Osmo Rätti

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.

A TRADE-OFF BETWEEN CURRENT REPRODUCTION AND MOLT IN THE PIED FLYCATCHER - AN EXPERIMENT

1. Mechanisms causing costs of reproduction in birds are poorly understood. Here we focus on the renewing of feathers (= moult) which may be a possible physiological link between successive breeding attempts. 2. We performed clutch size manipulations to study whether the reproductive effort of the Pied Flycatcher (Ficedula hypoleuca) has any effect on the initiation and progress of the moult in the late nesting period. 3. The absolute timing of breeding did not affect the onset of parents moult, i.e. latebreeding individuals did not start moulting before nestlings were fledged more frequently than early ones. This indicates that moult was closely related to the breeding schedule of each individual bird. 4. The timing of moult was both sex and age related. Males and young birds were more likely to start moulting during the nestling period than females and older birds. 5. Both females with large original clutches and females with enlarged clutches delayed the onset of moult. This suggests a brood size-dependent regulation of moult. 6. We suggest that a trade-off between moult and current reproduction could be one possible mechanism causing costs of reproduction in birds.

Population genetic structure of male black grouse (Tetrao tetrix L.) in fragmented vs. continuous landscapes

We investigated the association of habitat fragmentation with genetic structure of male black grouse Tetrao tetrix. Using 14 microsatellites, we compared the genetic differentiation of males among nine localities in continuous lowland habitats in Finland to the genetic differentiation among 14 localities in fragmented habitats in the Alps (France, Switzerland and Italy). In both areas, we found significant genetic differentiation. However, the average differentiation, measured as θ, was more than three times higher in the Alps than in Finland. The greater differentiation found in the Alps is probably due to the presence of mountain ridges rising above natural habitats of the species, which form barriers to gene flow, and to a higher influence of genetic drift resulting from lower effective sizes in highly fragmented habitats. The detection of isolation by distance in the Alps suggests that gene flow among populations does occur. The genetic variability measured as gene diversity HE and allelic richness A was lower in the Alps than in Finland. This could result from the higher fragmentation and/or from the fact that populations in the Alps are isolated from the main species range and have a lower effective size than in Finland. This study suggests that habitat fragmentation can affect genetic structure of avian species with relatively high dispersal propensities.

BLOOD PARASITES AND MALE FITNESS IN THE PIED FLYCATCHER

In vertebrates the effect of parasites on host ecology has almost been ignored. Recently the view that well-adapted parasites do not harm their hosts has been challenged and there is growing evidence that parasites do have a present-day effect on a great variety of host fitness components. The pied flycatcher is a small migratory passcrine bird. Any decrease in condition caused by disease should affect its ability to cope with physical demands of migration. Here we examine whether blood parasites have any effect on male arrival time. Males infected with Trypanosoma arrived on average 2 days later than males with no Trypanosoma infection. Infected males also had shorted tails and tended to have shorter wings. By contrast, there was no difference in male arrival time between males infected with Haemoproteus and healthy males. It seems that Trypanosoma infection lowered male condition and consequently the ability to moult and migrate. The difference in length of feathers may have generated the difference in arrival times. Early arrival is highly important for males, since only the first males become polygynous and breeding prospects deteriorate rapidly with any delay in egg laying. Estimated reduction in breeding success for infected males was about 20%.

Sindbis Virus Infection in Resident Birds, Migratory Birds, and Humans, Finland

Resident grouse may be involved in the epidemiology of SINV in humans.

Orthomyxo-, paramyxo- and flavivirus infections in wild waterfowl in Finland

BackgroundScreening wild birds for viral pathogens has become increasingly important. We tested a screening approach based on blood and cloacal and tracheal swabs collected by hunters to study the prevalence of influenza A, paramyxo-, flavi-, and alphaviruses in Finnish wild waterfowl, which has been previously unknown. We studied 310 blood samples and 115 mixed tracheal and cloacal swabs collected from hunted waterfowl in 2006. Samples were screened by RT-PCR and serologically by hemagglutination inhibition (HI) test or enzyme-linked immunosorbent assay (ELISA) for influenza A (FLUAV), type 1 avian paramyxo-(APMV-1), Sindbis (SINV), West Nile (WNV) and tick-borne encephalitis (TBEV) virus infections.ResultsFLUAV RNA was found in 13 tracheal/cloacal swabs and seven strains were isolated. Five blood samples were antibody positive. Six APMV-1 RNA-positive samples were found from which four strains were isolated, while two blood samples were antibody positive. None of the birds were positive for flavivirus RNA but three birds had flavivirus antibodies by HI test. No antibodies to SINV were detected.ConclusionWe conclude that circulation of both influenza A virus and avian paramyxovirus-1 in Finnish wild waterfowl was documented. The FLUAV and APMV-1 prevalences in wild waterfowl were 11.3% and 5.2% respectively, by this study. The subtype H3N8 was the only detected FLUAV subtype while APMV-1 strains clustered into two distinct lineages. Notably, antibodies to a likely mosquito-borne flavivirus were detected in three samples. The screening approach based on hunted waterfowl seemed reliable for monitoring FLUAV and APMV by RT-PCR from cloacal or tracheal samples, but antibody testing in this format seemed to be of low sensitivity.

NO EVIDENCE FOR EFFECTS OF BREEDING DENSITY AND MALE REMOVAL ON EXTRAPAIR PATERNITY IN THE PIED FLYCATCHER

Abstract Molecular methods have brought new insight to the study of mating patterns. Extrapair fertilizations (EPF) have proven to be widespread among bird species irrespective of social relationships. Ecological factors, such as breeding density and synchrony, have been suggested as contributors to variation in EPF rates. Absence of a male during the female fertile period may also increase the probability of EPFs. In this study, we examined experimentally whether breeding density and male absence before egg-laying influence the EPF rate in Pied Flycatchers (Ficedula hypoleuca). DNA fingerprinting revealed that 4.4% (10/225) of nestlings were the result of EPFs and 7.0% (3/43) of broods included at least one offspring sired by a male other than that attending the nest. We did not find any evidence of higher EPF rate with higher breeding density as stated by the density hypothesis. Contrary to expectation, EPFs were more frequent, though not quite statistically significantly, at low breeding density: all three EPF nests were found in low-breeding-density areas. There was no evidence that EPF rate was affected by a 4 h male removal. In all cases of EPF, an old female was mated with a yearling male, which suggests that older females mated with browner yearling males may have adjusted their initial mate choice through EPCs to acquire indirect genetic benefits. Pied Flycatcher females may be constrained to accept a mate of lower than preferred quality, especially at low breeding density, due to the cost of searching for alternative males.

Properties of food loads delivered to nestlings in the pied flycatcher : effects of clutch size manipulation, year, and sex

Abstract Experimental manipulation of the number of altricial offspring is supposed to modify parental expenditure in birds. In addition to the observed increase in parental feeding rate, it is also possible that the choice of prey or the size of load may change with the changing demand for food. Sexual differences in the provisioning response are also expected, on the basis of earlier studies. We examined the effect of brood size manipulation on choice of prey brought to nestlings and load size in the pied flycatcher. The composition and size of loads differed between years, possibly depending on varying availability of different prey types. Males responded to brood size enlargement by gathering heavier loads, whereas females showed no response. The alteration of load size in males was not explained by a larger number of prey items or mean prey size, but was a combination of these components. It is likely that males also increased their work rate in response to increased food demand at the nest. The absence of response in females might be because they are unable to increase work rate any further, or because food delivery rate in females can not be optimized by changing load properties.

Parasitized grouse are more vulnerable to predation as revealed by a dog-assisted hunting study

Sublethal parasite infections may cause mortality indirectly by exposing the host to predation. Intestinal helminth parasites are common in forest grouse, the capercaillie Tetrao urogallus, the black grouse Tetrao tetrix and the hazel grouse Bonasa bonasia, and these grouse are valuable prey for several species of predators. We evaluated the hypothesis that parasite infection makes the host more vulnerable to predation by comparing the intestinal parasite infection status of grouse hunted with a trained dog to that of grouse hunted without a dog. Cestode infections were more common in grouse hunted with a dog supporting the hypothesis. Cestodes were mostly parasites of juvenile grouse but even among juveniles only, cestodes were more prevalent in dogassisted hunting bag. The results suggest that mammalian predators could prey more selectively on parasitized individuals and that intestinal parasites may contribute to the high mortality of juvenile grouse through increased predation.

Low male return rate due to clutch enlargements in the pied flycatcher (Ficedula hypoleuca)

Abstract:Increased investment in reproduction during current breeding event may entail future fitness costs. Even though a wide array of both theoretical and empirical work has been devoted to solve the problem of optimal reproductive rate, evidence for costs of reproduction has been equivocal. In the present study we examined the survival of pied flycatcher parents after a clutch size manipulation where we altered clutch size with one or two eggs. We monitored return rates and dispersal of parents during subsequent years after manipulation. An artificial increase in reproductive effort caused lowered return rates of males. Results on breeding dispersal did not support the explanation that observed low return rate was due to differences in dispersal. Thus, it seemed that low return rate of males with increased reproductive effort was due to lower local survival. No survival cost on females was evident, but return rate of females was too low for a proper test. An analysis on reproductive success revealed t...