Behaviour (2017) DOI:10.1163/1568539X-00003464

brill.com/beh

Urban mountain chickadees (Poecile gambeli) begin
vocalizing earlier, and have greater dawn chorus
output than rural males
Kristen L.D. Marini a,∗ , Matthew W. Reudink a ,
Stefanie E. LaZerte b,c and Ken A. Otter c
a

Department of Biological Sciences, Thompson Rivers University, 805 TRU Way,
Kamloops, BC, Canada V2C 0C8
b
Department of Geography, Thompson Rivers University, 805 TRU Way,
Kamloops, BC, Canada V2C 0C8
c
Natural Resources and Environmental Studies, University of Northern British Columbia,
3333 University Way, Prince George, BC, Canada V2N 4Z9
* Corresponding author’s e-mail address: kld.marini@gmail.com
Received 22 July 2017; initial decision 30 August 2017; revised 20 October 2017;
accepted 15 November 2017; published online ???

Abstract
Vocal output during the dawn chorus is often an honest indicator of male quality, where males
with greater access to food and in better condition produce more vocalizations. We compare the
vocal output among male mountain chickadees living along an urbanization gradient to assess how
urbanization affects male signalling. Chickadees forage in the canopy, and because urban habitats
are associated with lower canopy volume, we predicted that urban habitats may offer lower food
and thus lead to reduced song output. Contrary to our predictions, males in more urbanized habitats
had greater vocal output. We suggest that despite decreased canopy cover, urban birds may have
greater access to food in both the breeding and pre-breeding seasons due to differences in both
supplementary resources and vegetation composition of urban vs rural landscapes in our area.
Living in urban habitats may allow males to enter the breeding season in better condition.

Keywords
Poecile gambeli, song, urbanization, mountain chickadee, condition dependent trait, habitat
quality.

1. Introduction
With increasing world-wide urbanization, understanding whether urban areas constitute high- versus low-quality habitats for different species has
© Koninklijke Brill NV, Leiden, 2017

DOI 10.1163/1568539X-00003464

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Behaviour (2017) DOI:10.1163/1568539X-00003464

important conservation implications. Urban habitats are often highly fragmented (reviewed in Marzluff, 2001), and contain novel challenges such as
increased noise (Arroyo-Solís et al., 2013), artificial light (Da Silva et al.,
2014), and differences in resource availability (Anderies et al., 2007), which
may all affect the experienced habitat quality and the resulting condition of
individuals. The changes to habitats associated with urbanization may also
affect species differently, based on how much urban habitats differ from the
habitats in which the species evolved and how sensitive the species is to
change. One means of determining how species experience the relative quality of urban habitats is to compare the expression of condition-dependent
traits of individuals living along an urbanization gradient (Godfrey, 2003). If
urban habitats offer a lower quality of resources compared to rural habitats,
then there should be measurable reductions in traits known to covary with
individual condition, such as song output by male birds.
Previous studies have largely focused on the communication-masking effect that urban noise has on vocalizations and song. Even on relatively quiet
urban streets, birds face frequent loud noises (e.g., cars) that can interrupt
or mask aspects of their song (Arroyo-Solís et al., 2013). To compensate
for this, some species living in noisy areas may change the timing of their
vocalizations (e.g., the spotless starling, Sturnus unicolor, house sparrow,
Passer domesticus, Arroyo-Solís et al., 2013; several species including blue
tit, Parus caeruleus, Gil et al., 2015), while other species may shift the frequencies of their songs away from lower-frequencies that are more likely to
be masked by urban noise (e.g., great tits, Parus major, Slabbekoorn & Peet,
2003; song sparrows, Melospiza melodia, Wood & Yezerinac, 2006; reed
buntings, Emberiza schoeniclus, Gross et al., 2010; black-capped chickadee,
Poecile atricapillus, Goodwin & Podos, 2013; LaZerte et al., 2016). In a
recent study on the effects of experimental noise on mountain chickadees,
LaZerte et al. (2017) found that males living in noisy areas sang songs with
higher dominant frequencies (which varied by location), and in response
to experimental noise, males not only shifted to use more songs than calls
(which are known to transmit better in urban noise; LaZerte et al., 2015),
but also increased the pitch of dee notes in the calls they did use (LaZerte
et al., 2017). Beyond changes in timing and frequency shifts birds may also
adjust song amplitude (Nemeth et al., 2013), or the rate at which songs are
sung. However, studies on different species have had mixed results with respect to song rate: silvereyes (Zosterops lateralis) decreased their song rate

K.L.D. Marini et al. / Behaviour (2017)

3

in urban areas (Potvin et al., 2011) while Serins (Serinus serinus, Díaz et
al., 2011) and great tits (Slabbekoorn & den Boer-Visser, 2006) increased
their song rate. LaZerte et al. (2017) found no change in mountain chickadee
vocalization rates in response to experimental noise exposure.
Increased light levels in urban areas can also change the timing of vocalizations. A study of common European songbirds found that increased light
levels in urban areas caused many bird species to begin singing earlier in
the morning compared to birds in unlit habitats (Da Silva et al., 2014), and
similar results have been found on other species (Kempenaers et al., 2010);
but while light pollution may promote the early onset of singing, this alone
is unlikely to extend song rates or length of time spent singing unless simultaneously associated with increased individual condition (e.g., through
increased access to resources). Thus, increases or decreases in song output
in urban habitats are more likely reflective of differences in resources available to the target species.
Urban habitats often have dramatically different vegetation structure and
resource availability compared to rural habitats, resulting in novel challenges
and/or benefits to birds. Urban habitats may offer increased abundance of total food resources (Anderies et al., 2007), but with this benefit comes the
potential costs of increased predation (Baker et al., 2008; Rodewald et al.,
2010) and habitat fragmentation (Weldon & Haddad, 2005). Further, if supplemental food is available, it may be accessible for only part of the year
— for example, winter bird feeders may offer few resources in the spring
when many bird species, like chickadees, switch their diet to insect prey
(McCallum et al., 1999; Foote et al., 2010). Thus, even if food is occasionally abundant, urban areas may still be populated by a higher proportion of
relatively low-quality individuals, due to the cumulative costs of these habitats outweighing occasional benefits. One means of determining how males
experience urbanization is to compare the expression of condition-dependent
traits, such as song output, along an urbanization gradient.
There are several potential factors limiting how much a bird can sing or
call. Aggression from other males (Catchpole & Slater, 2008), increased
predation risk while singing (Catchpole & Slater, 2008), physical and developmental constraints (Ryan & Brenowitz, 1985; Nowicki et al., 1998;
Doutrelant et al., 2000; Nowicki et al., 2000), and immune or hormonal
costs (Nowicki et al., 1998; Buchanan et al., 1999) have all been identified as potential factors that limit vocal output, but perhaps the most well

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Behaviour (2017) DOI:10.1163/1568539X-00003464

documented limitation is energetic constraint. Singing males face a two-fold
energetic cost; there is the cost directly associated with physically singing,
as well as the cost of lost time that could otherwise be spent foraging or
on other activities (Gil & Gahr, 2002). Because singing is costly, the quality and quantity of vocal output during the dawn chorus is, in many species,
considered to be an honest indicator of male quality; males in better relative
condition vocalize more (e.g., barn swallow, Hirundo rustica, Møller, 1991;
black-capped chickadee, Poecile atricapillus, Otter et al., 1997; eastern kingbird, Tyrannus tyrannus, Murphy et al., 2008). This increase in vocal output
appears to reflect relative access to resources, as supplemental feeding has
been shown to increase song output in black-capped chickadees (Grava et
al., 2009), silvereyes (Zosterops lateralis, Barnett & Briskie, 2007), common
blackbirds (Turdus merula, Cuthill & MacDonald, 1990), and Australian
reed warblers (Acrocephalus australis, Berg et al., 2005). Females appear to
use song output as a performance indicator to assess relative male condition,
as evidenced by females showing preference for males with higher rates of
singing (e.g., pied flycatcher, Ficedula hypoleuca, Alatalo et al., 1990; whitethroated sparrows, Zonotrichia albicollis, Wasserman & Cigliano, 1991) or
for those that have consistent, highly stereotyped songs (e.g., black-capped
chickadees, Poecile atricapillus, Hoeschele et al., 2010). Thus, song output
is a useful metric to assess relative condition, likely driven by differences in
food availability among habitats.
To determine if the expression of vocal output during the dawn chorus
differed with changing levels of urbanization, we recorded the dawn chorus of mountain chickadees (Poecile gambeli) in Kamloops, BC, Canada
during the 2013, 2014, and 2015 breeding seasons. Among black-capped
chickadees, dominant males (generally better relative condition individuals)
begin singing earlier, have higher song rates, and sing for longer overall periods than subordinate males (Otter et al., 1997), and parallel differences
in song output occur among males occupying higher-quality versus lowerquality habitat (van Oort et al., 2006). Because mountain chickadees are
closely related to black-capped chickadees and share not only many aspects
of their life-history, but also have similar chorusing behaviour (Grava et al.,
2013), we expected similar condition-dependence associated with vocal output during dawn singing. Further, recent studies on other members of this
family suggest that urban habitats may represent poor-quality habitat relative to native woodlands, as seen by reduced reproductive success (blue

K.L.D. Marini et al. / Behaviour (2017)

5

tits, Gladalski et al., 2015; great tits, Wawrzyniak et al., 2015; Salmón et
al., 2016; but see Saarikivi & Herczeg, 2014). Mountain chickadees prefer
high-elevation, conifer-dominated forests in western Canada (McCallum et
al., 1999), which have both a greater canopy volume and higher conifer representation than most suburban neighbourhoods and urbanized areas where
mountain chickadees typically settle. Because of these differences between
urban and natural habitats, we predicted urban habitats may represent lowerquality habitat to mountain chickadees, which would be settled by younger,
inexperienced males of lower social rank than in neighbouring rural areas.
Consequently, we predicted that that males living in urban areas would have
lower vocal output during dawn singing than their rural counterparts.
2. Methods
2.1. Study species
Mountain chickadees have a large vocal repertoire consisting of multiple
song and call elements that can be arranged into many distinct vocalizations (Gaddis, 1985; Bloomfield et al., 2004). Unlike other chickadee species
which only use songs (e.g., black-capped chickadee, Carolina chickadee,
Poecile carolinensis) or only calls (e.g., chestnut-backed chickadee, Poecile rufescens, Dahlsten et al., 2002; boreal chickadee, Poecile hudsonicus,
Ficken et at., 1996) during dawn singing, mountain chickadees use a combination of ‘chick-a-dee’ calls and songs (McCallum et al., 1999; Grava et
al., 2013). Mountain chickadee song varies regionally, but usually consists
of 2 to 6 ‘fee’ and/or ‘bee’ notes at up to 3 different frequencies (Figure 1;
Gaddis, 1985; McCallum et al., 1999).
During the winter, mountain chickadees rely on cached seed store, and
will readily utilize bird feeders when available, and as the breeding season
progresses, they switch their diet to various species of arthropods (McCallum
et al., 1999).
2.2. Study site
We collected data for this study in and around Kamloops, BC, Canada in the
spring and summer of 2013, 2014 and 2015. Our primary rural study sites
were located in Kenna Cartwright park (50°40.232 N, 120°23.855 W), an
800 ha municipal forest reserve consisting of mature, open ponderosa pine
(Pinus ponderosa) and Douglas fir (Pseudotsuga menziesii) forests, which

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Behaviour (2017) DOI:10.1163/1568539X-00003464

Figure 1. Spectrogram of the most common song type (A) and call (B) recorded from male
mountain chickadees during the dawn chorus in our Kamloops populations.

is representative of the natural vegetation of the region with only minor disturbance in the form of walking trails. In 2015, we also collected data at
Paul Lake Provincial Park (50°44.975 N, 120°6.726 W). This park, located
approximately 22 km away from Kenna Cartwright Park, is a higher elevation mixed forest composed of mature Douglas fir, pine, and aspen (Populus
tremuloides). Our urban study sites were located throughout southern Kamloops, including the Thompson Rivers University campus, neighbourhood
parks, and residential properties. Vegetation at these urban sites was highly
variable, with pine, Douglas fir, as well as various species of deciduous trees
(e.g., mountain ash, Sorbus aucuparia; maple, Acer spp.; various ornamental fruit trees). Mountain chickadees were found at higher densities in rural
areas than in urban areas (pers. observation, KLDM, SEL). Over the two
breeding seasons, we recorded a total of 63 full and partial choruses, with 26
recordings from urban and 37 from rural areas.
2.3. Field methods
We recorded the dawn vocalizing of male chickadees in areas of varying levels of urbanization from 1 May until 16 May each season using a Sennheiser
ME67/K6 microphone with either an Olympus LS-14 or a Marantz PMD670
digital recorder. Recordings were made on settings of at least 44 kHz sampling frequency and 16 bit digitization, or higher. Recording locations were
selected by scouting potential locations beforehand and noting the presence
of chickadees singing or calling. We recorded at rural sites one morning then
at more urbanized sites the next morning, alternating between habitat types

K.L.D. Marini et al. / Behaviour (2017)

7

to ensure balanced sampling throughout the season. We recorded the GPS
coordinates for each recording location using a Garmin Montana 600 GPS.
To prevent multiple recordings of the same male, we ensured recording locations were at least 150 m from recordings made on previous days, and
neighbouring males were recorded on the same morning.
We arrived on site approximately 30 min before sunrise, to ensure that
we could record the start of the dawn chorus; we recorded the entire singing
bout of the first male(s) that began vocalizing. On a typical morning, we
had at least two researchers in the field recording dawn songs and calls.
Dawn vocalizing was considered to be finished after a five-minute period of
silence following the last vocalization of the focal male. We obtained a total
of 23 partial and 40 complete recordings. The mean length of a complete
dawn recording was 47 min (SD = 15.1 min). Any recording where we were
unable to obtain a start or end time was counted as a partial recording, and
so long as they were of adequate length (e.g., >30 min, approximately 70%
the length of an average, complete dawn recording), these partial recordings
were included in analysis. It was not possible to record blind data because
our study involved the observation and recording of focal males in the field.
2.4. Data analysis
We adjusted sampling frequency to 44 kHz at 16 bit digitization in AvisoftSASLab Pro v 5.2.08 (Specht, 2012), then we recorded the start time, end
time, number of calls and songs present, as well as the number of ‘dee’ notes
within each call. From these data, we calculated several variables of vocal
output, including total duration of vocalizations (i.e., the total number of
minutes spent vocalizing), total number of vocalizations (i.e., the total number of songs and calls produced during the recording), the most consecutive
songs in a row (i.e., the greatest number of songs produced before a call),
the most consecutive calls in a row (i.e., the greatest number of calls produced before a song), and proportion of songs (i.e., of the total vocalization
produced, what proportion were songs). Using principal components analysis, we collapsed the variables for start time, duration and total vocalizations
into a single variable for vocal output (PC1), which explained 68% of the
variance in our data (variable loadings: start time = −0.59, duration = 0.91,
total vocalizations = 0.92). Larger values for vocal output are associated
with males starting vocalizing earlier, vocalizing for longer, and producing
more total vocalizations. We checked the suitability of these variables for inclusion in the PCA using the Kaiser–Meyer–Olkin factor adequacy test. All

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Behaviour (2017) DOI:10.1163/1568539X-00003464

three variables had MSA values above 0.5 and so were deemed suitable for
further analysis (start time MSA = 0.89, duration MSA = 0.55, total vocalizations MSA = 0.55). The other variables, relating to the number of songs
relative to calls were assessed with urbanisation, as past studies have shown
mountain chickadee songs transmit better than calls in urban noise (LaZerte
et al., 2015), so differences between these features in urban vs rural birds
may suggest that vocal patterns during dawn signalling is being affected by
noise pollution.
We included partial dawn recordings that were at least 31.0 min in length
(mean − 1 SD) in our analyses, as they should still be long enough to
represent vocal ability, resulting in 4 additional recordings and a total of
44 recordings used in the analysis. Of these 4 incomplete recordings, 1 was
missing the start time, while the other 3 did not have accurate end times (one
due to battery failure, two due to the presence of a bear that necessitated
early termination of recording). In these instances, we used the duration and
start/end times of the recordings in place of the duration and start/end times
of the chorus. To check if the addition of these partial recordings affected our
analysis, we re-ran all analyses with and without the additional recordings,
and found no effect on in our overall results.
Because our study sites varied along a gradient from natural habitats to
suburban neighbourhoods, we calculated a habitat index based on ground
cover types (e.g., natural vegetation or man-made structures) and used this
index to classify habitats (Rolando et al., 1997; Dowling et al., 2012; LaZerte
et al., 2017). Following LaZerte et al. (2017), we used a combination of automated and manual methods to create a habitat index for the areas around
each recording location. We used an R script to create KML files depicting a
circle with a 75 m radius around each recording location (roughly the size of
an average chickadee territory) in Google Earth and the image of the territory
was exported. Using image manipulation software (GIMP; The GIMP Team,
2014) we manually classified the types of ground cover present as buildings,
pavement, coniferous trees, or deciduous trees. We then grouped buildings
and pavement together into single urban features variable, and used a principle components analysis (PCA) in R version 3.3.3 (R Core Team, 2017) to
collapse deciduous trees, coniferous trees, and urban features into an index
of urbanization. We retained the first principal component, PC1, which accounted for 76% of the total variation in habitat ground cover type. Smaller

K.L.D. Marini et al. / Behaviour (2017)

9

PC1 values correspond to decreasing cover of coniferous trees (native vegetation), with increasing cover of deciduous trees (non-native vegetation) and
urban features (PC1 loadings: coniferous trees = 0.53, deciduous trees =
−0.60, urban features = −0.60). Thus, lower PC1 values correspond to habitats with more urban features and deciduous trees, with fewer coniferous
trees (which are representative of the natural habitat in the area). We used
this continuous measure of habitat in all statistical analyses.
2.5. Statistical analysis
We constructed several linear mixed-effects models using recording date
and habitat index as fixed effects to model changes in vocal output (PC1),
proportion of songs, number of ‘dee’ notes, the most consecutive songs in
a row, and the most consecutive calls in a row. We also included year as
a random effect (as environmental differences between years could affect
condition). We used a backwards stepwise elimination approach to model
selection, eliminating non-significant variables from the full model:
y ∼ Habitat index + Recording date
+ (Habitat index × Recording date) + (1|Year)
All statistical analyses were conducted in R version 3.3.3 (R Core Team,
2017) using the R package ‘lme4’ (v1.1.12; Bates et al., 2017). Degrees
of freedom were calculated with the Satterthwaite approximation from the
R package ‘lmerTest’ (v2.0.33; Kuznetsova et al., 2016), and figures were
created using the ‘ggplot2’ (v2.2.1; Wickham, 2009) packages for R.
3. Results
As the season progressed, males across all habitats displayed increased vocal
output, but there was also an independent effect of habitat; vocal output
increased with the level of urbanization (Table 1; Figure 2). We found no
effects of habitat index or any seasonal changes on the ratio of songs to calls
in the dawn vocalization bouts, highest number of consecutive calls, highest
number of consecutive songs, or number of ‘dee’ notes in chick-a-dee calls
(Table 2).
4. Discussion
We found clear differences in song output between habitats, as well as seasonal changes in dawn chorus output. Contrary to our predictions though,

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Behaviour (2017) DOI:10.1163/1568539X-00003464
Table 1.
Final best fit linear model examining the effects of habitat index,
year, and recording date on vocal output for N = 44 recordings.
Factor

Habitat index
Recording date

Vocal output
Estimate

SE

t

p

−0.23
0.17

0.09
0.05

−2.39
3.59

0.022∗
0.0009∗

∗ Significant result, p < 0.05.

we found that males in more urban habitats had increased vocal output,
a holistic measure indicating earlier vocalization start times, longer durations, and more total vocalizations, compared to males in more rural areas.
Vocal output is an honest indicator of quality in the closely-related blackcapped chickadee (Otter et al., 1997; Grava et al., 2009), and vocal output
is condition-dependent across a variety of species (Cuthill & MacDonald,
1990; Thomas, 1999; reviewed in Gil & Gahr, 2002; Berg et al., 2005; Bar-

Figure 2. Vocal output (A) increased in male mountain chickadees living in habitats with
more urban features (lower habitat index scores) compared to those living in more natural
habitats (higher habitat index scores), and at the same time, vocal output increased through
the season (B), regardless of habitat type. Represented are the result of a linear model with
N = 44 males.

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K.L.D. Marini et al. / Behaviour (2017)

Table 2.
Final best fit linear models examining the effects of habitat index, year and recording date on
the number of consecutive calls, number of consecutive songs, ratio of songs to calls and the
maximum number of ‘dee’ notes in calls for N = 44 recordings.
Factor

Estimate

SE

t

p

Number of consecutive calls
Habitat index

−9.29

11.76

−0.79

0.434

Number of consecutive songs
Habitat index

−11.82

6.22

−1.90

0.064

Ratio of songs to calls
Habitat index

−0.82

2.37

−0.35

0.732

Maximum “dee” notes
Habitat index
Recording date
Habitat index × Recording date

−4.73
0.06
0.04

3.89
0.06
0.03

−1.22
1.03
1.22

0.23
0.31
0.23

nett & Briskie, 2007; Ritschard & Brumm, 2012). We did not however find
any differences in ratio of songs to calls, despite previous research that determined mountain chickadee songs transmit better in urban noise (LaZerte et
al., 2017). Thus, our results show that males living in urban areas have higher
vocal output, likely due to interacting factors such light pollution, noise pollution, and better condition individuals or individuals with more access to
food.
Though increased levels of ambient light and noise pollution may contribute to some of the changes in vocalizations we found, it is unlikely that
they can fully account for these differences. For many species, increased
ambient light levels cause males to begin singing earlier (Kempenears et al.,
2010; Da Silva et al., 2014, 2015), but if ability to maintain sustained song
output is resource-limited (e.g., Grava et al., 2009), then singing earlier in
relation to artificially-advanced light levels is unlikely entirely to account
for the increased vocal output we also found. Likewise, increased noise pollution is also associated with earlier vocalization start times (Arroyo-Solís
et al., 2013; Gil et al., 2015; Dominoni et al., 2016), but this most likely
represents a temporal shift in vocalizations to avoid periods of heavy traffic
noise. This too would not solely account for increased vocal output we saw,
especially as the extended length of the chorus we witnessed would negate
anti-masking advantages of starting to sing earlier to signal before the traffic noise begins to increase. Acute exposure to noise pollution may result in

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short-term changes to song-to-call ratios (LaZerte et al., 2017), but their research found that changes were only associated with a change in vocalization
type, and the rate of vocalizing did not change.
A possible explanation for the increase in vocal output in urban areas is
an increase in food availability during the pre-breeding season. During the
winter (pre-breeding season), birds in our urban study areas have access to
bird feeders (KLDM, personal observation), a consistent and abundant food
source (Robb et al., 2008). Increased vocal output has been directly linked
to measures of local food availability across bird species (Cuthill & MacDonald, 1990; Thomas, 1999; reviewed in Gil & Gahr, 2002; Berg et al.,
2005; Barnett & Briskie, 2007; Ritschard & Brumm, 2012). However, dawn
singing was measured during the spring, when pairs have moved onto individual breeding territories, and this typically coincides with a shift away
from seeds to primarily insect prey in chickadees (Smith, 1991). We suspected that the shift in diet could reduce male condition in urban habitats,
which typically have a lower overall canopy density (this is reflected in our
habitat index by more urban areas having a much lower conifer density,
which in turn results in a much lower overall canopy cover in these plots).
However, there are substantially more deciduous trees present in our urban
study areas compared to surrounding rural areas — while this is insufficient
to create a closed canopy, it does potentially affect potential food availability.
When we surveyed tree cover in a 75 m radius around recording locations or
active nest boxes, rural areas had a greater mean percentage of tree cover
(65% versus only 18% in urban areas), but the area covered by trees in urban areas had a much higher proportion of deciduous trees (33%) compared
to rural areas (0.08%). In general, deciduous trees are associated with both
a greater abundance and diversity of insects compared to coniferous trees
(Southwood, 1961; Brändle & Brandl, 2001), thus living in urban areas may
grant mountain chickadees greater access to insects despite the reduced tree
density, and this may be reflected in the chorusing of the males.
One factor that may have affected chorusing behaviour in our study area
is relative timing of egg laying. In a related study on the reproductive success of urban versus rural chickadees, we found that females in urban areas
begin laying earlier than those in rural areas, possibly as a result of greater
food abundance (Marini et al., 2017) or warmer temperatures in urban areas
slightly advancing seasonality. Foote et al. (2008) found that black-capped
chickadees had higher vocal output in the nest building versus the egg-laying

K.L.D. Marini et al. / Behaviour (2017)

13

stages. As urban birds may have been more likely to be recorded during egg
laying, and rural birds during the nest building/early egg-laying stages, our
results could have been affected if parallel changes in song output occur in
mountain chickadees. However, if this effect had created bias in our results,
we would have predicted that rural birds in our study would have had higher
song output, rather than the lower song output that we found. Given that urban birds may have been recorded later in relation to egg laying, the higher
vocal output we saw among these males may even be conservative estimates
of differences in vocal output between habitats. Studies investigating the relationship between vocal output and breeding status in mountain chickadees
would help clarify this relationship.
If urban areas do have a greater abundance of food resources, then, in addition to starting the breeding season earlier than rural birds, urban males
may be able to start the breeding season in better condition, find prey items
more easily, and thus devote more time and energy to singing than rural
males. Future studies examining differences in insect availability, such as
through measuring frass and monitoring the types of prey items provisioned
to offspring at the nest (see Seki & Takano, 1998), could help us determine if
differences in food availability are driving the differences in song output either directly, through changes to condition, and/or indirectly through changes
to timing of breeding.
The range of novel challenges and benefits associated with urban habitats
make predicting the response of individual species to urbanization a particular challenge. Here, we demonstrated that male mountain chickadees living
in urban areas begin singing earlier, sing for longer, and produce more vocalizations overall compared to rural males. Song output has been extensively
linked to breeding status (Foote et al., 2008), individual condition (Møller,
1991; Otter et al., 1997; Murphy et al., 2008), food availability (Cuthill &
MacDonald, 1990; Berg et al., 2005; Barnett & Briskie, 2007; Grava et al.,
2009), and habitat quality (van Oort et al., 2006) suggesting that for male
chickadees, urban habitats may actually be of higher-quality, perhaps due
to increased food availability. This effect could arise from food availability/
conditions present during the early breeding season (i.e., greater insect abundance; Southwood, 1961), or may represent a carry-over effect from improved winter conditions (i.e., access to bird feeders; Robb et al., 2008),
either of which may lead to increased body condition. Future experiments are
needed to determine the relative effects that light pollution, noise pollution,

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Behaviour (2017) DOI:10.1163/1568539X-00003464

and food availability have on urban vocal output and dawn chorus structure.
However, these results may indicate that urban chickadees experience improved breeding condition resulting from greater resource availability.
Acknowledgements
The authors would like to thank all the field technicians and the members of
the BEAC Lab at Thompson Rivers University for assisting with recording
chickadee vocalizations and other field work. Funding was provided by the
Natural Sciences and Engineering Research Council of Canada Discovery
Grants to M.W.R. and K.A.O., as well as a Natural Sciences and Engineering Research Council of Canada Industrial Postgraduate Scholarship to
K.L.D.M.
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