The influence of weather and parental provisioning on fledging
success depends on nest box type in a cavity-nesting passerine,
the Mountain Bluebird (Sialia currucoides)
Author(s): Sarah L. Leroux, Ann E. McKellar, Nancy J. Flood, Mark J. Paetkau,
Jacob M. Bailey, and Matthew W. Reudink
Source: The Wilson Journal of Ornithology, 130(3):708-715.
Published By: The Wilson Ornithological Society
https://doi.org/10.1676/17-084.1
URL: http://www.bioone.org/doi/full/10.1676/17-084.1

BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the
biological, ecological, and environmental sciences. BioOne provides a sustainable online
platform for over 170 journals and books published by nonprofit societies, associations,
museums, institutions, and presses.
Your use of this PDF, the BioOne Web site, and all posted and associated content
indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/page/
terms_of_use.
Usage of BioOne content is strictly limited to personal, educational, and non-commercial
use. Commercial inquiries or rights and permissions requests should be directed to the
individual publisher as copyright holder.

BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit
publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to
critical research.

The Wilson Journal of Ornithology 130(3):708–715, 2018

The influence of weather and parental provisioning on fledging success depends on
nest box type in a cavity-nesting passerine, the Mountain Bluebird (Sialia
currucoides)
Sarah L. Leroux,1,2 Ann E. McKellar,3 Nancy J. Flood,1 Mark J. Paetkau,4 Jacob M. Bailey,1,5 and
Matthew W. Reudink1*
ABSTRACT—Both weather and parental care can influence avian reproductive success, yet few studies have investigated
these 2 factors simultaneously. Examining these factors under a common framework is informative because they may interact
to influence overall productivity; for example, weather could directly influence nestling survival or could act indirectly by
influencing rates of provisioning. To tease apart these possibilities, we used piecewise structural equation modeling and path
analysis to assess the relative influence of local weather (temperature and rainfall) and rates of provisioning on the fledging
success of Mountain Bluebirds (Sialia currucoides) breeding in nest boxes. Both ambient temperature during the nestling
period and provisioning rates influenced fledging success, but this finding was dependent on nest box entrance type.
Bluebirds nesting in boxes with a hole-shaped entrance had higher overall fledging success than those using boxes with a
slot-shaped entrance and exhibited a positive association between fledging success and provisioning rates but a negative
association with temperature. Bluebirds nesting in boxes with a slot-shaped entrance experienced reduced fledging success,
and success was only weakly associated with provisioning rates. Reduced fledging success for birds nesting in slot boxes
may be due to increased exposure and higher susceptibility to stochastic events (e.g., storms), which may also mask any
effects of parental effort on success rates. Based on these findings, we recommend the use of nest boxes with hole-shaped
rather than slot-shaped entrances when managers and conservation groups establish new bluebird routes or replace existing
boxes. Received 7 July 2017. Accepted 27 March 2018.
Key words: fledging, mountain bluebird, nest box, parental care, provisioning, weather.
L’influence des conditions météorologiques et de l’approvisionnement parentale sur le succès d’envol chez un
passereau nicheur cavicole dépend du type de nichoir
RÉSUMÉ (French)—Les conditions météorologiques ainsi que l’approvisionnement parentale peuvent influencer le succès reproducteur
aviaire; peu d’études, cependant, ont exploré ces deux facteurs simultanément. L’examen de ces facteurs dans le cadre d’un même programme
d’étude est informatif puisque ces facteurs peuvent interagir de façon à influencer la productivité totale; par exemple, les conditions
météorologiques pourraient directement influencer la survie des oisillons ou agir indirectement en influençant le taux d’approvisionnement.
Pour distinguer ces influences directes et indirectes, nous avons employé une modélisation par équation structurelle séquentielle ainsi que
l’analyse des trajectoires, permettant de déterminer l’influence des conditions météorologiques locales (température et précipitation) et de
l’approvisionnement sur le succès d’envol de merlebleus azurés (Sialia currucoides) utilisant des nichoirs. La température ambiante pendant la
période de nidification de même que le taux d’approvisionnement ont influencé le succès d’envol, mais le résultat variait selon le type de
nichoir. Les merlebleus utilisant des nichoirs avec trou d’entrée circulaire avaient un succès d’envol plus élevé que ceux utilisant des nichoirs
avec trou d’entrée en forme de fente verticale, et le succès d’envol était positivement lié au taux d’approvisionnement mais négativement lié à
la température. Les merlebleus utilisant des nichoirs avec entrée en forme de fente avaient un succès d’envol réduit, et le succès d’envol était
faiblement lié au taux d’approvisionnement. Le succès d’envol inférieur observé parmi les oiseaux utilisant les nichoirs avec entrée en forme
de fente était possiblement dû à une plus grande exposition et sensibilité du nid aux événements stochastiques (e.g. tempêtes), ce qui pourrait
également masquer les effets de l’approvisionnement parentale sur le taux de succès d’envol. Compte tenu de ces résultats, nous
recommandons de munir les nichoirs d’une entrée circulaire plutôt que d’une entrée en forme de fente verticale lorsque gestionnaires et
groupes de conservation cherchent à créer de nouveaux sentiers de nichoirs ou veulent remplacer des nichoirs existants.
Mots-clés: approvisionnement, conditions météorologiques, envol, merlebleu azuré, nichoir, soins parentaux.

1

Department of Biological Sciences, Thompson Rivers
University, Kamloops, BC, Canada
2
Current Address: Ministry of Forests, Lands and
Natural Resource Operations, BC Public Service Agency,
Vernon, BC, Canada
3
Environment and Climate Change Canada, Saskatoon, SK, Canada
4
Department of Physics, Thompson Rivers University,
Kamloops, BC, Canada
5
Current address: Natural Resources and Environmental Studies, University of Northern British Columbia,
Prince George, BC, Canada
* Corresponding author: mreudink@tru.ca

Weather conditions during the breeding season
can influence avian reproductive success in several
ways. For example, extreme temperatures (Pipoly
et al. 2013) and rainfall events (George et al. 1992,
Grant et al. 2000) can directly influence hatching
and fledging success. In addition, weather can
indirectly influence reproductive success through
habitat changes (e.g., drought conditions; Ludlow
et al. 2014) or changes in food availability and
abundance (Grant et al. 2000). Weather may also
indirectly affect reproductive success through its

708

Leroux et al.  Mountain Bluebird fledging success

effects on levels of parental care, such as nestling
provisioning rates (Siikamäki 1998, Hoset et al.
2004).
Variation in parental investment in the form of
provisioning can have a major impact on the
reproductive success of individuals in species with
altricial young (Wright et al. 1998, Rauter et al.
2000). Increased parental care can improve
nestling growth rates (Klug and Bonsall 2014),
leading to greater fledgling mass and better overall
condition (Lifjeld et al. 1998, Soma et al. 2006,
Wilkin et al. 2009). In turn, these factors can
increase offspring survival and recruitment (NaefDaenzer et al. 2001, Monrós et al. 2002).
Because weather can influence levels of parental
provisioning, it can thus also influence reproductive success indirectly. For example, in Water
Pipits (Anthus spinoletta), females increase provisioning rates with decreasing ambient temperature
(Rauter et al. 2000), as is true for Snow Buntings
(Plectrophenax nivalis) breeding in the Arctic
(Hoset et al. 2004). The availability of insect prey,
which influences the rate at which parents can
provision their offspring, can also be mediated by
weather conditions (White 2008). Thus, while both
weather and provisioning can affect reproductive
success, the relative importance of each factor may
depend on the species and the weather conditions
experienced. In this study, we examined the
relative importance of weather and parental
provisioning rates for predicting fledging success
of a cavity-nesting passerine, the Mountain
Bluebird (Sialia currucoides).
For cavity-nesting birds that readily accept
boxes for nesting, further variation in reproductive
success might be introduced by specific characteristics of the box, such as orientation, entrance size,
or inner dimensions (Lambrechts et al. 2010). For
example, in a long-term study of Great Tits (Parus
major) breeding in Wytham Woods in the United
Kingdom, the implementation of predator-proof
nest boxes resulted in marked changes in clutch
size, local recruitment, and adult survival
(McCleery et al. 1996, Julliard et al. 1997). Nest
box design and construction materials often differ
geographically for the same study species, but the
benefits of such differences (e.g., more insulated
boxes in colder environments) or their potential
confounding effects on comparisons among populations have rarely been considered (Lambrechts
et al. 2010). Even within a single study population,

709

box types might differ, for example if new designs
are introduced gradually over time. This is the case
at our study site in British Columbia, Canada,
where boxes with 2 different entrance types (slot
or hole; Fig. 1) are distributed throughout the
region.
Previously, we demonstrated that weather conditions were associated with fledging success in
Mountain Bluebirds at our study site (McArthur et
al. 2017); however, whether this effect acts directly
(through nestling mortality) or indirectly (through
a reduction in provisioning) remains unknown. In
this study, we first asked whether fledging success
differed between boxes with the 2 types of
entrances. We then used path analyses to examine
the relative direct and indirect influences of local
weather and level of parental provisioning on
fledging success.

Methods
Study species
Mountain Bluebirds are obligate secondary
cavity-nesting thrushes that readily breed in nest
boxes throughout western North America’s grasslands. These birds are migratory and arrive in
interior British Columbia in late winter/early
spring (late Feb–Mar) before initiating breeding
in early May. Predominantly ground-foraging
insectivores during the breeding season, their diet
at this time consists mostly of Coleoptera,
Orthoptera, Formicidae, Lepidoptera, Hymenoptera, and Hemiptera (Power and Lombardo 1996).
Mountain Bluebirds are socially monogamous but
utilize a mixed mating strategy (Balenger et al.
2007); both males and females provision offspring,
but females tend to provision at higher rates, and
only females brood (Power and Lombardo 1996).
Mountain Bluebirds can sometimes have more
than one brood in a season (Power and Lombardo
1996), but multiple broods are relatively infrequent in our population and our analyses only
included first clutches.
Field methods
Fieldwork for this project was conducted on
bluebird trails maintained by the Kamloops
Naturalist Club in Knutsford, British Columbia,
Canada (50.628N, 120.338W) from May to August
2011–2014. Every 1–3 d, we recorded the number

710

The Wilson Journal of Ornithology  Vol. 130, No. 3, September 2018

Figure 1. Hole opening nest box (left) and slot opening nest box (right).

of eggs laid (n ¼ 531), number of nestlings (n ¼
459), and number of fledglings (n ¼ 341) for each
nest box (n ¼ 101 boxes: 72 hole boxes, 29 slot
boxes). Hole and slot entrance boxes were
distributed across routes relatively evenly (Table
1); other than the clear difference in entrance hole

Table 1. Number of hole and slot boxes occupied by
Mountain Bluebirds on each monitoring route. Edith Lake,
Jackson Rd, and Long Lake were used in primary analyses;
the remaining boxes were only used for an expanded sample
to examine the effect of box type on fledging success.
Route name

Hole boxes

Slot boxes

Campbell Range
Dewdrop
Edith Lake
Jackson Rd
Juniper
Lac du Bois
Long Lake
Pritchard East
Rosehill 1
Rosehill 2
Rosehill 3
Rosehill Ranch
Scott Rd
South Thompson

19
2
6
15
1
18
22
20
15
23
25
9
2
62

2
0
8
5
0
4
4
0
8
0
0
1
9
0

construction, both slot and hole nest boxes were
made of 0.5 inch plywood and did not vary
systematically in their construction. Parents at
these boxes were caught and each banded with a
unique combination of an aluminum Canadian
Wildlife Service band and 3 color bands.
Parental provisioning rates were quantified
during the early nestling stage (3–5 d after
hatching) and the late nestling stage, (14–16 d
after hatching), as described in Morrison et al.
(2014) and Evans et al. (2015). Early and late
provisioning rates were strongly correlated (n ¼
72, r ¼ 0.37, P ¼ 0.001). Sample size was smaller
in the late nestling stage because of mortality
occurring between these 2 stages, so only early
nestling stage provisioning was included in our
analysis. Parents at each nest were video recorded
for 2 h periods with a Sony Handycam DCR-SX45
(Sony, Toyko, Japan), a GoPro HD Hero2, or a
GoPro HD Hero3þ (GoPro, San Mateo, CA).
Cameras were stationed on a fencepost ~5–10 m
away from the nest. Video recordings began on
average at 09:15 (SD 80 min), and provisioning
rates were quantified as the number of trips to the
nest per hour per chick for both parents, after
removing the first 10 min of recording to allow
time for the birds to acclimatize to the presence of

711

Leroux et al.  Mountain Bluebird fledging success

the camera. Provisioning rates ranged from 0.4 to
18.8 trips/h/chick (mean: 6.01[SD 3.22] trips/h/
chick). Our methods followed Balenger et al.
(2007) and are consistent with previous work
quantifying parental provisioning rates (e.g.,
Moreno et al. 1997, Smiseth et al. 2001, Germain
et al. 2010, Osmond et al. 2013).
Weather data
We obtained local weather information by
accessing online Environment Canada weather
station archives for the Kamloops Pratt Road
station, located at 50.608N, 120.208W, ~10 km
from our study site. We calculated the mean
temperature and total rainfall during the nestling
period for each active nest along each route for
each year from 2011 through 2014. The nestling
period was defined as the time from the day eggs
hatched to the day offspring fledged for each nest.
Rainfall ranged from 0 to 68.6 mm during the
nesting period (mean: 30.41 [SD 16.64] mm)
while the average temperature ranged from 15.5 to
24.4 8C (mean: 17.90 [SD 2.31] 8C).
Statistical analyses
To determine whether reproductive success
differed between box types, we constructed linear
mixed models with number of eggs laid, hatching
success (number of nestlings/number of eggs laid),
and fledging success (number of fledglings/number
of eggs laid) as response variables and nest box
type (slot or hole) as a main effect. To account for
multiple years of data and individuals present in
multiple years, we used year and female band
number as random effects to avoid issues of
pseudoreplication. Because other microclimatic
factors and individual factors may influence
reproductive success, we also included the following fixed effects: male age, female age, aspect of
nest box opening, distance to the nearest tree,
distance to nearest Mountain Bluebird, distance to
nearest Tree Swallow nest, elevation, and percent
tree cover within 100 m. We then used a backward
stepwise procedure to eliminate nonsignificant
effects and arrive at a final best fit model using a
conservative alpha value of 0.10 to ensure we
captured potentially important habitat effects. We
also conducted a simple nominal logistic regression to ask whether male or female size (wing

chord, tarsus length, tail length) predicted nest box
type.
We used piecewise structural equation modelling (SEM) to investigate the correlations among
fledging success, weather conditions, and parental
provisioning rates. We created a path analysis
diagram to visualize the decomposition of these
relationships with each piecewise model in the
structural equation. We constructed 16 models that
related fledging success (as defined above) to the
direct effects of mean nestling period temperature,
total nestling period rainfall, and provisioning rate,
and to the combined effects of temperature and
rainfall, temperature and provisioning rate, rainfall
and parental care, and temperature, rainfall and
provisioning rate. Because we found no correlation
between provisioning rate and time of observation,
we did not include time of observation in our
models. We included box number as a random
effect in all models. Models were run separately
for hole and slot nest boxes (discussed later). The
fit of each model in the SEM was determined using
D-separation tests, and models were compared
using Akaike’s information criterion adjusted for
small sample size (AICc), estimated from Dseparation tests (Shipley 2013).

Results
Comparing the success of Mountain Bluebirds
in boxes with the 2 different types of entrances (n
¼ 72 hole, 29 slot) as well as age and several
microclimate characteristics, we found that entrance type was the greatest predictor of reproductive success (Table 2). Birds nesting in hole boxes
produced significantly more eggs (F1,95.44 ¼ 4.98,
P ¼ 0.03) and experienced significantly greater
fledging success (F1,93.66 ¼ 4.46, P ¼ 0.04; Fig. 2)
than did those nesting in slot boxes. Percent tree
cover within 100 m was also marginally positively
associated with fledging success (F1,89.56 ¼ 3.71, P
¼ 0.06). Neither box type nor any other microclimate characteristic was associated with hatching
success. No differences in body size of either
males or females was noted between box types (all
P . 0.17). Because of the observed difference in
reproductive success between hole and slot boxes,
we utilized an expanded dataset to examine
fledging success across 147 (2013; n ¼ 122 hole,
25 slot) and 134 (2014; 117 hole, 17 slot) active

712

The Wilson Journal of Ornithology  Vol. 130, No. 3, September 2018

Table 2. Best fit linear mixed models explaining variation in
number of eggs laid, hatching success (number of nestlings/
number of eggs), and fledging success (number of
fledglings/number of eggs) of Mountain Bluebirds, using
nest box type, aspect of nest box opening, distance to the
nearest tree, distance to nearest neighbour, elevation, and
percent tree cover within 100 m as main effects, and box
number and year as random effects.
Factor

Estimate

SE

F

df

Number of eggs
Box type
5.17
0.09
4.72 52.8
Hatching success
—
—
—
—
—
Fledging success (number fledged/clutch size)
Box type
0.100 0.040 2.23 37.31
Percent tree cover 0.008 0.004 2.21 51.65

p

0.03
—
0.03
0.03

Mountain Bluebird boxes monitored by the
Kamloops Naturalists Club. Similar to our results,
a linear mixed model using this larger sample
revealed a strong effect of box type on fledging
success (F1,157.4 ¼ 8.15, P ¼ 0.005). Complete
nestling mortality was more common in slot boxes
(logistic regression: v2 ¼ 9.07, P ¼ 0.003).
Because of the significant differences we
observed in reproductive success between box
types, we ran separate path analyses for hole and
slot boxes. For hole boxes, both weather and
provisioning rate exerted strong effects on fledging
success. Provisioning rate was the best predictor
of, and explained the most variance in, fledging
success based on a comparison of model fit (P) and
AICc (Table 3). When considering SEM linear
coefficients, the effect of parental care was positive
and that of temperature was negative (temperature:
b ¼ 0.21, P ¼ 0.04; parental care: b ¼ 0.31, P ¼
0.01; Fig. 2, Table 4), indicating that higher levels
of provisioning, and to a lesser extent lower
temperatures, were associated with higher fledging
success. For slot boxes, the model that explained
the most variance in fledging success included
provisioning rate (Table 3), but when considering
SEM linear coefficients, the effect of provisioning
rate was nonsignificant (b ¼ 0.14, P ¼ 0.22; Fig. 3,
Table 4).

Discussion
Many studies have assessed the influence of
local weather and provisioning rates on reproduc-

Figure 2. Box plot illustrating the number of offspring
fledged; nest boxes with slot entrances had significantly
lower fledging success. Box illustrates the median and
interquantile range (IQR), while whiskers are 1.5 3 IQR.

tive success separately (e.g., Grant et al. 2000,
Hoset et al. 2004). Few, however, have simultaneously evaluated the relative influence of these 2
factors (e.g., Öberg et al. 2015). Here, we
examined the effects of parental provisioning and
the direct and indirect effects of weather on the
reproductive success of a population of Mountain
Bluebirds breeding in a semiarid grassland of
interior British Columbia. We found that the direct
effects of provisioning rate and temperature were
the best predictors of Mountain Bluebird fledging
success. Although fledging success of Mountain
Bluebirds was associated with provisioning rates
and breeding season temperature, this association
was dependent on nest box opening type, a finding
that has important implications for naturalist clubs
and citizen scientists constructing nest boxes for
bluebirds. Most notably, reproductive success was
higher in nest boxes with hole-shaped entrances
compared to those with slot-shaped entrances (Fig.
2), after accounting for other potential microclimate differences among boxes.
Parental provisioning rates were strongly correlated with fledging success (number fledged/
number eggs) in hole boxes (Fig. 3, Table 4). This
result is consistent with other work demonstrating
the importance of parental care in influencing the
success of nestlings (e.g., Wright et al. 1998,

713

Leroux et al.  Mountain Bluebird fledging success

Table 3. Candidate path models created using piecewise
SEM path analysis to evaluate the effect of temperature
(temp), rainfall, and provisioning rates on the fledging
success of Mountain Bluebirds.
Model

Hole boxes
Parental care
Temp
Temp þ rainfall
Null
Rainfall
Parental care þ rainfall
Parental care þ temp þ
rainfall
Parental care þ temp
Slot boxes
Parental care
Null
Temp
Temp þ rainfall
Rainfall
Parental care þ temp
Parental care þ temp þ
rainfall
Parental care þ rainfall

Fit (P)

K

AICc

D AIC

0.11
0.05
0.01
0.01
0.005
0.15
0.11

3
3
4
2
3
7
8

13.88
15.71
17.29
19.46
21.36
25.11
25.82

0
1.83
3.41
5.58
7.48
11.23
11.94

0.1

7

26.46

12.58

0.80
0.50
0.49
0.33
0.25
0.93
0.80

3
2
3
4
3
7
8

8.6
9.822
10.37
11.9
12.36
21.22
24.84

0
1.22
1.77
3.3
3.76
12.62
16.24

0.47

7

24.96

16.36

Rauter et al. 2000). We did not directly assess the
mechanism driving increased fledging success, but
previous work has linked increased provisioning to
nestling growth rates (Klug and Bonsall 2014) and
condition (Soma et al. 2006, Wilkin et al. 2009).
While we were not able to quantify the amount or
quality of food delivered per visit, our results
nonetheless indicate provisioning rate is an
important driver of reproductive success in
Mountain Bluebirds, which may potentially buffer
against the effects of adverse weather conditions.
While provisioning rate was the most important
determinant of reproductive success, temperature
also exerted an effect on Mountain Bluebird
reproduction, although this effect was dependent
on the type of nest box opening. For birds nesting
in boxes with hole-shaped entrances, higher
temperatures were associated with reduced fledging success. This contrasts with findings in other
species that demonstrate improved hatching success (Martin 1987) and fledging success (Reid et
al. 2000, Ardia et al. 2010) when weather is
warmer. One possibility for our different result is
that the effect of lower temperatures is indirect and
actually related to earlier nesting, which is often
associated with larger clutch sizes (Klomp 1970,

Table 4. Linear coefficients from the structural equation
model decomposing independent weather and parental
provisioning effects on the fledging success of Mountain
Bluebirds.
Hole boxes

Slot boxes

Estimate

Standard
error

p

Estimate

Standard
error

p

0.21
0.005
0.31

0.1
0.015
0.12

0.04
0.77
0.01

0.26
0.006
0.17

0.28
0.029
0.14

0.36
0.84
0.22

Crick et al. 1993, Brown and Brown 1999) and
increased reproductive success (Lozano et al.
1995, Reudink et al. 2009). If that were the case,
however, we might have expected birds nesting in

Figure 3. Path analysis of mean nestling period temperature,
total nestling period rainfall, and total parental provisioning
on fledging success of Mountain Bluebirds (proportion of
eggs that fledged) for hole- and slot-opening type nest
boxes. The thickness of the arrows represents the magnitude
of the effect (b; shown in parentheses) as well as the
significance. A solid black arrow indicates a significant
positive effect; a dotted black arrow represents a significant
negative effect.

714

The Wilson Journal of Ornithology  Vol. 130, No. 3, September 2018

hole boxes to lay their clutches earlier, but no
difference was noted in first egg dates between
birds nestling in hole and slot boxes at our study
site (MWR unpubl. data).
Birds nesting in boxes with hole-shaped entrances had significantly higher productivity;
Mountain Bluebirds nesting in these boxes laid
more eggs and experienced greater fledging
success. Despite Mountain Bluebirds generally
preferring open grassy areas, we also detected a
weak positive effect of percent tree cover on
fledging success, possibly due to greater foraging
opportunities with more tree cover. Our study site
is largely composed of grasslands, however, so this
possibility would require further study. Because
the size of a nest box entrance can determine how
much protection it offers to its occupants (Lambrechts et al. 2010), boxes with hole-type openings
may provide better shelter from exposure (e.g., to
wind and rain entering the nest especially during
cold spells) and predation. We found greater total
nest failure in boxes with slot-type entrances,
which reinforces the idea that a high degree of
exposure likely accounted for a high level of
mortality. Interestingly, we found no influence of
weather on fledging success for birds nesting in
slot boxes, in contrast to the situation for hole
boxes. Perhaps hole boxes, although providing
better protection in most weather conditions,
become overheated in hot weather, thus contributing to greater nestling mortality in these situations,
although we note this has not been observed in our
population. More research into the differences in
insulative properties between box types would be
needed to test such a hypothesis. Another possible
contributing factor to the differences in productivity between hole boxes and slot boxes is that
differences in individual quality existed among
individuals nesting in each type of box. Although
we detected no difference in the ages or body size
of birds nesting in each type of box, birds selecting
hole and slot boxes possibly differed in some other
measure of quality.
In conclusion, we demonstrate that nest box
type, provisioning, and temperature all have
important effects on reproduction in Mountain
Bluebirds. Birds nesting in hole boxes experienced
greater reproductive success, and the influence of
weather on fledging success was more apparent for
these birds, perhaps because of differences in
insulative properties between box types. Our

results reinforce the need for more research into
the influences of nest box characteristics on
reproductive success (Lambrechts et al. 2010),
especially for species such as the Mountain
Bluebird, whose populations are heavily dependent on nest box programmes (Power and
Lombardo 1996). Furthermore, we recommend
the use of nest boxes with hole-shaped entrances
over those with slot-shaped entrances for managers
and conservationists interested in aiding populations of Mountain Bluebirds, although we caution
that more research is needed to determine the
mechanisms underlying the differences in reproductive success between box types.
Acknowledgments
We thank G. Dreger, P. and J. Gray, S. Weilandt, and the
undergraduate students who assisted on this project. Thanks
also to J. Lefcheck for help with statistical analysis. Thank
you to S. Joly and numerous undergraduate field technicians
for assistance in the field. Funding for this project was
provided by a Natural Sciences and Engineering Research
Council Discovery Grant (MWR), and a North American
Bluebird Society Research Grant (SLM). This work was
conducted under permit number BC-14-0025 granted by the
Canadian Wildlife Service. The Thompson Rivers University Animal Care Committee approved this research, file
number 10603, and no animals were harmed during this
study.

Literature cited
Ardia DR, Pérez JH, Clotfelter ED. 2010. Experimental
cooling during incubation leads to reduced innate
immunity and body condition in nestling tree swallows.
Proceedings of the Royal Society B. 277:1881–1888.
Balenger SL, Johnson LS, Brubaker JL, Ostlind E. 2007.
Parental effort in relation to structural plumage
coloration in the Mountain Bluebird (Sialia currucoides). Ethology. 113:838–846.
Brown CR, Brown MB. 1999. Fitness components associated with clutch size in cliff swallows. Auk. 116:467–
486.
Crick HQP, Gibbons DW, Magarath RD. 1993. Seasonal
changes in clutch size in British birds. Journal of
Animal Ecology. 62:263–273.
Evans DR, McArthur SL, Bailey JM, Church JS, Reudink
MW. 2015. A high-accuracy, time-saving method for
extracting nest watch data from video recordings.
Journal of Ornithology. 156:1125–1129.
George TL, Fowler AC, Knight RL, McEwen LC. 1992.
Impacts of a severe drought on grasslands birds in
western North Dakota. Ecological Applications. 2:275–
284.
Germain RR, Reudink MW, Marra PP, Ratcliffe LM. 2010.
Carotenoid-based male plumage predicts parental

Leroux et al.  Mountain Bluebird fledging success
investment in the American Redstart. Wilson Journal of
Ornithology. 122:318–325.
Grant PR, Grant BR, Keller LF, Petren K. 2000. Effects of
El Niño events on Darwin’s finch productivity.
Ecology. 81:2442–2457.
Hoset S, Espmark Y, Moksnes A, Haugan T, Ingebrigtsen
M, Lier M. 2004. Effect of ambient temperature on
food provisioning and reproductive success in Snow
Bunting Plectrophenax nivalis in the high arctic.
Ardea. 92:239–246.
Julliard R, McCleery RH, Clobert J, Perrins CM. 1997.
Phenotypic adjustment of clutch size due to nest
predation in the Great Tit. Ecology. 78:394–404.
Klomp H. 1970. The determination of clutch size in birds: a
review. Ardea. 58:1–121.
Klug H, Bonsall MB. 2014. What are the benefits of parental
care? The importance of parental effects on developmental rate. Ecology and Evolution. 4:2330–2351.
Lambrechts MM, Adriaensen F, Arida DR, Artemyev AV,
Atiénzar F, et al. 2010. The design of artificial
nestboxes for the study of secondary hole-nesting
birds: a review of methodological inconsistencies and
potential biases. Acta Ornithologica. 45:1–16.
Lifjeld JT, Slagsvold T, Ellegren H. 1998. Experimentally
reduced paternity affects paternal effort and reproductive success in Pied Flycatchers. Animal Behaviour.
55:319–329.
Lozano GA, Perrault S, Lemon RE. 1995. Age, arrival date
and reproductive success of male American Redstarts
Setophaga ruticilla. Journal of Avian Biology. 27:164–
170.
Ludlow SM, Brigham RM, Davis SK. 2014. Nesting
ecology of grassland songbirds: effects of predation,
parasitism, and weather. Wilson Journal of Ornithology. 126:686–699.
Martin TE. 1987. Food as a limit on breeding birds: a lifehistory perspective. Annual Review of Ecology and
Systematics. 18:453–487.
McArthur SL, McKellar AE, Flood NJ, Reudink MW. 2017.
Local weather and regional climate influence breeding
dynamics of Mountain Bluebirds (Sialia currucoides)
and Tree Swallows (Tachycineta bicolor): a 35-year
study. Canadian Journal of Zoology. 95:271–277.
McCleery RH, Clobert J, Julliard R, Perrins CM. 1996. Nest
predation and delayed cost of reproduction in the Great
Tit. Journal of Animal Ecology. 65:96–104.
Monrós JS, Belda EJ, Barba E. 2002. Post-fledging survival
of individual Great Tits: the effect of hatching date and
fledging mass. Oikos. 99:481–488.
Moreno J, Potti J, Merino S. 1997. Parental energy
expenditure and offspring size in the Pied Flycatcher
Ficedula hypoleuca. Oikos. 79:559–567.
Morrison A, Flood NJ, Reudink MW. 2014. Reproductive
correlates of plumage coloration of female Mountain
Bluebirds. Journal of Field Ornithology. 85:168–179.
Naef-Daenzer B, Widmer F, Nuber M. 2001. Differential
post-fledging survival of Great and Coal tits in relation

715

to their condition and fledging date. Journal of Animal
Ecology. 70:730–738.
Öberg M, Arlt D, Pärt T, Laugen AT, Eggers S, Low M.
2015. Rainfall during parental care reduces reproductive and survival components of fitness in a passerine
bird. Ecology and Evolution. 5:345–356.
Osmond MM, Reudink MW, Germain RR, Marra PP,
Nocera JJ, et al. 2013. Relationships between carotenoid-based female plumage and age, reproduction, and
mate colour in the American Redstart (Setophaga
ruticilla). Canadian Journal of Zoology. 91:589–595.
Pipoly I, Bókony V, Seress G, Szabó K, Liker A. 2013.
Effects of extreme weather on reproductive success in a
temperate-breeding songbird. PLOS ONE. 8:e80033.
Power HW, Lombardo MP. 1996. Mountain Bluebird (Sialia
currucoides). In: Poole A, editor. Birds of North
America Online. Ithaca (NY): Cornell Laboratory of
Ornithology. https://birdsna.org/Species-Account/bna/
species/moublu/
Rauter CM, Brodmann P, Reyer HU. 2000. Provisioning
behaviour in relation to food availability and nestling
food demand in the Water Pipit (Anthus spinoletta).
Ardea. 88:81–90.
Reid JM, Monaghan P, Ruxton GD. 2000. Resource
allocation between reproductive phases: the importance
of thermal conditions in determining the cost of
incubation. Proceedings of the Royal Society of
London B. 267:37–41.
Reudink MW, Marra PP, Kyser TK, Boag PT, Langin KM,
Ratcliffe LM. 2009. Non-breeding season events
influence sexual selection in a long-distance migratory
bird. Proceedings of the Royal Society of London B.
276:1619–1626.
Shipley B. 2013. The AIC model selection method applied
to path analytic models compared using a d-separation
test. Ecology. 94:560–564.
Siikamäki P. 1998. Limitation of reproductive success by
food availability and breeding time in Pied Flycatchers.
Ecology. 79:1789–1796.
Smiseth PT, Ornborg J, Andersson S, Amundsen T. 2001. Is
male plumage reflectance correlated with paternal care
in Bluethroats? Behavioral Ecology. 12:164–170.
Soma M, Takahasi M, Ikebuchi M, Yamada H, Suzuki M, et
al. 2006. Early rearing conditions affect the development of body size and song in Bengalese Finches.
Ethology. 112:1071–1078.
White TCR. 2008. The role of food, weather and climate in
limiting the abundance of animals. Biological Reviews.
83:227–248.
Wilkin TA, King LE, Sheldon BC. 2009. Habitat quality,
nestling diet, and provisioning behaviour in Great Tits
Parus major. Journal of Avian Biology. 40:135–145.
Wright J, Both C, Cotton PA, Bryant D. 1998. Quality vs.
quantity: energetic and nutritional trade-offs in parental
provisioning strategies. Journal of Animal Ecology.
67:620–634.