What is behind the variation in mate quality dependent sex ratio adjustment? - A meta-analysis

Theory predicts that parents adjust the sex ratio of their brood to the sexually selected traits of their mate because the reproductive success of sons may be more dependent on inherited paternal attractiveness than that of daughters. Empirical studies vary in terms of whether they support the theory, and this variation has often been regarded as evidence against sex ratio adjustment or has been ascribed to methodological differences. Applying phylogenetic meta-analyses, we aimed to find biological explanations for the variation observed in songbirds. In particular, we tested the role extra-pair paternity, because infidelity occurs in the majority of these species and may reduce the adaptive value of adjusting brood sex ratio to the phenotype of the social mate. However, we found that the variation in effect sizes was unrelated to the proportion of extra-pair paternity. Thus future studies should consider that mate quality dependent sex ratio adjustment may be driven by direct (material) rather than indirect (genetic) benefits. We also tested if the effect sizes are influenced by whether the focal male trait is indeed under sexual selection as it is assumed by the sex allocation theory. We found that for male traits with proven role in sexual selection, effect sizes significantly differed from the null expectation of random production of sons and daughters. For male traits with only presumed sexual role in sexual selection, the deviation from the null expectation was less convincing, and the effect sizes were significantly smaller. This result indicates that studies that neglect the assumptions of the hypotheses concerned, may lead to the underestimation of the mean effect size and, eventually, false conclusions

COMMON GUILLEMOTS URIA AALGE DIFFERENTIATE THEIR NICHE TO COEXIST WITH COLONIZING GREAT CORMORANTS PHALACROCORAX CARBO

Colonization of new species into an established community generally results in interspecific competition over resources between the colonist and existing members of the community. Interspecific competition has been suggested to influence extinction rates, population dynamics, community structure, niche differentiation and evolution. In this study, we observe possible interspecific competition over breeding sites resulting in niche differentiation and coexistence of Great Cormorants Phalacrocorax carbo and Common Guillemots Uria aalge in a seabird cliff community. In Sweden, Great Cormorants have naturally increased and expanded during the last two decades. Here, we show that most Common Guillemots previously bred on cliff ledges with high roof heights before the studyisland was colonized by Great Cormorants, but are now mainly found breeding on cliff ledges with lower roof heights. A temporary decline in the Common Guillemot population coincided with the colonization event and we discuss the potential for this decline to be caused by increased nest-site competition combined with high nest-site fidelity

COMMON GUILLEMOTS URIA AALGE DIFFERENTIATE THEIR NICHE TO COEXIST WITH COLONIZING GREAT CORMORANTS PHALACROCORAX CARBO

Colonization of new species into an established community generally results in interspecific competition over resources between the colonist and existing members of the community. Interspecific competition has been suggested to influence extinction rates, population dynamics, community structure, niche differentiation and evolution. In this study, we observe possible interspecific competition over breeding sites resulting in niche differentiation and coexistence of Great Cormorants Phalacrocorax carbo and Common Guillemots Uria aalge in a seabird cliff community. In Sweden, Great Cormorants have naturally increased and expanded during the last two decades. Here, we show that most Common Guillemots previously bred on cliff ledges with high roof heights before the studyisland was colonized by Great Cormorants, but are now mainly found breeding on cliff ledges with lower roof heights. A temporary decline in the Common Guillemot population coincided with the colonization event and we discuss the potential for this decline to be caused by increased nest-site competition combined with high nest-site fidelity

Fågelinventering Bästeträsk : Delrapport 2019

Syftet med denna inventering har varit att öka kunskaperna om fågelförekomsten inom Bästeträsk liksom områdets betydelse för fåglar. Denna rapport är en delrapport som kortfattat redovisar delar av resultaten från inventeringar utförda under maj och juni 2019. En fortsättning av inventeringenhar genomförts efter den senaste inventeringen som redovisas i denna rapport och det pågår för närvarande undersökningar utanför häckninsperioden för fåglar och där havskustennärmast sjön ingår. Resultat och innehåll i denna rapport ska därför ses som en första del i att bättre kunna beskriva fågelförekomsten i och omkring Bästeträsk

Fågellivet vid Bästeträsk : Invnetering av fåglar 2019-2020

Uppdraget har varit begränsat till att undersöka fågellivet inom sjön Bästeträsk varför in-venteringarna har fokuserats till sjön, men även den närmaste strandzonen har ingått i undersökningen (0-150 m från strandlinjen). Dispens från reservatsföreskrifterna att kunna beträda tillträdesförbud inom fågelskyddsområde har sökts och erhållits. Inventeringarna har utförts under åren 2019 och 2020 . Under 2019 genomfördes under-sökningar vid 3 tillfällen i maj och därefter vid 1-2 tillfällen per följande månader. Under 2020 genomfördes 1-4 inventeringar per månad under januari – augusti utom februari då ingen inventering genomfördes på grund av väderförhållanden. Totalt omfattar studien 25 inventeringstillfällen varav 10 st under 2019 och 15 st under 2020. Delar av sjön och strandpartierna främst i södra delen, inklusive öarna har även inventerats med hjälp av ka-not. Vid varje enskilt inventeringstillfälle har 1 – 3 personer deltagit. Inga undersökningar har skett under natten. Den totala inventeringstiden består av drygt 350 fälttimmar förde-lat på 25 tillfällen och 47 personbesök. Inventeringsområdet har utgjorts av ungefär 665 hektar vattenyta och 400 hektar landyta. Inventeringarna i fält har utförts av Måns Hjernquist, Clas Hermansson, Per Smitterberg, Mia Holmebrant, Mårten Hjernquist, Sivert Söderlund, Annika Jörnemark och Jörgen Petersson. Samtliga är verksamma i Gotlands Ornitologiska Förening

Living in a Variable Environment : Reproductive Decisions in Wild Bird Populations

In nature, environments are often variable and heterogeneous influencing ecological and evolutionary processes. This thesis focus on how animals interact with their environment and how that affects the reproductive decisions they make. Using empirical data collected from wild collared flycatcher populations, experiments and molecular approaches I try to unveil some of these relationships and the evolutionary, ecological and conservation implications of these findings are discussed. Firstly, collared flycatchers were shown to use breeding densities of their own and other species using similar resources when assessing costs and benefits associated to breeding in specific habitats. However, species will vary in how informative they are, and the worst competitor – with whom you overlap most in resources needs – also provides the best source of information. Collared flycatcher parents will also benefit differentially from investments in sons and daughters due to habitat characteristics and dispersal differences between the sexes. Here, I show that they will produce more of the sex that will give the highest expected fitness return given the environment they are in. These results also provide a reciprocal scenario to Clark's (1978) classical study of sex ratio adjustment in relation to local resource competition (LRC), as more of the natal philopatric sex is produced when LRC is low. Secondly, the effect of elaborated ornaments on paternity in the socially monogamous collared flycatcher was shown to be of more importance in areas where the intensity of intra- and intersexual conflicts are expected to be elevated. Hence, ornamentation by environmental interactions determines paternity, illustrating that sexual selection through extra-pair paternity is context dependent. Finally, even though the collared flycatcher populations that this thesis is based on have been studied on their breeding grounds for more then 25 years, we know little of where they are when they are not breeding. Here, stable isotope signatures in winter-grown feathers suggests that they may spend their winter with their breeding ground neighbours and do so repeatedly over years. Differences between breeding populations at this small scale should have many impactions for evolutionary and ecological processes as it will, for example, determine with whom individuals interact throughout their life