Some results from trapping rooks

Green, Paul T.

doi:10.1080/03078698.1981.9673781

Cited by 10 publications

(4 citation statements)

References 16 publications

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“…For example, the increased energetic costs of breeding and maintaining a nest could cause decreases in neophobia because hunger stimulates risk taking (Damsgard & Dill, 1998). Accordingly, rooks are more likely to take risks while foraging in the wild during the breeding season (Green, 1981), and those that take risks are more likely to be in poorer body condition (Patterson, Dunnet, & Goodbody, 1988). Moreover, baseline levels of glucocorticoid stress hormones are known to be higher during the breeding season in a range of bird species (Romero, 2002) and the extent of these changes can vary depending on dominance status (Kotrschal, Hirschenhauser, & Mostl, 1998).…”

Section: Discussionmentioning

confidence: 99%

Seasonal changes in neophobia and its consistency in rooks: the effect of novelty type and dominance position

et al. 2016

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Neophobia, or the fear of novelty, may offer benefits to animals by limiting their exposure to unknown danger, but can also impose costs by preventing the exploration of potential resources. The costs and benefits of neophobia may vary throughout the year if predation pressure, resource distribution or conspecific competition changes seasonally. Despite such variation, neophobia levels are often assumed to be temporally and individually stable. Whether or not neophobia expression changes seasonally and fluctuates equally for all individuals is crucial to understanding the drivers, consequences and plasticity of novelty avoidance. We investigated seasonal differences and individual consistency in the motivation and novelty responses of a captive group of rooks, Corvus frugilegus, a seasonally breeding, colonial species of corvid that is known for being neophobic. We tested the group around novel objects and novel people to determine whether responses generalized across novelty types, and considered whether differences in dominance could influence the social risk of approaching unknown stimuli. We found that the group's level of object neophobia was stable year-round, but individuals were not consistent between seasons, despite being consistent within seasons. In contrast, the group's avoidance of novel people decreased during the breeding season, and individuals were consistent year-round. Additionally, although subordinate birds were more likely to challenge dominants during the breeding season, this social risk taking did not translate to greater novelty approach. Since seasonal variation and individual consistency varied differently towards each novelty type, responses towards novel objects and people seem to be governed by different mechanisms. Such a degree of fluctuation has consequences for other individually consistent behaviours often measured within the nonhuman personality literature.

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Section: Discussionmentioning

confidence: 99%

Seasonal changes in neophobia and its consistency in rooks: the effect of novelty type and dominance position

et al. 2016

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“…This higher density may also protect against the abrasive effects of bill wiping behaviour, commonly thought to serve as a cleaning mechanism (Cuthill, Witter & Clarke, ). Nevertheless, the consensus is that bill growth and abrasion tend to balance each other out, although with temporal, species, sex, or individual‐specific variation contributing to dynamic changes in bill size (Green, ; Swennen et al ., ; Hulscher, ; Matthysen, ; van de Pol et al ., ). Net bill growth is assessed by measuring culmen length or bill depth in individuals over time.…”

Section: Background: Function Anatomy Growth and Evolutionmentioning

confidence: 99%

“…The ramphotheca appears to grow primarily from the proximal half (Hulscher, ), presumably where cellular proliferation is most abundant, which ‘pushes’ the bill tissue forward towards the tip. Typically, the upper mandible grows ‘over’ the lower mandible, due to differential rates of tissue growth, but during the time of year of peak feeding, bill wear occurs, associated with excessive use from foraging behaviours such as digging, hammering, or sifting for food within a hardened substrate (Green, ). Overall seasonal variation in bill size results from the differential growth and wear (see Section IV.6).…”

Section: Background: Function Anatomy Growth and Evolutionmentioning

confidence: 99%

The evolution of the avian bill as a thermoregulatory organ

2016

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The avian bill is a textbook example of how evolution shapes morphology in response to changing environments. Bills of seed-specialist finches in particular have been the focus of intense study demonstrating how climatic fluctuations acting on food availability drive bill size and shape. The avian bill also plays an important but under-appreciated role in body temperature regulation, and therefore in energetics. Birds are endothermic and rely on numerous mechanisms for balancing internal heat production with biophysical constraints of the environment. The bill is highly vascularised and heat exchange with the environment can vary substantially, ranging from around 2% to as high as 400% of basal heat production in certain species. This heat exchange may impact how birds respond to heat stress, substitute for evaporative water loss at elevated temperatures or environments of altered water availability, or be an energetic liability at low environmental temperatures. As a result, in numerous taxa, there is evidence for a positive association between bill size and environmental temperatures, both within and among species. Therefore, bill size is both developmentally flexible and evolutionarily adaptive in response to temperature. Understanding the evolution of variation in bill size however, requires explanations of all potential mechanisms. The purpose of this review, therefore, is to promote a greater understanding of the role of temperature on shaping bill size over spatial gradients as well as developmental, seasonal, and evolutionary timescales.

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“…Jackdaws and Magpies are similar sized birds, but differ in the ratio of bill length to depth, the Jackdaw having a somewhat shorter and stubbier bill (measurements available in Witherby et al 1938, Holyoak 1970, Picozzi 1975, Olsson and Persson 1979, Higstedt 1980b, Green 1981, and Waite 1982. The Rook has a relatively longer, more slender bill which lacks the tearing edge of the other three species.…”

Section: Introductionmentioning

confidence: 99%

Winter Habitat Selection and Foraging Behaviour in Sympatric Corvids

Waite¹

1984

Ornis Scandinavica

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. . Wiley and Nordic Society Oikos are collaborating with JSTOR to digitize, preserve and extend access to Ornis Scandinavica. Waite, R. K. 1984. Winter habitat selection and foraging behaviour in sympatric corvids. -Ornis Scand. 15: 55-62.The winter foraging ecology and habitat use of four sympatric corvid species on agricultural land is described. Overlap in habitat use was mostly high (range = 0.50-0.81). Most individuals of each species occurred on grassland, especially permanent pasture where invertebrate populations were highest. Overlap in intake rates of different prey types and sizes from above or beneath the soil surface, and from animal dung or surface debris, was low (range = 0.15-0.41), except between Jackdaws and Magpies (0.72). Discriminant analysis indicated significant differences in foraging behaviour between species, but Magpies retained little unique niche space.

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Some results from trapping rooks

Cited by 10 publications

References 16 publications

Seasonal changes in neophobia and its consistency in rooks: the effect of novelty type and dominance position

Seasonal changes in neophobia and its consistency in rooks: the effect of novelty type and dominance position

The evolution of the avian bill as a thermoregulatory organ

Winter Habitat Selection and Foraging Behaviour in Sympatric Corvids

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