Shrikes are territorial, and these territories are defended from other pairs. - loggerhead shrike migration -

In open terrain, this predatory songbird watches from a wire or other high perch, then pounces on its prey: often a large insect, sometimes a small bird or a rodent. Our results suggest isotopic analysis may be a method by which both can be quantified. If you do not receive an email within 10 minutes, your email address may not be registered, Based on replicate (n = 5) analyses of each standard during analytical runs, measurement error is estimated to be ±2 ‰. Loggerhead Turtle Migration Follows Magnetic Map . Sample areas that fell along the Atlantic Coast (Region 1), the Gulf Coast and throughout Texas (Region 3), and throughout Mexico (Regions 3 and 4) supported proportionately more migrants than other sample areas within each region (Figure 2). Analysis of genetic admixture coefficients showed differential representation among subspecies within each region (Figure 3). We quantified migratory patterns and connectivity in two ways. Our results imply a need for further detailed quantification of migration patterns and assessment of overwintering ecology in the species main wintering areas. Our best model, which included parameters for latitude, age, and region, received 86% of the support among the candidate set of models (Table 1). Our results suggest some individuals undertake long‐distance movements that cannot be attributed to environmental factors. The Loggerhead Shrike (Lanius ludovicianus) is one of only two species of shrikes (Order Passeriformes) that occur in North America, and the only species of “true shrike” (Subfamily Laniinae, Family Laniidae) endemic to the continent. Lanius l. excubitorides, whose range also falls almost exclusively above 40°N, was found in all regions except the Eastern United States (Region 1), with the majority occurring in Region 3 and 4 (Figure 3). This process resulted in a spatially explicit posterior probability density surface for each individual, which we visualized by graphically depicting the δ2Hf values for all individuals combined within each of our regions (Figure 1). Habitat management for Loggerhead shrikes should focus on providing suitable nest trees and perches and maintaining a healthy prey population. Lacking a raptor’s talons, Loggerhead Shrikes skewer their kills on thorns or barbed wire or wedge … Don and Andre Cuddy and Susan Craig provided invaluable help in the field. With the exception of the Gulf Coast region in northern Mexico, where the species is believed to occur only in the nonbreeding season (Yosef, 1996), the wintering range of migratory Loggerhead Shrikes entirely overlaps that of nonmigratory conspecifics (Yosef, 1996). Results from long‐term banding studies of the species (Chabot, Hobson, Craig, & Lougheed, 2018) suggest that male shrikes are experiencing higher overwintering mortality rates than females, in particular during their first wintering season. The strength of migratory connections is the result of both evolutionary and ecological processes (Marra, Norris, Haig, Webster, & Royle, 2006; Webster et al., 2002), and we are only just beginning to understand the factors that shape inter‐ and intraspecific differences in migratory patterns and their implications (Elser, 2000; Marra, Hunter, & Perrault, 2011; Runge, Martin, Possingham, Willis, & Fuller, 2014; Webster & Marra, 2005). Enter your email address below and we will send you your username, If the address matches an existing account you will receive an email with instructions to retrieve your username, Predicted origins of migratory adult (ASY) and juvenile (SY) Loggerhead Shrike from joint analysis of δ, Proportion of individual Loggerhead Shrike assigned as migratory and nonmigratory within each sample area based on genetic admixture coefficient, The proportion of winter adults assigned to a subspecies in each nonbreeding region based on admixture coefficients (, By continuing to browse this site, you agree to its use of cookies as described in our, orcid.org/http://orcid.org/0000-0002-6770-3080, orcid.org/http://orcid.org/0000-0002-6742-4567, I have read and accept the Wiley Online Library Terms and Conditions of Use, Information theory as an extension of the maximum likelihood principle, Second International symposium on information theory, Spring predictability and leapfrog migration, A quantitative measure of migratory connectivity, Saving our shared birds: Partners in flight Tri‐National Vision for Land bird Conservation, Integrated analysis of genetic, stable isotope, and banding data reveal migratory connectivity and flyways in the Northern Yellow Warbler (Dendroica petechia; Aestiva group), Global applications of stable hydrogen and oxygen isotopes to wildlife forensics, Model selection and inference: A practical information‐theoretic approach, Long‐distance movements by Loggerhead Shrikes, Changes in distribution and abundance of the loggerhead shrike, Population demographics of the Loggerhead Shrike: insights into the species decline from a long‐term study in the Midewin National Tallgrass Prairie, Moult in the Loggerhead Shrike Lanius ludovicianus is influenced by sex, latitude and migration, Advances in linking wintering migrant birds to their breeding‐ground origins using combined analyses of genetic and stable isotope markers, The Impact of Migration on the Evolution and Conservation of an Endemic North American Passerine: Loggerhead Shrike (Lanius ludovicianus), Light‐level geolocators reveal strong migratory connectivity and within‐winter movements for a coastal California Swainson's thrush (, COSEWIC assessment and status report on the Loggerhead Shrike Eastern subspecies Lanius ludovicianus ssp. Migratory connectivity, as defined by Webster, Marra, Haig, Bensch, and Holmes (2002), is the extent to which individuals from the same breeding area migrate to the same stopover sites or wintering areas and vice versa. Loggerhead Shrikes were captured using a modified Potter trap, similar to that designed by Craig (1997), which was baited with a live mouse (Mus mustellus) held in a protective wire “hardware‐cloth” cage. However, our understanding of the conditions leading to patterns of winter distribution among populations is still incomplete. Range: Pre-breeding migration This map depicts the range boundary, defined as the areas where the species is estimated to occur at a rate of 5% or more for at least one week within the pre-breeding migration season. Learn more. Pérez and Hobson (2009) found that wintering habitat use among nonmigratory and migratory Loggerhead Shrikes differed in Mexico, and thus it is likely that this differential use of resources occurs elsewhere in the species’ wintering range. First, limiting factors may be more wide‐spread and/or drastic—for example, habitat loss and degradation may be more severe. Results indicated fine‐scale patterns of differential migration, with ASY birds preferentially using more coastal sites, and SY birds occurring in more inland areas (Craig & Chabot, 2012). When used together in a Bayesian approach, the two allow precise and accurate delineation of migratory connectivity on an individual‐by‐individual basis (Chabot, Hobson, Van Wilgenburg, McQuat, & Lougheed, 2012).

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