Observations of Apis mellifera foraging at sapsucker drill holes were made during February 1988 in southwestern Virginia. Foraging bouts were dependent upon temperature; more bees visited drill holes when ambient temperatures exceeded 10oC. Honeybees did not feed directly at drill holes but collected congealed sap from bark surfaces

Williams, Charles E

English

ValpoScholar

The Great Lakes Entomologist 
Volume 23 
Number 1 - Spring 1990 Number 1 - Spring 1990 Article 5 
April 1990 
Late Winter Foraging by Honeybees (Hymenoptera: Apidae) at 
Sapsucker Drill Holes 
Charles E. Williams 
Washington and Lee University 
Follow this and additional works at: https://scholar.valpo.edu/tgle 
 Part of the Entomology Commons 
Recommended Citation 
Williams, Charles E. 1990. "Late Winter Foraging by Honeybees (Hymenoptera: Apidae) at Sapsucker Drill 
Holes," The Great Lakes Entomologist, vol 23 (1) 
Available at: https://scholar.valpo.edu/tgle/vol23/iss1/5 
This Peer-Review Article is brought to you for free and open access by the Department of Biology at ValpoScholar. 
It has been accepted for inclusion in The Great Lakes Entomologist by an authorized administrator of ValpoScholar. 
For more information, please contact a ValpoScholar staff member at scholar@valpo.edu. 
1990 THE GREAT LAKES ENTOMOLOGIST 29 
LATE WINTER FORAGING BY HONEYBEES 
(HYMENOPTERA: APIDAE) AT SAPSUCKER DRILL HOLES 
Charles E. Williams l 
ABSTRACT 
Observations of Apis melli/era foraging at sapsucker drill holes were made during 
February 1988 in southwestern Virginia. Foraging bouts were dependent upon tem­
perature; more b es visited drill holes when ambient temperatures exceeded lOoC. 
Honeybees did not feed directly at drill holes but col cted congealed sap from bark 
surfaces. 
The yellow-bellied sapsucker, Sphyrapicus varius, feeds in part upon sap procured 
from holes it drills into tree trunks. Sap-rich drill holes also provide a food resource 
for other birds, mammals, and insects (Batts 1953, Kilham 1953, 1958, Nickell 1965, 
Foster and Tate 1%6, Southwick and Southwick 1980). Through their drilling activi­
ties, sapsuckers furnish access to a supply of carbohydrate often unavailable from 
alternate sources, particularly in late winter and early spring when floral nectar is 
virtually nonexistent (Southwick and Southwick 1980). 
Insect!: of 
various orders have been observed feeding at sapsucker drill holes. 
Most insect observations, however, are made 
in summer when alternate carbohy­
drate sources are abundant and ambient temperatures are high (Nickell 1965, Foster 
and Tate 1966). This note reports observations of late winter foraging by honeybees, 
Apis 
melli/era 
L., at sapsucker drill holes in southwestern Virginia, the first pub­
lished record of honeybees foraging at sapsucker drills during any season. Daily 
visitation patterns of honeybee workers at drill holes, and ambient temperatures 
during foraging periods, are described. Observations of winter foraging by honey­
bees 
are rare; energetic constraints and low nectar availability greatly restrict honey­
bee foraging during winter months (Heinrich 1979, Seeley 
1985). 
MATERIALS AND METHODS 
The study was conducted in Blacksburg, Montgomery County, Virginia during 
February 1988. The focus of honeybee foraging observations was a multi-trunked 
sugar maple (Acersaccharum) having four trunks ranging in size from ll.S to 33.7 
cm dbh. They were the only tree trunks in a wooded corridor that were extensively 
drilled by sapsuckers. Drill holes were confined to the southward (170° S of N) face 
of 
the tree and were distributed from 1 to 
10m above ground level. Observations of 
foraging honeybees were restricted to a 2 m vertical section of the tree trunks 
extending upward from the ground, where the majority of drill holes occurred. 
IDepartment of Biology, Washington and Lee University, Lexington, VA 24450. Current 
address: Department of Zoology, Miami University, Oxford, OH 45056. 
1
Williams: Late Winter Foraging by Honeybees (Hymenoptera: Apidae) at Sapsuc
Published by ValpoScholar, 1990
30 THE GREAT LAKES ENTOMOLOGIST Vol. 23, No.1 
Honeybees foraged almost exclusively within this height range during observation 
periods. 
To determine visitation patterns of honeybees at drill holes, I conducted counts of 
foraging workers on 22, 8, and 29 February, from 1100 to 1700 h. At 15 minute 
intervals, I counted all actively foraging workers on each tree trunk. Counts were 
typically completed in 30 sec or less and were conducted within I m of the tree. 
Ambient temperature was recorded immediately after each bee count with a Wexler 
bimetal thermometer suspended 30 em from the tree surface. Attempts were also 
made to conduct bee counts from 23 to 27 February but freezing temperatures, high 
winds, and (or) rain provided no opportunity for honeybees to forage on these 
days. 
I collected samples of tree sap at hourly intervals from 1200 to 1600 h on 22 
February to obtain an estimate of sap sugar content. Sap flow was extremely vari­
able among drill holes so samples were pooled from several actively flowing drills. 
Sap was collected with clean eyedroppers, placed into small glass vials, and immedi­
ately frozen. Sugar content (sucrose is the predominant sap constituent in woody 
plants [Bidwell 1979]) was determined for subsamples of each hourly collection with 
a handheld, temperature-compensated refractometer (Reichert model 10431). Sap 
sugar concentrations are presented in °Brix (g solute per 100 g solution), as sug­
gested by Bolton et al. (1979). 
RESULTS AND DISCUSSION 
Temperature and visitation patterns: Mean ambient temperatures differeqamong 
observation dates. The lowest mean temperature was ~corded on 28 Feb. (X 8.2 
± OAoC SE) whereas temperature means for 22 Feb. (X = 11.3 ± 0.3°C SE) and 29 
Feb. (X = 11.7 ± 0.2°C SE) were similar. Temperatures generally increased during 
observation periods (Figs. 1-3), and o  all three dates, clear weather prevailed and 
insolation was high. 
Visitation patterns of honeybees were noticeably influenced by temperature dur­
ing the study. On 28 Feb., when the meal!.ambient temperature was 8.2°C, the mean 
number of bees foraging at_drill holes (X 3.2 ± 0.8 S~ was less than half that 
observed on either 22 Feb. (X = 6.7 ± 1.6 SE) or 29 Feb. (X = 8.2 ± 1.8 SE), when 
mean temperatures exceeded 10°C (Figs. 1-3). Foraging duration (the total length of 
time in hours that bees were observed foraging at drill holes), similar for 22 and 28 
Feb. (3.2 hours), was greater by 1.3 hours on 29 Feb. The shift in foraging activity 
toward the later, warmer part of the day on 28 Feb. illustrates the potential role of 
temperature in regulating winter foraging activity. Heinrich (1979) also observed 
decreased honeybee activity at 9°C, even during copious Eucalyptus nectar flows. 
Observations suggest that honeybees may receive thermal benefit from the tree 
trunks on which they forage. The southward face of the drilled sugar maple received 
high insolation for most f the day; thus honeybees probably gained heat from solar 
radiation and from the warmed tree surface. Bees were often observed on trunks 
receiving greater amounts of insolation during cooler portions of the day. 
Sap sugar content and foraging behavior: Sugar concentrations of sugar maple 
sap collected from drill holes were considerably variable for a single source (4.5-28.5 
°Brix, n = 38 samples). The lowest sugar concentrations were similar to those 
previously reported for sugar maple sap (2-3070 sugar [Zimmerman and Brown 
1980]). Honeybees, however, did not forage directly on sap at drill holes; rather, 
they usually foraged on congealing sap that had collected in furrows of bark below 
the drills. By virtue of evaporation, the actual sugar content of sap that bees foraged 
upon was probably much higher than that escaping from drill holes (sugar content 
of 
congealed sap 
was not determined as adequate bark-free quantities could not be 
collected), An alternate nectar source, a patch of flowering purple dead-nettle 
2
The Great Lakes Entomologist, Vol. 23, No. 1 [1990], Art. 5
https://scholar.valpo.edu/tgle/vol23/iss1/5
NUMBER OF 
..... I\) 
o 0 ~ 
00.......... 

0(.) .......... 

001\) .....1t=====. 
0(.)1\)..... 1 '< 
-t 00(.) ..... Jl====:::;---'
-31: 
0(.)(.) ..... 1m 
o OO~ ..... i 
II 
~ 
O(.)~ ..... 
000)..... 
0(.)0)..... 
00........... I 
( \ 
(.\) 
WORKERS 
...... 
\0 
~ 
I\) ~..... ~ o o 
It!I I j I • I 1-m~1 n~~~ 1 I I 
FORAGING 
..... 
o ~ 
I\) ..... 
>-:l 
:I: 
tn 
o 
:;tI 
tn 
~ 
t"'" 
> ~ 
Vl 
tn 
Z 
d 
o 
~ 
t"'" 
o 
a 
~ 
! 
~ Q) ~ ffi ~ Q) ~ ffi ~ Q) ~ 0) 
AMBIENT TEMPERATUR E (Oc) 
w 
Figures 1-3. Number of foraging honeybees and ambient temperature recorded from 1100 to 1700 h on each of three dates: 
(I) 22 
February, 
(2) 28 February, (3) 29 February 1988. Open bars = number of honeybees, solid lines temperature. 
3
Williams: Late Winter Foraging by Honeybees (Hymenoptera: Apidae) at Sapsuc
Published by ValpoScholar, 1990
32 THE GREAT LAKES ENTOMOLOGIST Vol. 23, No. 1 
(Lamium purpureum), occurred near the observation tree (ca. 20 m distant), but no 
honeybees were observed visiting flowers during sap flows. 
In summary, sapsucker drill holes offer a unique carbohydrate source for over­
wintering honeybees. Use of this resource is, however, subject to the vagaries of the 
winter climate. Conditions favorable for winter foraging by honeybees, particularly 
ambient temperatures above lO"C (Heinrich 1979, Seeley 1985), may occur on few 
winter days depending on the region. When environmental conditions permit, active 
drill holes can provide a dependable food resource for overwintering honeybees. 
ACKNOWLEDGMENTS 
Kim 
Williams assisted with field observations and, along with two anonymous 
referees, provided constructive comments on earlier drafts 
of this note. John Ran­
dall loaned m refractometers, Tom Wieboldt identified Lamium purpureum, and 
Garth and Barbara Wilkes permitted me to conduct studies on their land. 
LITERATIJRE CITED 
Batts, H. L. 1953. Siskin and goldfinch feeding at sapsucker tree. Wilson Bull. 65:198. 
Bidwell, R. G. S. 1979. Plant physiology. 2nd. ed. MacMillan Pub\. Co., Inc. New York, NY.
Bolton, A. B., P. Feinsinger, H. G. Baker and I. Baker. 1979. On the calculation of sugar 
concentration in flower nectar. Oecologia 41:301-304. 
Foster, W. L. and J. Tate. 1966. The activities and coactions of animals at sapsucker trees. 
Living Bird 5:87-113. 
Heinrich, B. 1979. Thermoregulation of African and European honeybees during foraging, 
attack, and hive exits and returns. J. Exp. BioI. 80:217-229. 
Kilham, L. 1953. Warblers, hummingbird, and sapsucker feeding on sap of yellow birch. 
Wilson Bull. 65:198. 
Kilham, L. 1958. Red squirrels feeding at sapsucker holes. J. Mamm. 39:596-597. 
Nickell, W. P. 1965. Birds and insects feed at sapsucker trees. Bird-Banding 36:192. 
Seeley. T D. 1985. Honeybee ecology. Princeton Univ. Press. Princeton, NJ. 
Southwick, E. E. and A. K Southwick. 1980. Energetics of feeding on tree sap by ruby­
throated hummingbirds in Michigan. Am. MidI. Nat. 104:328-334. 
Zimmerman, M. H. and C. L. Brown. 1980. Trees: structure and function. Springer-Verlag. 
New 
York, 
NY. 
4
The Great Lakes Entomologist, Vol. 23, No. 1 [1990], Art. 5
https://scholar.valpo.edu/tgle/vol23/iss1/5


Late Winter Foraging by Honeybees (Hymenoptera: Apidae) at Sapsucker Drill Holes

Valparaiso University

The Great Lakes Entomologist Volume 23 Number 1 - Spring 1990 Number 1 - Spring 1990 Article 5 April 1990 Late Winter Foraging by Honeybees (Hymenoptera: Apidae) at Sapsucker Drill Holes Charles E. Williams Washington and Lee University Follow this and additional works at: https://scholar.valpo.edu/tgle  Part of the Entomology Commons Recommended Citation Williams, Charles E. 1990. "Late Winter Foraging by Honeybees (Hymenoptera: Apidae) at Sapsucker Drill Holes," The Great Lakes Entomologist, vol 23 (1) Available at: https://scholar.valpo.edu/tgle/vol23/iss1/5 This Peer-Review Article is brought to you for free and open access by the Department of Biology at ValpoScholar. It has been accepted for inclusion in The Great Lakes Entomologist by an authorized administrator of ValpoScholar. For more information, please contact a ValpoScholar staff member at scholar@valpo.edu. 1990 THE GREAT LAKES ENTOMOLOGIST 29 LATE WINTER FORAGING BY HONEYBEES (HYMENOPTERA: APIDAE) AT SAPSUCKER DRILL HOLES Charles E. Williams l ABSTRACT Observations of Apis melli/era foraging at sapsucker drill holes were made during February 1988 in southwestern Virginia. Foraging bouts were dependent upon tem­perature; more b es visited drill holes when ambient temperatures exceeded lOoC. Honeybees did not feed directly at drill holes but col cted congealed sap from bark surfaces. The yellow-bellied sapsucker, Sphyrapicus varius, feeds in part upon sap procured from holes it drills into tree trunks. Sap-rich drill holes also provide a food resource for other birds, mammals, and insects (Batts 1953, Kilham 1953, 1958, Nickell 1965, Foster and Tate 1%6, Southwick and Southwick 1980). Through their drilling activi­ties, sapsuckers furnish access to a supply of carbohydrate often unavailable from alternate sources, particularly in late winter and early spring when floral nectar is virtually nonexistent (Southwick and Southwick 1980). Insect!: of various orders have been observed feeding at sapsucker drill holes. Most insect observations, however, are made in summer when alternate carbohy­drate sources are abundant and ambient temperatures are high (Nickell 1965, Foster and Tate 1966). This note reports observations of late winter foraging by honeybees, Apis melli/era L., at sapsucker drill holes in southwestern Virginia, the first pub­lished record of honeybees foraging at sapsucker drills during any season. Daily visitation patterns of honeybee workers at drill holes, and ambient temperatures during foraging periods, are described. Observations of winter foraging by honey­bees are rare; energetic constraints and low nectar availability greatly restrict honey­bee foraging during winter months (Heinrich 1979, Seeley 1985). MATERIALS AND METHODS The study was conducted in Blacksburg, Montgomery County, Virginia during February 1988. The focus of honeybee foraging observations was a multi-trunked sugar maple (Acersaccharum) having four trunks ranging in size from ll.S to 33.7 cm dbh. They were the only tree trunks in a wooded corridor that were extensively drilled by sapsuckers. Drill holes were confined to the southward (170° S of N) face of the tree and were distributed from 1 to 10m above ground level. Observations of foraging honeybees were restricted to a 2 m vertical section of the tree trunks extending upward from the ground, where the majority of drill holes occurred. IDepartment of Biology, Washington and Lee University, Lexington, VA 24450. Current address: Department of Zoology, Miami University, Oxford, OH 45056. 1Williams: Late Winter Foraging by Honeybees (Hymenoptera: Apidae) at SapsucPublished by ValpoScholar, 199030 THE GREAT LAKES ENTOMOLOGIST Vol. 23, No.1 Honeybees foraged almost exclusively within this height range during observation periods. To determine visitation patterns of honeybees at drill holes, I conducted counts of foraging workers on 22, 8, and 29 February, from 1100 to 1700 h. At 15 minute intervals, I counted all actively foraging workers on each tree trunk. Counts were typically completed in 30 sec or less and were conducted within I m of the tree. Ambient temperature was recorded immediately after each bee count with a Wexler bimetal thermometer suspended 30 em from the tree surface. Attempts were also made to conduct bee counts from 23 to 27 February but freezing temperatures, high winds, and (or) rain provided no opportunity for honeybees to forage on these days. I collected samples of tree sap at hourly intervals from 1200 to 1600 h on 22 February to obtain an estimate of sap sugar content. Sap flow was extremely vari­able among drill holes so samples were pooled from several actively flowing drills. Sap was collected with clean eyedroppers, placed into small glass vials, and immedi­ately frozen. Sugar content (sucrose is the predominant sap constituent in woody plants [Bidwell 1979]) was determined for subsamples of each hourly collection with a handheld, temperature-compensated refractometer (Reichert model 10431). Sap sugar concentrations are presented in °Brix (g solute per 100 g solution), as sug­gested by Bolton et al. (1979). RESULTS AND DISCUSSION Temperature and visitation patterns: Mean ambient temperatures differeqamong observation dates. The lowest mean temperature was ~corded on 28 Feb. (X 8.2 ± OAoC SE) whereas temperature means for 22 Feb. (X = 11.3 ± 0.3°C SE) and 29 Feb. (X = 11.7 ± 0.2°C SE) were similar. Temperatures generally increased during observation periods (Figs. 1-3), and o  all three dates, clear weather prevailed and insolation was high. Visitation patterns of honeybees were noticeably influenced by temperature dur­ing the study. On 28 Feb., when the meal!.ambient temperature was 8.2°C, the mean number of bees foraging at_drill holes (X 3.2 ± 0.8 S~ was less than half that observed on either 22 Feb. (X = 6.7 ± 1.6 SE) or 29 Feb. (X = 8.2 ± 1.8 SE), when mean temperatures exceeded 10°C (Figs. 1-3). Foraging duration (the total length of time in hours that bees were observed foraging at drill holes), similar for 22 and 28 Feb. (3.2 hours), was greater by 1.3 hours on 29 Feb. The shift in foraging activity toward the later, warmer part of the day on 28 Feb. illustrates the potential role of temperature in regulating winter foraging activity. Heinrich (1979) also observed decreased honeybee activity at 9°C, even during copious Eucalyptus nectar flows. Observations suggest that honeybees may receive thermal benefit from the tree trunks on which they forage. The southward face of the drilled sugar maple received high insolation for most f the day; thus honeybees probably gained heat from solar radiation and from the warmed tree surface. Bees were often observed on trunks receiving greater amounts of insolation during cooler portions of the day. Sap sugar content and foraging behavior: Sugar concentrations of sugar maple sap collected from drill holes were considerably variable for a single source (4.5-28.5 °Brix, n = 38 samples). The lowest sugar concentrations were similar to those previously reported for sugar maple sap (2-3070 sugar [Zimmerman and Brown 1980]). Honeybees, however, did not forage directly on sap at drill holes; rather, they usually foraged on congealing sap that had collected in furrows of bark below the drills. By virtue of evaporation, the actual sugar content of sap that bees foraged upon was probably much higher than that escaping from drill holes (sugar content of congealed sap was not determined as adequate bark-free quantities could not be collected), An alternate nectar source, a patch of flowering purple dead-nettle 2The Great Lakes Entomologist, Vol. 23, No. 1 [1990], Art. 5https://scholar.valpo.edu/tgle/vol23/iss1/5NUMBER OF ..... I\) o 0 ~ 00.......... 0(.) .......... 001\) .....1t=====. 0(.)1\)..... 1 '< -t 00(.) ..... Jl====:::;---'-31: 0(.)(.) ..... 1m o OO~ ..... i II ~ O(.)~ ..... 000)..... 0(.)0)..... 00........... I ( \ (.\) WORKERS ...... \0 ~ I\) ~..... ~ o o It!I I j I • I 1-m~1 n~~~ 1 I I FORAGING ..... o ~ I\) ..... >-:l :I: tn o :;tI tn ~ t"'" > ~ Vl tn Z d o ~ t"'" o a ~ ! ~ Q) ~ ffi ~ Q) ~ ffi ~ Q) ~ 0) AMBIENT TEMPERATUR E (Oc) w Figures 1-3. Number of foraging honeybees and ambient temperature recorded from 1100 to 1700 h on each of three dates: (I) 22 February, (2) 28 February, (3) 29 February 1988. Open bars = number of honeybees, solid lines temperature. 3Williams: Late Winter Foraging by Honeybees (Hymenoptera: Apidae) at SapsucPublished by ValpoScholar, 199032 THE GREAT LAKES ENTOMOLOGIST Vol. 23, No. 1 (Lamium purpureum), occurred near the observation tree (ca. 20 m distant), but no honeybees were observed visiting flowers during sap flows. In summary, sapsucker drill holes offer a unique carbohydrate source for over­wintering honeybees. Use of this resource is, however, subject to the vagaries of the winter climate. Conditions favorable for winter foraging by honeybees, particularly ambient temperatures above lO"C (Heinrich 1979, Seeley 1985), may occur on few winter days depending on the region. When environmental conditions permit, active drill holes can provide a dependable food resource for overwintering honeybees. ACKNOWLEDGMENTS Kim Williams assisted with field observations and, along with two anonymous referees, provided constructive comments on earlier drafts of this note. John Ran­dall loaned m refractometers, Tom Wieboldt identified Lamium purpureum, and Garth and Barbara Wilkes permitted me to conduct studies on their land. LITERATIJRE CITED Batts, H. L. 1953. Siskin and goldfinch feeding at sapsucker tree. Wilson Bull. 65:198. Bidwell, R. G. S. 1979. Plant physiology. 2nd. ed. MacMillan Pub\. Co., Inc. New York, NY.Bolton, A. B., P. Feinsinger, H. G. Baker and I. Baker. 1979. On the calculation of sugar concentration in flower nectar. Oecologia 41:301-304. Foster, W. L. and J. Tate. 1966. The activities and coactions of animals at sapsucker trees. Living Bird 5:87-113. Heinrich, B. 1979. Thermoregulation of African and European honeybees during foraging, attack, and hive exits and returns. J. Exp. BioI. 80:217-229. Kilham, L. 1953. Warblers, hummingbird, and sapsucker feeding on sap of yellow birch. Wilson Bull. 65:198. Kilham, L. 1958. Red squirrels feeding at sapsucker holes. J. Mamm. 39:596-597. Nickell, W. P. 1965. Birds and insects feed at sapsucker trees. Bird-Banding 36:192. Seeley. T D. 1985. Honeybee ecology. Princeton Univ. Press. Princeton, NJ. Southwick, E. E. and A. K Southwick. 1980. Energetics of feeding on tree sap by ruby­throated hummingbirds in Michigan. Am. MidI. Nat. 104:328-334. Zimmerman, M. H. and C. L. Brown. 1980. Trees: structure and function. Springer-Verlag. New York, NY. 4The Great Lakes Entomologist, Vol. 23, No. 1 [1990], Art. 5https://scholar.valpo.edu/tgle/vol23/iss1/5

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Late Winter Foraging by Honeybees (Hymenoptera: Apidae) at Sapsucker Drill Holes

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