Clutch-size variation in the Pied Flycatcher Ficedula hypoleuca

Variation in clutch-size of the Pied Flycatcher Ficedula hypoleuca was studied simultaneously in relation to latitude, longitude, altitude, laying date and habitat, using data from 103 areas from north Africa to north Norway (latitudinal range about 3900 km). Clutch-size variation was significantly related to altitude and habitat, small clutches being laid at high altitude and in coniferous forests. In contrast to some earlier studies, latitudinal or longitudinal clutch-size trends were not found.     

Association between haematozoan infections and reproduction in the Pied Flycatcher

1. Parasites may affect breeding success of their host since they compete for the same resources as their hosts. Reproduction may also increase the susceptibility of a host to parasite infections owing to lowered resistance to parasites during breeding.
2. We studied the association between breeding performance and haematozoan parasite infection in the Pied Flycatcher ( Ficedula hypoleuca ) by using both natural data on reproduction and data from clutch size manipulations.
3. The most frequent blood parasites of the Pied Flycatcher in central Finland were Haemoproteus pallidus , Haemoproteus balmorali and Trypanosoma avium complex.
4. We did not find evidence that these haematozoan parasites have any debilitating effects on either reproduction or survival. The variation in reproductive effort did not seem to influence susceptibility to new blood parasite infections.
5. The intensity of Haemoproteus balmorali tended to increase in infected males as the brood size was artificially enlarged. Also, in females intensity of H. pallidus infection tended to increase with the level of clutch size manipulation. Thus, increased reproductive effort seems to debilitate the ability of Pied Flycatcher to control chronic infections.
6. Individuals with enlarged clutches/broods increased their reproductive effort at the expense of defence towards parasites. The cost of current reproduction may then be at least partly mediated by haematozoan infections.     

Divergent character displacement in the song of two allospecies: the Pied Flycatcher Ficedula hypoleuca, and the Collared Flycatcher Ficedula albicollis

Songs of the three flycatcher forms, Ficedula hypoleuca hypoleuca, Ficedula albicollis albicollis and Ficedula albicollis semitorquata , were distinguishable from one another using a multivariate analysis. F. albicollis semitorquata , which has an intermediate song character, is considered to be a primary allopatric form while the nominate subspecies of albicollis is assumed to be dispersed into sympatry with F. h. hypoleuca . The differences in song between the nominate albicollis and F. hypoleuca are accentuated in their zone of sympatry and are mostly due to divergence in the albicollis song. The song is primarily an epigamic vocalization in the two species and conforms to the pattern characteristic of divergent character displacement associated with reproductive behaviour. Two alarm calls are quite similar in the two species and are the main vocalizations associated with territorial combat. Their interspecific territorial behaviour has apparently not been affected in areas of sympatry.     

Geographic variation in breeding parameters of the Pied Flycatcher Ficedula hypoleuca

Variation in laying date, clutch-size and number of fledglings of the Pied Flycatcher Ficedula hypoleuca was studied in relation to altitude, habitat and latitude, using data from 99 breeding areas from 35̀ N to 70̀ N. Laying date significantly increased with altitude and showed a significant quadratic relationship with latitude, with the earliest values at about 50̀ N. This quadratic relationship shows the same pattern as the relationship between arrival time of adults on the breeding areas and latitude. Clutch-size variation was significantly related to altitude and habitat, small clutches being laid at high altitude and in coniferous forests. Number of fledglings was significantly affected by habitat type, with lower values in the coniferous than in the deciduous forest. Mean clutch-size and mean number of fledglings showed the same quadratic relationship with latitude. In contrast to some earlier studies, an increased clutch-size with latitude was found, mainly because of new data from areas in the southern part of the species' distribution.     

Experimentally induced clutch size enlargements affect reproductive success in the Pied Flycatcher

We performed a food provisioning experiment in a population of Pied Flycatchers Ficedula hypoleuca breeding at high altitude in central Spain to test if food availability before and during laying determines clutch size. Food was provided to one of two pairs with the same date of initiation of nest-building (15 dyads of subsequently reproducing pairs were thus created). Food provisioning began on the day of initiation of nest-building and ended on the day after the last egg was laid. Although laying date was unaffected by the experiment, clutch size in the experimental treatment was significantly larger. This result could indicate that food availability at laying (1) proximately constrained clutch size or (2) that females evaluated future conditions for incubating eggs and feeding nestlings based on food availability at laying. Reproductive success (proportion of eggs that resulted in fledged young) was significantly reduced in the experimental treatment. This effect suggest that supplemented females were tricked by the experiment into laying more eggs than the number of eggs they were able to incubate with success and the number of nestlings they were able to feed, a source of error in clutch size adjustment which could be common in non-experimental situations.     

Female Contests for Nest Sites and Mates in the Pied Flycatcher Ficedula hypoleuca

Predictions of game theory models about the outcome of animal conflicts have most often been tested using male contests for mates, territories or food. We studied female contests for nest sites and mates in the pied flycatcher, Ficedula hypoleuca, and asked which factors affect the outcome and duration of the contests. Conflicts over residency were experimentally induced, but natural cases in which both females regarded themselves as owners were also included in the analyses. The ensuing escalated contests involved physical fighting, defence of the nestbox of the male and alarm calling. Contrary to expectations from game theory, fighting seemed to occur most often at the start of conflicts, whereas alarm calling occurred towards the end and nestbox visits throughout the conflict. The outcome of the contests was not determined by asymmetries in body size or age, nor by a simple previous-present owner asymmetry. Instead, it depended on the relative residence times of the opponents. The duration of the contests tended to increase with decreasing asymmetry in the residence times of females, whereas body size asymmetries had no influence. Because there is intense competition between females for a mate in the pied flycatcher, we suggest that females do not respect asymmetries in residency and body size, but fight in relation to the value of the mating opportunity. In particular, we point to the possibility that the value of a mating opportunity may increase with residence time because knowledge of other mating options may become outdated.     

The Breeding Distribution and Habitats of the Pied Flycatcher (Muscicapa Hypoleuca) in Britain

Examination of the plumage of Palaearctic warblers as migrants or wintering birds at Kampala, Uganda, provided useful material for a consideration of moult in relation to the timing of spring and autumn migration. Reasons are suggested for observed interspecific differences in the moult pattern, and for the variation reported from different wintering areas in the African continent.     

Acoustic Monitoring Reveals Congruent Patterns of Territorial Singing Behaviour in Male and Female Tropical Wrens

Many animals defend territories against conspecific individuals using acoustic signals. In birds, male vocalizations are known to play a critical role in territory defence. Territorial acoustic signals in females have been poorly studied, perhaps because female song is uncommon in north‐temperate ecosystems. In this study, we compare male vs. female territorial singing behaviour in Neotropical rufous‐and‐white wrens Thryothorus rufalbus, a species where both sexes produce solo songs and often coordinate their songs in vocal duets. We recorded free‐living birds in Costa Rica using an eight‐microphone Acoustic Location System capable of passively triangulating the position of animals based on their vocalizations. We recorded 17 pairs of birds for 2–4 consecutive mornings and calculated the territory of each individual as a 95% fixed kernel estimate around their song posts. We compared territories calculated around male vs. female song posts, including separate analyses of solo vs. duet song posts. These spatial analyses of singing behaviour reveal that males and females use similarly sized territories with more than 60% overlap between breeding partners. Territories calculated based on solo vs. duet song posts were of similar size and similar degrees of overlap. Solos and duets were performed at similar distances from the nest for both sexes. Overall, male and female rufous‐and‐white wrens exhibit very similar spatial territorial singing behaviour, demonstrating congruent patterns of male and female territoriality.     

Sex-Specific Territorial Behaviour in the Banggai Cardinalfish, Pterapogon kaunderni

In a field experiment, we studied how levels of aggression in males and females in established pairs of the Banggai cardinalfish were influenced by the sex of an experimentally introduced individual larger and more attractive than its resident counterpart. Contrary to previous studies on other cardinalfish species, and contrary to expectations in a sex role reversed species, the male was the main aggressor towards an intruder. Moreover, residents were more aggressive towards an intruder of the same sex as themselves. Furthermore, even though females often courted introduced, larger males, no intruder managed to take over the partnership of any resident. We suggest that our findings imply relatively equal sex roles in the Banggai cardinalfish and we discuss the evolution of sex specific territory defence and its significance in the Banggai cardinalfish as well as the implications of such behaviour in the interpretations of sex roles in general.     

Correlation between egg size and clutch size in the Pied Flycatcher Ficedula hypoleuca in cold and warm summers

The correlation between egg size and clutch size was studied in the Pied Flycatcher Ficedula hypoleuca in Finnish Lapland from 1975 to 1994. The hypothesis tested was that the tradeoff phenomenon is masked by warm weather. When data for 20 years were pooled, there was no correlation. However, when years were analysed separately, a negative correlation was observed for five of the years. Over 12 years, the correlation coefficient between egg size and clutch size was not significant, and for 3 years it was significantly positive. The size and magnitude of the correlation were related to temperature during the pre-laying and egg-laying periods. Of the annual variation, 34% was explained by the mean temperature in early summer. It is suggested that trade-off between egg size and clutch size may not be apparent in central (southern) parts of the distribution area of the species where climate is warmer. In the future, global warming may alter reproductive strategies of birds. Long-term data may thus be useful in the analysis of such effects and in testing of theoretical questions in ecology.     

Mobbing in the Pied Flycatcher. Effect of Experiencing a Live Owl on Responses to a Stuffed Facsimile

A surprisingly high proportion (42 %) of breeding pied flycatchers failed to mob a stuffed pygmy owl placed near the nests. To determine whether the range of effective stimulus objects eliciting mobbing could be extended in these “non-mobbers”, a live owl, resembling the ineffective dummy in nearly all static owl traits, was briefly exposed. It evoked strong mobbing from all birds, as did the stuffed specimen on a subsequent presentation. The role of experience with live predators and the effect of labile properties of the latter on the mobbing response are discussed.     

Wulst Neurons in Nestlings of the Pied Flycatcher Ficedula hypoleuca at the Pre-Visual Stage of Development

Neurons of the Wulst region, an analog of the mammalian visual cortex, were studied in Golgi-impregnated preparations of brain of non-precocial 1-day old nestlings of the pied flycatcher Ficedula hypoleuca. At this age, vision does not function in nestlings, their behavior is provided by an acoustic analyzer. Two populations of nerve cells, large and small juvenile neurons, were differentiated at visual examination. The comparative morphometry has shown these groups to differ significantly from each other by most studied parameters: the area of the profile field of their soma, the total length of dendrites, branching of the cell, the number of the maximal branching foci, the character of distribution of dendrite free endings in three concentric zones of the cell dendritic field. The distribution of dendrites in the dendritic neuron field was similar in the both groups of neurons. An increased density of dendrites was observed from the side of the afferent input. At the same time, study of orientation of the longest dendrite has shown it to be located parallel to the plane of the afferent input practically in all cells of the both groups. It is suggested that such orientation of the longest dendrite broadens the area of cell contacts, which is necessary for search for the maximal number of afferents. The predominant orientation of dendrites in the direction to the afferent input forms foundation for establishing a more extended zone of contacts with growing visual afferents.     

Influence of Age and Prior Experience on Territorial Behavior and the Costs of Defense in Male Collared Lizards

In polygynous species where males maintain strong interseasonal philopatry to the same breeding territories, older individuals have prior experience defending their areas, whereas younger individuals are defending a territory for the first time. Theoretical and empirical studies predict that under such conditions the cumulative costs of defense may be lower for older experienced males as a consequence of familiarity with environmental and/or social conditions in their particular local habitats. We used quantitative data from focal observational studies and introduction experiments to test the hypothesis that older collared lizard males (Crotaphytus collaris) with prior territorial experience (3 yr+ males) acquire larger territories allowing them to court more, different females, with greater frequency without incurring higher defense costs. Consistent with this hypothesis, 3 yr+ males controlled significantly larger territories and courted more females, without having significantly higher rates of territory patrol, frequencies of advertisement display, or aggressive interactions with same‐sex competitors. Moreover, the intensity of responses to size‐ and age/experience‐matched tethered intruders by 3 yr+ males was lower than that by 2 yr males in their first season of territory defense. Our results support the hypothesis that age/prior occupancy of territories lowers defense costs allowing males to defend larger areas and increase opportunities to court females, perhaps increasing mating opportunities. By contrast, 2 yr males may need to respond more aggressively to intruders because their ownership of territories is tenuous as a consequence of shorter territory occupancy.