Experimental ghrelin administration affects migratory behaviour in a songbird.

Twice a year, billions of birds take on drastic physiological and behavioural changes to migrate between breeding and wintering areas. On migration, most passerine birds regularly stop over along the way to rest and refuel. Endogenous energy stores are not only the indispensable fuel to complete long distance flights, but are also important peripheral signals that once integrated in the brain modulate crucial behavioural decisions, such as the decision to resume migration after a stopover.

Using breath δC analysis to determine the effects of dietary carbohydrate and protein on glucose and leucine oxidation at rest in the yellow-rumped warbler (Setophaga coronata).

Fat is the major fuel for migratory flight of birds, but protein is also catabolized. Flight range could be reduced if protein is used too quickly from muscles and organs, and it is important to understand factors that influence protein catabolism. Previous correlative studies suggested high protein diets may increase protein use in flight, although a wind tunnel study with yellow-rumped warblers (Setophaga coronata) did not support this relationship.

Reproductive consequences of an extra long-term sperm storage organ.

Background: Sperm storage plays a key role in the reproductive success of many sexually-reproducing organisms, and the capacity of long-term sperm storage varies across species. While there are theoretical explanations for why such variation exists, to date there are no controlled empirical tests of the reproductive consequences of additional long-term sperm storage. While Dipterans ancestrally have three long-term sperm organs, known as the spermathecae, Drosophila contain only two.

Elevated incubation temperature improves later-life swimming endurance in juvenile Chinook salmon, Oncorhynchus tshawytscha.

The effect of incubation and rearing temperature on muscle development and swimming endurance under a high-intensity swimming test was investigated in juvenile Chinook salmon (Oncorhynchus tshawytscha) in a hatchery experiment. After controlling for the effects of fork length (L ) and parental identity, times to fatigue of fish were higher when fish were incubated or reared at warmer temperatures. Significant differences among combinations of pre- and post-emergence temperatures conformed to 15-15°C > 15-9°C > 9-9°C > 7-9°C > 7-7°C in 2011 when swimming tests were conducted at 300 accumulated temperature units post-emergence and 15-9°C > (7-9°C = 7-7°C) in 2012 when swimming tests were conducted at an L of c.

Stopover refuelling, movement and departure decisions in the white-throated sparrow: The influence of intrinsic and extrinsic factors during spring migration.

Differential migration timing between sex or age classes is an example of how migratory movement strategies can differ among subgroups within a population. However, in songbirds, evidence for intrinsic differences in en route migratory behaviour is often mixed, suggesting that the local environmental context may play a role in accentuating or diminishing patterns. We evaluated how multiple intrinsic and extrinsic variables influenced refuelling rates, local movement behaviour and departure decisions in the white-throated sparrow Zonotrichia albicollis during spring migration.

Size-selective fishing and the potential for fisheries-induced evolution in lake whitefish.

The long-term evolutionary effects of fishing on maturation schedules can depend on gear type, the shape of the gear type's size-selectivity function, and the size and age structure of a population. Our goal was to better understand how environmentally induced differences in somatic growth influence the evolutionary effects of size-selective fisheries, using lake whitefish () in Lake Huron as a case study. Using a state-dependent optimization model of energy allocation parameterized for lake whitefish, we show that fishing with gill nets (bell-shaped selectivity) and trap nets (sigmoid-shaped selectivity) can be potent agents of selection on size thresholds for maturity.

Female-biased dimorphism in size and age at maturity is reduced at higher latitudes in lake whitefish Coregonus clupeaformis.

Female-biased sexual dimorphism in size at maturity is a common pattern observed in freshwater fishes with indeterminate growth, yet can vary in magnitude among populations for reasons that are not well understood. According to sex-specific optimization models, female-biased sexual size dimorphism can evolve due to sexual selection favouring earlier maturation by males, even when sexes are otherwise similar in their growth and mortality regimes. The magnitude of sexual size dimorphism is expected to depend on mortality rate.

Egg size and the adaptive capacity of early life history traits in Chinook salmon ().

Offspring traits are greatly influenced by maternal effects, and these maternal effects may provide an important pathway through which populations can adapt to changing thermal environments. We investigated the effect of egg size on the among- and within-population variation in early life history traits among introduced Great Lakes Chinook salmon () populations under varying thermal conditions. We reared Chinook salmon from three populations in a common-garden hatchery study at 6.

Adcyap1 polymorphism covaries with breeding latitude in a Nearctic migratory songbird, the Wilson's warbler (Cardellina pusilla).

Understanding the genetic background of complex behavioral traits, showing multigenic control and extensive environmental effects, is a challenging task. Among such traits, migration is known to show a large additive genetic component. Yet, the identification of specific genes or gene regions explaining phenotypic variance in migratory behavior has received less attention.

Evidence for the secondary sexual development of the anal fin in female kokanee salmon Oncorhynchus nerka.

This study examines whether the anal fin undergoes secondary sexual development similar to other reproductive traits in salmonids. This hypothesis was tested by comparing the anal-fin size of female kokanee salmon Oncorhynchus nerka that were in the early and late stages of sexual development. Females in an advanced stage of maturation had significantly larger anal fins relative to females in an early state of maturation (+4-7%), indicating that the anal fin undergoes secondary sexual development.

Time scale matters: genetic analysis does not support adaptation-by-time as the mechanism for adaptive seasonal declines in kokanee reproductive life span.

Seasonal declines of fitness-related traits are often attributed to environmental effects or individual-level decisions about reproductive timing and effort, but genetic variation may also play a role. In populations of Pacific salmon (Oncorhynchus spp.), seasonal declines in reproductive life span have been attributed to adaptation-by-time, in which divergent selection for different traits occurs among reproductively isolated temporal components of a population.

A genetic test of sexual size dimorphism in pre-emergent chinook salmon.

Sex differences in early development may play an important role in the expression of sexual size dimorphism at the adult stage. To test whether sexual size dimorphism is present in pre-emergent chinook salmon (Oncorhynchus tshawytscha), alevins were reared at two temperatures (10 °C and 15 °C) and sexed using the OtY1 marker on the Y-chromosome. Linear mixed models were used to test for sex differences in alevin size within families while controlling for the random effects of sire and dam nested within sire.

Protandry, sexual size dimorphism, and adaptive growth.

Adaptive growth refers to the strategic adjustment of growth rate by individuals to maximize some component of fitness. The concept of adaptive growth proliferated in the 1990s, in part due to an influential theoretical paper by Peter Abrams and colleagues. In their 1996 paper, Abrams et al.

Migration timing of female kokanee salmon Oncorhynchus nerka: diel patterns and effects of maturation state.

Diel patterns of migration and migration speed were compared between reproductive timing phenotypes in female kokanee salmon Oncorhynchus nerka. Females of varying degrees of reproductive maturation were captured on their migration route to the Meadow Creek Spawning Channel (British Columbia, Canada), were tagged with passive-integrated transponders (PIT tags) and were subsequently monitored with stationary receivers. Females showed crepuscular migration timing, with approximately equal detections at dawn and dusk.

Physiological correlates of seasonal growth patterns in lake trout Salvelinus namaycush.

Physiological correlates of seasonal growth patterns were measured in lake trout Salvelinus namaycush from two populations with contrasting diets (zooplankton-dominated diet in Louisa Lake; fish-dominated diet in Opeongo Lake). Fish in Opeongo Lake grew faster and were in better condition than fish in Louisa Lake. The most prominent biochemical difference between populations was higher citrate synthase (CS) and cytochrome c oxidase activity in the white muscle of fish from Opeongo Lake, indicating greater sustained swimming activity in this lake.

Rapid senescence in pacific salmon.

Any useful evolutionary theory of senescence must be able to explain variation within and among natural populations and species. This requires a careful characterization of age-specific mortality rates in nature as well as the intrinsic and extrinsic factors that influence these rates. We perform this task for two populations of semelparous Pacific salmon.

The interaction between reproductive lifespan and protandry in seasonal breeders.

The timing and duration of reproductive activities are highly variable both at the individual and population level. Understanding how this variation evolved by natural selection is fundamental to understanding many important aspects of an organism's life history, ecology and behaviour. Here, we combine game theoretic principles governing reproductive timing and the evolutionary theory of senescence to study the interaction between protandry (the earlier arrival or emergence of males to breeding areas than females) and senescence in seasonal breeders.

Adaptive variation in senescence: reproductive lifespan in a wild salmon population.

The antagonistic pleiotropy theory of senescence postulates genes or traits that have opposite effects on early-life and late-life performances. Because selection is generally weaker late in life, genes or traits that improve early-life performance but impair late-life performance should come to predominate. Variation in the strength of age-specific selection should then generate adaptive variation in senescence.

Timing games in the reproductive phenology of female pacific salmon (Oncorhynchus spp.).

We use a game-theoretic framework to investigate the reproductive phenology of female kokanee (Oncorhynchus nerka). As in the other semelparous species of Pacific salmon, females construct nests in gravel, spawn with males, bury their fertilized eggs, and defend their nest sites until they die several days later. Later-breeding females may reuse previous nest sites, and their digging behavior is thought to subject previously buried eggs to mortality.

Parental provisioning, nestling departure decisions and prefledging mass recession in Cassin's auklets.

We investigated how parental provisioning and nestling departure behaviour interact to produce prefledging mass recession in Cassin's auklets, Ptychoramphus aleuticus. Under our hypothesis, auklet parents are reluctant provisioners and should be increasingly likely to terminate or reduce provisioning of their single nestling as it matures. For the nestling, remaining in the nest presents a risk of losing mass (if the parent does not provision) but also a possibility of additional provisioning.