<Li> P. s . arboricola of western mountains is large with females paler on underparts . </Li> <P> Purple martins' breeding range is throughout temperate North America . Their breeding habitat is open areas across eastern North America, and also some locations on the west coast from British Columbia to Mexico . Martins make their nests in cavities, either natural or artificial . In many places, humans put up real or artificial hollow gourds, or houses for martins, especially in the east, where purple martins are almost entirely dependent on such structures . As a result, this subspecies typically breeds in colonies located in proximity to people, even within cities and towns . This makes their distribution patchy, as they are usually absent from areas where no nest sites are provided . Western birds often make use of natural cavities such as old woodpecker holes in trees or saguaro cacti . </P> <P> The purple martin migrates to the Amazon basin in winter . Its winter range extends into Ecuador but does not seem to ascend far up the Andean foothills . </P> <P> 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 . </P>

When do purple martins migrate to south america