Separating the effects of predation risk and interrupted foraging upon mass changes in the blue tit<i>Parus caeruleus</i>

Rands, Sean A.; Cuthill, Innes C.

doi:10.1098/rspb.2001.1653

Cited by 33 publications

(34 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For example, Rands & Cuthill (2001) found that the mean reserves of blue tits during June and July increased in response to interruptions but decreased in response to simulated predation. Our model shows that encounters with predators can decrease mean reserves, but it can also produce a greater increase than expected from an interruption.…”

Section: Discussionmentioning

confidence: 99%

“…Models predict that increasing the frequency of interruptions should increase optimal levels of fat (e.g. Houston & McNamara 1993), so it has been suggested that presenting a bird with a model of a predator might increase its fat reserves (Lilliendahl 1998;Pravosudov & Grubb 1998;van der Veen & Sivars 2000;Gentle & Gosler 2001;Rands & Cuthill 2001). There are two problems with viewing the presence of a predator as just an interruption.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A theoretical investigation of the effect of predators on foraging behaviour and energy reserves

McNamara¹,

Barta

Houston³

et al. 2005

Proc. R. Soc. B.

View full text Add to dashboard Cite

Data show that when small birds are exposed to a model of a predator, their body mass may either increase or decrease. Although attempts have been made to explain the data using previous models, these models are based on a constant level of predation and hence are not appropriate for making predictions about the response of a bird to the sight of a predator. We have developed a novel model that includes encounters between a bird and potential predators. We show that, depending on the biology of the predator, optimal body mass may either increase or decrease. The model also makes predictions about the foraging behaviour of the bird after it has seen a predator.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A theoretical investigation of the effect of predators on foraging behaviour and energy reserves

McNamara¹,

Barta

Houston³

et al. 2005

Proc. R. Soc. B.

View full text Add to dashboard Cite

show abstract

“…v www.esajournals.org stimulate the bird to increase fat reserves in the newly unpredictable foraging environment (McNamara et al 1994, Rands andCuthill 2001). Fat has increased in response to measures of increased predation risk (Fransson and Weber 1997, Lilliendahl 1998, Pravosudov and Grubb 1998, Bautista and Lane 2000.…”

Section: Background Theorymentioning

confidence: 99%

Testing optimal body mass theory: Evidence for cost of fat in wintering birds

Rogers

2015

Ecosphere

View full text Add to dashboard Cite

Abstract. Optimal body mass models for small wintering birds are central to animal ecology, and offer insights into maximizing individual fitness in a complex environment. Such models assume both costs and benefits of fat deposition, and consider how they affect winter survival probability. Hypothesized massdependent costs of elevated fat include increased wing load and subsequent reduced ability to avoid predators, as well as increased predator exposure while feeding to fatten. A likely benefit of winter fat is increased fasting capacity during resource shortages. Here I test optimal body mass theory by searching for both cost and benefits of winter fattening, utilizing interspecific variation in winter fat in natural populations. If increased predation risk is a mass-dependent cost of fattening, wintering birds occupying dense (closed) winter habitat offering low exposure to predators should show (1) higher fat reserves, and (2) higher wing load, than wintering birds occupying less dense (open) habitat offering less protection from predators. This prediction was tested in the two winters in south-central Kansas, a north temperate region with winter precipitation falling as snow and low ambient winter temperatures. The predicted patterns in wing load and winter fat reserve were observed: with phylogeny controlled, both were significantly lower in two open cover species (Dark-eyed Junco Junco hyemalis, American Tree Sparrow Spizella arborea) than in eight closed cover species (seven sparrow species in the genera Melospiza, Passerella, and Zonotrichia, and the Spotted Towhee Pipilo maculatus). Body mass increased with wing area at a greater rate in the closed than in the open cover group, indicating lower body-size specific wing load in the latter group. With phylogeny controlled, fat level varied inversely with resource predictability among three winter foraging guilds occupying a vertical gradient of snowfall probability, indicating both costs and benefits exist in the study system. This study is the first to support the existence of fat cost with a positive fat-cover relationship in natural populations. These results serve to verify the cost-benefit approach widely taken by optimal body mass models, to studying the relationship between a surrogate fitness variable and factors affecting it in a variable winter environment.

show abstract

“…Two main methods are used: a) if the bird is captured and handled directly, the bird is bagged and weighed on a scale. This method can stress the bird and cause body mass reduction in a short time (Rands & Cuthill, 2001), a fact that should be taken into account when analysing data. b) When we do not wish to capture the bird, attracting it to a place situated on a scale which automatically records mass variation will suffice.…”

Section: What Measures Should Be Taken Into Accountmentioning

confidence: 99%