2007 NORTHEASTERN NATURALIST 14(1):145–149
Use of a Robin’s Nest as a Cache Site for Truffles by a
Karl Vernes1,* and Nelson Poirier2
Abstract - A Turdus migratorius (American Robin) nest was found in southern New
Brunswick, Canada, containing 52 mature sporocarps (“truffles”) of Elaphomyces
granulatus (false truffle), a species of hypogeous fungus common across North
America. Teeth marks on the truffles indicated they had been cached in the nest by a
Tamiasciurus hudsonicus (red squirrel). The truffles appeared to have been air-dried
before caching and were well preserved. Mean (± SD) weight of each truffle was 3.3
± 1.4 g, with a total weight of cached material of 173 g. Although caching of
epigeous fungus by squirrels is well documented in the literature, records of cached
hypogeous fungi are relatively uncommon, and caches involving disused bird nests
appear to be rarely encountered.
Although Tamiasciurus hudsonicus (Erxleben) (red squirrels) are
known to rely heavily on conifer seeds for nutrition (Hurley and Robertson
1990, Rusch and Reeder 1978, Steele 1998), they also consume a wide
variety of foods such as nuts, buds, fruits, bark, small mammals, fledgling
birds (Klugh 1927, Layne 1954, Smith 1968), mushrooms (Buller 1920,
Cram 1924, Currah et al. 2000, Dice 1921, Smith 1968), and a great variety
of hypogeous (“truffle-like”) fungi (Fogel and Trappe 1978, Smith 1968,
Vernes et al. 2004). In southern New Brunswick, Canada, the diet of the
red squirrel can comprise anywhere between 45 and 95% fungus, with
fungal dependency related to season, and possibly, the variability in conifer
seed production and availability (Vernes et al. 2004). Red squirrels in
southern New Brunswick consume at least 19 species of truffle-like hypogeous
fungi, but the diversity changes seasonally, being high in summer
(11–16 taxa), low in fall (5 taxa), and remaining low during winter and
spring (3–7 taxa; Vernes et al. 2004). Fungi consumed in the winter are
mostly from sporocarps collected, dried, and cached in the summer and fall
(Hardy 1949, Murie 1927, Smith 1968).
Red squirrels are usually “larder hoarders” (Steele 1998), caching large
quantities of food items in a few selected locations. The most commonly
seen (and documented) squirrel larder is the cache of conifer cones stored on
the forest floor, usually beneath a midden of discarded cone fragments (Hatt
1943, Steele and Koprowski 2001). Caches containing fungi are less commonly
documented, probably because these are usually hidden within tree
1Ecosystem Management, The University of New England, Armidale, New South
Wales 2351, Australia. 2PO Box 25091, Moncton, New Brunswick E1C 9M9,
Canada. *Corresponding author - email@example.com.
146 Northeastern Naturalist Vol. 14, No. 1
hollows, in “witches brooms” (a dense cluster of twigs in a tree caused by an
environmental or biological stressor) high in the canopy, and within dead
standing trees (Buller 1920, Cram 1924, Hardy 1949, Laursen et al. 2003).
Methods and Results
In April 2002, a cache of Elaphomyces granulatus Fries (false truffles)
was brought to our attention in a suburban backyard in the city of Moncton,
NB (46°07'N, 64°41'W). The cache was found on the margin of a forested
block, abutting a relatively new housing subdivision. The cache was unusual
in that the truffles had been stored within a nest (Fig. 1) made by a Turdus
migratorius Linnaeus (American Robin). A robin had been observed using
the nest during the preceding summer (2001), and a red squirrel had been
seen active in the vicinity of the nest later that year, so the squirrel may have
begun using the nest following fledging of chicks and migration south by the
robins prior to winter. The nest was approximately 2 m above the ground in
a young Abies balsamea L. (balsam fir) tree. In total, 52 E. granulatus
truffles had been stored in the nest (Fig. 2), and most of the truffles bore the
teeth marks of a small mammal (Fig. 3), presumably made when the truffles
were gathered and transported to the cache. Using museum skulls (teaching
collection of Mount Allison University, NB) from red squirrels (N = 10),
Tamias striatus Linnaeus (eastern chipmunks; N = 2) and Glaucomys
sabrinus Shaw (northern flying squirrels; N = 3) collected in southern New
Figure 1. Robins’ nest in a young balsam fir tree in suburban Moncton, NB, packed
by a red squirrel with 52 false truffles.
2007 K. Vernes and N. Poirier 147
Brunswick, we were able to confidently match the bite marks to a red
squirrel. Our examination of these skulls suggested that eastern chipmunk
skulls and teeth were too small to have made the puncture marks, while the
lower incisors of northern flying squirrels were too broad for a suitable
match. However, the upper and lower incisors of the red squirrel skulls
articulated well with the bite marks.
Figure 2. Robins’ nest and the false truffles that had been stored within it by a red
Figure 3. Example of the bite
marks (indicated by arrows)
seen on false truffles that we
attributed to a Tamiasciurus
hudsonicus (red squirrel),
based upon the shape and size
of incisors examined from the
three species of small sciurids
that potentially occurred at the
148 Northeastern Naturalist Vol. 14, No. 1
Mean (± SD) weight of each truffle recovered from the nest was 3.3 ± 1.4 g
(range 1.2–6.8 g), with a total weight of the cached fungus being 173 g. The
truffles were preserved in reasonably good condition, although those lower in
the nest had a light covering of mould on their surface. The general lack of
deterioration of the truffles, despite them being packed tightly together,
suggests that they might have been air dried by the squirrel elsewhere before
caching, but we have no direct evidence for this. That the cache was found
towards the end of winter is probably also an indication that the squirrel that
preserved and stored the fungus either died during the winter before the cache
could be utilised or misplaced the location of the cache.
Caching of epigeous (above-ground “mushroom”) fungi by red squirrels
is well documented in the literature. Buller (1920), Cram (1924) and Murie
(1927) observed that red squirrels dried mushroom fungi in summer and fall,
doing so by hanging them among the branches of trees before storing them in
knot holes, hollow branches, and nests of twigs high in the canopy, as well as
in holes beneath logs and stumps at ground level. In Alaska, Laursen et al.
(2003) reported that red squirrels cache both epigeous and hypogeous fungal
sporocarps in “witches brooms” caused by mistletoe infection of spruce
trees. Garnett et al. (2004) also report Sciurus aberti Woodhouse (Abert’s
squirrel) using “broomed” Pinus ponderosa Douglas ex C. Lawson (ponderosa
pine) regularly as cache sites in northern Arizona. Similarly, Sciurus
vulgaris Linnaeus (European red squirrel), a scatterhoarder, has been observed
drying and caching fungi on the branches of trees in Scotland (Lurz
and South 1998). In a singular observation, Dice (1921) noted that a red
squirrel had packed dried mushrooms into empty cans in an abandoned cabin
in Alaska after first drying them on shelves and other surfaces, showing the
adaptability and opportunism displayed by the species in utilising novel
cache sites. Relatively fewer records of caches of hypogeous (“truffle-like”)
fungi have been reported, although Hardy (1949) gives a detailed account of
a red squirrel cache in a burnt-out tree stump in British Columbia containing
59 sporocarps belonging to 13 species of fungi, many of which were hypogeous
The earliest and most detailed treatment of fungal caching by red squirrels
was by Buller (1920), who presented several accounts of fungal caches
by red squirrels, and was the first to report that squirrels dry fungi in the
branches of trees. Buller (1920) also recounts a letter received by him from a
resident of Manitoba, Canada, that states “The chief place I have found
fungus stores have been woodpeckers’ holes, hollow trees, and birds nests—
especially crows’ nests.” However, further detail concerning the use of
birds’ nests as cache sites for fungus are lacking from that account, and we
could find no other accounts in the literature of birds’ nests as cache sites,
suggesting that this phenomenon is rarely observed.
2007 K. Vernes and N. Poirier 149
We thank Noella Gagnon for bringing this observation to our attention, and Felix
Bärlocher, Mount Allison University, for hosting the senior author while on study
leave, during which time this paper was prepared. Colleen Barber, David Richardson,
and two anonymous referees made suggestions that improved an earlier draft of the
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