Rauno V. Alatalo

Why do pied flycatcher females mate with already-mated males?

Abstract The contribution of the pied flycatcher Ficedula hypoleuca male in parental care was studied to examine why some females mate with already-mated males. No difference in feeding rate was found between older and yearling monogamous males, when comparing nests at the same time. Monogamous and primary females were helped significantly more in parental care by the male than were secondary females of polygynous males. Females could only partly compensate for the absence of a male and of nestlings were reduced in nests with low male assistance. Differences in mate and territory quality were far too slight to make it advantageous for females to choose already-mated males instead of mating with monogamous males. We suggest that males, by being polyterritorial, deceive females into accepting polygyny; and females can be deceived since they do not have time to find out the marital status of males.

Biometry, habitat distribution and breeding success in the Pied Flycatcher Ficedula hypoleuca

Pied Flycatcher Ficedula hypoleuca Pall. populations in deciduous and coniferous habitats around Uppsala, Central Sweden, were compared. In deciduous as compared to coniferous habitat, males, but not females, were larger, territories were occupied and egg laying started one week earlier, and final breeding success was higher. The size-related assortment of individuals upon the two habitats was interpreted as the outcome of competitive interactions. This finding and the lower reproductive success in the less preferred habitat are in accordance with Fretwells ideal despotic distribution model.

Extra-pair copulations and mate guarding in the polyterritorial pied flycatcher, Ficedula hypoleuca

1. Seven out of 24 observed copulations (= 29% ) in the pied flycatcher were extra-pair copulations (EPCs). There was no significant difference between EPCs and pair copulations (PCs) with respect to timing and duration, possibly indicating that both are equally successful. Thus, proportion of copulations may reflect share of paternity. 2. Females usually do not solicit EPCs and often try to avoid them. We cannot find that females have much to gain from EPCs, while attempts to resist forced copulations may impose some costs. The fact that EPCs still are rather frequent suggests that it might be cheaper for a female to accept an EPC than to resist it. 3. Males spend much of their time mate guarding but the distance between pair members is longer for polyterritorial males than for monoterritorial males. Still, we cannot find any significant differences in risks or possibilities of EPCs between males of different mating status. However, the relaxed mate guarding by polyterritorial males suggests that these males might take higher risks, and they also suffer more territory intrusions. 4. It is most likely that male reproductive strategies are not maintained as a frequency-dependent mixed ESS with equal pay-offs for all paired males. Instead, male strategies are conditional on phenotype and breeding circumstances.

Hybridization between Pied and Collared Flycatchers—sexual selection and speciation theory

The Pied Flycatcher Ficedula hypoleuca and the Collared Flycatcher F. albicollis hybridize frequently on the islands of Gotland and Öland in the Baltic. Hybrids have highly reduced fertility, but introgression is likely to occur. Mating is incompletely species‐assortative and mixed pairs are common. In Central Europe, Pied Flycatcher males are brown in areas of sympatry, and thus have less resemblance to the black Collared Flycatcher males. It has been suggested that females could use male colour to increase the probability of assortative mating, and hence that a speciation process by reinforcement might be taking place. However, we found no indications that the colour of male Pied Flycatchers had an influence on their risk of disassortative mating, and therefore reinforcement probably cannot explain the geographical pattern of colour variation in Pied Flycatcher males. The song and the white collar of Collared Flycatcher males are features more likely to serve in species recognition. The songs of the two species differ greatly, but in areas of sympatry, “mixed” singing by Pied Flycatcher males was common, and this is likely to increase the risk of hybridization. It seems that interactions between the two species are far more complex than predicted by the theory of speciation by reinforcement.

The sexy son hypothesis: data from the pied flycatcher Ficedula hypoleuca

Abstract The sexy son hypothesis has been proposed as a possible explanation for polygyny in territorial birds. Females mated with polygynous males are assumed to derive benefits in future generations through their ‘sexy’ sons, and hence they can afford to produce fewer offspring than simultaneously breeding monogamous females, the polygyny threshold thus being reduced. In the pied flycatcher, secondary females are not fully aided by males in feeding the nestlings, and they produce only 65% as many fledglings as do simultaneous monogamous and primary females. We have proposed male deception through polyterritoriality as the explanation for females ending up as secondary females, while some authors have advocated the sexy son hypothesis as an alternative. However, secondary females do not achieve benefits in future generations in this species. Repeatability of male mating status is far too low to grant any significant benefits through grandsons. In fact, offspring hatched in secondary female nests suffer from food shortage and therefore are of poor phenotypic quality with low fledging weight and short tarsus length. Therefore they are likely to enjoy lower reproductive success than offspring born in monogamous nests, as is illustrated by data on the relation between lifetime reproductive success and tarsus length. Altogether the applicability of the sexy son hypothesis is limited since it is based on the unrealistic assumption of relatively high heritability for a character with great influence on male fitness.

Fluctuating asymmetry and copulation success in lekking black grouse

In lekking black grouse, Tetrao tetrixmales at the centre of the leks obtain more copulations than males at the edges. We found that males with territories at the edge of the lek obtained fewer matings and also have the most asymmetric tarsi. However, when considering the tail ornament (the lyre) no correlation between asymmetry and mating success was found. Although females are unlikely to select males on the basis of tarsus symmetry, asymmetry in this trait may reflect male condition. We suggest that males in poor condition, as reflected by higher levels of fluctuating asymmetry in the tarsi, do not achieve central positions on the lek arena. This would account for the lower success of males with higher levels of fluctuating tarsus asymmetry.