Extrapair paternity in a flock-living passerine, the vinous-throated parrotbill Paradoxornis webbianus

Understanding the factors that affect the occurrence of extrapair paternity (EPP) is one of the central issues in sexual selection. We investigated genetic parentage and the ecological factors affecting patterns of EPP in the vinous-throated parrotbill, Paradoxornis webbianus , a flock-living species with double broods. Using microsatellite DNA fingerprinting, we determined parentage of 246 offspring in 50 broods over two years (2005 and 2006). Nineteen offspring (8%) from 13 broods (26%) were sired by extrapair males and one offspring (0.4%) was probably the result of intraspecific brood parasitism. The prevalence of EPP varied significantly through the breeding season: 95% of broods with EPP (12/13) occurred in the first of two laying peaks. Parentage assignment revealed that half of extrapair males (6/12) were adjacent neighbours. The distribution of EPP was not significantly related to the ecological factors including breeding density and breeding synchrony. Instead, we suggest that social characteristics such as flocking and weak territoriality may determine the observed pattern of EPP in this study.     

Parental provisioning behaviour plays a key role in linking personality with reproductive success

Repeatable behavioural traits (‘personality’) have been shown to covary with fitness, but it remains poorly understood how such behaviour–fitness relationships come about. We applied a multivariate approach to reveal the mechanistic pathways by which variation in exploratory and aggressive behaviour is translated into variation in reproductive success in a natural population of blue tits, Cyanistes caeruleus. Using path analysis, we demonstrate a key role for provisioning behaviour in mediating the link between personality and reproductive success (number of fledged offspring). Aggressive males fed their nestlings at lower rates than less aggressive individuals. At the same time, their low parental investment was associated with increased female effort, thereby positively affecting fledgling production. Whereas male exploratory behaviour was unrelated to provisioning behaviour and reproductive success, fast-exploring females fed their offspring at higher rates and initiated breeding earlier, thus increasing reproductive success. Our findings provide strong support for specific mechanistic pathways linking components of behavioural syndromes to reproductive success. Importantly, relationships between behavioural phenotypes and reproductive success were obscured when considering simple bivariate relationships, underlining the importance of adopting multivariate views and statistical tools as path analysis to the study of behavioural evolution.     

Fitness consequences of male provisioning of incubating females in a desert passerine bird

Male provisioning of incubating females can increase reproductive success by maintaining physiological condition of females and consistency of incubation. The effects of male provisioning on the maintenance of incubation temperature and embryo development should be particularly pronounced in environments where ambient temperature exceeds the tolerance of unincubated eggs and where consistency of female incubation might be particularly important for hatching success. Here, we investigated the reproductive consequences of incubation feeding in a desert population of House Finches (Carpodacus mexicanus) in southwestern Arizona. We found that greater nest attentiveness by females was related to higher minimum incubation nest temperature, that in turn was closely associated with hatching success. Only 44% of males regularly provisioned their incubating females. Although provisioned females maintained higher incubation temperature and took fewer incubation breaks than non-provisioned females, overall, male provisioning did not influence incubation dynamics or hatching success. Further, a male’s incubation feeding rate did not correlate with male provisioning of nestlings. These results corroborate the finding that, in male House Finches, neither provisioning of incubating females nor pre-incubation courtship feeding are associated with increases in circulating pituitary prolactin––the hormone regulating male provisioning of nestlings. We suggest that incubation provisioning by male might be a component of pair maintenance behavior and that variation in male incubation behavior is best understood in relation to asymmetries in residual reproductive values between the mates.     

Brain size,head size and behaviour of a passerine bird

A recent increase in comparative studies of the ecological and evolutionary consequences of brain size in birds and primates in particular have suggested that cognitive abilities constitute a central link. Surprisingly, there are hardly any intraspecific studies investigating how individuals differing in brain size behave, how such individuals are distributed and how brain size is related to life history and fitness components. Brain mass of the barn swallow Hirundo rustica was strongly predicted by external head volume, explaining 99.5% of the variance, allowing for repeatable estimates of head volume as a reflection of brain size. Repeatability of head volume within and between years was high, suggesting that measurement errors were small. In a 2 years study of 501 individual adult barn swallows, I showed that head volume differed between sexes and age classes, with yearlings having smaller and more variable heads than older individuals, and females having smaller and more variable heads than males. Large head volume was not a consequence of large body size, which was a poor predictor of head volume. Birds with large heads arrived early from spring migration, independent of sex and age, indicating that migratory performance may have an important cognitive component. Head volume significantly predicted capture date and recapture probability, suggesting that head volume is related to learning ability, although morphological traits such as wing length, aspect ratio and wing area were unimportant predictors. Intensity of defence of offspring increased with head volume in females, but not in males. Barn swallows with large heads aggregated in large colonies, suggesting that individuals with large heads were more common in socially complex environments. These results suggest that brain size is currently under natural and sexual selection, and that micro‐evolutionary processes affecting brain size can be studied under field conditions.     

Parental provisioning behaviour in Pied Flycatchers Ficedula hypoleuca is well adjusted to local conditions in a mosaic of deciduous and coniferous habitat

Capsule Pied Flycatchers are better able than Great Tits to adjust their feeding behaviour to varying conditions in the same area.

Aims Great Tits breeding in a mosaic of deciduous and coniferous forests in the northern temperate region exhibit consistently lower breeding success in their preferred deciduous habitat than in coniferous habitat. This was explained by the unexpectedly poor nestling feeding conditions in deciduous forests of this region. We studied whether the same paradox applies to Pied Flycatchers that occupy the same habitats in the same area.

Methods Parental provisioning behaviour was studied using video‐recording and experimental manipulation. Caterpillar abundance and basic breeding parameters were measured in different habitat types.

Results Parental provisioning frequency and the proportion of caterpillars in nestling diet was lower, while food objects were on average larger, in coniferous compared with deciduous habitat. However, the total volume of caterpillars and adult Lepidoptera delivered to nestlings did not differ between habitats. In contrast to Great Tits, offspring body parameters in Pied Flycatchers did not differ between habitat types.

Conclusions These results demonstrate how the relative suitability of particular habitat types varies between species and is dependent upon geographical location.     

Heterothermy in an Australian passerine, the Dusky Woodswallow (Artamus cyanopterus)

Information regarding passerine heterothermy and torpor is scant, although many species are small and must cope with a fluctuating food supply and presumably would benefit from energy savings afforded by torpor. We studied whether insectivorous Dusky Woodswallows (Artamus cyanopterus; ∼35 g) enter spontaneous torpor (food ad libitum) when held outdoors as a pair in autumn/winter. Woodswallows displayed pronounced and regular daily fluctuations in body temperature (T _b) over the entire study period. The mean T _b ranged from ∼39°C to 40°C (photophase, day time) and ∼33°C to 36°C (scotophase, night time). However, on 88% of bird nights, nocturnal T _b minima fell to < 35°C. The lowest T _b observed in air was 29.2°C. However, when a bird fell into water its T _b dropped further to ∼22°C; this T _b was regulated for several hours and the bird survived. Our observations suggest that heterothermy is a normal part of the daily thermal regime for woodswallows to minimise energy expenditure. Spontaneous nocturnal torpor in captive woodswallows suggests that torpor in the wild may be more pronounced than recorded here because free-living birds are likely challenged by both low food availability and adverse weather.     

Heritability of selectively advantageous foraging behaviour in a small passerine

Summary I measured the heritability of foraging patch choice in a laboratory population of zebra finches (Taeniopygia guttata). Mothers and offspring were tested for their ability to discriminate between four foraging patches which provided four different rates of energy gain. Use of a foraging patch with a high rate of energy gain has been shown to confer a selective advantage on zebra finches in a similar experimental system. In this population of zebra finches there was a large amount of variation in foraging patch choice behaviour both within and among individuals. I determined that foraging patch choice was a phenotypically labile trait with a degree of stereotypy or repeatability, much lower than those typically recorded for morphological traits. The mating behaviour of zebra finches required that heritability be determined from a mother—offspring regression, which showed that narrow sense heritability of foraging patch choice was approximately 0.346. This heritability was significantly different than zero, as was heritability when it was limited by repeatability to 0.246. Foraging patch choice, a behaviour that has a demonstrated fitness consequence, had a heritable component in this laboratory population of zebra finches.     

Parental provisioning in the Dunnock Prunella modularis: the effects of a variable mating system

The feeding rates to nestlings by adult Dunnocks Prunella modularis in monogamy, cooperative polyandry (the beta male helped) and uncooperative polyandry (where the beta male did not help) at various chick ages were examined. The presence of a helper at the nest did not lead to a significant reduction in the provisioning rate by the other parents. During the first four days of chick feeding, females in all the mating systems examined appeared to provision the chicks at a higher rate than males.     

Parental provisioning, nestling departure decisions and prefledging mass recession in Cassin's auklets

We investigated how parental provisioning and nestling departure behaviour interact to produce prefledging mass recession in Cassin's auklets, Ptychoramphus aleuticus. Under our hypothesis, auklet parents are reluctant provisioners and should be increasingly likely to terminate or reduce provisioning of their single nestling as it matures. For the nestling, remaining in the nest presents a risk of losing mass (if the parent does not provision) but also a possibility of additional provisioning. As the nestling matures and becomes increasingly capable of independence, the benefits of remaining in the nest decrease and nestlings should be increasingly likely to fledge. Nestlings also should be more likely to fledge when the expectation of additional provisioning is low. Data on parental provisioning (based on growth increments) and nestling departure were consistent with our hypothesis. Older and heavier nestlings had smaller growth increments than younger and lighter nestlings, suggesting that parents were reluctant to provision old and heavy nestlings. Older and heavier nestlings also were increasingly likely to fledge. We hypothesized that nestlings might use the intensity of mass loss to gauge parental reluctance to provision, and accordingly, nestlings were increasingly likely to fledge after experiencing a greater amount of mass loss. Copyright 1999 The Association for the Study of Animal Behaviour.     

Sex-specific provisioning behaviour in a monomorphic seabird with a bimodal foraging strategy

Sexual differences in foraging and provisioning behaviour have been observed in several size-dimorphic seabird species. These differences are usually thought to be driven by size-related mechanisms such as the ability to compete for food or defend the nest. However, recent studies on monomorphic species suggest that sexual differences in foraging may arise independently of size. Selective forces driving sex-specific patterns are poorly known but essential to understand parental strategies. In this study, we examine sex differences in the provisioning behaviour of a monomorphic species, the Little Auk Alle alle . Using automated recording systems during two consecutive seasons at two colonies, we found that both sexes used a bimodal foraging strategy in which they regularly alternated single foraging trips of long duration with a cycle of several short-trips. The duration of long-trips was substantially longer in females than in males, and the sexes differed in the number of short-trips they performed in between long-trips, resulting in male-biased provisioning rates in both years. In species with a bimodal foraging strategy, long-trips have been interpreted as self-feeding trips to replenish body reserves. Our results therefore suggest that female Little Auks allocate more time to self-maintenance at the cost of chick provisioning, possibly due to different energetic constraints of the sexes prior and/or subsequent to chick-rearing. Our findings contribute to accumulating evidence that sex-specific foraging patterns may be widespread in sexually size-monomorphic seabird species.     

Determinants of reproductive success in a Mediterranean multi-brooded passerine: the Black WheatearOenanthe leucura

The factors affecting individual variation in reproductive success in a multibrooded passerine, the Black WheatearOenanthe leucura, were studied during five years in a dry inland depression in SE Spain. Black Wheatear pairs initiated 1–5 breeding attempts in a season, including relayings, and managed to raise 0–3 broods and 0–13 fledglings. The onset of breeding for different pairs spanned several months. The number of breeding attempts and the proportion of young resulting in fledged young (excluding predated broods) were the best predictors of seasonal reproductive success. Clutch size showed a quadratic relationship with laying date. Female age and time of residency and indexes of parental condition such as discontinuities in feather growth or prevalence of ectoparasites had significant effects on breeding productivity. Repeatabilities of breeding performance for males, females or in territories were not significant.Zusammenfassung Am Beispiel des Trauersteinschmätzers, einem Singvogel mit mehreren Jahresbruten, wurden in einer trockenen Inlandniederung Südostspaniens die Faktoren untersucht, die individuelle Unterschiede im Fortpflanzungserfolg bedingen. Die Paare unternahmen einschließlich Ersatzgelege ein bis fünf Brutversuche pro Saison und können maximal bis 3 Bruten aufziehen. Hieraus ergibt sich eine große Variation der Produktivität. Der Legebeginn zog sich bei den einzelnen Paaren über mehrere Monate hin. Die Zahl der Brutversuche, die vom Termin des ersten Legebeginns abhängig waren, und die Qualität der elterlichen Brutpflege, gemessen an dem Anteil der Eier, die flügge Junge ergaben (ohne Fälle von Nestraub), ließen den Bruterfolg pro Saison am besten bestimmen. Gelgegegröße variierte nur gering (4 Eier im Mittel) und zeigt die quadratische Beziehung zum Legedatum, wie für mehrfachbrütende Sperlingsvögel typisch. Eltern, die intensiver am Nest fütterten, waren die produktivsten, fütterten auch intensiver nach dem Flüggewerden der Jungen und zeigten kürzere Intervalle zwischen aufeinanderfolgenden Bruten. Einjährige Weibchen oder Weibchen, die mit einjährigen Männchen verpaart waren, hatten geringeren Erfolg gemessen an Zahl der flüggen Jungen; Weibchen, die das erste Mal in einem Revier brüteten, begannen später zu legen. Unregelmäßigkeiten in der letzten Mauser, wie sie an Ungleichmäßigkeiten der Wachstumsbänder der Federn zu erkennen waren, hatten negativen Effekt auf die Produktivität der Weibchen und auf die Abstände zwischen aufeinanderfolgenden Bruten bei Männchen. Männchen mit vielen Ektoparasiten waren weniger produktiv. Die Wiederholbarkeit des Fortpflanzungsverhaltens von Männchen, Weibchen oder in einzelnen Revieren war relativ niedrig und nicht signifikant. Die langen und variablen Fortpflanzungsperioden und die starken Einflüsse auf die individuelle Kondition bei Produktion und Fürsorge der Eier und Jungen ist wohl für trockene und wenig produktive Landschaften des Mittelmeerbeckens typisch.     

Mobbing behaviour in a passerine community increases with prevalence in predator diet

Mobbing behaviour against predators is well documented but less is known about the factors influencing variation in behavioural response between prey species. We conducted a series of playback experiments to examine how the mobbing responses of prey species differed according to their relative risk of predation by the Eurasian Pygmy Owl Glaucidium passerinum, a predator of passerines. We found that mobbing among 22 passerine prey species was positively correlated with their prevalence in the Pygmy Owl diet. To compare mobbing behaviour between two seasons, we conducted playback experiments during spring (breeding season) and autumn (non‐breeding season). Contrary to previous studies, we found that mobbing intensity was greater during autumn than in spring. Our study shows a differential mobbing response of 22 species to the calls from one predator species and underscores the importance of considering seasonal variation in mobbing behaviour. Mobbing response differences observed among bird species strongly suggest different cooperation behaviour at the community level.     

Light affects parental provisioning behaviour in a cavity‐nesting Passerine

Nocturnal bird species possess special adaptations to maximise visual efficiency under low light levels. However, some typically diurnal species also experience low‐light environments. For example, cavity‐nesting Passerines raise broods in dark cavities and search for food in light‐abundant surroundings. It is not clear whether they possess special adaptations for low light vision or breed in cavities at the expense of impaired parental care. In this study, we tested whether light conditions affect the provisioning efficiency of great tits. We experimentally tested how the level of natural and artificially increased illumination inside nest boxes affects parental feeding duration, frequency and timing. We monitored 15‐h of provisioning activity of great tit parents when nestlings were day seven post hatch. We used traditional ‘dark’ nest boxes and ‘bright’ nest boxes with increased illumination obtained by using semi‐transparent plastic windows. The duration of single feedings were, on average, shorter in brightened nest boxes compared to dark ones. This difference tended to be higher early in the morning and in the evening, when the illumination in dark nest boxes was the lowest. Nest box type, however, did not influence feeding frequency or times of the onset and the end of feeding. Our findings provide new evidence for impaired efficiency of parental care due to lowered light conditions. Further research is needed to test whether prolonged feeding duration has negative effects on adult time budgets and nestling energy expenditures.     

Heavy metal pollution affects dawn singing behaviour in a small passerine bird

Although several studies have suggested that behavioural measures may be more comprehensive than other biomarkers for indicating an organism’s health or welfare, this has rarely been investigated in free-living terrestrial vertebrates. Here we examine the expression of dawn singing behaviour in a free-living small songbird in relation to environmental pollution. We compared the singing behaviour of male great tits Parus major inhabiting an area extremely polluted with heavy metals with that of males inhabiting areas of low(er) pollution (at 4 and 20 km distance from the pollution source). Males at the most polluted site had a significantly smaller repertoire size than males at the two other sites. They also produced a significantly lower total amount of song during the dawn chorus than the males at a distance of 4 km from the pollution source. Our results, although non-experimental and obtained in field conditions, strongly suggest that heavy metal pollution might affect the expression of singing behaviour. Taking into account that previous studies were not able to detect clear, straightforward differences between the health of great tits at the most polluted site and at 4 km distance from the pollution source, our results suggest that the singing behaviour of great tits may be a useful indicator of environmental stress at the population level.     

Parental behaviour in Mongolian gerbils (Meriones unguiculatus). II. Parental interactions

Twelve pairs of Mongolian gerbils were observed raising 15 litters. Both parents performed parental activities. Within pairs, associations were found between the behaviours of the parents. If one parent was active outside the nest, the other was likely to be relatively inactive in the nest. These non-random behavioural associations existed even though overall activity tendencies of members of pairs were similar. As a consequence of these patterns of behaviour, the pups were seldom left unattended, and the adaptive significance of parental presence is discussed.     

Corticosterone manipulations alter morph-specific nestling provisioning behavior in male white-throated sparrows, Zonotrichia albicollis

In the polymorphic white-throated sparrow (Zonotrichia albicollis), tan-striped males provision nestlings at higher rates than do white-striped males. In a previous study, we found that tan-striped males had lower baseline corticosterone levels than white-striped males during the nestling stage. To determine if this variation in corticosterone influences morph-specific differences in nestling provisioning behavior, we used intraperitoneal osmotic pumps to increase baseline corticosterone levels in tan-striped males (TS CORT) and administer RU486, a glucocorticoid receptor antagonist, in white-striped males (WS RU486). These manipulations essentially reversed morph-specific nestling provisioning behavior in males. TS CORT males fed nestlings at lower rates than TS controls (vehicle-only implant), and at similar rates to WS controls (vehicle-only implant), while WS RU486 males fed nestlings at higher rates than WS controls, and at similar rates to TS controls. These results demonstrate that (1) increases in baseline corticosterone (i.e., below concentrations associated with the adrenocortical response to stress) can directly or indirectly inhibit nestling provisioning behavior, and (2) corticosterone influences morph-specific variation in parental behavior in male white-throated sparrows. This study contributes to the growing evidence that modulating baseline CORT mediates parental care and self-maintenance activities in birds, and thus may serve as a mechanism for balancing current reproductive success with survival.     

Parental behaviour in the Lapwing Vanellus vanellus

Parental behaviour of monogamous and polygynous Lapwings was studied during incubation and brood care. Both parents attended the nest in 86% of monogamous pairs ( n = 29 pairs). In 14% of pairs, only the male parent continued incubation until the eggs hatched, whereas the female deserted the clutch before or at the end of incubation. There was a clear division of parental roles during incubation. Females spent more time incubating (64% of time) than their mates (27%), whereas males spent more time defending the nest (3%) than females (>1%). Time spent incubating did not differ between monogamous and polygynous males. However, polygynous females spent more time incubating (primary females: 95%; secondary females: 97%) than monogamous females. Biparental care was the most common pattern of post-hatching care, although in some broods either the male or the female parent deserted before the chicks fledged. Division of sex roles was less pronounced in brood care than during incubation. Females spent more time brooding (21%) than males (3%), and females attended their chicks more closely than males. Nevertheless, males and females spent similar amounts of time defending the brood from predators and conspecifics. We suggest that the apparent division of parental roles may be explained by sexual selection, i.e. the remating opportunities for male Lapwings might be reduced if they increase their share in incubation. However, the different efficiency of care provision, for example in ability to defend offspring, may also influence the roles of the sexes in parental care.     

Habitat quality, nestling diet, and provisioning behaviour in great tits Parus major

Variation in early nutrition is often a strong predictor of offspring condition and fitness. In the case of woodland passerine birds, nestling diet is determined by the spatiotemporal distribution of prey items such as caterpillars during the nestling period, and is usually quantified as differences in provisioning behaviour between habitats. However, the habitat level does not account for variation between individual territories, the level at which competition and selection are assumed to operate. Here we use nestbox cameras and Radio Frequency Identification technology (RFID) to simultaneously assess variation in both nestling diet (components) and provisioning rates (quantity) among a sample (n=22) of different quality great tit Parus major territories selected from a larger breeding population (n=310 fledged broods) in a single year. Caterpillars were by far the most numerous item provisioned to nestlings (mean=75% of prey items), as expected given the known importance of this food source for this species. Broods raised close to an oak tree, or far from the woodland edge, were provisioned the highest proportion of caterpillars. Provisioning rates declined seasonally and there was a weak association between low provisioning rates and caterpillar rich diets. During the first week of the nestling stage, nestling condition was unrelated to the proportion of caterpillars in the diet, provisioning rates and oak proximity. Condition at fledging was slightly improved in broods fed a higher proportion of caterpillars in the diet and in broods raised close to an oak tree. However, in our data early breeding was the only predictor of recruitment success, although power was low for this test. Analyses of long‐term data (41 years) from the same population confirmed a relationship between oak proximity and fledgling mass, but not recruitment success. Our results suggest that territory level environmental variation can affect offspring condition, probably through observed changes in nestling diet, but that such variation does not necessarily produce discernable effects on offspring fitness.