SHORT COMMUNICATIONS 
165 
overwinters throughout much of Mexico, the 
eastern United States, and Canada (Howell 1952, 
Walters et al. 2002). The Yellow-bellied Sap- 
sucker, like other North American woodpeckers, 
forages on a variety of foods including fruits and 
insects; however, sapsuckers are also known to 
consume sap as a primary food source (Beal 1911, 
Howell 1952, Tate 1973, Williams 1975, Wilkins 
2001, Walters et al. 2002). Sapsuckers in winter 
and early spring, obtain sap from small, circular 
wells excavated in the xylem tissue of trees 
(Foster and Tate 1966, Tate 1973). Wells 
excavated in phloem tissue of trees are used for 
foraging during the summer months (Tate 1973, 
Eberhardt 1994). The placement of sap wells 
excavated by Yellow-bellied Sapsuckers has been 
previously studied in relation to preferred tree 
species (Conner and Kroll 1994, Eberhardt 1994), 
bark- and phloem thickness (Wilkins 2001), tree 
health (i.e., fungal infections and wounds from 
lightening) (Ohman and Kessler 1964, Lawrence 
1967), bark moisture (Eberhardt 2000), tree 
density (Eberhardt 2000), proximity to nest site 
(Eberhardt 1994), and sucrose content of sap 
(Kilham 1964, Tate 1973, Wilkins 2001). How¬ 
ever, factors that influence spatial orientation of 
sap wells around tree boles remain unclear. 
Observations by Kilham (1956) imply that 
sunlight and sap flow rates may dictate sap well 
orientation. He noted that Yellow-bellied Sap¬ 
suckers could be observed excavating wells in the 
morning hours and returning to these wells to feed 
in the afternoon when sap flow was at its peak. 
My objective was to ascertain if orientation of sap 
wells excavated around tree boles in eastern 
Kansas is nonrandom. I predicted that sap wells 
would be oriented toward the south-southwest, the 
side of the tree most exposed to sunlight during 
daylight hours at this latitude throughout months 
when sapsuckers are present. 
METHODS 
I measured the orientation of sap wells (relative 
to magnetic north; 0-359°) excavated by Yellow- 
bellied Sapsuckers in March and April 2008 at 
five sites in Emporia, Kansas, USA (38" 24' 29" 
N, 96° 11' 13" W; Lyon County). The study sites 
were on public property (e.g., city parks) within 
the city limits of Emporia and were landscaped 
with a variety of native and non-native deciduous 
and coniferous tree species generally planted in 
single, evenly spaced rows to serve as wind blocks 
around the perimeter of each property. Detailed 
temperature- (collected from 1971 to 2010) and 
wind data (collected from 2005 to 2010) were 
obtained through the National Climatic Data 
Center (http://www.ncdc.noaa.gov/oa/ncdc.html). 
Emporia’s average monthly temperatures ranged 
from 2 to 21° C during the time of year when 
Yellow-bellied Sapsuckers are present in this 
region (Oct-Mar; Walters et al. 2002). Average 
monthly wind speeds for this same time period (i.e., 
Oct-Mar), ranged from 16.8 to 19.9 kph and 
average monthly wind orientations (relative to 
magnetic north) were between 1 and 36°, indicating 
that prevailing winds are from the north when 
sapsuckers are present. 
Sap wells were identified as small, evenly 
distributed holes excavated in horizontal lines on 
tree boles. Other sapsuckers excavate wells in 
similar patterns, but the Yellow-bellied Sapsucker 
is the only sapsucker species known to overwinter 
in this region. Sap well orientation was measured 
as the direction of highest sap well concentration 
when >10 sap wells were observed on a single 
tree. I estimated the area of highest sap well 
concentration as the side of the tree bole 
containing >50% of the sap wells excavated 
and recorded sap well orientation from the center 
of the sap well cluster. No distinction was made 
between newly- and previously excavated wells 
due to uncertainties regarding time since sap well 
excavation. I also measured the diameter at breast 
height (DBH; cm) and distance from ground to 
sap well cluster (m) for each tree where sap well 
orientation was recorded. 
Mean DBH, mean distance from ground to sap 
well cluster, and their associated standard devia¬ 
tions were calculated. Analyses for circular 
distributions (Zar 1999) were used to examine 
mean orientation (a) and circular standard devi¬ 
ation (s) of sap wells excavated by Yellow-bellied 
Sapsuckers. I used Rayleigh’s test of uniform 
distribution to examine if sap well orientation was 
nonrandom (Zar 1999). Approximate P-values 
were obtained using 5,000 permutations and 
macros created for the SAS system (SAS Institute 
Inc. 2003) by Kolliker and Richner (2004). The 
alpha level for Rayleigh’s test was set at 0.05. 
RESULTS 
Sap wells excavated by Yellow-bellied Sap¬ 
suckers were observed exclusively on pine trees 
(Pinus spp.) at the study sites. Thirty-eight percent 
of the pine trees examined (n = 114) contained 
evidence of foraging by Yellow-bellied Sapsuck- 
