Arne Lundberg

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.

HERITABILITY AND SELECTION ON TARSUS LENGTH IN THE PIED FLYCATCHER (FICEDULA HYPOLEUCA)

The heritability estimate (±SE) for tarsus length in the pied flycatcher is 0.53 ± 0.10, based on mother‐offspring regressions. The heritability is almost the same (0.50 ± 0.22) for offspring transferred to other nests and reared by foster parents, whereas there is no resemblance (0.04 ± 0.23) between the offspring and their foster mothers. Hence, the nest environment does not affect parent‐offspring resemblance. However, a full‐sib correlation yields an estimate of the heritability twice as high as the parent‐offspring regression did, indicating that shared environment effects, which are not correlated with the tarsus length of parents, must be important. An environmental deviation due to food factors affecting tarsus length is demonstrated. The most important food factors are probably associated with 1) polygyny, which leads to reduced paternal feeding at secondary nests, 2) high breeding density, and 3) progress of the breeding season. All three are associated with reductions in offspring mean tarsus length.

Phenotypic Selection on Heritable Size Traits: Environmental Variance and Genetic Response

PHENOTYPIC SELECTION ON HERITABLE SIZE TRAITS - ENVIRONMENTAL VARIANCE AND GENETIC RESPONSE

The search cost in mate choice of the pied flycatcher

Alcock, J. 1973. Cues used in searching for food by redwinged blackbirds (Agelaius phoeniceus). Behaviour, 46, 174-188. Anderson, J. 1980. Cognitive Psychology and its Implications. San Francisco: Freeman. East, R. & Pottinger, R. 1975. Starling (Sturnus vulgaris L.) predation on grass grub (Costelytra zeelandica White, Melolonthinae) populations in Canterbury, New Zealand. N.Z.J. Agric. Res., 18, 417-452. Feare, C. 1984. The Starling. Oxford: Oxford University Press. Hollis, K. 1982. Pavlovian conditioning of signal-centred action patterns and autonomic behaviour: a chronological analysis of function. Advances in the Study of Behaviour. Vol. 12 (Ed. by J. Rosenblatt, R. Hinde, C. Beer & M. Busnell), pp. l~a4. London: Academic Press. Johnston, T. 1982. Selective costs and benefits in the evolution of learning. In: Advances in the Study of Behaviour. Vol. 12 (Ed. by J. Rosenblatt, R. Hinde, C. Beer & M. Busnell), pp. 65-106. London: Academic Press. Kamil, A. & Yoerg, S. 1982. Learning and foraging behavior. In: Perspectives in Ethology. Vol. 5 (Ed. by P. Bateson & P. Klopfer), pp. 325-364. New York: Plenum Press. Miller, R., Tamm, S., Sutherland, G. & Gass, C. 1985. Cues of orientation in hummingbird foraging: color and position. Can. J. Zool., 63, 18-21. Tinbergen, J. 1976. How starlings (Sturnus vulgaris L.) apportion their foraging time in a single-prey situation on a meadow. Ardea, 64, 155-170. Tinbergen, J. 1981. Foraging decisions in starlings (Sturnus vulgaris L.). Ardea, 69, I~i7. Tinbergen, J. & Drent, R. 1980. The starling as a successful forager. In: Bird Problems in Agriculture (Ed. by E. Wright, I. Inglis & C. Feare), pp. 8347. Croydon: British Crop Protection Council.

Inbreeding depression and male fitness in black grouse

The male lifetime lekking performance was studied, and related to inbreeding‐outbreeding in a wild population of black grouse (Tetrao tetrix) in central Finland between 1989 and 1995. Inbreeding was measured as the mean heterozygosity and mean d2 of 15 microsatellite loci. We found a significantly positive relationship between mean d2 and lifetime copulation success (LCS), while the relationship between heterozygosity and LCS was close to significant. We also found that males that never obtained a lek territory had significantly lower mean heterozygosity than males that were observed on a territory at least during one mating season in their life. Furthermore, among males that were successful in obtaining a lek territory, LCS and mean d2 were highest for those males that held central territories. We suggest that inbred males have a disadvantage (or outbred males have an advantage) in the competition for territories that may explain the relationships with LCS and inbreeding. Furthermore, the fact that mean d2 was positively correlated with LCS whereas heterozygosity was not when we restricted the analysis to territorial males, suggests that mean d2 provides more information about levels of inbreeding‐outbreeding than heterozygosity alone, and potentially highlights the effects of heterosis. To our knowledge, this is the first time that measures of inbreeding and lifetime fitness have been linked in a non‐isolated population. This is important in establishing that the relationships found in previous studies are not artefacts of low gene flow created by limited dispersal but a general feature of wild vertebrate populations.

Sexual selection in a monomorphic lek-breeding bird: correlates of male mating success in the great snipe Gallinago media

SummaryIn the lek-breeding great snipe, male morphology, behaviour, and territory features were recorded for individually marked birds on two adjacent leks. Partial correlation sshowed that male mating success, expressed as the number of female solicitations and copulations, was negatively correlated with the distance of a display territory to the lek center and positively correlated with the number of displays per unit time given by a male. No other variables were directly correlated with male matin success. Thus, central males obtain more matings than peripheral males and successful males display more per unit time than do less successful males, independently of position on the lek. Central males were found to be older than peripheral ones and were present more often on the lek. Furthermore, central males had a larger number of white tail feathers, which are usea as visual signals in the displays, but this may be explained by the fact that these males were older. It is suggested that male great snipe are subject to sexual selection mainly in behavioural and vocal cues and that this may explain the absence of size and plumage dimorphism in this species.

Microsatellite markers reveal the potential for kin selection on black grouse leks

The evolution of social behaviour has puzzled biologists since Darwin. Since Hamiltons theoretical work in the 1960s it has been realized that social behaviour may evolve through the effects of kinship. By helping relatives, an individual may pass on its genes despite negative effects on its own reproduction. Leks are groups of males that females visit primarily to mate. The selective advantage for males to join such social groups has been given much recent attention, but no clear picture has yet emerged. Here we show, using microsatellite analysis, that males but not females of a lekking bird (the black grouse, Tetrao tetrix) are genetically structured at the lek level. We interpret this structuring to be the effects of strong natal philopatry in males. This has the consequence that males on any specific lek should be more related than expected by chance as indicated by our genetic data. Our results thus suggest that kin selection is a factor that needs to be considered in the evolution and maintenance of the lek mating system in black grouse and sheds new light on models of lek evolution.

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.

Male Coloration and Species Recognition in Sympatric Flycatchers

Currently favoured views for explaining ornaments in males emphasize female preference such that females benefit from increased offspring production, good genes of the offspring, or the attractiveness of sons. Results from long-term studies in the pied flycatcher Ficedula hypoleuca suggest that factors associated with species recognition may also be important for male coloration. In sympatry the collared flycatcher F. albicollis is dominant in competition for nesting sites over the pied flycatcher. Bright pied flycatcher males resemble collared flycatcher males and suffer from interspecific interference, whereas dull and female-like males can acquire nesting sites close to those of the collared flycatcher. (A similar aggression release mechanism had previously been suggested to influence the evolution of colour differences in coral reef fishes.) Additionally, the risk of hybridization was low for the dullest pied flycatcher males, resurrecting the idea that avoiding mating with wrong species might currently be under selection. Thus interspecific effects related to species recognition can probably explain the dull plumage colour of pied flycatcher males in sympatry. In allopatry, intraspecific sexual selection for bright coloration in males seems to be weak, and even a low level of gene flow between sympatric and allopatric populations may maintain the high variation in this highly heritable trait.