Purple Martin
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[Photo] Purple Martin from USFWS
The Purple Martin (Progne subis) is the largest North American swallow at 20 cm length. Adults have a slightly forked tail. These "aerial acrobats" have speed and agility in flight, and when approaching their housing, will dive from the sky with their wings tucked at great speeds.
Proper identification of Purple Martins is determined by their age. It takes two years for this species to reach their full adult breeding plumage. This makes identification complicated. There are some common acronyms used in identifying the age and sex of Purple Martins. "HY" means "hatching year", "SY" means "second year" and "ASY" means "after second year".
ASY (adult birds)
Adult males are entirely black with glossy steel blue sheen, and adult females are dark on top with some steel blue sheen, and lighter underparts.
SY (subadult birds)
Females look similar to "ASY" females minus the steel blue sheen on the back. Males look very much like females at this age, but they will have solid black feathers starting to emerge on their chest in a blotchy, random pattern as they moult to their adult plumage.
Their breeding habitat is open areas across eastern North America, and also some locations on the west coast from British Columbia to Mexico. It is seldom found in Florida (AOU 2000). This species typically breeds in colonies located in close proximity to human housing.
The eastern nominate race P. s. subis nests exclusively in man-made bird houses, of which about a million are provided. It is the only bird totally dependent on humans for nest sites. It is important to note that unmonitored Purple Martin houses often become breeding colonies for House Sparrows and Common Starlings ??? invasive species responsible for declining Martin populations across North America. Both of these aggressive non-native species were introduced from Europe and often kill Martins for their nest cavity. If House Sparrows and/or Starlings are not actively controlled and removed from the housing site, the Martins will lose their eggs and young causing the martins to abandon the site. Because of the devastating effects on Purple Martins, many landlords trap the invasive species to ensure the survival of their colony of martins.
The paler subspecies P. s. hesperia of Arizona and western Mexico uses only woodpecker holes in Saguaro and other large cacti, and the large pale west coast form P. s. arboricola utilises woodpecker and other natural cavities as well as nesting boxes and gourds.
The Purple Martin migrates to the Amazon basin in winter. The first record of this species in Europe was a single bird on Lewis, Scotland on 5-6 September 2004, and the second was on the Azores on 6 September 2004.
Purple martins are aerial insectivores, meaning that they catch insects from the air. The birds are agile hunters and eat a variety of winged insects. Rarely, on occasion, they will come to the ground to eat insects. They usually fly relatively high, so, contrary to popular opinion, mosquitos do not form a large part of their diet.
The call is described as: "Throaty and rich tchew-wew, etc., or pew pew. Song gurgling, ending in a succession of low rich gutturals".
http://en.wikipedia.org/wiki/Purple_Martin
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