About Purple Martins

About Purple Martins

Purple Martins (Progne subis) are the largest member of the swallow family in North America, measuring 7 1/2 inches (19 cm) long and weighing 1.9 ounces (55 grams). Taxonomically they are placed in the Kingdom: Animalia; Phylum: Chordata; Subphylum: Vertebrata; Class: Aves; Order: Passeriformes; and Family: Hirundinidae. Three races (subspecies) are recognized: Progne subis subis breeding in eastern North America and eastern Mexico; Progne subis hesperia breeding in the deserts of Arizona, western Mexico, and Baja California; and Progne subis arboricola breeding along the Pacific coast of the United States and Canada, and in the Rocky Mountains.

Purple Martins (PUMAs) spend the non-breeding season in Brazil then migrate to North America to nest. East of the Rockies they are totally dependent on human-supplied housing! It is believed that Native Americans played a strong role in the behavioral shift from cavity nesting in the wild to community nesting in man-provided housing.    (http://purplemartin.org/update/Indigenous.html)

The male and female cooperate equally in building the nest. The female lays two to seven pure-white eggs at a rate of one egg per day. The female incubates the clutch for approximately fifteen days, then the young hatch. Both parents feed the young continuously for a period of 26-32 days until the young fledge (leave the nest). The young continue to be dependent on their parents for food and training for an additional one to two weeks after fledging. It's not uncommon for the fledglings to return to their human-supplied housing at night to sleep during this period.

Martins, like all swallows, are aerial insectivores. They eat only flying insects, which they catch in flight. They typically forage at an altitude of approximately 30 to 60 feet. Their diet is diverse, including dragonflies, damselflies, flies, midges, mayflies, stinkbugs, leafhoppers, Japanese beetles, June bugs, butterflies, moths, grasshoppers, cicadas, bees, wasps, flying ants, and ballooning spiders. Martins are not, however, prodigious consumers of mosquitoes. Since Purple Martins feed only on flying insects, they are extremely vulnerable to starvation during extended periods of cool and/or rainy weather.

The plight of the aerial insectivore:

Aerial insectivores (specialized birds who eat only flying insects and include whip-poor-wills, nighthawks, swifts, swallows, and flycatchers) are experiencing population declines at an alarming rate as indicated by a USGS Breeding Bird Survey results (http://www.mbr-pwrc.usgs.gov/bbs/specl09.html for all birds, and http://www.mbr-pwrc.usgs.gov/cgi-bin/atlasa09.pl?06110&1&09 for PUMA).

In Canada, during the last two decades alone, populations of PUMAs have fallen over 50%, while Barn Swallows and Chimney Swifts have declined 70%!  PUMAs are currently experiencing an annual decline of approximately 5% in Pennsylvania.  Geography seems to play a role in that declines are more pronounced in the north and east. Several hypotheses have been formed including insect population declines but no definitive cause has yet to be substantiated.  (See: http://www.bsc-eoc.org/downloa/BWCwi08.pdf).

Most songbird studies rely on information gathered from the birds' breeding grounds, which represent only a small percent of each bird’s lifecycle.  Geolocators allow us to gain insight into activity along migration routes as well as on the wintering grounds.  We are now able to determine migration stop-over sites, more precise routes, and timing. This knowledge can be the basis for valuable conservation efforts.


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