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Title:Is meadowlark habitat segregation within sympatry behaviorally mediated?
Author(s):Elbert, Daniel C.
Advisor(s):Molano-Flores, Brenda
Department / Program:Natural Res & Env Sci
Discipline:Natural Res & Env Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Grassland Birds
interspecific aggression
experimental song playback
Abstract:The Eastern Meadowlark (Sturnella magna) and Western Meadowlark (Sturnella neglecta) are morphologically and ecologically similar species that co-occur within a recently expanded zone of secondary contact. Although spatial patterns of sympatric meadowlark populations have been previously compared, these comparisons have been qualitative in nature and lack the quantitative evidence necessary to provide a rigorous understanding of meadowlark habitat use within sympatry. At the patch scale, area-sensitivity, vegetation structure, and vegetation composition have been identified as important factors influencing habitat selection. It is also widely recognized that community assemblage is influenced by mechanisms beyond simple habitat relationships, such as interspecific competition. Within sympatry, Eastern and Western Meadowlarks establish and maintain mutually exclusive, multi-use territories. However, the influence this aggressive behavior may have on ecological relationships between these species is not well understood. In the following investigation, I examined environmental factors and behavioral mechanisms influencing Eastern Meadowlark and Western Meadowlark habitat use and distribution patterns at a large remnant sand prairie in northwestern Illinois. In the first study, I examined habitat use of both species occurring in the same area at the same time. Complementary to the habitat study, I examined the response of Eastern and Western Meadowlarks to conspecific and congeneric playback. Fieldwork was conducted during the 2007, 2008, and 2009 breeding seasons at the Lost Mound Unit of the Upper Mississippi National Wildlife and Fish Refuge in Carroll and Jo Daviess counties, IL. Meadowlarks responded to habitat features in different ways. Eastern Meadowlark density was best predicted by increasing cover of standing dead vegetation and decreasing exposure of bare ground, while Western Meadowlark density was best predicted by increasing cover of crown vetch (Securigera varia). Meadowlarks were also segregated across the study area. The relative composition of meadowlarks among study plots differentiated along vegetation gradients such that plots were likely to be dominated by Eastern Meadowlarks as percent graminoid cover increased and crown vetch cover decreased. In addition to segregating ecologically, male meadowlarks were capable of discriminating congenerics from conspecifics. Although both species responded to both conspecific and congeneric playback, males responded more to conspecific than congeneric playback. However, I found that Eastern Meadowlarks responded stronger to congeneric playback than did Western Meadowlarks. The results of the experimental playback study suggest that Eastern Meadowlarks are socially dominant to Western Meadowlarks, and may play an important role in shaping the patch-scale spatial patterns I observed between these species at Lost Mound.
Issue Date:2011-01-14
Rights Information:Copyright 2010 Daniel C. Elbert
Date Available in IDEALS:2011-01-14
Date Deposited:December 2

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