Sex-dependent risk-taking behaviour towards different predatory stimuli in the collared flycatcher (original) (raw)
Related papers
Animal Behaviour, 2000
An increased mortality rate is a cost of parental care, and can be high during the provisioning phase of altricial nestlings. When a parent stops feeding the nestlings temporarily after seeing a predator, it can reduce its own predation risk, but the suspension of parental care may also reduce its offspring's chances of surviving. We modelled this situation by exposing a stuffed sparrowhawk near collared flycatcher nests and removing it when both parents had seen it. We measured the time (return time) between the removal and when each parent entered the nestbox. The parents' risk taking and the return time are assumed to be inversely related. We studied which brood variables the parents take into account when deciding how much risk they are willing to take during the provisioning period. Males took more risk for older and better-quality nestlings and earlier broods. The females' behaviour was opposite to that of the males: they took significantly less risk for older and better-quality offspring and visited the nestbox later for earlier broods. The males' behaviour supported the reproductive value hypothesis, that risk taking is related to brood value and survival chances, whereas the females' behaviour supported the harm to offspring hypothesis, that risk taking is related to the broods' vulnerability.
Behavioral Ecology and Sociobiology
Individuals of many animal species show consistent differences in ecologically relevant behaviours, and these individual-specific behaviours can correlate with each other. In passerines, aggression during nest-site defence is one of those behaviours that have been steadily found to be repeatable within individuals. Furthermore, in several cases, aggression was related to some estimates of reproductive investment. Here, we studied the possibility that behaviour of males toward a male rival predicts the amount of their future parental care. This could be beneficial to the females, because during mate choice, they could use male aggressive behaviour as a cue for parental quality. We performed the study by video recording the nestling feeding activity of male collared flycatchers (Ficedula albicollis) that were assayed for aggression during the courtship period. The level of aggression was not related to feeding rate in males. Feeding rate of males differed between the study years, but it did not correlate with the feeding rate of their mates, neither was it related to the morphological traits of the parents. We may conclude that nest-site defence aggression of males does not predict their parental commitment. This may be surprising given that higher testosterone levels that may be expected in aggressive males often suppress parental care. However, among-individual variance in male testosterone profiles found to be decrease from the courtship to the parenting period in flycatchers, and this may explain why differences in territorial aggression did not manifest in differences in nestling provisioning. The correlation between behaviours that are expressed in distinct periods of the annual cycle of songbirds needs further investigation. Significance statement Male songbirds, when attracting mates, are often confronted with each other over nest-sites, and these male-male confrontations may be witnessed by females. If performance during territory defence predicts the quality of parental care that a male will provide for its nestlings, females could use defence behaviour as a cue for mate choice. To explore this possibility, we investigated the relationship between territorial aggression and nestling feeding activity of male collared flycatchers. We performed simulated territorial intrusions to measure the aggression of males and recorded their nestling feeding rate about a month later. We found that territorial aggression did not correlate with nestling feeding rate. This suggests that nest-site defence behaviour in the beginning of the breeding season does not carry information for females about what to expect from potential mates in terms of parental care.
Behavioral Ecology, 2002
The evolution of different parental care strategies is thought to result from variation in trade-offs between the costs and benefits associated with providing care. However, changing environmental conditions can alter such fitness trade-offs and favor plasticity in the type or amount of parental care provided. Avian incubation is a form of parental care where parents face changing environmental conditions, including variation in the risk of nest predation. Because parental activity can draw attention to the location of the nest, a reduction in nest visitation rates is a predicted response to an increased, immediate predation risk. Here, we experimentally increased the risk of nest predation using model presentations at nests of five coexisting species that differ in their ambient levels of nest predation. We examined whether individuals detect changes in nest predation risk and respond by reducing visitation to the nest. We also tested whether this behavioral response differs among species relative to differences in their ambient risk of nest predation. We found that males of all species detected the increased predation risk and reduced the rate at which they visited the nest to feed incubating females, and the magnitude of this change was highly correlated with differences in the risk of nest predation across species. Hence, as the vulnerability to nest predation increases, males appear more willing to trade the cost of reduced food delivery to the female against the benefit of reduced predation risk. Our results therefore suggest that nest predators can have differential effects on parental behaviors across species. We discuss how the comparative nature of our results can also provide insight into the evolution of behavioral plasticity.
Different experiences from the past may have influence on individual's behaviour through feedback me cha nisms that can weaken or preserve the withinindividual consistency of behavioural traits. Here, we aimed to find evidence for such feedback mechanisms that may operate on risk-taking behaviour via the effect of former experience to potential predation events in male Collared Flycatchers (Ficedula albicollis). We predicted that risk-taking of males would decrease after experiencing a predator's attack in previous breeding seasons (negative feedback). We assessed risktaking by flight initiation distance (FID) that is the distance at which an individual flees from an approaching pre dator, which was estimated for 234 individuals from different breeding seasons. Information on predation experience (i.e. occurrence of nest predation, the incidence of capture by human observers) was available from our long-term database on individual life histories. In a horizontal approach, we found no difference in FID when comparing males with former experience to predation with males naive to predators. A longitudinal approach relying on the repeated tests of the same individuals from different years yielded analogous results, we could not show a significant change in the riskta king behaviour of the males as a consequence of experience to predation in past years. However, we found that individuals systematically took less risk over the years, which might be a consequence of acquiring general experience with age.
Ethology, 2014
Correlations between behavioural traits constrain animals to a limited range of behavioural choices and set a limit to the available variation in behavioural phenotype of a population. These constraints are especially important during stressful situations, potentially limiting the ability to cope with stress appropriately. As yet, very little consideration has been given to a possible role for sexual selection in maintaining differences in behavioural stability within individuals: sex-specific differences in behavioural correlations have been seldom studied, especially in the wild. In this field study, we investigated associations between neophobia (latency to enter nest in the presence of a novel object), nest defence (response to a model predator) and breathing rate in response to handling in breeding pied flycatchers (Ficedula hypoleuca). We did not find any significant difference in antipredator responses between males and females, which indicates low sexual conflict over parental care in the pied flycatcher. However, females were more neophobic than males, while males and females did not differ in their breathing rates. Further, our study demonstrated a strong positive correlation between nest defence behaviour and neophobia in male, but not in female pied flycatchers. Males that defended their nest more had lower breathing rate and higher latency to resume nestling feeding after encountering a predator decoy than males that mobbed less intensely. We found only weak evidence that nest partners might affect each other's behaviour in these contexts.
Risk-taking restraints in a bird with reduced egg-hatching success
Proceedings of the Royal Society B: Biological Sciences, 2000
Risk taking, as is any other phenotypic and/or behavioural trait, is determined by proximate constraints related to time or resource availability and by evolutionary adaptive restraints related to the di¡erences in the costs of risk taking and its bene¢ts in terms of ¢tness. Because risk taking is in£uenced by many confounding variables related to experimental design, environment, parents and o¡spring, few ¢eld studies have been reported which unambiguously separate the e¡ects of restraints from those of constraints. We compared parental risk taking in blue tits (Parus caeruleus) during brood defence towards a nest predator in broods with experimentally reduced and natural egg-hatching success leaving the original number of eggs in the nest. The experimentally reduced broods had more time or resources available and lower risk-taking bene¢ts compared to the control broods.`Constraint' would predict more risk taking in broods having experimentally reduced egg-hatching success, whereas`restraint' would predict the opposite e¡ect with more risk taking in broods with natural egg-hatching success. We report, to our knowledge, the ¢rst ¢eld study experimentally demonstrating a brood defence restraint in response to reduced egg-hatching success. This demonstration was only possible after controlling for more than 20 potential confounding variables showing once more how complicated it is to separate proximate from evolutionary levels of analyses in natural populations.
Indirect cues of nest predation risk and avian reproductive decisions
Biology Letters, 2009
Current life-history theory predicts that increased mortality at early stages of life leads to reduced initial investment (e.g. clutch size) but increased subsequent investment during the reproduction attempt. In a field experiment, migratory pied flycatchers Ficedula hypoleuca perceived differences in mammalian nest predation risk and altered their reproductive strategies in two respects. First, birds avoided nest sites manipulated to reflect the presence of a predator. Second, birds breeding in risky areas nested 4 days earlier and laid 10 per cent larger clutches than those in safe areas, a result that runs counter to the prevailing life-history paradigm. We suggest that the overwhelming importance of nest predation to individual fitness reduces the value of collecting other information on habitat features leading to expedited onset of nesting, and, consequently, to larger clutch size.
How robust are risk-taking associations in incubating birds? A test and a review
Behavioral Ecology and Sociobiology, 2019
Flushing distance (FD, the horizontal distance between a parent bird when it leaves its nest and an approaching predator) is one measure of nest defense and of risk-taking; parents that stay too long risk being killed, whereas those that flush too early risk at the very least impairing development of their young, and at the very worst leaving them unprotected against predators. Thus, FD should be under strong natural selection. A general prediction is that incubating birds will remain on a nest being approached by a predator until risks of staying reach a threshold that outweighs costs of fleeing. This threshold is predicted to vary depending on a brood's value, parental characteristics, environmental conditions, and learning that repeated visits pose a limited or no threat. We evaluated FD in a nest box population of tree swallows (Tachycineta bicolor) relative to each of these. We obtained 246 FDs from 66 different nests over 2 years. We found some evidence that FD increased with clutch size (tendency), female age, and air temperature, and decreased with greater overhead vegetation density; six additional associations were not significant. Given the lackluster support for the predictions we tested, we did a review of the literature and similarly found limited support for most of the associations we tested despite the entrenched view that these relationships are commonplace. We submit that further insights are needed into understanding predictors of FD in incubating birds. Significance statement Parent birds sitting on eggs are proverbial sitting ducks, although they do have the option of fleeing predators. However, parents may be willing to sacrifice themselves to protect their eggs if the latter become sufficiently valuable. One assumption is that eggs increase in value closer to hatch, and one prediction is that parents will be more reluctant to fly from their nests later in incubation. We tested this and other predictions in a population of nest-box-using tree swallows in eastern North America. The relatively weak support we obtained for our predictions suggests that we need to reevaluate our assumptions in this area of research.
acta ethologica, 2013
When faced with a predator near the nest, breeding birds faced a dilemma: to continue providing parental care to their offspring exposing themselves to risk or to desert the nest for a brief period of time, exposing their offspring to harm due to the suspension of parental brooding and feeding. In this study, we analysed the response of nesting Southern house wrens (Troglodytes aedon musculus) to a predator model placed near the nest. The experiment was performed in 56 nests when nestling were 3-4 or 10-12 days old. The model (a plastic decoy of the Great Horned Owl Bubo virginianus) was placed at 3 m from the nest. Parent risk-taking was measured as the time elapsed for males and females to resume parental activities during the exposition to the model. We found that males and females delayed parental visits when exposed to the predator model, but females resumed them faster than males, irrespectively of the nesting stage. We also found that males refused to enter to the nest more frequently than females when exposed to the predator model. No effect of breeding experience or nesting stages was noted in the risk taking behaviour of adults. We suggest that sexual differences detected in this species reflect the higher ability of females to cope with the nestling needs and its lower lifetime expectancy.
Behavioral Ecology, 2014
Predation risk can inflict profound effects on prey by influencing prey behavior and other traits. Prey are often subjected to a diversity of predators, which can exert differential predation pressures on prey life-history strategies. In birds, breeding adults and offspring (as eggs, nestlings, and fledglings) are susceptible to different types of predators, and life-history theory predicts that breeding birds can adjust to adult versus offspring predation risk differentially via allocation of breeding investment. Here, we experimentally tested for the effects of perceived adult versus offspring predation risk on breeding birds' reproductive strategy and performance. On study plots with nest boxes used by the cavity-nesting Eastern bluebird Sialia sialis, we manipulated vocal cues of 3 avian predators that preferentially prey on either bluebird adults, or offspring, or both. We found that 1) increased perception of predation risk by all predator treatments reduced bluebird parental investment in egg production and/or post-egg nesting performance, and 2) increased perception of adult and offspring predation risks affected bluebirds differentially, with bluebirds exhibiting shorter nestling rearing periods under offspring, but not adult, predation risk. Our results provide experimental evidence for the nonconsumptive effects of predation risk on avian breeding behavior that can influence demographic vital rates and highlight the mechanisms by which breeding birds can adjust reproductive strategies under different predation risk situations.