttering characteristic sounds that attract other prey individuals to the vicinity. Mobbing causes a predator to vacate its immediate foraging area, which gives an opportunity for prey individuals to continue their interrupted daily activity. Besides the increased benefits, mobbing behaviour also has its costs owing to injuries or death. The initiator of mobbing may be at increased risk of predation by attracting the predator's attention, especially if not joined by other neighbouring prey individuals. Communities of breeding birds have always been considered as temporal aggregations. Since an altruist could not prevent cheaters from exploiting its altruism in an anonymous community, this excluded any possibility of explaining mobbing behaviour in terms of reciprocal altruism. However, sedentary birds may have become acquainted since the previous non-breeding season. Migrant birds, forming anonymous communities at the beginning of the breeding season, may also develop closer social ties during the course of the breeding season. We tested whether a male chaffinch, a migrant bird, would initiate active harassment of a predator both at the beginning of the breeding season and a week later when it has become a member of a non-anonymous multi-species aggregation of sedentary birds. We expected that male chaffinches would be less likely to initiate a mob at the beginning of the breeding season when part of an anonymous multi-species aggregation of migratory birds. However, their mobbing activity should increase as the breeding season advances. Our results support these predictions. Cooperation among individuals belonging to different species in driving the predator away may be explained as interspecific reciprocity based on interspecific recognition and temporal stability of the breeding communities.     

Testing the flexibility of song type bout duration in the chaffinch, Fringilla coelebs

Many songbird species with small song type repertoires repeat each type a few times before switching to the next. Thus, their singing style may constrain their ability to switch. However, the proximate causation of song type switching is poorly understood. We exposed male chaffinches to (nonoverlapping) playbacks of single renditions of their own songs rather than a series of songs, thus stimulating them with a single external auditory event. The most prominent effect of the playback was an increase in the duration of the current song type bout. If the song type played back was different to that the subject was singing at the time, bout duration increased less than if it was of the same song type. The short-term changes induced by the playback suggest that the auditory input increases the motivational level for a particular song type. In the chaffinch this results in a delayed switch rather than in song type matching as a reaction to acoustic stimulation by conspecific song. Copyright 2000 The Association for the Study of Animal Behaviour.     

Genetic diversity and morphological variation of the common chaffinch Fringilla coelebs in the Azores

We present new insights into the genetic diversity and phylogeography of the common chaffinch Fringilla coelebs from the Azores, based on sequences of mitochondrial and nuclear genes from 44 individuals and an outgroup/comparison of 44 birds from Madeira, the Canary Islands and the Continental Western Palearctic. To understand the level of concordance between the genetic data and morphometric variability we analysed eight morphometric characters from 413 adult living birds from all the Azores islands and compared the population genetic distances with quantitative morphometric traits. Our results indicate the occurrence of gene flow among the common chaffinch populations in the archipelago revealing the lack of current genetic structure within it and the existence of two co‐occurring lineages. Results also indicate the existence of morphometric differences among islands that could be due to ecological features instead of island isolation. This study also confirms the genetic distance among the common chaffinch populations within Macaronesia and between these archipelagos and the Continental Western Palearctic.     

Anti‐Predator Signals in the Chaffinch Fringilla coelebs in Response to Habitat Structure and Different Predator Types

Many animals respond to the presence of predators with conspicuous signals such as alarm calling. These signals may aid the detection of the predator by conspecifics or may deter the predator from attack. The advantages of such signals may be dependent upon predator type and habitat type. We measured signalling behaviours (alarm calling and tail flicking) in foraging chaffinches in response to different predator models (hawk and pigeon control, cat and plastic box as control). In addition we measured responses to a cat model when chaffinches were foraging in different habitat structures (obstructed vs. open). There was no difference in the number of individual chaffinches alarm calling in obstructed vs. open habitat, but birds tail flicked more in open habitat, suggesting that tail flicking acts as a visual signal to the predator or conspecifics and therefore unlike auditory cues is influenced by habitat structure. Chaffinches were also more likely to tail flick in response to the cat model than the other three models. Our results are consistent with the idea that animals may respond to ground predators, which spend a large amount of time observing prey before attack, by using signalling behaviours, such as tail flicking and alarm calling. Further work on prey selection by predators is needed to separate the functions of signalling behaviour in response to predators.     

Interaction between seed crypsis and habitat structure influence patch choice in a granivorous bird, the chaffinch Fringilla coelebs

Food abundance is an important determinant in habitat and patch selection but food accessibility and detectability is less often considered. Foraging on more cryptic seeds may increase predation risk by increasing the length of head down periods. Habitat structure may interact with this as birds are less able to detect predators with their head lowered in riskier obstructed habitats. We investigated patch choice in chaffinches Fringilla coelebs foraging in obstructed and open habitats and artificially manipulated the search times of seeds by colouring them either yellow or black. One trial consisted of a choice between the conspicuous seed in the open patch, and the cryptic seed in the obstructed patch; in the second trial the treatments were reversed. Individuals were more willing to forage in the obstructed habitat when the yellow seeds were present (43% of pecks made in the obstructed patch) than when the black seeds were present (18% of pecks in the obstructed patch). Differences in search time are likely to explain this result: yellow seeds were located almost twice as fast (1.26±0.60 seconds) as black ones (2.36±0.88 seconds). This experiment shows that individual foraging decisions may be influenced not only by food abundance but by the properties of individual food items (in this case seed crypsis) and the structure of the habitat they are present in.     

The Mode of Orientation during Flight and Approach to Landing in two Phyllostomid Bats

The use of vision during flight and approach to a landing site in two phyllostomid bat species, Phyllostomus discolor and Desmodus rotundus was investigated. Three individuals of each species were trained to traverse a 3-m flight tunnel and to land at a small illuminated grid that was randomly changed between two positions on a front wall. Analysis of the flight path by observation and different technical methods revealed that the bats oriented themselves toward the grid quite early. When the illumination was switched off the flight path diverged much later. With a dark landing grid on one side and an optical projection of it on the other the bats aimed towards this dummy, interrupted the approach 20–40 cm in front of the illusion and then tried to reach the other side or turned back. Whether microchiroptera may rely in the medium range more on vision than usually is thought is discussed.     

Seasonal dynamics of population of the feather mite Monojoubertia microphylla (Astigmata: Analgoidea: Proctophyllodidae) in the chaffinch Fringilla coelebs

The seasonal dynamics of the Monojoubertia microphylla micropopulations in different sex and age groups of the chaffinch Fringilla coelebs (Passeriformes: Fringillidae) have been studied during the nest and migration periods in the North-West of Russia. Three bird groups were determined within the chaffinch population during the study: adult males, adult females, immature chaffinches. Total number of bird specimens examined--353. In all chaffinch groups, the mean mite numbers and age structure of mite micropopulations were similar during the spring migration. The number of mites gradually increased from April to May. During the nest and autumn migration periods the seasonal dynamics of M. microphylla micropopulations were quite different on adult males and females of the chaffinch, because of different roles of male and female in the process of infestation the young bird generation. On the adult chaffinch males, the mite number continued to increase during the breeding period (June) and began to decrease significantly in July because of the postbreeding plumage moult. The mite number slowly decreased in the end of summer and the autumn migration. On the adult chaffinch females, the mite number decreased abruptly during the nest period. During this period, the chaffinch female sits together with nestlings for a long time, and the great number of its mites (about 60% of mite micropopulation) moves from the female onto the nestlings. The mite micropopulation migrated onto nestling is represented mainly by males, females (about 25% each) and tritonymphs (38%). Total mite number on the chaffinch females continued to decrease in July under the influence of postbreeding moult and slightly increased up to the autumn migration only. On the young chaffinches, the number of M. microphylla quickly increased during the second part of summer. It is the result of the great quota of mite instars being ready for the reproduction (imago, tritonymphs) within the micropopulation migrated from the chaffinch female onto the nestlings. The decrease of the M. microphylla micropopulation on the young birds was observed in the autumn only. In the end autumn migration (October), the mean numbers of mites on all chaffinch groups became approximately similar, but did not reach the mean rate observed in the beginning of the spring migration. During both migration periods, the imago and all preimaginal instars of M. microphylla were active, the diapause was not observed. In the beginning of spring migration and the end of autumn migration the main part of the mite micropopulations was represented by females, while in all other periods of chaffinch's stay in the North-West of Russia the immature instars predominated.     

The Direction of Celestial Rotation Affects the Development of Migratory Orientation in Pied Flycatchers,Ficedula hypoleuca

The migratory direction in young passerine migrants is based on innate information, with the geomagnetic field and celestial rotation as references. To test whether the direction of celestial rotation is of importance, hand-raised pied flycatchers in Latvia were exposed during the premigratory period to a planetarium rotating in different directions. During autumn migration, when their orientation behavior was recorded in the local geomagnetic field in the absence of celestial cues, birds that had been exposed to a sky rotating in the natural direction showed a unimodal preference of their south-westerly migratory direction. Birds that had been exposed to a sky rotating in the reversed direction, in contrast, showed a bimodal preference of an axis south-west-north-east. Their behavior was similar to that of pied flycatchers that had been raised without access to celestial cues. In Latvia, the magnetic field alone allows only orientation along the migratory axis, and celestial rotation enables birds to select the correct end of this axis. Our findings show that the direction of rotation is of crucial importance: celestial rotation is effective only if the stars move in the natural direction.     

Use of an Inclination Compass during Migratory Orientation by the Bobolink (Dolichonyx oryzivorus)

Adult bobolinks were tested in a planetarium under patterns of nonrotating artificial stars to determine the influence of natural and modified magnetic fields on their migratory orientation. The modified magnetic field was of the same total intensity as the natural field, but the vertical vector was reversed, causing the resulting total vector to point up and north (compared to the natural northern hemisphere vector pointing down and north). When exposed to the artificial magnetic field, the birds reversed their preferred headings relative to the stellar and geographic references. This response is consistent with the use of an inclination compass. Although 60 % of the individuals reversed their headings the first night, some individuals took up to 5 nights (mean = 2.1 nights).