Group size modulates time budget and foraging efficiency in captive Skylarks, Alauda arvensis

Powolny, Thibaut; Éraud, Cyril; Bretagnolle, Vincent

doi:10.1007/s10336-011-0764-4

Cited by 9 publications

(11 citation statements)

References 39 publications

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“…This anti-predator response can be related to the group-living strategy adopted by this species outside the breeding season. Skylarks are highly gregarious both during winter and migration, hence vigilance time in skylarks is unsurprisingly related to group-size [48]. It is worth noting that our current results are opposed to the predictions that could be made from the studies of Butler et al .…”

Section: Discussioncontrasting

confidence: 99%

Sex-Related Differences in the Trade-Off between Foraging and Vigilance in a Granivorous Forager

et al. 2014

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The relationship between intake rate and food density can provide the foundation for models that predict the spatiotemporal distribution of organisms across a range of resource densities. The functional response, describing the relationship between resource density and intake rate is often interpreted mechanistically as the relationships between times spend searching and handling. While several functional response models incorporate anti-predator vigilance (defined here as an interruption of feeding or some other activity to visually scan the environment, directed mainly towards detecting potential predators), the impacts of environmental factors influencing directly anti-predator vigilance remains unclear. We examined the combined effects of different scenarios of predation risk and food density on time allocation between foraging and anti-predator vigilance in a granivorous species. We experimentally exposed Skylarks to various cover heights and seed densities, and measured individual time budget and pecking and intake rates. Our results indicated that time devoted to different activities varied as a function of both seed density and cover height. Foraging time increased with seed density for all cover heights. Conversely, an increased cover height resulted in a decreased foraging time. Contrary to males, the decreased proportion of time spent foraging did not translate into a foraging disadvantage for females. When vegetation height was higher, females maintained similar pecking and intake rates compared to intermediate levels, while males consistently decreased their energy gain. This difference in anti-predator responses suggests a sexually mediated strategy in the food-safety trade-off: when resource density is high a females would adopt a camouflage strategy while an escape strategy would be adopted by males. In other words, males would leave risky-areas, whereas females would stay when resource density is high. Our results suggest that increased predation risk might generate sexually mediated behavioural responses that functional response models should perhaps better consider in the future.

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Section: Discussioncontrasting

confidence: 99%

Sex-Related Differences in the Trade-Off between Foraging and Vigilance in a Granivorous Forager

et al. 2014

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“…Birds were fed ad libitum with a commercial seed mix, grit, oilseed rape and tap water (Powolny et al, 2012). Food and water were respectively dispensed on three synthetic green turfs (height: 1 cm; density: 12 blades/cm 2 ) and three cup of water (1l each) scattered at different spots in the outdoors aviaries changed daily.…”

Section: Capture and Housing Conditions Of Skylarksmentioning

confidence: 99%

“…Theses cages contained no perches, food or water (during the trials) and were placed on a shaven green fitted carpet to facilitate the location of remaining seeds without eliminating foraging time. During winter, skylarks adopt particular aggregative strategies and sharply restrict its foraging behaviour in the absence of conspecifics (Powolny et al, 2012). Hence, one non-focal bird was randomly assigned to each trial, and individually kept in identical wire mesh cages at a distance of 15 cm from the focal individual.…”

Section: Pairsmentioning

confidence: 99%

Skylarks trade size and energy content in weed seeds to maximize total ingested lipid biomass

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Powolny

et al. 2014

Behavioural Processes

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“…Second, individuals may differ in their use of thermal microhabitats, which may be dependent on their sex, age, and/or position in the social hierarchy. Skylarks flock in winter (Powolny et al 2012), and differences in social dominance could result in differences in monopolizing the best food sources (Piper 1990) or nocturnal roosts (Koivula et al 1995). Thus, dominant individuals (males) could take advantage of shelters or microhabitats where heat gain might reduce their thermoregulation costs, which in turn would be reflected in individual variation in hypothermia.…”

Section: Sex Difference In Nightly Hypothermiamentioning

confidence: 99%

Cold Tolerance and Sex-Dependent Hypothermia May Explain Winter Sexual Segregation in a Farmland Bird

Powolny

Bretagnolle

Dupoué

et al. 2016

Physiological and Biochemical Zoology

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Migration is an important event in the life cycle of many organisms, but considerable intraspecific variation may occur in its timing and/or destination, resulting in sexual segregation during wintering periods. In this study, we tested the body size hypothesis, or cold tolerance hypothesis, which predicts that body size dimorphism modulates metabolic costs associated with cold climate. Using the Eurasian skylark, we first investigated whether this species showed sexual differential migration. Then we explored the body size hypothesis by experimentally testing the effect of low ambient temperature (Ta) on both metabolic rate (MR) and body temperature (Tb). We tested for sex-related differences in metabolism and in energy-saving mechanism (hypothermia). We found clear differential migration by sex in skylark wintering populations, with a male-biased sex ratio decreasing toward southern latitudes. Measurements on captive birds at 20°, 6°, and -5°C demonstrated a significant increase in MR when Ta decreased, but there is no difference between sexes. While both males and females reduced their Tb overnight, Tb reduction was more pronounced in females exposed to the coldest temperature treatment. In addition, we found that individuals with the most reduced Tb lost less body weight during the night, suggesting that Tb reduction may help minimize energy expenditure when conditions become constraining. Our study suggests that functional mechanisms may be involved in latitudinal segregation between sexes and supports the hypothesis that sex-specific physiological strategies and thermal tolerance may explain segregation between sexes.

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Group size modulates time budget and foraging efficiency in captive Skylarks, Alauda arvensis

Cited by 9 publications

References 39 publications

Sex-Related Differences in the Trade-Off between Foraging and Vigilance in a Granivorous Forager

Sex-Related Differences in the Trade-Off between Foraging and Vigilance in a Granivorous Forager

Skylarks trade size and energy content in weed seeds to maximize total ingested lipid biomass

Cold Tolerance and Sex-Dependent Hypothermia May Explain Winter Sexual Segregation in a Farmland Bird

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