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Plot 1, which is my property in
Matchedash, ( Lat 44 47 and Long 79 35 ) was the initial site studied, and casual observations there
led to our winter project.
Yellow-bellied Sapsucker holes have been observed in this area so
frequently on Eastern Hemlock trees that we considered
the holes diagnostic of this commonly found tree. These holes are usually
found in rows, most often horizontally, but often vertically,
as well as casual holes sprinkled throughout. The holes are commonly at
eye-level, and above, and can be found almost to the
snow-covered base. The sapsucker is looking for the phloem (sap), which
attracts insects, especially ants. The bird bundles up the
ants in the phloem, and flies the food to the nestlings. It is reported
that the birds reopen these holes when they return in the spring.
Most local observers would be aware of these holes –there is even an
interpretive sign at Grant’s Woods.
We studied the Ironwood, or Hop
Hornbeam Tree. The bark is grayish, and loose at both ends.
According to “Trees in Canada”, they are small trees, up to 12 meters
high and 25 cm (9.8 inches) in diameter, occasionally larger.
The fungus was Aleurodiscus oakesii, which is rarely reported. Until this winter we
only knew of 2 sites in our area near Orillia.
According to Tom Volk (Fungus of the Month) Aleurodiscus oakesii is
a small but a very commonly overlooked crust fungus.
The food source for the fungus is actually the dead bark of the tree – a
saprophyte. The outer bark of woody trees
is no longer functioning in the transport of sugars. This task is taken by
the inner bark with its functional secondary phloem.
While this fungus is reported to grow on oak trees, it is most commonly
found in the Northeastern USA
on Ironwood trees (report of Sam Ristich from Maine).
Our fungus was confirmed by Bernhard de Vries of the Netherlands.
We also noted that the large
Ironwood trees with this fungus were covered with Yellow-bellied
Sapsucker holes.
HYPOTHESIS: The fungus made the
tough tree suitable for Yellow-bellied sapsuckers.
The question: must the Hop-hornbeams be infected before the YBSS is
interested, or is the size of the tree the determining
factor for both the fungus and the bird, with no relevance to each other?
OBSERVATIONS: YBSS holes were found
on Eastern Hemlocks, American Elms, and Ironwoods.
We only looked at and measured trees easily accessible beside the trails
because of the snow cover.
The depth of the holes, as measured was about 0.3 cm..
Hemlocks appear to be the preferred
trees for YBSS, both in groves and singly. They prefer mid size trees
10.8 – 14.6 inches diameter at breast height( DBH) .
Almost all hemlocks in this size range have been used by the birds. Most
holes are horizontal lines, occas. some vertical lines, but also random
holes.
3 American Elms with a circumference
of greater than 12.8 inches DBH were found with abundant holes, often
horizontally, as well as random holes.
Because of the Elm die off in the last 30 years, there were few trees to
study.
Ironwoods (Hop-Hornbeams) are also
used. There were 2 large trees with abundant holes.
First tree was split near to the ground, and each trunk was measured
18.8 inches (DBH) and 14.9 inches (DBH).
Another tree was measured at 8.91 inches (DBH). Both these trees were
abundantly covered with Aleurodiscus oakesii
Although we had not previously realized it, there are many more
Ironwoods when we continued on the trail, which are favoured by YBSS.
YBSS holes were found on all trees greater than 8.28 inches DBH.
Although trees greater than 5.09 (DBH) had no holes, most of this size
had the saprophytic fungus.
CONCLUSION:
Ironwoods are favoured trees for Yellow-bellied sapsucker holes, and for
Aleurodiscus oakesii
but their use depends on the size of the tree, rather than the presence of
the fungus.
(Nevertheless, no Ironwoods that were not host trees to the fungus were
used by the Sapsuckers, so maybe .. )
We have spent 1-3 hours at 6 other
sites, and observations and discussion can be found
link here.
Other areas and other forest types have been studied in the literature,
and have been conducted during the season when the Sapsuckers are
nesting.
One of us (MH) may do further studies when the birds arrive back,
depending on her tolerance for the black flies.
Studies by Nancy Ironside, with
assistance from Mary and Omer Mick, Joan Rosebush, Wendy Hutchings,
Ellen Dennig,
Leonore Wianko and Margo Holt (who is especially involved in the
literature search).
Editorial assistance from Tony Wright ( Mycological Society of Toronto)
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