Winter Foraging and Diet Composition of Northern Shrikes in Idaho

Atkinson, Eric C.; Cade, Tom J.

doi:10.2307/1369596

Cited by 16 publications

(11 citation statements)

References 14 publications

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“…1, 3a, b) reflects that fact that Vireos are more migratory than either Shrikes or Crows despite being intermediate on the buffering scale, and breeding at lower latitudes. However the non-buffered ordination of shrikes may be confounded by their ability to switch to vertebrate prey in winter and so remain relatively close to the breeding area (Atkinson and Cade 1993). Evidence derived from North American passerines therefore supports the hypothesis of a general relationship between resource buffering and migrancy, and adds to the evidence gathered from a range of avian communities for an association between the two.…”

Section: Discussionmentioning

confidence: 61%

Resource buffering and the evolution of bird migration

Bell¹

2010

Evol Ecol

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Variation in migratory behaviour among birds is thought to reflect the relative variability in abundance of resources used by different species. Here I present evidence that increased migrancy among North American passerines is associated with greater reliance on food resources that vary in abundance because they occur in microhabitats that are exposed both to consumers and environmental fluctuation, and that residency is associated with use of food resources that occur in more 'buffered' microhabitats, and so are relatively invariant in abundance. Evidence from a variety of sources suggests that migrants and residents also differ in their use of foraging actions and methods of exploring the environment, with migrants using a rapid, extensive method of exploration, and a plastic, opportunistic foraging mode, while residents explore more methodically and use more stereotyped foraging actions. This suggests that the degree of migrancy exhibited by a species may be part of a suite of coadaptations for exploitation of foraging microhabitats at a particular position on the buffering scale, and I propose a selective typology involving feedback loops that could generate such coevolution. I also explain established patterns of difference between migrants and residents in morphology, and in resource use and distribution, as outcomes of the evolutionary scenario described.

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Section: Discussionmentioning

confidence: 61%

Resource buffering and the evolution of bird migration

Bell¹

2010

Evol Ecol

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“…Several researchers have demonstrated that shrikes prefer to forage in habitats with abundant large insects (Atkinson and Cade 1993;Hernández 1993;Lefranc and Worfolk 1997;Karlsson 2004). On the Canary Islands, Southern Grey Shrikes in the high mountain zone of Tenerife captured the largest invertebrate prey.…”

Section: Prey Selectionmentioning

confidence: 99%

“…Based on trophic patterns observed in continental populations of shrikes (Hernández et al 1993;Karlsson 2004), we expected to find more pronounced seasonal diet variation in the climatically variable high mountain zones than in the more homogeneous coastal zones. Shrikes are usually opportunist predators that select foraging habitats with an abundance of large prey and short sparse vegetation that permits good prey visibility (Atkinson and Cade 1993;Lefranc and Worfolk 1997;Tryjanowski et al 1999;Karlsson 2004). Under harsh conditions, usually with low prey availability, an effective method to obtain the highest possible amount of energy is selectively to capture larger prey (Craig 1978;Karlsson 2001).…”

Section: Introductionmentioning

confidence: 99%

Trophic ecology of the Southern Grey Shrike (Lanius meridionalis) in insular environments: the influence of altitude and seasonality

et al. 2009

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The seasonal diet and prey selection of the Southern Grey Shrike (Lanius meridionalis) was studied in two different insular habitats: shrub environments of the Canary Islands in coastal and high mountain zones. We measured, in each season, food availability and prey size in order to determine prey size selection of shrikes along an altitudinal gradient. Moreover, we compared the diet patterns observed with those documented on the continent, to determine if Southern Grey Shrikes in the islands' high mountain zone (which has a continental climate) showed seasonal diet variation similar to those in northern continental areas. We analysed a total of 1,139 shrike pellets collected in 1 year and identified 10,179 prey items. Numerically arthropods (91%), and in terms of biomass lizards (70%) were the main prey consumed by the shrikes. The proportions of the main prey items differed significantly between seasons and habitats. Diet in the coastal areas was less variable than in the high mountain zone. The greater seasonal climatic variation in the high mountain zone was associated with diet patterns similar to those found in some northern continental areas, such as the Iberian Peninsula and southern France. Finally, shrikes selected the largest prey in the high mountain habitat. This suggests that foraging behaviour in this species is related to climatic conditions, as the biggest and most profitable prey were consumed in the most harsh habitats.

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“…It may have resulted from the conservative hunting strategy of this species (Cade 1967;Olsson 1984;Schön 1996;Karlsson 2001). This method of feeding gives excellent results for hunting insects, which make up about 90% of their summer diet (Grönlund et al 1970;Huhtala et al 1977;Olsson 1986;Atkinson & Cade 1993;Hromada & Krištín 1996;Karlsson 2002). However, in winter insects may comprise a significant part of their diet as well (Haensel & Heuer 1970;Hromada & Krištín 1996).…”

Section: Discussionmentioning

confidence: 99%

“…During a particularly severe winter birds are an alternative food source (Cade 1967;Olsson 1984;Lorek et al 2000). Atkinson & Cade (1993) and Karlsson (2001) consider perching as a hunting technique less effective for small vertebrates than for insects. However, the present results show perching as a basic technique probably preferred due to lower energy expenditure.…”

Section: Discussionmentioning

confidence: 99%

Density changes and habitat shift of great grey shrike Lanius excubitor during the non-breeding season

2007

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Bird population density and their behaviour during non-breeding periods are determined mainly by meteorological conditions which force birds to use alternative strategies -migration to areas with more advantageous conditions or adaptation to existing conditions. During the 2002/03-2004/5 non-breeding seasons in the open habitats of the Kotlina Orawsko-Nowotarska valley (S Poland) studies on population dynamics, behaviour and habitat use of great grey shrike were conducted. Results were grouped into four meteorological periods (autumn, early winter, winter and early spring). Density changes were seen between subsequent seasons (from 0.34 to 1.9 ind./10 km), as well as between meteorological periods (from 0.48 to 2.70 ind./10 km). Perching was the most frequently observed behaviour. The foraging habitats used changed in frequency. In subsequent meteorological periods a decrease of open habitats used was noted with a simultaneous increase in afforestations used. These changes did not depend on lasting snow cover. Changes in vegetation type used during hunting were not observed. Great grey shrikes most frequently used natural perches (trees, shrubs and high vegetation).

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Winter Foraging and Diet Composition of Northern Shrikes in Idaho

Cited by 16 publications

References 14 publications

Resource buffering and the evolution of bird migration

Resource buffering and the evolution of bird migration

Trophic ecology of the Southern Grey Shrike (Lanius meridionalis) in insular environments: the influence of altitude and seasonality

Density changes and habitat shift of great grey shrike Lanius excubitor during the non-breeding season

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