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THE WILSON JOURNAL OF ORNITHOLOGY • Vol 123, No. 1, March 2011 
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FIG. I. Orientation (relative to magnetic north" n ' 3 sq°\ nf >. 
trees (Pinus spp.) ( n = 43) i n eastern r ’ 9 ^ of sap wells excavated by Yellow-bellied Sapsuckers on pine 
ansas. Bars along the radial axes indicate the number of trees within 30° intervals. 
ers and a sufficient number of sap wells tc 
ascertain the orientation of the sap well cluster. 
ree species loraged upon included Austrian pine 
n ' ,ll S ra ' n ~ ^ trees), red pine (P. resinosa\ n = 
- trees), and white pine (P. strobus ; n = 38 trees) 
Average DBH was 37.87 ± 13.78 cm (SD) and 
average distance from ground to sap well cluster 
was 1.16 ± 0.48 m (SD). Sap wells were not 
randomly distributed around tree boles and 
L- = 5^ Si§nifiCant southwesterly orientation 
(a 246.04 , s = 65.46°, P = 0.004; Fig. 1). 
DISCUSSION 
Observed patterns of nonrandom sap well 
orientation on pines in eastern Kansas may be a 
.esult of Yellow-bellied Sapsucker avoidance of 
e northern side of tree boles, rather than selection 
of the southwestern side. Trees foraged upon by 
this species in this region of the United States are 
often planted as single row wind breaks, greatly 
exposing foraging sapsuckers to high velocity 
winds from the north during the winter months 
Benefits of southwesterly sap well orientation may 
include decreased metabolic stress (i.e., fewer 
calories burned and/or reduced probability of 
desiccation) or increased perching stability as a 
result of wind avoidance. 
Exposure to solar radiation can result in 
significant temperature differences between ex¬ 
posed and shaded sides of trees (Derby and Gates 
1966). More optimal foraging opportunities exist 
for sap feeding organisms that select feeding sites 
where ambient temperature or solar radiation 
positively influence the rate of sap flow (Gold- 
ingay 1987, Howard 1989, Pejchar and Jeffrey 
2004). Pejchar and Jeffrey (2004) found that the 
Akiapolaau ( Hemignathus munroi ), an endan¬ 
gered endemic species of Hawaiian Honeycreeper 
that uses similar foraging techniques as sapsuck¬ 
ers, feeds preferentially on ohia (. Metrosideros 
polymorpha) trees on slopes that receive the 
greatest intensity of sunlight and, therefore, have 
the highest rates of sap flow. Yellow-bellied 
Sapsuckers in eastern Kansas may similarly 
