ig. 26.—Adult male purple martin. 
colonies in upland habitats, but this void may 
reflect the inadequate level of ornithological ex- 
tion of Illinois. The percentage of the state 
lation nesting in natural cavities is unknown, but 
ibly very small. Martins have also been recorded 
1g in the walls of buildings (Blocker 1933; 
ks, unpublished notes 1889) , and in bridge super- 
ures, besides bird houses of many designs (Anon. 
side from recommendations on the placement of 
boxes—13-18 feet high, in the open (Widmann 
and Gault 1934-1935) —there are no data on the 
cteristics of even the domestic habitat of purple 
ns, though Widmann (1907) believed that old 
towns were most favored. There are, or have 
active colonies in the business districts of small 
€g., Durand, LeRoy and Griggsville, Ilinois, 
S near the Chicago loop as Lincoln Park, but the 
ce limits of martins to human traffic, as well 
ir essential habitat requirements, are unknown. 
than most Illinois species though, the martin 
seems safe from habitat destruction, what with the 
expanding acreage of human residential areas. 
There are few population measurements for the 
purple martin in Illinois. Our strip censuses of urban 
areas in 1958 showed densities of 25 martins per 100 
acres in northern Illinois towns, 11 per 100 acres in 
central Illinois, and 42 per 100 acres in southern 
Illinois. We recorded measurable populations of pur- 
ple martins away from human residential habitat only 
in northern Illinois, where martins were foraging over 
fallow fields (about 4 birds per 100 acres) , shrub areas 
(2 per 100 acres), oat fields (2 per 100 acres), soy- 
bean fields (1 per 100 acres), alfalfa fields (1 per 100 
acres), and cornfields (0.2 per 100 acres). 
In 1907-1909 Alfred Gross (personal communica- 
tion) recorded June foraging densities for the martin 
in southern Illinois as follows: about 1 martin per 100 
acres over fallow fields and pastures, 0.5 per 100 over 
cornfields, and 0.3 per 100 acres over hayfields. As 
all of these figures were based on cross-country cen- 
suses, the location of colonies in relation to available 
29 
