Spring migration is coming to an end.\u00a0 Bringing up the rear are Black-billed Cuckoos, Yellow-bellied Flycatchers, Nelson\u2019s Sparrows and Saltmarsh Sparrows.\u00a0 The north-flowing river of birds is running dry.<\/p>\n
We see an almost synchronous arrival of a guild of songbirds collectively called the leaf-gleaning insectivores.\u00a0 These birds include our vireos, warblers and tanagers.\u00a0 All of them make a living by preying on caterpillars and other herbivores that attack the leaves of deciduous trees.\u00a0 The leaf-gleaning herbivores are the friends of the trees, gobbling up the leaf-eating insects. A cascade of events occurs in spring allowing the warblers and vireos to return: leaf-out, followed by emergence of caterpillars, followed by the arrival of the leaf-gleaning birds.\u00a0 In central and southern Maine, the first ten days of May capture the arrival of many of these birds.<\/p>\n
Among these arrivals are Red-eyed Vireos.\u00a0 I daresay that Red-eyed Vireos vie for the title of most common woodland bird in eastern North America.\u00a0 A bird of treetops, Red-eyed Vireos are much more often heard than seen.<\/p>\n
Hearing a Red-eyed Vireo is a snap because they sing vigorously all through the day.\u00a0 Their song is a series of two- and three-note phrases. An effective mnemonic for learning the song is \u201chere-I-am, where-are-you, over-here, in-the-tree\u201d.<\/p>\n
The song is rather monotonous and dry. Despite the seeming monotony of their song, Red-eyed Vireos show remarkable diversity in their two- and three-note phrases.\u00a0 A typical Red-eyed sings around 45 phrases.\u00a0 Those phrases are strung together to make a distinctive song type.\u00a0 Each song type consists of the same one to five phrases.\u00a0 A typical male sings about 30 song types.<\/p>\n
A less common vireo breeding in Maine, the Philadelphia Vireo, needs to be considered in this column.\u00a0 Red-eyed and Philadelphia vireos share an intriguing overlap in their song.<\/p>\n
The Philadelphia Vireo closely resembles the Red-eyed Vireo but has a less distinct line above the eye and has a yellow wash on the underparts.\u00a0 The Philadelphia Vireo is also smaller, averaging 12 grams in weight to the 17-gram weight of a typical Red-eyed Vireo.<\/p>\n
Most nesting male songbirds defend their territories against other males of its species but not against males of other species. However, Red-eyed Vireos and Philadelphia Vireos defend their territories against their own species and against the other species.<\/p>\n
The song of the Philadelphia Vireo is very similar to the song of the Red-eyed Vireo song.\u00a0 Even highly experienced birders pass off singing Philadelphia Vireos as the more common Red-eyed Vireos.\u00a0 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.\u00a0 Because both vireos eat the same 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.\u00a0 Instead, a territorial bird proclaims his ownership of a territory by singing from perches throughout his territory.\u00a0 Similarly adjacent territory owners sing throughout their territory.\u00a0 The neighboring birds recognize unseen but real boundaries, avoiding physical interactions.<\/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 Vireo that may be trying to expand his territory.\u00a0 Philadelphia Vireos have solved the problem by becoming a social mimic.\u00a0 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.\u00a0 No wonder birders have trouble telling the two species apart by song!\u00a0 On the other hand, Philadelphia Vireos can distinguish between a Philadelphia Vireo song and a Red-eyed Vireo song.<\/p>\n
Philadelphia Vireos mimic the song of the Red-eyed Vireo to level the playing field; it\u2019s a case of deception over brawn.<\/p>\n\n
Spring migration is coming to an end.\u00a0 Bringing up the rear are Black-billed Cuckoos, Yellow-bellied Flycatchers, Nelson\u2019s Sparrows and Saltmarsh Sparrows.\u00a0 The north-flowing river of birds is running dry. We see an almost synchronous arrival of a guild of songbirds collectively called the leaf-gleaning insectivores.\u00a0 These birds include our vireos, warblers and tanagers.\u00a0 All of […]<\/p>\n","protected":false},"author":146,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_s2mail":"yes","ngg_post_thumbnail":0,"footnotes":""},"categories":[4625,420],"tags":[],"builder_content":"","_links":{"self":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/799"}],"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=799"}],"version-history":[{"count":1,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/799\/revisions"}],"predecessor-version":[{"id":800,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/799\/revisions\/800"}],"wp:attachment":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/media?parent=799"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/categories?post=799"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/tags?post=799"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}