Feather Mites Associated with Eastern Bluebirds (Sialia
sialis L.) in Georgia, Including the Description of a New
Species of Trouessartia (Analgoidea: Trouessartiidae)
Reneé E. Carleton and Heather C. Proctor
Southeastern Naturalist, Volume 9, Issue 3 (2010): 605–623
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2010 SOUTHEASTERN NATURALIST 9(3):605–623
Feather Mites Associated with Eastern Bluebirds (Sialia
sialis L.) in Georgia, Including the Description of a New
Species of Trouessartia (Analgoidea: Trouessartiidae)
Reneé E. Carleton1,* and Heather C. Proctor2
Abstract - Eastern Bluebirds inhabiting a grass-dominated agricultural environment
within a northwestern Georgia land tract were examined over the course of three
breeding seasons (2004 through 2006) to assess the presence of ectosymbionts. More
than 90% of bluebirds examined harbored plumicolous feather mites of four species:
Pterodectes sialiarum (Proctophyllodidae), Mesalgoides sp. (Psoroptoididae), Analges
sp. (Analgidae), and a previously undescribed Trouessartia sp. The recovery of
P. sialiarum represented the second report of this species, which had previously been
recorded from Eastern Bluebirds in Guatemala. New host records for Mesalgoides
sp. and Analges sp., and a description of Trouessartia sialiae sp. nov. also resulted
from the study. Mite abundance did not vary among groups of birds categorized by
subjective quantification, with the exception of a group of a few individuals harboring
a vast number of mites. Abundance was not correlated with mean host body mass
or body condition and was also independent of host sex. Feather mites were most
commonly found on primary remiges, occasionally on secondary remiges, and rarely
on rectrices; each mite species was located on a specific type of feather. Lice were
also occasionally recovered, but were reported separately.
Astigmatan feather mites are common symbionts of nearly every avian
family. Members of this highly diverse assemblage (superfamilies Analgoidea,
Freyanoidea, and Pterolichoidea) occur worldwide and include more
than 2000 described species, with at least that many awaiting description
(Dabert and Mironov 1999, Gaud and Atyeo 1996, Proctor 2003). Feather
mites that dwell on the vanes of flight feathers are considered non-parasitic
based on evidence that they feed on uropygial secretions, pollen, and possibly
accumulations of microorganisms rather than host tissues (Blanco and
Frias 2001, Blanco et al. 1997, Proctor 2003, Proctor and Owens 2000). Host
specificity varies from a single host species per mite species to multiple host
species from several families; however, most well-studied feather mites appear
to be restricted to hosts within a single genus or family (H.C. Proctor,
pers. observ.). Means of dispersal and colonization of new hosts by feather
mites is unclear. Direct contact between conspecifics is the most likely method
of transfer between hosts (Proctor 2003). A form of horizontal transfer
involving hippoboscid flies may occur occasionally (Philips and Fain 1991),
1Department of Biology, School of Mathematical and Natural Sciences, Berry College,
2277 Martha Berry Highway NW, Mount Berry, GA 30149. 2Department of
Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9 Canada. *Corresponding
author - firstname.lastname@example.org.
606 Southeastern Naturalist Vol. 9, No. 3
although one recent study found no instances of phoresy by feather-dwelling
mites on hippoboscids (Jovani et al. 2001). Vane-dwelling feather mites are
highly adapted to aerodynamic stresses associated with specific flight feathers,
although members of a given mite species do vary their locations within
and among feathers depending on host activity, feather age, and ambient
temperature (Dubinin 1951, Jovani and Serrano 2004, Proctor 2003).
Although there is little evidence that vane-dwelling mites negatively affect
their hosts, feather mite-host relationships have been frequently studied
to determine effects of parasites on host condition and fitness (Behnke et al.
1995, Figuerola 2000, Pérez-Tris et al. 2002, Rózsa 1997). Some studies suggest
feather mite abundance is positively correlated with the presence of viral
lesions (Thompson et al. 1997) and negatively correlated with amount of pectoral
muscle mass (Harper 1999). If this is the case, then even if feather mites
are not directly affecting host condition, their presence and abundance on
hosts may provide clues about the health status of many avian populations.
We observed numerous feather mites during a banding study of a Sialia
sialis L. (Eastern Bluebird) population nesting on a grass-dominated agricultural
site in Georgia. Only three species of feather mites, Pterodectes sialiarum
(Stoll 1893) (Proctophyllodidae), Proctophyllodes vesca Atyeo and Braasch
(1966) (Proctophyllodidae), and Trouessartia sp. (Trouessartiidae) (Forrester
and Spalding 2003; J. Mertins, USDA, APHIS, National Veterinary Services
Laboratory, Ames, IA, pers. comm.) have been previously reported from Eastern
Bluebirds. Objectives of this study were to identify mite species associated
with the population, estimate mite prevalence, and make preliminary observations
of ecological relationships between mite abundance and host condition.
The study was conducted on a land tract in Floyd County (34.282799°N,
85.191803°W) that lies within the Ridge and Valley physiographic region
of Georgia. The study area consisted of three non-contiguous sites of
grass-dominated agricultural management: a Cynodon dactylon (L.) Pers.
(Bermuda Grass)-dominated field managed for hay production, a cattle pasture
with Festuca sp. (perennial fescue) and mixed low-growing herbaceous
plants, and a low-management field with features of early succession.
We conducted the study during the breeding seasons (March through
August) of 2004, 2005, 2006, 2008, and 2009. Adult Eastern Bluebirds (n =
228) were captured within nest boxes using a trap-door apparatus. Captures
were attempted within five days after a clutch hatched and between
07:00 am–12:00 pm. Adults were banded for identification purposes with
individually numbered United States Geological Survey aluminum leg bands
on initial capture. Sex of each individual was recorded. Birds were weighed
to the nearest 0.5 g using a spring scale and cloth bag, and the amount of visible
subcutaneous fat in the depression between the furcula (SFS) was scored
as no fat (0) or fat present (1) (Krementz and Pendleton 1990). A subjective
2010 R.E. Carleton and H.C. Proctor 607
measurement of pectoral muscle mass (PMS) was scored as emaciated (E),
thin (T), muscled (M), well-muscled (W), or robust (R) (Graham 1993).
Feather mites were detected by visual examination (see McClure 1989)
aided by manual ruffling of feathers and extension of both wings to allow maximum
exposure of flight feathers (remiges). Tail feathers (rectrices) were also
examined for mites. Feather mite presence, specific feathers inhabited on each
wing and the tail, and a subjective estimation of mite abundance were recorded
for all birds. The small size of the mites and the need to minimize handling
time prevented quantitative measurement of mite numbers. We subjectively
defined abundance as very abundant (5), abundant (4), moderately present (3),
rare (2), and very rare (1) based on the number of feathers inhabited and distribution
of mites on individual wing feathers (Fig. 1). Representative feather
sections harboring mites were snipped from 14 adults during 2004 and preserved
in 70% ethanol (EtOH) for mite identification.
Figure 1. Illustration depicting feather mites on Eastern Bluebird primary remiges
corresponding to abundance scores: 1 = very rare, 2 = rare, 3 = moderate, 4 = abundant,
5 = very abundant.
608 Southeastern Naturalist Vol. 9, No. 3
Fourteen male bluebirds were sacrificed during the latter six weeks of the
2006 season for necropsy and quantification of feather mite loads. Each carcass
was placed in a sealed plastic bag and refrigerated before post-mortem
examination. Following the method described by Clayton and Walther (1997),
a solution of water, 10% isopropyl alcohol, and household detergent was
added to each bag. The contents were agitated for 5 min to dislodge ectosymbionts.
After the solution was decanted into a large beaker, the carcass was
removed and both the plastic bag and carcass were rinsed with clean water to
remove any remaining fauna. Arthropods were recovered by filtering wash and
rinse solutions. Each filter paper was examined using a dissecting microscope,
and recovered specimens were placed into vials containing 70% EtOH.
Mite-bearing Eastern Bluebird feathers that were snipped in 2004 were
soaked in 80% EtOH to hydrate and preserve the mites. One of us (H.C.
Proctor) examined feathers and the preservative under a dissecting microscope
and removed the mites. Exemplars of each morphotype were cleared
in lactic acid for a minimum of 12 hours, slide-mounted using commercially
available poly-vinyl alcohol (PVA) (BioQuip Products, Rancho Dominguez,
CA), and then cured for 4 days at ca. 40 °C on a slide-warmer. Mites were
identified using a Leica DMLB compound microscope with differential
interference contrast (DIC) lighting and the following literature: Gaud and
Atyeo (1996), Santana (1976), and Stoll (1893). Mites from four genera were
identified: Mesalgoides (Psoroptoididae), Analges (Analgidae), Pterodectes
(Proctophyllodidae), and Trouessartia (Trouessartiidae). Exemplars of each
taxon are deposited in the E.H. Strickland Entomological Museum, Department
of Biological Sciences, University of Alberta, Edmonton, AB, Canada
(UASM) Specimens of Pterodectes sialiarum (Stoll) (Proctophyllodidae)
were sent to experts in Brazil for confirmation of their identity (Valim and
Hernandes 2008). Additional specimens of P. sialiarum are deposited in the
collection of Acari of the Departamento de Zoologia et Botânica da Universidade
Estadual Paulista, São Paulo, Brazil.
The Trouessartia proved to be a new species, which we describe here. Pencil
drawings were made by H.C. Proctor of a male and a female mite at 400x
using a 1x drawing tube attached to a Leica DMLB compound microscope
with differential interference contrast (DIC) lighting. Measurements were
taken at 200x and 400x using a calibrated ocular micrometer. The drawings
were digitized using a flatbed scanner and then traced in Adobe Illustrator CS
version 11.0.0 (Adobe Systems Incorporated, 1987–2003). A Canon Power-
Shot S40 digital camera was used to photograph some aspects of morphology.
The species description incorporates the formats used by Santana (1976),
Mironov and Kopij (2000), and OConnor et al. (2005). Ten adult mites of
each sex were measured; all measurements are in micrometers (μm). It is possible
that the Mesalgoides and Analges recovered from the Eastern Bluebird
samples are also species new to science; however, the taxonomy of these two
genera is in too poor a state to determine this without great effort.
JMP 8.0 Statistical Software (SAS Institute, Cary, NC) was used for all
statistical analysis; a priori significance was set at α = 0.05. Pearson χ2 test
of independence was used to evaluate relationships between subjective mite
2010 R.E. Carleton and H.C. Proctor 609
abundance categories and host sex, body condition scores, and subcutaneous
fat scores. One-way ANOVA was used to test for differences in body mass
among mite abundance categories.
Feather mites were noted on 223 of 228 (97.8%) adult bluebirds, and
when present, were always observed on primary remiges (100%), often on
secondary remiges (56.1%), and occasionally on rectrices (10.7%). Mite
abundance scores were somewhat normally distributed among the categories
“abundant” (13.6%), “moderate” (38.5%), “rare” (22.9%), or “very rare”
(17.9%). Abundance on eleven birds (4.8%) was scored as “very abundant”
(Fig. 2). No feather damage was noted on areas harboring mites. Philopterus
sialii (Osborn) (Lice) were occasionally recovered, but are reported elsewhere
(Carleton et al., in press).
Mites were located most commonly on the right and left eighth, ninth,
and tenth primaries. Most birds (86.0%) had mites on three to five remiges,
and 30.7% had mites on only three primaries of each wing. Mites located on
secondary remiges were typically on the third through sixth and tenth and
eleventh secondaries, and most commonly on the fourth or fifth secondaries.
Although mites were found on both wings of most birds, a small number of
birds (2.2%) had mites only on the right wing. These birds were included
in the “very rare” category of mite loads. Mites located on primaries were
attached to the ventral surface of barbs and oriented anteriorly toward the
shaft, whereas mites located on secondary remiges and rectrices were only
found on the dorsal surface. Mites on primaries were always located within
the middle third of each feather, while those on secondaries or rectrices were
always located within the proximal third of the feather and covered by the
greater secondary coverts or upper tail coverts.
There was no difference in mean host body mass (mean = 29.7 g, SD ±
0.95) among birds that differed in mite abundance levels (F5,227 = 0.5390,
Figure 2. Histogram of feather
mite abundance scores among
a sample of Eastern Bluebirds
(n = 228) nesting in northwestern
2008–2009) with percentages of
each score. Abundance scores: 0
= none, 1 = very rare, 2 = rare,
3 = moderate, 4 = abundant, 5 =
610 Southeastern Naturalist Vol. 9, No. 3
P = 0.746; Fig. 3). Mite abundance was independent of host sex (Pearson χ2 =
8.805, 5 df, P = 0.117) and was not associated with host condition as estimated
by subcutaneous fat score (Pearson χ2 = 7.848, 5 df, P = 0.165; Fig. 4). There
was some evidence of an association between mite abundance and pectoral
muscle score (Pearson χ2 = 31.435, 15 df, P = 0.0074; Fig. 5).
Four species of feather mites were identified from samples collected by
live examinations and body washes of the 14 necropsied birds (Table 1). Pterodectes
sialiarum was the only species associated with the primary remiges that
were collected during live examinations. A Mesalgoides sp. and a previously
unidentified Trouessartia sp. (described below as T. sialiae sp. nov.) were
the only species associated with collected secondary feathers. Trouessartia
spp. are unusual among feather mites because they often occupy the dorsal
rather than ventral surface of flight feathers (Dubinin 1951). The Trouessartia
sp. was also the only species of feather mite found on rectrices. Pterodectes
sialiarum, Mesalgoides sp., Trouessartia sp., and Analges sp. were recovered
from wash samples. Recovery of the Analges sp. only by washing is not
Figure 3. Box plots of Eastern
Bluebird body mass (g) by
feather mite abundance scores.
Abundance scores: 0 = none,
1 = very rare, 2 = rare, 3 = moderate,
4 = abundant, 5 = very
Figure 4. Histograms showing
categories of subcutaneous fat
(SFS) located between the furcula
of Eastern Bluebirds (n =
228) by feather mite abundance
scores with percentages. SFS 0:
subcutaneous fat absent; SFS 1:
subcutaneous fat present. Abundance
scores: 0 = none, 1 = very
rare, 2 = rare, 3 = moderate, 4 =
abundant, 5 = very abundant.
2010 R.E. Carleton and H.C. Proctor 611
unexpected because members of this genus are typically associated with body
feathers rather than flight feathers (Dubinin 1951).
Family Trouessartiidae Gaud 1957
Genus Trouessartia Canestrini 1899
Trouessartia sialiae sp. nov. (Figs. 6–10)
Holotype: male, 19 June 2004, Mount Berry, GA (34.282799oN,
85.191803oW), from Sialia sialis (Linneaus 1758) (Eastern Bluebird). Coll.
Figure 5. Histograms showing
categories of pectoral muscle
mass scores (PMS) by feather
mite abundance scores with
percentages from a sample of
Eastern Bluebirds (n = 228)
nesting in northwestern Georgia
Pectoral muscle mass scores:
W = well muscled, M = muscled,
T = thin. Abundance scores: 0 =
none, 1 = very rare, 2 = rare,
3 = moderate, 4 = abundant, 5 =
Table 1. Feather mites collected from Sialia sialis (Eastern Bluebird) by body wash prior
to necropsy (n = 14) and from feathers collected during live examination (n = 14) during
2004–2006 and 2008–2009.
Prevalence (%) / range, Presence (X) on collected feathers
Mite species by body wash Primaries Secondaries Rectrices
Pterodectes sialiarum 100.0 / 5–226 X
Trouessartia sialiae (sp. nov.) 85.0 / 0–19 X X
Mesalgoides sp. 35.7 / 0–11 X
Analges sp. 28.3 / 0–30
612 Southeastern Naturalist Vol. 9, No. 3
R. Carleton. Deposited in the Museum of Zoology, University of Michigan,
Ann Arbor, Michigan (UMMZ).
Paratypes: 9 males, 10 females, same location and host species, dates May–
July 2004. Coll. R. Carleton. 2 male and 2 female paratypes deposited in the
UMMZ, 7 male and 8 female paratypes in the University of Alberta E.H.
Strickland Museum of Entomology, Edmonton, AB, Canada (UASM).
Male (holotype, range given for 9 paratypes unless otherwise mentioned;
Figs. 6, 7, 10). Dorsum (Fig. 6). Length of idiosoma excluding terminal
Figure 6. Trouessartia sialiae sp. nov., male: dorsal view; gla = gland opening.
2010 R.E. Carleton and H.C. Proctor 613
lamella 503 (485–520), width of idiosoma as measured between bases of
setae c2 210 (195–213, from 8 paratypes). Length of prodorsal shield 153
(148–160), width of shield as measured at level of setae se 170 (163–178);
with narrow lateral extensions between bases of legs I, II; surface uniformly
granular, without lacunae. Setae si narrowly lanceolate, 30 in length (28–30,
from 7 paratypes); bases separated by 65 (65–73). Humeral shield with setae
c2 narrowly lanceolate, 48 in length (45–53). Setae c3 lanceolate, 23 in length
(23–25). Dorsal hysterosoma with unsclerotized gap between prohysteronotal
shield and lobar shield anterior to setae e2; gap broadest at lateral margins of
Figure 7. Trouessartia sialiae sp. nov., male: ventral view; TLA = translobar apodeme.
614 Southeastern Naturalist Vol. 9, No. 3
Figure 8. Trouessartia sialiae sp. nov., female: dorsal view; gla = gland opening.
shields, and very narrow medially. Length of prohysteronotal shield 220 (200–
222); maximum width 185 (170–188); surface granular and without lacunae;
lateral margins with heavily sclerotized notches near level of setae d2 (Fig. 6);
2010 R.E. Carleton and H.C. Proctor 615
Figure 9. Trouessartia sialiae sp. nov., female: ventral view.
616 Southeastern Naturalist Vol. 9, No. 3
d2 present as small hairlike setae, all other prohysteronotal setae represented
only by alveoli. Length of lobar shield along midline, excluding lamellae, 90
(88–98). Terminal lamellae leaflike, tapered to blunt points distally, margins
entire, faint longitudinal striations present. Distance from base of free terminal
cleft to lamellar apices 53 (48–58). Setae ps2 and h1 setiform; bases of h1
anterior to bases of h2; ps1 represented only by alveoli.
Venter (Fig. 7). Epimerites I free. Rudiments of epimerites IIa small,
circular. Setae sR of trochanters III lanceolate with acute tips, length 14
(10–15). Genital apparatus massive (Fig. 10a), situated between levels of
trochanters III, IV; length 80 (75–90), width at base anterior to setae g 48
(40–53); small ovoid pregenital apodeme present. Anterior and posterior
genital papillae equidistant from midline. Bases of setae g clearly separated,
distance between them 10 (9–12). Translobar apodeme present (TLA,
Fig. 7). Setae ps3 on small triangular platelets anterolateral to adanal discs.
Button-like setae d, e on tarsus IV separated by 3 (2–4), a distance approximately
equal to width of one of these setae.
Female (range for 10 paratypes unless otherwise mentioned). Dorsum
(Figs. 8, 10b). Length of idiosoma including terminal lamellae 575–628;
width of idiosoma as measured between bases of setae c2 203–225 (from
9 paratypes). Prodorsal shield as in male, 153–170 in length, 173–190 in
width as measured at level of setae se; setae si narrowly lanceolate, 28–30
in length, bases separated by 73–83. Humeral shield with setae c2 narrowly
lanceolate, 45–53 in length. Setae c3 lanceolate, 23–25 in length. Hysteronotal
shield length to base of terminal cleft 253–270; maximum width
173–195; numerous ovoid lacunae mostly restricted to the middle third of
the shield between setal bases (Figs. 8, 10b); lateral margins with heavily
sclerotized notches near level of setae d2; d2 present as small hairlike setae,
all other hysteronotal setae anterior to h1 represented only by alveoli. Setae
Figure 10. Trouessartia sialiae sp. nov., photographs of details of morphology: (a)
male genital capsule, (b) female dorsal shield sculpture.
2010 R.E. Carleton and H.C. Proctor 617
h1 robust and lanceolate, 18–28 long (depending on angle of observation),
bases separated by 58–65; direct distance from bases of h1 to bases of h2
28–35; direct distance from bases of h1 to nearest lateral margin of hysteronotal
shield 20–25. Width of opisthosoma at level of setae h2 115–128.
Setae ps1 minute, hairlike, visible only under oil; positioned dorsally 14–19
anterior to bases of setae h3. Distance from bases of h2 to apices of lobar lamellae
110–135. Setae f2 not apparent. Supranal concavity open posteriorly.
Length of terminal cleft 118–145, width of cleft at level of setae h3 38–55.
Venter (Fig. 9). Epimerites I free. Setae sR on trochanter III lanceolate
and 15–18 in length. Interlobar membrane very reduced, apparently restricted
to area of supranal concavity rather than extending between lobes
(Fig. 8b). Primary spermaduct terminating prior to interlobar region, exiting
ventrally on small membranous protuberance (Fig. 10). Length of secondary
spermathecal ducts 25–34 (from 8 paratypes).
Etymology. The specific epithet is derived from the generic name of
Differential diagnosis. Trouessartia sialiae sp. nov. displays an unusual
combination of characters in which males have leaf-shaped, apically pointed
lamella with complete edges and females lack a tubular external spermaduct.
Other described species with these features include T. bifurcata (Trouessart),
T. carpi Till, T. rubecula Jabłonska, T. simillima Gaud, T. subacuta
Gaud & Mouchet, T. swidwiensis Jabłonska, T. trouessarti Oudemans, and
T. unicolor Berla. With the exception of T. unicolor, males of these other
species have small, narrow genital apparati in which the width at the base is
at most 1/3 the length and the bases of setae g are apposed. In T. sialiae sp.
nov., the width of the genital apparatus is almost half the length, and setae
g are clearly separated. Trouessartia sialiae sp. nov. can be differentiated
from T. unicolor by the following features: setae c2 narrowly lanceolate in
both sexes of T. sialiae (with filiform tips in both sexes of T. unicolor); setae
h3 with long filiform tips in males (lack filiform extensions in T. unicolor);
prohysteronotal and lobar shields completely separate in males (partially
fused in T. unicolor); setae g in males clearly posterior to 4a (slightly anterior
to 4a in T. unicolor); anterior and posterior genital papillae in males
same distance from midline (anterior pair further from midline than posterior
in T. unicolor); setae h1 in females robust, long, tips reaching to bases of
h2 (narrow and not reaching h2 in T. unicolor) (see illustrations in Santana
1976). Trouessartia unicolor has been collected from Haplospiza unicolor
Cabanis (Emberizidae) in South America (Santana 1976).
There have been few reports of feather mites associated with Eastern
Bluebirds despite a large volume of research on this species. The recovery of
Pterodectes sialiarum represents a new host distribution record and is only
the second report since the original discovery in Guatemala over a century
ago (Stoll 1893). The northern-most distribution of P. sialiarum is probably
not limited to the southeastern United States and Central America, given
618 Southeastern Naturalist Vol. 9, No. 3
that migration patterns of the more northern Eastern Bluebird populations
are highly variable and appear to fluctuate with degree of winter severity
(Gowaty and Plissner 1998). Recovery records from Michigan indicated
some individuals migrating southward passed over areas with winter residents
(Pinkowski 1971). Bird Banding Laboratory data reported the farthest
migration occurred between southwestern Manitoba in Canada and Texas
(Gowaty and Plissner 1998). Many bluebirds banded during the course of
the study have been observed during winter months (R.E. Carleton, pers.
observ.), suggesting that this population is non-migratory. The extent to
which migratory bluebirds overwinter in the area and interact with residents
is not known. The other two Sialia species, S. currucoides (Bechstein)
(Mountain Bluebird) and S. mexicana Swainson (Western Bluebird), have
been examined for feather mites but have yielded only Proctophyllodes spp.
(Proctophyllodidae) (Atyeo and Braasch 1966; H.C. Proctor, unpubl. data
for S. currucoides in Alberta, Canada).
Our generic records of the unidentified Mesalgloides sp. and Analges sp.
are the first for the genus Sialia. We recovered these species of feather mites in
relatively low numbers and at a lower prevalence than the other two species.
Recovery of Mesalgoides from collected secondary feathers represents an
unusual within-host distribution because members of this genus display morphological
adaptations for living in down feathers rather than flight feathers
(Dabert and Mironov 1999). Analges sp. and Mesalgoides sp. are commonly
found on several bird species that inhabit our study area; these include Cardinalis
cardinalis (L.) (Northern Cardinal) (Wilson and Durden 2003), Sturnus
vulgaris L. (European Starling) (Boyd 1951, Mitchell and Turner 1969),
Turdus migratorius L. (American Robin) (Threlfall and Wheeler 1986), and
Tachycineta bicolor (Vieillot) (Tree Swallow) (Lombardo and Thorpe 2000,
Shutler et al. 2004). As obligate cavity-nesters, bluebirds, starlings, and swallows
may occupy old nesting cavities previously used by non-conspecifics.
Our nest-box design excluded starlings, but Tree Swallows occasionally
usurped bluebirds from nest boxes. Although it is possible that transfer among
host species occurs during use of old nesting cavities, there are no documented
cases of this, and we consider mite movement between bluebirds and other
species using nest boxes to be unlikely.
Trouessartia sialiae sp. nov. represents a previously undescribed species
of feather mite and is the first species in this genus to be recorded from the
genus Sialia. Although there is a report of a Trouessartia sp. recovered from
an Eastern Bluebird in Florida (J. Mertins, pers. comm.; Forrester and Spalding
2003), no formal description of this specimen was made. Trouessartia is
one of the most species-rich genera of feather mites with approximately 100
named species and at least as many as yet undescribed. Trouessartia species are
restricted to passeriform hosts (Mironov and Kopij 2000). Other genera of the
family Turdidae that have had Trouessartia collected from them include Alethe,
Brachypteryx, Catharus, Neocossyphus, Turdus, and Zoothera (Table 2).
The locations of P. sialiarum and T. sialiae sp. nov. on specific types
of feathers appeared to be consistent among individual bluebirds and was
not influenced by relative mite abundance. Whether or not these species
2010 R.E. Carleton and H.C. Proctor 619
Table 2. Records of Trouessartia species from members of the family Turdidae.
Host genus Host species Author Trouessartia sp. Author Location Reference
Alethe castanea (Cassin) longifolia Gaud & Mouchet Cameroon Zumpt (1961)
Brachypteryx leucophris (Temminck) Unidentified sp. Asia McClure et al. (1973)
montana Horsfield Unidentified sp. Asia McClure et al. (1973)
Catharus minimus (Lafresnaye) Unidentified sp. Newfoundland Wheeler and Threlfall (1986)
ustulatus (Nuttall) Unidentified sp. Newfoundland Wheeler and Threlfall (1986)
ustulatus (Nuttall) Unidentified sp. Alaska Wilson and Haas (1980)
Neocossyphus fraseri (Strickland) stizorhinae Gaud and Mouchet Cameroon, Congo, Gabon Zumpt (1961), Santana (1976)
Sialia sialis (L.) sialiae sp. nov. Proctor and Carleton Georgia This paper
sialis (L.) Unidentified sp. Florida Forrester and Spalding (2003)
Turdus albicollis Vieillot mangaratibensis Berla Brazil Santana (1976)
albicollis Vieillot serrana Berla Argentina, Brazil, Surinam Santana (1976)
chrysolaus Temminck Unidentified sp. Asia McClure et al. (1973)
libonyanus (Smith) incisa Gaud Cameroon Gaud and Mouchet (1958)
merula L. corvina* (Koch) no location given Santana (1976)
merula L. incisa Gaud England, Morocco Santana (1976)
obscurus Gmelin Unidentified sp. Asia McClure et al. (1973)
pallidus Gmelin Unidentified sp. Asia McClure et al. (1973)
poliocephalus Latham Unidentified sp. New Hebrides Marshall (1976)
Zoothera citrina (L.) Unidentified sp. Asia McClure et al. (1973)
dauma (Latham) Unidentified sp. Asia McClure et al. (1973)
sibirica (Pallas) Unidentified sp. Asia McClure et al. (1973)
*Santana (1976) considers this mite-host record to be questionable.
620 Southeastern Naturalist Vol. 9, No. 3
invariably remain in place or occasionally move to other feathers or body
areas is unknown. Feather mites have been shown to avoid moulting feathers
(Jovani and Serrano 2001, Pap et al. 2006) and to migrate from tertiary to
primary and secondary feathers during seasonal and daily ambient temperature
change (Wiles et al. 2000). During the present study, all examinations
and collections occurred only within morning hours.
We found no association between feather mite abundance scores and
body mass or amount of furcular fat in the population under study. Although
there was statistical evidence of an association between mite abundance and
pectoral muscle mass, we suspect that this was not actually the case. Only
a very small portion of the population was scored as emaciated (0.44%) or
well-muscled (7.9%); no birds were scored as robust. Percentage-wise, more
birds that were scored as “well-muscled” were also scored as “very abundant”
in mite abundance compared to birds that were scored as “emaciated”,
“thin”, or “muscled”. However, as many “well-muscled” birds were scored
as “moderate” in mite abundance as those that were scored as “very abundant”.
The single emaciated bird had very few mites. Previous studies of the
relationships between host condition and mite load have returned contradictory
findings (summarized in Proctor 2003). For example, Rózsa (1997)
reported a positive relationship between mite abundance and body mass,
while Poulin (1991) and Figuerola (2000) found no such relationship.
Relative abundance of each mite species recovered could not be estimated
by visual examination because the method only allowed recognition
of mite presence per se, rather than identification of individual species (Mc-
Clure 1989). Based on results obtained by body washing and examination
of feather samples, P. sialiarum and T. sialiae were common throughout the
population; however, estimates based on small sample sizes, as in the case of
our sample obtained during necropsy (n = 14 birds, all male), may be suspect
(Gregory and Blackburn 1991).
Our findings yielded additional information about feather mite distribution
and the relationship between mite abundance and host condition. Manipulation
of mite abundances among hosts, such as by removal and addition, would allow
better evaluation of relationships between host condition and mite abundance,
and would also allow experimental determination of whether “misplaced”
mites move to colonize the feathers on which they are typically found
Authors’ note: Just before publication of this paper, we learned that
Pterodectes sialiarum had been moved to Amerodectes sialiarum (Valim and
This study was supported by faculty research funding provided by the School of
Mathematical and Natural Sciences of Berry College to R.E. Carleton, and Natural
Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant
funding to H.C. Proctor. We thank D.B. Conn, J. Graham, and D. Davin for access to
the study area, A. Watson, B. Daniels, H. Pruett, and J. Christian for their assistance
in monitoring nest boxes, P.A. Gowaty, under whose master permit all banding in this
study was supervised, and Fabio Akashi Hernandes (Universidade Estadual Paulista,
2010 R.E. Carleton and H.C. Proctor 621
São Paulo, Brazil) and Michel Valim (Istituto Oswaldo Cruz, Brazil) for confirming
the identity of Pterodectes sialiarum. J. Mertins (APHIS, USDA) kindly provided
information about an earlier record of Trouessartia on Sialia sialis. Deepest gratitude
is also extended to S.H. Schweitzer for suggestions regarding this manuscript.
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