<?xml version='1.0' encoding='utf-8'?>
<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:creator>J.A. Sedgwick</dc:creator>
  <dc:date>2001</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;The vocal signatures of the primary song form (“&lt;/span&gt;&lt;i&gt;fitz-bew&lt;/i&gt;&lt;span&gt;”) of the endangered Southwestern Willow Flycatcher (&lt;/span&gt;&lt;i&gt;Empidonax traillii extimus&lt;/i&gt;&lt;span&gt;) and its northern counterpart, &lt;/span&gt;&lt;i&gt;E. t. adastus,&lt;/i&gt;&lt;span&gt; are distinctive. Songs of the &lt;/span&gt;&lt;i&gt;extimus&lt;/i&gt;&lt;span&gt; subspecies are longer (total song, note, internote) and frequencies at maximum amplitude are lower than those of &lt;/span&gt;&lt;i&gt;adastus.&lt;/i&gt;&lt;span&gt; I used vocal evidence to clarify the distributional limits of the Southwestern Willow Flycatcher and that of the geographically adjacent subspecies, &lt;/span&gt;&lt;i&gt;E. t. adastus.&lt;/i&gt;&lt;span&gt; Unweighted pair-group method using averaging (UPGMA) cluster analysis and canonical discriminant analysis revealed that (1) low elevation, southerly desert populations (Arizona, New Mexico, and southern Utah) have a unique vocal identity corresponding to populations in the range of &lt;/span&gt;&lt;i&gt;E. t. extimus&lt;/i&gt;&lt;span&gt;; (2) northerly song groups (Oregon, Colorado, and northern Utah) share a different song type corresponding to populations in the range of &lt;/span&gt;&lt;i&gt;E. t. adastus;&lt;/i&gt;&lt;span&gt; and (3) a departure from vocal and morphological congruence occurs for a population of high-elevation Arizona birds that, although in the currently accepted range of &lt;/span&gt;&lt;i&gt;E. t. extimus,&lt;/i&gt;&lt;span&gt; sings songs acoustically similar to more northern populations (&lt;/span&gt;&lt;i&gt;E. t. adastus&lt;/i&gt;&lt;span&gt;). Multiple regression of song distance on latitude and elevation, and a comparison of a matrix of song distances with a matrix of latitude and elevation dissimilarities, demonstrated that song populations sort out by both latitude and elevation: birds with the vocal identity of &lt;/span&gt;&lt;i&gt;extimus&lt;/i&gt;&lt;span&gt; occur as far north as 37°N if at low elevation, and those acoustically similar to &lt;/span&gt;&lt;i&gt;adastus&lt;/i&gt;&lt;span&gt; occur as far south as 33.7°N if at high elevation. The vocal background of northern New Mexico birds appears to be intermediate between that of &lt;/span&gt;&lt;i&gt;extimus&lt;/i&gt;&lt;span&gt; and &lt;/span&gt;&lt;i&gt;adastus,&lt;/i&gt;&lt;span&gt; suggesting that northern New Mexico is a zone of intermixing and intergradation between the subspecies. Pure forms of &lt;/span&gt;&lt;i&gt;E. t. extimus&lt;/i&gt;&lt;span&gt; apparently do not occur in Colorado because even the southernmost populations are acoustically similar to more northerly populations of &lt;/span&gt;&lt;i&gt;adastus.&lt;/i&gt;&lt;span&gt; A low-elevation population in western Colorado, however, stands apart from other &lt;/span&gt;&lt;i&gt;adastus&lt;/i&gt;&lt;span&gt; populations, suggesting moderate introgression of &lt;/span&gt;&lt;i&gt;extimus&lt;/i&gt;&lt;span&gt; genes into the &lt;/span&gt;&lt;i&gt;adastus&lt;/i&gt;&lt;span&gt; gene pool.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1642/0004-8038(2001)118[0366:GVITSO]2.0.CO;2</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>American Ornithological Society</dc:publisher>
  <dc:title>Geographic variation in the song of Willow Flycatchers: Differentiation between &lt;i&gt;Empidonax traillii adastus&lt;/i&gt; and &lt;i&gt;E. t. extimus&lt;/i&gt;</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>