Reproductive success of monogamous and polygynous pied flycatchers (Ficedula hypoleuca)

One of the most interesting aspects of the mating system of pied flycatchers is the regular occurrence of polygyny. Here we present data on the reproductive success of polygynously paired pied flycatcher males compared to monogamous males based on paternity analyses through DNA fingerprinting. Males paired with two females suffered a higher loss in reproductive output per female compared to monogamous males due to (1) a greater proportion of unhatched eggs in their broods, (2) greater nestling mortality and (3) a greater probability of being cuckolded. Nevertheless, the number of fledglings was significantly greater for polygynous males. Based on the number of nestlings that returned for subsequent breeding seasons, however, the reproductive success of monogamous and polygynous males did not differ significantly. These data raise the question as to why males attempt polygyny. Received: 16 August 1999 / Received in revised form: 15 March 2000 / Accepted: 18 March 2000     

Risk taking during parental care: a test of three hypotheses applied to the pied flycatcher

According to life-history theory, there will often be a conflict between investment in current versus future reproduction. If a predator appears during breeding, parents must make a compromise between ensuring the growth and survival of offspring (nest defence, feeding and brooding of young), and reducing the risk of predation to ensure their own survival. We model three hypotheses for the outcome of this conflict which are particularly relevant for altricial birds. They are not mutually exclusive, but focus on different costs and benefits. (1) Parental investment is determined by the parents’ own risk of predation. This hypothesis predicts that a lone parent should take smaller risks than a parent that has a mate. (2) Parental investment is related to the reproductive value of the offspring: Parents are predicted to take greater risks for larger broods, larger-sized or older offspring. (3) Finally, we present the new hypothesis that parental investment is related to the harm that offspring would suffer during a period of no parental care (incubation, brooding, feeding). This hypothesis predicts that parents should take greater risks for younger offspring, or for offspring in poorer condition, because the marginal benefit of parental care is largest in such cases. Hence, one may also expect that lone parents should take greater risks than two parents because their offspring are more in need of care. We tested these hypotheses on the pied flycatcher (Ficedula hypoleuca) by presenting a stuffed predator of the parents (a sparrowhawk, Accipiter nisus) close to the nest when parents were feeding the young. Risk taking was measured as the time that elapsed until the first visit to the nest. Most support was found for the ‘‘harm to offspring’’ hypothesis. Previous studies have usually measured the intensity of nest defence against typical nest predators, and have found evidence for the ‘‘reproductive value of offspring’’ hypothesis. However, our model predicts that the importance of the reproductive value of the offspring should decrease relative to the harm that offspring would suffer if they were not cared for when the predator type changes from a nest predator to a predator of adults, and when conditions for breeding turn from good to bad. Received: 13 April 1995/Accepted after revision: 11 March 1996     

Why do female pied flycatchers mate with already mated males: deception or restricted mate sampling?

The polygyny threshold model suggests that females make an optimal choice between mated and unmated males. However; in birds in which males provide parental care, the fitness of secondary females is often lower than expected from this model. This has been explained by the deception hypothesis, which states that males hide their mating status and deceive females into polygyny. Yet there is no direct evidence that secondary females are unaware of male mating status when they settle. Alternatively, females settle with mated males as a result of mate competition and costs of searching. We used videofilming at nestboxes defended by males to study mate sampling of female pied flycatchers Ficedula hypoleuca. The females visited on average only 2.74 males (range 1–8, n = 43). Most (16 of 19) of the polygynous matings occurred because females had only visited mated males, or the unmated males visited became occupied by competitors during the sampling period. Among females that could choose between both mated and unmated males, the majority (13 of 16) settled with unmated males. These results lend little support to the deception hypothesis but are consistent with the view that females are able to detect male mating status but sometimes settle with mated males because of cost of searching. Prospecting females seemed willing and able to suffer the cost of fighting with aggressive primary females in the males' secondary territory if no alternative mating options were available. In addition to male mating status, females took male quality (plumage colour, age) into account in mate choice but the former appeared to be the more important. Correspondence to: T. Slagsvold     

Local survival of pied flycatcher males and females in a pollution gradient of a Cu smelter

Survival is one of the most central population measures when the effects of the pollution are studied in natural bird populations. However, only few studies have actually measured rigorous survival estimates on adult birds. In recent years there has been a methodological advance in survival analyses by mark-recapture models. We modelled local survival (including mortality and emigration) with the program MARK in a population of a small insectivorous passerine bird, the pied flycatcher (Ficedula hypoleuca), around a point source of heavy metals. The local survival of females in the polluted area was about 50% lower than in the other areas. Males, however, survived relatively well in the heavily polluted area, but showed somewhat lower survival in the moderately polluted area. Different pollution effects between two sexes might be due to pollution-related differences in reproductive effort in females and males, and/or more intensive uptake of heavy metals by laying females.     

Does female aggression prevent polygyny? An experiment with pied flycatchers (Ficedula hypoleuca)

The female aggression hypothesis states that resident females may be able to prevent polygyny by behaving aggressively towards intruding females. A critical test of the hypothesis is to provide prospecting females with a choice between displaying mated males some of which have initial mates with artificially reduced levels of aggressiveness. Here we present a mate choice experiment on pied flycatchers Ficedula hypoleuca. The species is a cavity nester, and resident females were prevented from behaving aggressively by enclosing them within their own nestboxes: narrowing the entrance hole so that they could not escape but could still let their head out and have some contact with their mate. This treament had only a minor influence on male behaviour. We studied whether the experimental males were better able to attract a new female than a control group of mated males. Four predictions from the female aggression hypothesis were supported. (1) Mating success of control males was positively related to the distance between their primary and secondary territory. (2) For experimental males, mating success was unrelated to interterritorial distance. (3) Experimental males had higher mating success than control males when the interterritorial distance was short but (4) not when it was long. Experimental males had much lower mating success than unmated males, as would be expected if prospecting females are able to discover male mating status from cues other than visits by primary females to their mates' secondary nest sites. Received: 5 January 1998 / Accepted after revision: 30 December 1998     

Costs of overlapping reproduction and moult in passerine birds: an experiment with the pied flycatcher

The process of moult in birds requires the investment of substantial amounts of energy and nutrients in feather production and attendant processes. Flight performance may be reduced during the moult of the wing feathers, and moulting birds may suffer from an increased predation risk. These factors may explain why the moult is usually separated in time from other energetically demanding processes, such as reproduction. In this study, we investigated the importance of the temporal separation of moult from breeding activities in the pied flycatcher Ficedula hypoleuca. We induced a moult-breeding overlap by removing the two innermost primaries on both wings, thus imitating the natural loss of these feathers during the initial stage of the moult. The experiment probably did not stimulate feather regrowth, but may have reduced flight performance. Just before fledging of the young, manipulated males and females, as well as the fledglings, had a lower body condition than control birds. The return rate of adult males in the year following the manipulation was significantly lower for males in the manipulated group than for control males. The return rate of females was lower than that of males, but there was no difference between the two female groups. The number of nestlings recruited in the year after the manipulation was significantly lower for the group with an induced moult-breeding overlap than for the control group. The reproductive performance in recruited and returning old females was independent of the manipulation, and in returning adults and recruits the feather quality in terms of number of barbs/mm was independent of the manipulation. These results suggest that a moult-breeding overlap induces fitness costs in terms of reduced recruitment rate and adult survival in a long-distance migrant. Received: 17 September 1997 / Accepted after revision: 23 February 1998     

Reproductive Parameters of Adult Birds and Morphophysiological Characteristics of Chicks in the Pied Flycatcher (<Emphasis Type="Italic">Ficedula hypoleuca</Emphasis> Pall.) in Technogenically Polluted Habitats

Effects of toxic emissions (heavy metals and sulfur dioxide) on reproductive parameters of adult pied flycatchers (Ficedula hypoleuca Pall.) and morphophysiological characteristics of their progeny have been studied in the vicinity of the Middle Ural Copper-Smelting Plant. In polluted areas, the fecundity of adult birds is lower, mortality among the progeny is higher, and changes in the physiological parameters of birds are observed. The effects of toxic load are better manifested in nestlings than in adult birds. They include an increase in the liver index, the reduction of hemoglobin concentration, and an increase in the proportion of immature erythrocytes in the peripheral blood. The proportion of anemic birds also increases. The weakening of nestlings facilitates their infestation by the larvae of parasitic flies. Changes in the differential blood count of nestlings reflect the combined impact of toxic pollutants and parasites.     

Extra-pair paternity and male characteristics in the pied flycatcher

The pied flycatcher (Ficedula hypoleuca) is sexually dichromatic with extreme variation in male plumage coloration. The benefit for males of having black plumage is controversial, and few studies have found evidence for a sexual selection benefit of being black rather than brown. However, blacker males may be better able to achieve extra-pair fertilizations (EPFs), which may be an important component of sexual selection. We studied the role of EPFs in sexual selection in the pied flycatcher by establishing a set-up where two males with different back coloration (blacker vs browner) bred simultaneously near each other. DNA fingerprinting analysis revealed that 11% of offspring resulted from EPFs, and that 22% of broods included extra-pair young (EPY) among 36 nests containing 223 nestlings. We found no evidence that browner males suffered more often from EPFs than blacker males. There was no correlation of male or female morphology or age with EPF frequency. However, breeding pairs with low genetic similarity had EPY in their nests significantly more often. Thus we argue that females paired with genetically dissimilar males may try to avoid the effects of extreme outbreeding by seeking extra-pair copulations (EPCs). Alternatively, incompatibility between genetically dissimilar mates may simply expose females to more extra-pair copulations.     

Begging affects parental effort in the pied flycatcher, Ficedula hypoleuca

It has been suggested that nestlings use begging to increase their share of parental resources at the expense of current or future siblings. There is ample evidence that siblings compete over food with nestmates by begging, but only short-term effects of begging on parental provisioning rates have been shown. In this study, we use a new experimental design to demonstrate that pied flycatcher (Ficedula hypoleuca) nestlings that beg more are able to increase parental provisioning rates over the major part of the nestling period, thus potentially competing with future siblings. Parents were marked with microchips so that additional begging sounds could be played back when one of the parents visited the nest. By playing back begging sounds consistently at either male or female visits, a sex difference in provisioning rate that lasted for the major part of the nestling period was induced. If each parent independently adjusts its effort to the begging intensity of nestlings, begging may also be the proximate control mechanism for the sexual division of labour. Received: 24 January 1997 / Accepted after revision: 30 August 1997     

Female reactions to male absence after pairing in the pied flycatcher

Mating with an already mated pied flycatcher (Ficedula hypoleuca) male is costly for a female. Two hypotheses explain why some females still mate with already mated males. The deception hypothesis suggests that some females mate with already mated males since it is difficult to assess perfectly the mating status of a male with separate territories (polyterritoriality). The search cost hypothesis states that females are aware of male mating status but the costs of searching for an unmated male exceed costs associated with the status of secondary female. One potential cue that could disclose a male's mating status is the existence of brief visits to the primary territory by polyterritorial males. To mimic such visits I removed the male from the territory for 60 min soon after female settlement. Only few females abandoned their mates as a consequence of male removal even though they had available unmated males close by. This result is most consistent with the deception hypothesis. Females did not use occasional male absence as a cue to avoid presumably polyterritorial males and in this respect they were not perfect in assessing males.