Nestling development and the timing of tick attachments.
ABSTRACT Parasites exposed to fast-developing hosts experience a variety of conditions over a short time period. Only few studies in vertebrate-ectoparasite systems have integrated the timing of ectoparasite infestations in the host's development into the search for factors explaining ectoparasite burden. In this study we examined the temporal pattern of attachment in a nidicolous tick (Ixodes arboricola) throughout the development of a songbird (Parus major). In the first experiment, we exposed bird clutches at hatching to a mix of the 3 tick instars (larvae, nymphs and adults), and monitored the ticks that attached in relation to the average broods' age. In a complementary experiment we focused on the attachment in adult female ticks--the largest and most significant instar for the species' reproduction--after releasing them at different moments in the nestlings' development. Our observations revealed a positive association between the size of the attached instar and the broods' age. Particularly, adult females were less likely to be found attached to recently hatched nestlings, which contrasts with the smaller-sized larvae and nymphs. These differences suggest either an infestation strategy that is adapted to host physiology and development, or a result of selection by the hosts' anti-tick resistance mechanisms. We discuss the implications of our results in terms of tick life-history strategies.
- SourceAvailable from: Raphaël Arlettaz[show abstract] [hide abstract]
ABSTRACT: Summary 1. The mechanisms underlying host choice strategies by parasites remain poorly under- stood. We address two main questions: (i) do parasites prefer vulnerable or well-fed hosts, and (ii) to what extent is a parasite species specialized towards a given host species? 2. To answer these questions, we investigated, both in the field and in the lab, a host- parasite system comprising one ectoparasitic mite ( Spinturnix myoti ) and its major hosts, two sibling species of bats ( Myotis myotis and M. blythii ), which coexist intimately in colonial nursery roosts. We exploited the close physical associations between host species in colonial roosts as well as naturally occurring annual variation in food abund- ance to investigate the relationships between parasite intensities and (i) host species and (ii) individual nutritional status. 3. Although horizontal transmission of parasites was facilitated by the intimate aggre- gation of bats within their colonial clusters, we found significant interspecific differ- ences in degree of infestation throughout the 6 years of the study, with M. myotis always more heavily parasitized than M. blythii . This pattern was replicated in a laboratory experiment in which any species-specific resistance induced by exploitation of different trophic niches in nature was removed. 4. Within both host species, S. myoti showed a clear preference for individuals with higher nutritional status. In years with high resource abundance, both bat hosts har- boured more parasites than in low-resource years, although the relative difference in parasite burden across species was maintained. This pattern of host choice was also rep- licated in the laboratory. When offered a choice, parasites always colonized better-fed individuals. 5. These results show first that host specialization in our study system occurred. Sec- ond, immediate parasite choice clearly operated towards the selection of hosts in good nutritional state.Journal of Animal Ecology 08/2003; 72(5):866 - 872. · 4.84 Impact Factor
- The ecology of the hen flea Ceratophyllus gallinae and the moorhen flea Dasypsyllus gallinulae in nestboxes. 317-327..
Nestling development and the timing of tick attachments
D. J. A. HEYLEN, J. WHITE, J. ELST, I. JACOBS, C. VAN DE SANDE andE. MATTHYSEN
Evolutionary Ecology Group, Department of Biology, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerpen,
(Received 30 November 2010; revised 1 August and 24 November 2011; accepted 25 November 2011)
Parasites exposed to fast-developing hosts experience a variety of conditions over a short time period. Only few studies in
vertebrate-ectoparasite systems have integrated the timing of ectoparasite infestations in the host’s development into the
search for factors explaining ectoparasite burden. In this study we examined the temporal pattern of attachment in a
nidicolous tick (Ixodes arboricola) throughout the development of a songbird (Parus major). In the first experiment, we
exposed bird clutches at hatching to a mix of the 3 tick instars (larvae, nymphs and adults), and monitored the ticks that
ticks –the largest and most significant instar for the species’ reproduction –after releasing them at different moments in the
nestlings’ development. Our observations revealed a positive association between the size of the attached instar and the
broods’ age. Particularly, adult females were less likely to be found attached to recently hatched nestlings, which contrasts
with the smaller-sized larvae and nymphs. These differences suggest either an infestation strategy that is adapted to host
physiology and development, or a result of selection by the hosts’ anti-tick resistance mechanisms. We discuss the
implications of our results in terms of tick life-history strategies.
Key words: Ixodes, host preference, phenology, songbird, development.
By draining resources from their hosts, parasites
develop at the potential expense of the fitness of their
hosts (Price, 1980; Loye and Zuk, 1991; Clayton and
Moore, 1997; Fitze et al. 2004) . The harm caused by
the parasites (i.e. virulence) is largely determined by
and Verhulst, 1996; Wakelin, 1996). Many parasites
have developed adaptations allowing them to exploit
the most profitable host and/or at the most profitable
nutritional status are assumed to be of major im-
portance in most systems (Bize et al. 2008). Other
characteristics areknown to affect hostexploitation as
well, such as host body size (Duffy and Campos de
Duffy, 1986; Valera et al. 2004), skin thickness and
body temperature (Elliott et al. 2002). Since parasite
species and hosts greatly differ in ecological require-
ments and life-history traits (Roulin et al. 2003;
Reckardt and Kerth, 2009), establishing general
rules that determine host selection is difficult; never-
theless, it is crucial for the understanding of the
evolutionof host-parasite interactions.
In many parasites, maximizing temporal overlap
with the host and synchronizing infection to the
host’s reproductive cycle are common adaptations in
Nidicolous ectoparasites inhabiting nests of fast-
growing vertebrates are faced with potential hosts
that go through large physiological changes over a
relatively short period of time. The development of
host resistance (Edman and Scott, 1987; Davison
et al. 2008) and the changing morphology and
physiology (Olsen, 1974; Perrins, 1979; Harrison
and Harrison, 1986; Burtt et al. 1991; Gosler, 1993)
result in strongly changing conditions that challenge
parasites to fine-tune their timing of infestation.
Although the timing of ectoparasite infestation in the
host’s development is critical for the parasite’s
success, only few studies in vertebrate-ectoparasite
systems have integrated this aspect in the search for
factors explaining parasite burden and host prefer-
ence (Bize et al. 2008; Vaclavet al. 2008). Optimizing
timing of infestation is all the more important
and indeed crucial in the case of nidicolous ixodid
ticks, as each instar feeds only once during a non-
stop period of several days and invests considerable
amounts of resources in the attachment process
(Balashov, 1972; Sonenshine, 1991). Thus, the
choice of a single host has a decisive influence on
parasite fitness. In addition, ixodid tick life cycles
often strongly exceed the duration of the hosts’
attachment to the host to be under much more
stringent selection compared to intermittently feed-
Corresponding author: Tel: +32 3 265 34 70. Fax: +32 3
265 34 74. E-mail: Dieter.Heylen@ua.ac.be
Parasitology, Page 1 of 8.
© Cambridge University Press 2012
several generations within the hosts’ reproductive
cycle such as the hen flea (Ceratophyllus gallinae,
Schrank) (Harper et al. 1992; Tripet and Richner,
1999) and the tropical fowl mite (Ornithonyssus
bursa, Berlese) (Møller, 2002).
In this study we examine the temporal pattern of
Schulze and Schlottke) throughout the growth of one
of its most important and commonest hosts, the great
tit (Parus major, L.) (Hudde and Walter, 1988;
Hillyard, 1996). Both host and parasite are widely
distributed throughout the Palearctic region (Gosler,
1993; Liebisch, 1996). The great tit is a small hole-
breeding songbird (body mass: 15–20 g). This bird
during which its body mass increases 10-fold and its
naked body gets covered with feathers. Nestlings
fledge when they are approximately 21 days old
(Gosler, 1993). So, in the breeding season (April–
relatively short time-period (approximately 42 days
for a single reproductive cycle (Gosler, 1993)), after
which they leave the tree-holes for several months.
From early autumn onwards, great tits start re-
occupying tree holes by using them as roosting sites
(Perrins, 1979; Gosler, 1993).
Ixodes arboricola is a haematophagous ectoparasite
with an entire life-cycle restricted to natural tree-
holes where it infests birds that roost and breed
(Arthur, 1963; Hillyard, 1996). As in all ixodid ticks,
every instar (larva, nymph, adult female) typically
takes a single bloodmeal lasting several days before
detachment and moulting to the next development
stage, and thus spends at least 90% of its life off-host
(Hillyard, 1996). The 3 instars greatly differ in size
and the amount of blood required for continuation of
the life cycle. Engorgement weights of the adult
females (38·5 mg; body length unfed: 2·5mm) are on
average20 times greaterthan thatofnymphs (1·9 mg;
body length: 1·3mm) and more than 150 times
greater than that of larvae (0·25 mg; body length:
0·5 mm) (Hillyard, 1996; Heylen and Matthysen,
2011a) fed on great tits. Immediately after feeding,
the engorged immature tick instar (larva or nymph)
next instar (nymph or adult, respectively). Since the
moulting to next instar may occur within 2 weeks
tits within a single breeding event (D. Heylen,
unpublished data). This contrasts with the time
duration between female engorgement and the
emergence of larvae, which is longer than the great
tits’ breeding cycle (see Materials and Methods
section). Adult male ticks do not feed, and copulate
(Liebisch, 1996; Heylen, 2011).
The seasonal activity pattern of the different
developmental stages has been partly determined by
analysing data on tick infestations of full-grown tits
and records of engorged ticks inside tit nest boxes of
our Belgian study population (Heylen, 2011). Ixodes
arboricola can be found on the birds throughout the
year, even during the coldest winter months (Literak
et al. 2007). Lowest numbers of infested birds are
in the open (Hinde, 1952) and nestlings have fledged,
which is confirmed by the low numbers of recently
engorged ticks inside nest boxes during summertime
(Heylen, 2011). The highest numbers of unfed
early autumn, when up to 800 larvae emerge from a
single batch of eggs. Full-grown tits are generally
infested by the immature developmental stages only.
Most of the larval infestations have been registered
during autumn and winter, when birds roost inside
cavities. Most of the nymphal infestations are
observed during the birds’ pre-laying period (end of
February-start of April)and breedingseason. Several
hundreds of fed larvae inside nest boxes have been
observed during the nestling phase, despite that the
incidence of larval-infested nests during this time of
the year is much lower compared to the other tick
developmental stages. Larvae and nymphs are likely
the most important stages for the colonization of new
tree holes when birds change roosting site and/or
prospect potential breeding sites. By delayed detach-
ments in response to unsuitable environmental
conditions, bothlarvae and nymphs havethecapacity
to bridge long periods of several weeks when full-
grown birds move between successive home ranges
few records of adult female ticks have been registered
on adult and fledged birds (Walter et al. 1979; Hudde
and Walter, 1988; Heylen, 2011). Full-grown great
tits seem not that suitable for female infestations, as
is suggested in previous laboratory and field exper-
iments in which the attachment success of adult
female ticks is remarkably lower than that of the
immature instars (Heylen and Matthysen, 2010) due
to host-induced tick mortality or ticks that did not
want to attach. This contrasts with great tit nestlings,
in which experimental infestations have shown high
readiness in each tick instar to attach on 8-day-old
nestlings (Heylen and Matthysen, 2011a). Under
natural conditions, tit nestlings can be infested with
any of the parasitic instars; however, nymphs and
than larvae (Walter et al. 1979; Hudde and Walter,
1988; Hillyard, 1996; Heylen, 2011). Nestlings are
the most important host type for adult female ticks,
which is suggested by the high number of newly
engorged females found inside nest boxes during the
nestling phase (Heylen, 2011; Marcel Lambrechts,
unpublished data). Adult female ticks seldom infest
great tit parents during the pre-nestling phase. When
present in nest boxes, they delay infestations until
D. J.A. Heylen and others
nestlings have hatched, as is suggested by field obser-
vations and findings of experimentally exposed nests
at the start of the breeding cycle (D. Heylen,
The timing of attachment according to the host’s
development is particularly relevant to I. arboricola
for 2 main reasons. Firstly, I. arboricola can choose
among nestlings of different ages with contrasting
morphology and physiology. Secondly, the tick
instars may experience different constraints imposed
by their development durations, morphology and the
seasonal activity of the host. Here we report the
results of 2 experiments, in which tick attachments
were monitored throughout the growth of great tit
nestlings. In Exp. 1, we exposed clutches at hatching
to a mix of the 3 instars with tick burdens within the
natural exposure range, and registered the number of
ticks found attached to the nestlings in relation to the
brood’s age. We hypothesized that the observed
number of attached ticks of each of the instars differ
in accordance to the instars’ nutritional needs, the
availability of anti-grooming refuges (see Roulin
et al. 2003 and referencestherein) and theircapability
to get through more life stages when hosts are
available. In particular, we predict that the large
adult females are more often found attached to older
nestlings, because these provide better resources and
have better developed feathers under which ticks can
be sheltered. Due to the long duration between
female engorgement and the emergence of larvae,
adult females gain no advantage in attaching to
recently hatched nestlings. On the other hand, the
smaller instarsthat attach early in the development of
the nestlings have the opportunity to get through
more life stages while hosts are still available (cf. life
cycle of I. lividus (L.) infesting bank swallows
(Riparia riparia, L.) (Balashov, 1972; D. Heylen,
unpublished data)). Because of their smaller body size
and lower nutritional needs, larvae and nymphs may
find sufficient shelter and amounts of blood in the
early nestling stages. In acomplementaryexperiment
(Exp. 2) we focused on the attachment of adult
females –the largest instar and most significant for
the species’ reproduction –by releasing them at
different moments in the nestlings’ development. If
the observed I. arboricola female attachments are
independent of the birds’ developmental status, we
expect no correlation between the time delay until
If the observed tick attachments depend on the
nestlings’ developmental status, we expect to detect
attached I. arboricola females sooner when being
exposed toolderand largernestlingsthanwhenbeing
exposed to recently hatched nestlings.
MATERIALS AND METHODS
The fieldwork wascarried outinthe breedingseasons
(April–June) of 2009 and 2010, in a study site
consisting of several woodlots in the north of
Matthysen et al. 2001). Woodlots had been provided
with nest boxes, which are readily accepted as
surrogates for the tree holes in which great tits
naturally breed and roost. Inside the boxes we
frequently observe unfed and engorged I. arboricola
ticks belonging to the 3 instars. The removable nest
box lids allow easy access to the nest cup, the
nestlings, and the ticks that typically move towards
the top of the nestbox after feeding (Heylen, 2011).
All nest-boxes used in this study were checked for
naturally occurring ticks from the start of the
breeding season (end of March) until hatching, and
any ticks found were removed.
collected during the winter of 2007–2008 from
nestboxes in which great tits and blue tits (Cyanistes
caeruleus, L.) breed and roost. They developed to the
next developmental stages after experimental infesta-
tions of great tits during the breeding season and the
autumn of 2008 and 2009. Throughout the year,
except for the birds’ breeding season, tick individuals
were kept at the outside temperature and 85% relative
humidity in the dark. However, the second half of
April, when great tit females start breeding, ticks
were maintained in the dark at 20 °C until use. At the
beginning of March, we assembled the adult tick
developmental stages in a few vials (10 females with
Experiment 1: Attachment by different instars
May (2009), the apparent timing of tick attachments
was studied in relation to the brood’s age by exposing
recently hatched great tit nests to a fixed number of
ticks. Immediately after hatching (within 24h) we
added in each of the 15 randomly chosen nests: 150
and 2 unfed adult males obtained from a laboratory
colony (see above). The ticks were evenly distributed
in the nest cup after nestlings were briefly removed
(6 –11 nestlings per nest). The parasite load is con-
sistent with the natural range in different great tit
populations: up to 10 nymphs per nestling have been
found in a German population (Walter et al. 1979).
Furthermore, in our study population up to 30
nymphs, up to 10 adult females and several hundreds
of larvae per nest have been observed during the
to be sure that the females would attach and engorge.
In some ixodid tick species, adult females tend not to
attach to animals unless males of the same species are
present (Rechav et al. 1997; Sonenshine, 2004).
At 2, 6, 10 and 14 days after tick exposure, we
counted the number of newly attached ticks to the
Temporal pattern of tick attachment in bird nestlings
nestlings (inspection time on average 4 min per
nestling). We recorded the attachment sites and the
engorgement status on schematic drawings such that
ticks could be individually followed up. This enabled
us to distinguish newly attached ticks from ticks that
had already attached at a previous check, and hence
multiple observations of the same tick individuals in
the survival analyses could be avoided (see below).
With a 4-day interval between each check, we assume
that the number of non-detected ticks was low, given
that 4 days approximates the time to tick engorge-
ment (larvae: 3·6±0·2 (mean±standard error),
nymphs: 3·8±0·1; adult females: 5·3±0·2 days;
Heylen and Matthysen, 2011a). In addition, we
counted the newly detached and engorged I. arbor-
icola individuals found in the upper zone of the nest
box, and removed them at every nestling check and at
a final nest box check 18 days after tick exposure.
Comparison of the proportion of attached and
engorged ticks provides an indirect way to assess
the number of ticks that may have attached on the
parents instead of on the nestlings. A direct estimate
of parent infestation by I. arboricola was obtained on
the 8th day in the chicks’ development, when parents
were captured with nest traps as a standard field
procedure, and were thoroughly checked for ticks by
blowing and brushing the birds’ feathers apart.
Additional information of parental infestations was
obtained in 3 breeding female tits that were oppor-
tunistically caught at the first nestling check (i.e. 2
days after tick exposure).
The sum of the feeding duration (see above) and
development duration (duration until egg deposition
and emergence of the newborn larvae: 51·6±1·3
(mean±standard error) days; moult to next instar:
12·8±0·2 days in larvae; 13·3±0·1 days in nymphs;
all under 25 °C and 83% relative humidity; Heylen,
2011) exceed the inspection period of the nestlings.
Therefore it is very unlikely that an attached tick
that is not collected will be registered for the second
time when feeding in its subsequent developmental
Experiment 2: Attachment of adult female ticks in
relation to nestling age
In Exp. 2, which took place from 28 April to the 14
June (2010), 15 randomly chosen nests were exposed
(as in Exp. 1) to 4–6 adult female ticks as well as 2–3
adult male ticks.Agreat titnestconsists ofacohort of
chicks that are approximately the same age. Nest ages
ranged from 2 to 17 days. At 2, 4, 6, 8, 10 and 14 days
after tick exposure we counted the total number of
attached adult female ticks on the nestlings, and
collected the engorged ticks from the nest box wall
and lid. As in Exp. 1, drawings enabled us to
distinguish newly attached ticks from ticks that had
already attached at a previous check.
The durationuntil tick attachmentwasmodelledbya
marginal cox proportional hazards model for clus-
tered data at the level of the nest box (procedure
PROC PHREG in SAS v 9.2, SAS Institute, Cary,
North Carolina), with either the tick instar (for
Exp. 1), or the brood age at tick exposure (for Exp. 2)
added into the models. Those ticks that did not
attach, were handled as right-censored data. For
general information about modelling time-to-event
data we refer to Cox and Oakes (1984). Generalized
estimation equations (GEE) were fitted (PROC
GEE, logit-link, and binomial distributed residuals)
when modelling the proportion of ticks that success-
fully engorged and were harvested in relation to the
same exploratory variables as in the cox models, tak-
ments on the same nest. Also a GEE (cumulative
logit-link, and multinomial distributed residuals)
was fitted when modelling the tick instar– which is
considered as an ordinal response variable based on
their size (see Introduction section)– against the
moment when the maximum number of each of the
tick instars was observed. All estimates are reported
as mean±standard error, unless otherwise men-
tioned. α=0·05 was chosen as the lowest acceptable
level of significance.
Experiment 1: Attachment by different instars
The proportion of administered ticks that we found
attached on nestlings was 12·5±0·4% for adult
females, 8·1±2·1% of the nymphs and 9·2±3·3% of
the larvae. The average time until attachment was
9·1±1·1 days in adult female ticks, 4·3±0·4 days in
nymphs and 2·8±0·1 days in larvae, with a high
proportion of nymphs and larvae attaching within
6 days after their release (Fig. 1). The estimated
hazard to attach of adult female ticks (i.e. the
likelihoodofanadult female ticktobefound attached
to a nestling at the next nestling check) was 101·5%
(95% – confidence interval: 56·6−159·3%; χ2=26·72;
D.F.=1; P<0·0001) lower than in nymphs, and
180·9% (95% –confidence interval: 110·6−274·5%;
χ2=38·37; D.F.=1; P<0·0001) lower than in larvae.
Inaddition, theestimated hazard toattachinnymphs
was significantly lower (39·4%; 95% –confidence
interval: 24·6−56·0%; χ2=26·97; D.F.=1; P<0·0001)
than in larvae. When fitting the GEE, we found a
instars, and the time in the birds’ development when
their maximum number was observed (cumulative
logit: 0·52±0·09; Z-score: 5·82; P<0·001).
When the upper zone of the nest boxes was
checked, in total 21·8±6·4% of the administered
adult females, 27·6±7·2% of the nymphs and
23·1±8·2% of the larvae had engorged and were
D. J.A. Heylen and others
collected (Fig. 1). The pattern of collected ticks
proved to be highly similar to the pattern of ticks
developmental stages, the adult female ticks fed late
in the nestlings’ development (hazard ratio adult
females vs. larvae: 2·93; 95%–confidence interval:
2·13−4·06; χ2=42·58; D.F.= 1; P<0·0001; hazard
ratio adult females versus nymphs: 2·07; 95%–
confidence interval: 1·60−2·68; χ2=30·13; D.F.=1;
P<0·0001), and the engorged nymphs were found
significantly later in the nestlings’ development than
the larvae (hazard ratio nymphs versus larvae: 1·42;
95%–confidence interval: 1·25−1·62; χ2=27·95;
Neither in adult females (logitcollected – attached:
0·69±0·38; Z-score: 1·44; P=0·07), nor in larvae
(logitcollected – attached: 0·72±0·43;
between the proportion of ticks that attached to the
nestlings, and the proportion of ticks that were
collected inside the nestbox. In the nymphs, how-
ever, significantly less ticks were found attached to
the nestlings than collected from the nest box
(logitcollected – attached: 1·51±0·43; Z-score: 3·49; P=
0·0005) indicating that an important number of
nymphs had been overlooked, or had detached from
the parents inside the nest boxes. The latter was
confirmed by the observation of ticks attached to
parents at day 8 in the nestlings’ development
(1·3±0·4 nymphs, and 0·8±0·2 larvae per adult
bird), as well as in the three females opportunistically
caught whilst brooding 2-day-old nestlings (7·3±5·4
nymphs, and 6·6±6·6 larvae per adult bird). The
capture data show that several larvae had fed on the
parents as well. This was not detected in the
comparison between larval collected and attached
ticks, likely due to low statistical power.
Experiment 2: Attachment of adult female ticks in
relation to nestling age
During the course of the experiment, 49·4±10·1% of
the adult ticks were found attached to the nestlings,
while only 18·9±7·9% were collected as engorged
individuals in the upper zone of the nestbox. The
attached proportion (logit transformed) showed an
increase with nestling age at the time of tick release
(age: 1·1±0·4/day; Z-score: 3·23; P=0·001; age*age:
−0·06±0·02/day2; Z-score: −3·03; P=0·003). The
time delay between tick release and attachment was
significantly reduced in nests with older nestlings
(Fig. 2), as shown by a significant increase in
attachment hazard with nestling age (estimated
increase in hazard: 13·6%/day; 95%– confidence
In line with our expectations, the tick attachment in
great tit nestlings revealed an overall positive
association between the size of the tick instar, and
the age of the brood at which the tick attached. In
particular, both experiments provided complemen-
tary evidence that adult female ticks are less likely to
be found attached to recently hatched nestlings than
the smaller-sized tick instars (larvae and nymphs). In
Exp. 2, in which adult ticks were introduced to
nestlings as young as 2 days old, none attached to
tick release and attachment was significantly reduced
in nests with older nestlings, suggesting that adult
female ticks adopt a strategy based on the nestlings’
There are several potential explanations for the
observed patterns in our study. A first and proximate
explanation for the delayed attachment in the larger
tick instars may be a decrease in grooming effective-
ness of hosts, and/or decrease in immunological
resistance with the broods’ age, rather than an
attachment strategy by the tick. However, it is
generally believed that the nestlings’ grooming skills
(Moore, 2002) and immune function improve with
result in a decrease –and not an increase as observed
in the adult females –in successful attachments. It is
important to stress that in natural ixodid tick-host
resistance commonly does not occur (Randolph,
1979; Ribeiro, 1989; Fielden et al. 1992) and has
not been observed in songbirds (Heylen et al. 2010).
This implies that hatchlings are unlikely to receive
Proportion of administered ticks
Days after hatching
Fig. 1. The proportion of the ticks administered at
hatching that attached to great tit nestlings (filled bars)
and the proportion of the ticks collected 4 days later
inside the nest box (open bars) in relation to the age of
the brood. Mean values (bars) over the 15 nests+1
standard errors (whisker) are shown. The proportion and
standard error of the attached imago female ticks at day 6
equalled the proportion of the collected ticks four days
Temporal pattern of tick attachment in bird nestlings
maternally derived anti-tick immunoglobulines in
the eggs (e.g. Staszewski et al. 2007) that could have
affected the attachment patterns in some way. A
factor that could potentially facilitate tick attachment
is feather development. Better developed feathers
provide shelter to the larger, more conspicuous tick
instars (see Roulin et al. 2003 and references therein),
and thereforemayreducehost-induced tick mortality
via grooming and preening. From day 8 onwards, the
great tits’ feathers start to become conspicuous
(Winkel, 1970) which could allow the largest tick
instars of I. arboricola to shelter.
Tick mortality may play an important role in our
observations, as is suggested by the low infestation
successes inbothexperiments. Besides potential anti-
tick resistance mechanisms in the nestlings, host-
induced mortality may occur via parents that
eliminate ticks that have gone onto their body
through self-preening or allo-preening, or they
might eliminate the ticks that are in the nest through
nest sanitation. However, one should note that in
ticks that failed to engorge once attached to nestlings,
and scratches or injuries on the nestlings’ bodies at
the ticks’ attachment sites (D. Heylen, personal
observations), indicating that preening and grooming
during the nestling phase is likely to be of little
importance. Furthermore, to the best of our knowl-
edge, parental allopreening has never been recorded
in the paridae family.It islikelythatthe low visibility
inside the dark tree-hole environment makes the
detection of ectoparasites difficult for the birds.
Nest sanitation behaviour in female great tits has
been described as “a period of active search with the
head dug into the nest material” (Christe et al. 1996)
but it is unclear whether this kills or simply disperses
ectoparasites (Clayton et al. 2010). Therefore,
although it is possible that the temporal tick
attachment patterns are the result of parent-induced
tick mortality, there is no clear evidence supporting
A second and ultimate explanation is that the ticks
monitor the developmental status of the hatchlings,
and delay attachment until the nestlings have
developed to their most profitable status. Since
ixodid ticks normally obtain only a single bloodmeal
per instar and are therefore less able to sample
different hosts by feeding, attraction stimuli, e.g.
host vibrations, body heat, or odour (Steullet and
Guerin, 1992; Yunker et al. 1992; Osterkamp et al.
1999 ; Donze et al. 2004), can be used by I. arboricola
as identification cues for the most profitable host
types. The idea that tick attachment patterns may
reflect strategic choices in I. arboricola is further
supported by choice experiments under controlled
conditions showingthatnymphs attachpreferentially
to the more developed nestling when exposed for a
short time-period to pairs of siblings with contra-
sting developmental status (Heylen and Matthysen,
We propose thatolder nestlings aremore profitable
heavier, and hence may be of higher nutritional value
and provide more accessible food resource for the
higher food demands (Christe et al. 2003; Hawlena
et al. 2005). In addition, by selecting hosts in relation
to the required amount of blood, the relative harm to
nestlings may be reduced (i.e. virulence) which in
turn increases the chance of chick survival and
the reuse of the tree holes by the same hosts and/or
their offspring. Secondly, the improvement of
thermoregulation with nestling development –in
great tits believed to start from day eight after
hatching (Perrins, 1979) –may play a role in host
profitability as well, since high body temperatures
can facilitate blood acquisition in ixodid ticks
(Balashov, 1972). Thirdly, as already suggested
Mean nestling age (days)
Time until attachment (days)
Time until attachment (days)
024681012 1416 18
Attached proportion of ticks
> 0 - 6 days
> 6 - 12 days
> 12 - 18 days
Fig. 2. (A) Duration of time between the day when adult
female ticks were released and the first observation of
attachment to the great tit nestlings in relation to the
mean nestlings’ age at which the ticks were released in the
nest. Each symbol represents a single nest, with size
proportional to the proportion of ticks that attached
(maximum size: 75%; minimum size: 16%). Circles are
nests from Exp. 2, squares are nests from Exp. 1. (B)
Cumulative proportion of attached adult female ticks that
were released at different moments in the nestlings’
development. Ticks released at 0 days are from Exp. 1.
Open boxes represent censored ticks.
D. J.A. Heylen and others
above, better-developed feathers provide better
shelter against grooming for the larger tick instars.
In addition they may better protect the ticks against
the mechanical disturbances when the nestlings rub
their bodies against the nest material. This may
explain the higher infestation success of adult female
ticks in Exp. 2, in which more ticks were exposed to
older nestlings. Due to their body size, the smaller
immature tick stages may find refuges from early
onwards, which may explain their high readiness to
attach to recently hatched nestlings as well as older
birds likethe parents and the full-grown birds during
autumn and winter (Hudde and Walter, 1988;
Literak et al. 2007; Heylen and Matthysen, 2010).
From a life-history perspective, we expect that the
relation between delayed attachment and fitness may
be counteracted by selection on early attachment.
The relatively short occupancy of the tree holes by
the breeding great tits (approximately 42 days for a
single reproductive cycle (Gosler, 1993)) strongly
temporally constrains tick survival and reproduction,
and therefore, engorgement and detachment within
the breeding cycle of the birds should optimize
many months until they are used again for roosting
during autumn and winter (Hinde, 1952). This, and
the fact that the mortality rate of great tits in the first
weeks after fledging is very high (Naef Daenzer et al.
2001) imply that if I. arboricola ticks are still attached
after fledging, they will end in unfavourable habitats
for survival and reproduction (cf. Pellonyssus reedi,
Zumpt and Patterson (Szabo et al. 2008)). This also
indicates that the fledging period is unfavourable in
terms of dispersal success. Successful colonization of
othercavitiesprobablyoccurs during autumn, winter
and early spring when great tits use cavities on a
regular basis for roosting (Literak et al. 2007; Heylen
and Matthysen, 2010).
We speculate that instar-specific differences in
development explain part of the observed attachment
patterns, since they lead to different temporal
constraints. For the adult females, due to the long
period needed for emergence of the newborn larvae
(see Materials and Methods section) the fitness gain
of attaching early in the birds’ breeding cycle is low,
since the offspring has no opportunity to engorge in
the same great tit breeding cycle. The time constraint
on attachment should therefore be relatively low in
adult female ticks. On the other hand, in the
immature instars the development to the next instar
is short with respect to the length of the birds’
breeding season (see Materials and Methods section),
enabling them to optimize their fitness by reaching
the reproducing adult instars within the nestling
phase (cf. life cycle of I. lividus infesting bank
swallows (Balashov, 1972; Ulmanen et al. 1977)).
Moreover, since second broods are uncommon (less
than 10% of first brood parents) and have strongly
decreased in our study area (Husby et al. 2009),
opportunities for ticks to continue their life-cycle
after the first brood are highly reduced, further
reinforcing the time constraints on larvae and
nymphs in particular. To summarize, we hypoth-
esized there may be a trade-off between the benefit of
delaying attachment until nestlings grow larger, and
time pressures to complete the life cycle in
I. arboricola. For larvae and nymphs the benefit of
large nestlings is relatively small while the time
pressure to proceed to the next instar is high, leading
to the optimal strategy of attaching immediately. For
adults, the benefit to attach to older nestlings is large
while the time pressure to proceed to egg deposition
and larval development is low (probably due to
developmental constraints) and therefore the opti-
mum is to delay attachment.
In conclusion, our experiments demonstrate that
an important trait in an ectoparasite, the timing of
attachment to the host, is related to the host’s
developmental stage. The proposed hypotheses
imply that the host’s development sets no lower
limit on the attachments of the immature tick instars,
while this limit is likely set in adult female ticks.
Further experimental research will reveal to what
extent the attachment strategies are driven by the
birds’ physiology and development, and/or the hosts’
anti-tick resistance mechanisms.
Adriaensen and two anonymous referees on a previous
version of the manuscript. Experiments were carried out
under license of the Flemish Ministry (Agentschap Natuur
en Bos) and the experimental protocol was approved by the
Ethical Committee of the University of Antwerp. D. H.
and J. W. are supported by the FWO-Flanders. This study
was funded by FWO-project G.0049.10 awarded to E. M.
appreciate thethoughtfulcomments ofFrank
Apanius, V. (1998). Ontogeny of immune function. In Avian Growth and
Development: Evolution Within the Altricial-Precocial Spectrum (ed. Starck,
J. M. a. R., R.E.), pp. 203–222. Oxford University Press, Oxford, UK.
Arthur, D. R. (1963). British Ticks. Butterworths, London, UK.
Balashov, Y. S. (1972). Bloodsucking ticks (Ixodidea) –vectors of diseases
of man and animals. Miscellaneous Publications of the Entomological Society
of America 8, 159–376.
Bize, P., Jeanneret, C., Klopfenstein, A. and Roulin, A. (2008). What
makes a host profitable? Parasites balance host nutritive resources against
immunity. American Naturalist 171, 107–118.
Burtt, E. H., Chow, W. and Babbitt, G. A. (1991). Occurence and
demography of mites of tree swallow, house wren and eastern bluebird
nests. In Bird-Parasite Interactions: Ecology, Evolution and Behaviour (ed.
Loye, J. E. and Zuk, M.), pp. 104–122. Oxford University Press, Oxford,
Christe, P., Giorgi, M. S., Vogel, P. and Arlettaz, R. (2003). Differential
species-specific ectoparasitic mite intensities in two intimately coexisting
sibling bat species: resource-mediated host attractiveness or parasite
specialization? Journal of Animal Ecology 72, 866–872.
Christe, P., Richner, H. and Oppliger, A. (1996). Of great tits and fleas:
Sleep baby sleep. Animal Behaviour 52, 1087–1092.
Clayton, D.H., Jennifer, A.H., Koop, J. A.H., Harbison, C. W.,
Brett, R. M., Moyer, B. R. and Bush, S.E. (2010). How birds combat
ectoparasites. The Open Ornithology Journal 3, 41–71.
Temporal pattern of tick attachment in bird nestlings
Clayton, D.H. and Moore, J. (1997). Host-Parasite Evolution: General
Principles and Avian Models. Oxford University Press, Oxford, UK.
Cox, D. R. and Oakes, D. (1984). Analysis of Survival Data, 1st Edn.
Chapman and Hall, London, UK.
Davison, F., Kaspers, B. and Schat, K. A. (2008). Avian Immunology,
Elsevier, London, UK.
Donze, G., McMahon, C. and Guerin, P.M. (2004). Rumen metabolites
serve ticks to exploit large mammals. Journal of Experimental Biology 207,
Duffy, D.C. and Campos de Duffy, M. J. (1986). Tick parasitism at
nesting colonies of Blue-footed. Boobies in Peru and Galapagos. Condor 88,
Edman, J. D. and Scott, T.W. (1987). Host defensive behaviour and
the feeding success of mosquitoes. Insect Science and Its Application 8,
Elliott, S.L., Blandford, S. and Thomas, M. B. (2002). Host-pathogen
interactions in a varying environment: temperature, behavioural fever and
fitness. Proceedings of the Royal Society of London, B 269, 1599–1607.
Fielden, L. J., Rechav, Y. and Bryson, N.R. (1992). Acquired immunity
to larvae of Amblyomma marmoreum and A. hebraeum by tortoises, guinea-
pigs and guinea-fowl. Medical and Veterinary Entomology 6, 251–254.
consequences of ectoparasites. Journal of Animal Ecology 73, 216–226.
Gosler, A. (1993). The Great Tit, Hamlyn, London, UK.
Harper,G. H., Marchant, A.
The ecology of the hen flea Ceratophyllus gallinae and the moorhen
flea Dasypsyllus gallinulae in nestboxes. Journal of Animal Ecology 61,
Harrison, G.J. and Harrison, L.R. (1986). Clinical Avian Medicine,
Hawlena, H., Abramsky, Z. and Krasnov, B. R. (2005). Age-biased
parasitism and density-dependent distribution of fleas (Siphonaptera) on a
desert rodent. Oecologia 146, 200–208.
Heylen, D. J.A. (2011). Parasite-host interactions between ticks and hole-
breeding songbirds. Ph.D. dissertation in Biology, Universiteit Antwerpen,
Heylen, D.J.A., Madder, M. and Matthysen, E. (2010). Lack of
resistance against the tick Ixodes ricinus in two related passerine bird species.
International Journal for Parasitology 40, 183–191.
Heylen, D.J. A. and Matthysen, E. (2010). Contrasting detachment
strategies in two congeneric ticks (Ixodidae) parasitizing the same songbird.
Parasitology 137, 661–667.
Heylen, D.J. A. and Matthysen, E. (2011a). Differential virulence in
two congeneric ticks infesting songbird nestlings. Parasitology 138,
Heylen, D.J. A. and Matthysen, E. (2011b). Experimental evidence for
host preference in a tick parasitizing songbird nestlings. Oikos 120,
Hillyard, P. D. (1996). Ticks of North-West Europe, Backhuys Publishers,
Hinde, R.A. (1952). The behaviour of the Great Tit (Parus major) and
some other related species. Behaviour 2, 1–201.
Hudde, H. and Walter, G. (1988). Verbreitung und Wirtswahl der
Vogelzecke Ixodes arboricola (Ixodoidea, Ixodidae) in der Bundesrepublik
Deutschland. Vogelwarte 34, 201–207.
Husby, A., Kruuk, L. E. B. and Visser, M. E. (2009). Decline in the
frequency and benefits of multiple brooding in great tits as a consequence of
a changing environment. Proceedings of the Royal Society of London, B 276,
Lehmann, T. (1993). Ectoparasites: direct impact on host fitness.
Parasitology Today 9, 8–13.
Liebisch, G. (1996). Biology and life cycle of Ixodes (Pholeoixodes)
arboricola Schulze and Schlottke, 1929 (Ixodidae). In Acarology IX, Vol. 1
(ed. Mitchell, R., Horn, D.J., Needham, G.R. and Welbourn, W.C.), The
Ohio Biological Survey. pp. 453–455.
Literak, I., Kocianova, E., Dusbabek, F., Martinu, J., Podzemny, P.
and Sychra, O. (2007). Winter infestation of wild birds by ticks and
chiggers (Acari: Ixodidae, Trombiculidae) in the Czech Republic.
Parasitology Research 101, 1709–1711.
Loye, J. E. and Zuk, M. (1991). Bird-Parasite Interactions: Ecology,
Evolution and Behaviour, Oxford University Press, Oxford, UK.
Matthysen, E., Adriaensen, F. and Dhondt, A. A. (2001). Local
recruitment of great and blue tits (Parus major, P. caeruleus) in relation to
study plot size and degree of isolation. Ecography 24, 33–42.
Møller, A.P. (2002). Temporal change in mite abundance and its effect on
barn swallow reproduction and sexual selection. Journal of Evolutionary
Biology 15, 495–504.
and Boddington,D. H.
Moore, J. (2002). Parasites and the Behavior of Animals, Oxford University
Press, New York, USA.
Naef Daenzer, B., Widmer, F. and Nuber, M. (2001). Differential post-
fledging survival of great and coal tits in relation to their condition and
fledging date. Journal of Animal Ecology 70, 730–738.
edition edn. University Park Press, Baltimore, MD, USA.
Osterkamp, J., Wahl, U., Schmalfuss, G. and Haas, W. (1999). Host-
odour recognition in two tick species is coded in a blend of vertebrate
volatiles. Journal of Comparative Physiology a-Sensory Neural and
Behavioral Physiology 185, 59–67.
Perrins, C.M. (1979). British Tits, Collins, London, UK.
Poulin, R. (2007). Evolutionary Ecology of Parasites, 2 Edn. Princeton
University Press, Princeton, NJ, USA.
Price, P.W. (1980). Evolutionary Biology of Parasites, Princeton University
Press, Princeton, NJ, USA.
Randolph, S. E. (1979). Population regulation in ticks– role of acquired
resistance in natural and unnatural hosts. Parasitology 79, 141–156.
Rechav, Y., Goldberg, M. and Fielden, L.J. (1997). Evidence for
attachment pheromones in the Cayenne tick (Acari: Ixodidae). Journal of
Medical Entomology 34, 234–237.
Reckardt, K. and Kerth, G. (2009). Does the mode of transmission
a field study on bat fly and wing mite infestation of Bechstein’s bats. Oikos
Ribeiro, J.M. C. (1989). Role of saliva in tick host interactions.
Experimental and Applied Acarology 7, 15–20.
Roulin, A., Brinkhof, M. W.G., Bize, P., Richner, H., Jungi, T.W.,
parasites? The importance of host immunology vs. parasite life history.
Journal of Animal Ecology 72, 75–81.
Sheldon, B. C. and Verhulst, S. (1996). Ecological immunology: costly
parasite defenses and trade-offs in evolutionary ecology. Trends in Ecology
and Evolution 11, 317–321.
Sonenshine, D.E. (1991). Biology of Ticks. Oxford Univerity Press,
New York, USA.
Sonenshine, D.E. (2004). Pheromones and other semiochemicals of ticks
and their use in tick control. Parasitology 129, S405–S425.
Staszewski, V., Gasparini, J., McCoy, K. D., Tveraa, T. and
Boulinier, T. (2007). Evidence of an interannual effect of maternal
immunization on the immune response of juveniles in a long-lived colonial
bird. Journal of Animal Ecology 76, 1215–1223.
the Tropical Bont Tick, Amblyomma variegatum Fabricius (Ixodidae) .1.
Physiology a-Sensory Neural and Behavioral Physiology 170, 665–676.
Szabo, K., Szalmas, A., Liker, A. and Barta, Z. (2008). Adaptive host-
abandonment of ectoparasites before fledging? within-brood distribution of
nest mites in House Sparrow broods. Journal of Parasitology 94, 1038–1043.
Tripet, F. and Richner, H. (1999). Dynamics of hen flea Ceratophyllus
gallinae subpopulations in blue tit nests. Journal of Insect Behavior 12,
Ulmanen, I., Saikku, P., Vikberg, P. and Sorjonen, J. (1977). Ixodes
lividus (Acari) in Sand martin colonies in Fennoscandia. Oikos 28, 20–26.
Vaclav, R., Calero-Torralbo, M. A. and Valera, F. (2008). Ectoparasite
load is linked to ontogeny and cell-mediated immunity in an avian host
system with pronounced hatching asynchrony. Biological Journal of the
Linnean Society 94, 463–473.
Valera, F., Hoi, H., Darolova, A. and Kristofik, J. (2004). Size versus
health as a cue for host choice: a test of the tasty chick hypothesis.
Parasitology 129, 59–68.
Wakelin, D. (1996). Immunity to Parasites, 2nd Edn. Cambridge
University Press, Cambridge, UK.
Walter, G., Liebisch, A. and Streichert, J. (1979). Untersuchungen zur
Norddeutschland. Angewandte Ornithologie 5, 65–73.
White, J., Heylen, D. and Matthysen, E. (2011). Adaptive timing
of detachment in a tick parasitizing hole-nesting birds. Parasitology
doi: 10.1017/S0031182011001806 published online 09 November 2011.
Winkel, W. (1970). Hinweise zur Art- und Altersbestimmung von Nestlin-
Vogelwelt 91, 52–59.
Burridge, M. J. and Butler, J.F. (1992). Olfactory responses of adult
Amblyomma hebraeum and A. variegatum (Acari, Ixodidae) to attractant
chemicals in laboratory tests. Experimental and Applied Acarology 13,
D. J.A. Heylen and others