Purple Martin (Progne subis)
Associated Species: Other species that may use habitat in a similar way and/or respond similarly
to threats, management, and conservation activities include Violet-green Swallow, Mountain
Chickadee, White-breasted Nuthatch, House Wren, and Mountain Bluebird.
Distribution: Purple Martins breed across the eastern half of North America from southern
Canada south to south Florida, and from the east coast west to the central Canadian Provinces,
western Dakotas, Kansas, Oklahoma, and Texas. They are local and scattered breeders in the
Intermountain West and along the Pacific coast from Washington south to southern California.
Winters in South America east of the Andes Mountains south from Venezuela to northern Bolivia
and southeastern Brazil. In Colorado, they are an uncommon breeding species in the western
mountains and accidental east of the Continental Divide and on eastern plains. They are rare
spring and fall migrants in western valleys and on eastern plains.
Habitat Requirements: Purple Martins breed primarily along the edges of late-seral,
aspen-dominated woodlands, usually near water. They are obligate secondary cavity nesters,
using abandoned woodpecker cavities in isolated live aspen or aspen snags and rarely in
ponderosa pine or Douglas-fir. Key habitat features include live aspen trees or snags containing
cavities and averaging 36 cm (14 in) dbh, located within 50 m (175 ft) of the edge of mountain
parks, and within 300 m (1,000 ft) of surface water. The height of nest cavities in live aspen
averages 35% of tree height and are usually well below the tree crown.
Ecology: Purple Martins arrive in Colorado by early June and depart on autumn migration by late
August. They are loosely colonial, nesting in small, isolated colonies of one to three pairs. They
defend only the nest cavity, and a single tree may contain two or three nests. Nests are primarily
in abandoned Northern Flicker cavities. Mud is required for the nests. Their diet consists almost
entirely of insects captured in flight as they forage over mountain parks, riparian zones, reservoirs,
moderate-sized forest openings, and within open forest canopies. Martins are single-brooded.
Breeding site fidelity is high.
Management Issues and Conservation Recommendations: Preferred nesting trees are live and
located in parks, along forest edges, or in open-structured stands. Martin use of artificial nest
boxes is limited in the western U.S. Retain all live cavity- bearing trees and large diameter
snags. Retain a minimum of 8-12 snags or live cavity-bearing trees per 4 ha (10 ac), and all
snags greater than 48 cm (19 in) dbh, especially those near water, riparian corridors, or stand
edges. Retain broken and spike-topped trees.
Purple Martins have a very high fidelity to a limited number of nesting sites, which have rather
precise specifications. These number and general location of these sites appear to have remained
relatively stable over time. Maintain natural disturbance regimes and the dynamic nature of
aspen communities at the landscape scale. Where natural disturbance mechanisms cannot be
reintroduced, mechanical disturbance events should mimic, as closely as possible, the
disturbance history of the local area and surrounding habitats. Maintain sufficient live
cavity-tree and snag densities within and adjacent to commercial harvest areas.
Status and Reasons for Concern: Purple Martin is classified as a Sensitive Species in U.S.
Forest Service Region 2. Population trends of this species in Colorado are not adequately
monitored by the BBS. Population trends appear to be stable or increasing in the western U.S.,
but have declined significantly in recent years in the eastern portion of the species range. They
were present on an average of 5.18% (SE = 1.54) of the BBS routes run in Physiographic Area
62 in Colorado, 1988-1998, at an average abundance of 0.15 (SE = 0.05) individuals per route.
The mean number of routes run each year was 21.1 (SE = 3.06). CBO initiated a statewide
monitoring program in 1999, visiting known and likely nesting sites and initiating a database of
colony sites. They counted 174 birds at 31 active colonies. No birds were found at six historical
sites that were visited. The database contains 81 sites of reported martin use. This species is
monitored by MCB with a statewide census.
Biological Objective: Maintain current breeding densities at all known nest sites. Maintain or
increase the current number of colonies. Continue to monitor known breeding sites and survey
other potential nest sites within the state.
Selected References: Andrews and Righter 1992, Baicich and Harrison 1997, Dobkin 1994,
Ehrlich et al. 1988, Kingery 1998, Price et al. 1995, Reynolds et al. 1991, Svoboda et al. 1980,
Yanishevsky and Petring-Rupp 1998.