{"id":54,"date":"2008-07-30T10:05:00","date_gmt":"2008-07-30T14:05:00","guid":{"rendered":"http:\/\/web.colby.edu\/mainebirds\/2008\/07\/30\/54\/"},"modified":"2008-07-30T10:05:00","modified_gmt":"2008-07-30T14:05:00","slug":"54","status":"publish","type":"post","link":"https:\/\/web.colby.edu\/mainebirds\/2008\/07\/30\/54\/","title":{"rendered":""},"content":{"rendered":"

For the Birds: Red-eyed and Philadelphia Vireos<\/span><\/p>\n

Red-eyed Vireos have returned from their South American wintering grounds. One of the most common songbirds in North America, the Red-eyed Vireo\u2019s song is a distinctive but somewhat plain series of two- and three-note phrases. Some authors render the song in human terms as \u201chere-I-am, where-are-you, over-here, in-the-tree\u201d that will resonate with anyone who has heard a Red-eyed Vireo singing. Red-eyed Vireos are energetic songsters, singing throughout most of day with rates as high as 85 phrases\/minute.<\/p>\n

The Philadelphia Vireo occurs in northern New England and much of southern Canada. This vireo closely resembles the Red-eyed Vireo but has a less distinct line above the eye and has a yellow wash on the underparts. The Philadelphia Vireo is also smaller, averaging 12 grams in weight to the 17-gram weight of a typical Red-eyed Vireo. Both species can be found in the same deciduous woodlands.<\/p>\n

Most nesting male songbirds defend their territories against other males of its species. If you play a recording of a Yellow Warbler in the territory of a Yellow Warbler, the male will quickly come toward the source of the sound and look to chase off the unwelcome intruder. However, playing a tape of the song of a Black-throated Blue Warbler or a Chestnut-sided Warbler will produce no reaction by the Yellow Warbler. In general, male songbirds defend their territories against members of their own species but not against members of other species.<\/p>\n

The two vireo species above provide an exception to this rule. Red-eyed Vireos and Philadelphia Vireos defend their territories against their own species and against the other species. In other words, both vireos show interspecific (between-species) and intraspecific (within-species) territoriality.<\/p>\n

The song of the Philadelphia Vireo is very similar to the singsong phrases of the Red-eyed Vireo song. Even highly experienced birders pass off singing Philadelphia Vireos as the more common Red-eyed Vireos. The reason for the similarity will soon be apparent.<\/p>\n

In northern New England forests, insect prey may become quite hard to find during the breeding season. Because both vireos eat largely the same species of insects, there is an advantage for a territorial vireo to keep a member of its own species and members of the other vireo species away from its food sources.<\/p>\n

In most cases, the vireos avoid direct confrontations over the boundaries of a territory. Instead, a territorial bird proclaims his ownership of a territory by singing from perches throughout his territory. Similarly adjacent territory owners sing throughout their territory. The neighboring birds recognize unseen but real boundaries, avoiding physical interactions.<\/p>\n

In the case of actual fighting between the two vireo species, the smaller Philadelphia Vireo usually comes out on the short end. One observed fight involved three minutes of violent contact, wing beating and pecking, with the larger Red-eyed Vireo winning the battle.<\/p>\n

The problem the Philadelphia Vireo has is how to maintain exclusive ownership of a territory, defending against a larger and stronger Red-eyed Vireos that may be trying to expand his territory to find scarce food. Philadelphia Vireos have solved the problem by becoming a social mimic. These birds mimic the song of the Red-eyed Vireo. <\/p>\n

Play-back experiments have shown that Red-eyed Vireos cannot tell the difference between a Red-eyed Vireo song and a Philadelphia song. No wonder birders have trouble telling the two species apart by song! On the other hand, Philadelphia Vireos can distinguish between a Philadelphia Vireo song and a Red-eyed Vireo song.<\/p>\n

Red-eyed Vireos assume that a neighboring Philadelphia Vireo is a Red-eyed Vireo and accept it grudgingly as a neighbor. If the Red-eyed Vireo only knew its neighbor was the meek Philadelphia Vireo, the latter could be evicted. Philadelphia Vireos mimic the song of the Red-eyed Vireo to level the playing field; it\u2019s a case of brains over brawn.<\/p>\n

Computer analysis of the songs of these two species reveals that Red-eyed Vireos never sing the same phrase twice in succession. Philadelphia Vireos, occurring in the absence of Red-eyed Vireos, may sing the same phrase twice before a new song is sung. However, in the presence of a Red-eyed Vireo, the Philadelphia Vireo never gives identical consecutive phrases, indicating that the species actively mimics the Red-eyed Vireos. Pretty clever birds!<\/p>\n

[First published on May 31, 2008]<\/p>\n\n

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For the Birds: Red-eyed and Philadelphia Vireos Red-eyed Vireos have returned from their South American wintering grounds. One of the most common songbirds in North America, the Red-eyed Vireo\u2019s song is a distinctive but somewhat plain series of two- and three-note phrases. Some authors render the song in human terms as \u201chere-I-am, where-are-you, over-here, in-the-tree\u201d […]<\/p>\n","protected":false},"author":146,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_s2mail":"","ngg_post_thumbnail":0,"footnotes":""},"categories":[1],"tags":[],"builder_content":"","_links":{"self":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/54"}],"collection":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/users\/146"}],"replies":[{"embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/comments?post=54"}],"version-history":[{"count":0,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/54\/revisions"}],"wp:attachment":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/media?parent=54"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/categories?post=54"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/tags?post=54"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}