The Wilson Journal of Ornithology 122(2):318–325, 2010

CAROTENOID-BASED MALE PLUMAGE PREDICTS PARENTAL
INVESTMENT IN THE AMERICAN REDSTART
RYAN R. GERMAIN,1,4 MATTHEW W. REUDINK,1,2,3
PETER P. MARRA,2 AND LAURENE M. RATCLIFFE1
ABSTRACT.—We examined whether male plumage coloration signals parental quality in the American Redstart
(Setophaga ruticilla), a highly ornamented, migratory warbler. We measured the relationship between both adult male
arrival date and phenotype (morphology, melanin- and carotenoid-based plumage), and parental care levels of both parents.
Males with brighter flank feathers made more visits to the nest and spent more time at the nest, consistent with the ‘goodparent hypothesis’. Female parental care (number of visits) was negatively correlated with intensity of red of her mate’s tail
feathers and positively associated with her mate’s parental effort. These data indicate offspring of brighter males receive
more care from both parents. Our results suggest carotenoid-based plumage traits of male American Redstarts may have an
important role in intersexual signaling, and add to our understanding of the evolution of multiple ornaments. Received 10
July 2009. Accepted 20 January 2010.

Three major models have been developed to
explain patterns of association between male
ornamentation and parental care. The ‘goodparent’ hypothesis predicts that when paternal
care influences offspring viability directly, males
should signal their ability to provide for offspring
to prospective mates, and more attractive males
should provide more care (Heywood 1989,
Hoelzer 1989, Norris 1990, Hill 1999, Siefferman
and Hill 2003). Some evidence suggests female
parental care does not decrease in response to
increased care by their mate, resulting in a net
benefit to the offspring of ‘good-parent’ males
(Sanz et al. 2000, Schwagmeyer and Mock 2003,
but see Wright and Cuthill 1989, 1990; Markman
et al. 1995). Alternatively, the ‘differential
allocation’ hypothesis predicts females mated to
more attractive males increase their own level of
parental effort to avoid desertion by their mates
and to enhance their fitness through production of
high-quality offspring (Burley 1986, 1988; Studd
and Robertson 1988; Badyaev and Hill 2002). In
this model, attractive males restrict their parental
investment to allocate more energy towards their
own survival, resulting in a negative relationship
between male attractiveness and care (Burley
1986, 1988; Møller and Thornhill 1998). A third
1
Department of Biology, Queen’s University, Kingston,
ON K7L 3N6, Canada.
2
Smithsonian Migratory Bird Center, National Zoological Park, 3001 Connecticut Avenue, Northwest, Washington, D.C. 20008, USA.
3
Current address: Trent University, Forensic Science
Department, DNA Building, 2140 East Bank Drive,
Peterborough, ON K9J 7B8, Canada.
4
Corresponding author;
e-mail: ryan.germain@queensu.ca

alternative, the ‘trade-off hypothesis’, similarly
proposes that attractive males provide less care
towards their offspring (to be able to seek extra
mating opportunities), resulting in a negative
relationship between male attractiveness and level
of care (Williams 1966, Magrath and Komdeur
2003, Mitchell et al. 2007). Several studies have
failed to find a relationship between male
plumage and parental care (Rohde et al. 1999,
Smiseth et al. 2001, Cooper and Ritchison 2005).
Some of these studies, however, involve species
with multiple ornaments whose signal function
and context are not well understood.
The American Redstart (Setophaga ruticilla), a
small (7–8 g) neotropical migratory warbler, is
particularly suited for studies of male plumage
coloration and parental care. American Redstarts
are sexually dichromatic and yearling males
exhibit delayed plumage maturation, suggesting
strong sexual selection on plumage coloration.
Adult males are black with bright orange plumage
patches on their wings, tail, and sides of the breast
(flanks), and a white or black breast, depending on
bib size (Sherry and Holmes 1997). The plumage
of adult male American Redstarts is highly
variable, both in bib size (melanin-based plumage) and orange (carotenoid) coloration (Lemon et
al. 1992, Kappes et al. 2009, Reudink et al.
2009b). Recent evidence suggests tail feathers of
American Redstarts have an important role in
intrasexual signaling during the non-breeding
season, where males with brighter tails occupy
higher quality winter territories (Reudink et al.
2009a). Additionally, both bib size (Perreault et
al. 1997) and flank redness have been linked to a
male’s ability to secure paternity at his nest during

318

Germain et al. N AMERICAN REDSTART PLUMAGE AND PARENTAL CARE

the breeding season, and tail brightness to a
male’s chances of achieving polygyny (Reudink
et al. 2009b). In particular, flank feathers may
function as a sexual signal in American Redstarts,
as males will puff out their breast and flank
feathers in a ‘‘fluff display’’ during courtship
(Sherry and Holmes 1997).
Our objectives were to quantify variation in
plumage ornamentation, morphology, and arrival
behavior of adult male American Redstarts, and
levels of parental care provided by both parents to
offspring to identify which features may provide a
reliable signal to females of male parental effort
in this highly ornamented songbird. We predicted
male plumage coloration would correlate with
levels of parental care, based on recent evidence
suggesting that different plumage regions may be
used to signal information in different contexts
(Reudink et al. 2009a, b; Kappes et al. 2009);
however, we made no a priori predictions as to
which plumage region(s) might be important.
METHODS
Field Data and Feather Collection.—We conducted field work at the Queen’s University
Biological Station in southeastern Ontario,
Canada (44u 349 N, 76u 199 W), during two
consecutive breeding seasons (May–Jul 2006–
2007). The 60-ha study site is a mixed deciduous
forest, largely dominated by sugar maple (Acer
sacchurum) and eastern hop-hornbeam (Ostrya
virginiana). We surveyed transects from 0600 to
1200 hrs EST each day from 1 May to 1 July
across the study site to record the arrival date for
each individual. We designated arrival date as the
number of days after the arrival of the first male
each season (i.e., first date of male arrival 5 0;
male that arrived 5 days later 5 5) to standardize
arrival date across seasons. We captured adult
male redstarts on their respective territories using
mist nests and song playback, usually within
7 days of arrival, and females during the nesting
phase using mist nets near their nest location. All
birds were banded with a Canadian Wildlife
Service aluminum band (permit # 10766C) and a
unique combination of three color bands (excluding red and orange in males); we recorded
unflattened wing chord length (61.0 mm) as a
measure of relative body size. We plucked a
single tail feather (third rectrix; R3) and 12–15
orange flank feathers from each male (Quesada
and Senar 2006) (CWS collection permit # CA
0154). We classified adult male bib size using a

319

1–5 scale (1 5 small amount of black plumage, 5
5 large amount of black plumage with intermediates given half points) following Lemon et al.
(1992).
Parental Care Observations.—We monitored
American Redstart pairs each season (,40 pairs/
season) daily until their nest was found, and
observed nests every 1–2 days following completion of nest-building until hatching and recorded
the number of young. We confirmed the number
of nestlings again on day 5 after hatching and
continued to monitor nests until fledging. Fifty
nests were observed: 25 in 2006 and 25 in 2007.
We erected ground-based video cameras (Canon
ZR500) on tripods .5 m from the base of the nest
tree on days 5 and 7 after hatching to record
parental effort. Cameras were focused on the nest
and its immediate (,20 cm) surroundings, and
recording occurred between 0600 and 0900 hrs
EST. Each recording lasted 120 min and the first
5 min were discarded to allow parents time to
recover from human disturbance. The remaining
115 min were used to calculate provisioning rates
of males and females, and the time each parent
spent at the nest. We recorded and analyzed a total
of 148 hrs of video from 38 nests (n reduced due
to high predation rates). A trained observer
recorded the measures of parental care through
binoculars at a distance .10 m from the nest
using a stopwatch if there were more nests to be
watched than cameras available (2006—day 5: n
5 8, day 7: n 5 5; 2007—day 5: n 5 2, day 7: n
5 2). There was no difference between video
camera and trained observer nest watches in either
the number of visits to the nest, or total time at the
nest (2-sample t-test assuming unequal variance,
all P values . 0.09). Nests depredated between
days 5 and 7 were excluded from analysis (2006:
n 5 7; 2007: n 5 5).
We recorded both the total (i.e., sum of days 5
and 7) number of visits to the nest and the total
nest attendance (in sec) for males and females as
measures of parental care. Both variables are
effective measures of parental effort in small
insectivorous birds that make frequent trips to the
nest (Saetre et al. 1995). Total time at the nest for
males may include activities such as vigilance and
removal of fecal sacs, but does not necessarily
represent a direct benefit to rearing of offspring as
it would for females (i.e., brooding); trips to the
nest may serve as a more accurate representation
of care, as males are continually bringing food.
We divided both total number of visits per hour

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THE WILSON JOURNAL OF ORNITHOLOGY N Vol. 122, No. 2, June 2010

and total nest attendance per hour by the number
of chicks present in the nest to standardize for
brood size and recording time. We compared
standardized parental care variables with raw data
to ensure that parental effort/hr/chick was representative of total parental effort (linear regressions, all P , 0.0004). Six males in our study
were polygynous; however, primary and secondary nests were temporally separated, and we
included only data from the primary nest (during
the period when the male was caring exclusively
for the first nest). All individuals were identifiable
via color bands, and we were able to ensure that
our data set contained no pair duplications across
both years.
Color Analysis.—We mounted feathers from
each male on black paper (Colorline Ebony
#142), and stacked flank feathers as they would
naturally lie on the bird (Siefferman and Hill
2003, Quesada and Senar 2006). Mounting
feathers on a black background is a standard
technique (Siefferman and Hill 2003, Quesada
and Senar 2006), and the paper used had low
(,5%) reflectance, indicating it would have a
minimal impact on our analysis. We omitted
samples from further analysis (n 5 5) in
instances where there were too few flank feathers
or the orange area on the tail feather was too
small to obtain reliable readings. We analyzed
male plumage and parental care observations for
both males and females from 16 nests in 2006
and 17 nests in 2007.
We gathered reflectance spectra from flank and
tail feathers of each male using a PX-2 pulsed
xenon light source attached to an Ocean Optics
USB2000 spectrometer (Dunedin, FL, USA). We
took 25 readings throughout the orange (carotenoid-based) region for both flank and tail feathers
following Reudink et al (2009b). We gathered
raw reflectance data into 10 nm bins from 320
to 700 nm using CLR1.0.3 (Montgomerie 2008),
and averaged across the 25 measurements. We
calculated brightness for tail and flank feathers by
averaging percent reflectance from 320 to 700 nm
(color variable 1: ‘brightness’). The carotenoidbased plumage of American Redstarts consists of
peaks in both the UV and red/orange regions of
the spectrum. We used principal component
analysis (PCA) to collapse the spectrum into a
smaller set of independent variables that describe
the measures of hue and chroma based on shape of
the curve while controlling for variation in
brightness (Cuthill et al. 1999, Montgomerie

2006, Stein and Uy 2006, Reudink et al. 2009b).
We verified this method by calculating hue and
chroma using the equations: hue5arctan ([R4152510
2 R3202415)/R3202700]/[R5752700 2 R4152575)/
R3202700]), UV chroma 5 R3202415/R3202700, and
red chroma 5 R5752700/R3202700.
Flank PC I described 85.5% of the variation in
shape of the reflectance curve, and loaded
positively on short (UV) wavelengths and negatively on the longer (red/orange) wavelength
region of the spectrum. Flank PC I associated
negatively with both hue (r2 5 0.68, n 5 32, P ,
0.001) and red chroma (r2 5 0.99, n 5 32, P ,
0.001), and associated positively with UV chroma
(r2 5 0.81, n 5 32, P , 0.001). Tail feather PC I
explained 48.4% of the variation, and loaded
positively on both the shorter and longer wavelength regions of the spectrum, and negatively on
intermediate wavelengths. Tail PC I associated
positively with hue (r2 5 0.16, n 5 33, P 5 0.02)
and red chroma (r2 5 0.61, n 5 33, P , 0.001),
but had no association with UV chroma (r2 ,
0.001, n 5 33, P 5 0.94). The first principal
component from both plumage regions was used
to describe ‘redness’ (color variable 2 5 ‘redness’), where birds with greater ‘redness’ have
more negative flank PC I values, and more
positive tail PC I values.
Statistical Analysis.—All statistics were performed using JMP 7.0 (SAS Institute 2007) and R
2.6.1 for Windows (R Development Core Team
2007). We pooled data across both years of study
and, in instances where data for the same
individual were collected across 2 years (n 5 3),
avoided pseudoreplication by randomly selecting
1 year to exclude. We used paired t-tests to
compare the parental care variables across both
observation days (for both males and females), as
well as across gender, and linear regression to
examine the relationship between a pair’s number
of visits to the nest, and total nest attendance. All
plumage variables were tested for co-linearity
using Pearson’s pairwise analysis. We applied
backwards stepwise multiple regressions with
parental care variables (male visits/hr/chick,
female visits/hr/chick, male time at the nest/hr/
chick, female time at the nest/hr/chick) as the
response variable to calculate the factors that best
predicted both male and female parental care. We
used measures of male tail brightness, tail redness
(PC I), flank brightness, flank redness (PC I), bib
score, body size, year, and arrival date as our main
effects in each model.

Germain et al. N AMERICAN REDSTART PLUMAGE AND PARENTAL CARE

RESULTS
Male American Redstarts did not show a
difference in mean time (sec 6 SD) spent at the
nest between days 5 (108.21 6 112.53) and 7
(77.98 6 75.66) (paired t-test, t32 5 1.65, P 5
0.11); however, mean number of visits for males
on day 7 (1.92 6 0.73) after hatching were greater
than on day 5 (1.52 6 0.81) (paired t-test, t32 5
22.89, P 5 0.007). Females showed no difference
in the mean number of visits to the nest between
days 5 (1.56 6 0.59) and 7 (1.72 6 0.68) (paired
t-test, t32 5 21.78, P 5 0.09), but spent
significantly more time at the nest on day 5
(778.04 6 484.18 sec) than day 7 (616.68 6
523.90 sec) (paired t-test, t32 5 3.54, P 5 0.001).
Females did not visit the nest more or less
frequently than males (paired t-test, t32 5 1.27,
P 5 0.21), but did spend a greater amount of time
at the nest (paired t-test, t34 5 27.91, P ,
0.0001). There was a significant positive relationship between each member of a breeding pair for
number of visits (r2 5 0.21, F1,31 5 8.17, P 5
0.008) and nest attendance (r2 5 0.30, F1,31 5
13.11, P 5 0.001).
Pairwise correlations between all male plumage
variables revealed that tail brightness increased
with decreasing tail redness (PC I) (r2 5 0.12,
F1,31 5 4.30, P 5 0.05). No other plumage
variables were significantly correlated.
Plumage Color and Provisioning.—Results of a
backwards stepwise multiple regression revealed
total number of male visits/hr/chick was significantly predicted by the brightness of flank
feathers (Table 1). This data set contains one
high value for flank brightness (Fig. 1). This point
is not due to a technical error in measurement, as
readings taken before and after this point were
within the normal range, and this point remained
high after repeated measurements. This individual
was also within the normal range for all other
measures. The correlation between male flank
brightness and number of visits/hr/chick remained
significant when this point was excluded (Fig. 1).
Flank brightness was also a significant predictor
of total time spent by males at the nest (Table 1).
Female visits were significantly predicted by year
and mate’s tail redness (Table 1), where females
in 2007 made more trips to the nest than those in
2006 (two-sample t-test assuming unequal variance, t25 5 22.77, P 5 0.01). There was a
negative relationship between female visits to the
nest and male tail redness, where females which

321

made fewer trips to the nest were paired to males
with redder tails (Fig. 2). None of the remaining
variables related to arrival date, morphology, or
plumage predicted male or female levels of
parental care.
DISCUSSION
The brightness of flank feathers in adult male
American Redstarts predicted their total number
of visits to the nest, and total time spent at the
nest. Our results are consistent with the ‘goodparent’ hypothesis and suggest that flank feather
brightness may provide a reliable signal of
parental effort in adult male American Redstarts.
A significant negative correlation was found
between number of female visits to the nest and
redness of her mate’s tail feathers. We found a
strong positive correlation between breeding
partners for visits to the nest, and nest attendance.
The ‘good-parent’ hypothesis predicts that attractive males should signal their ability to provide
increased levels of parental care, compared to less
attractive males (Heywood 1989, Hoelzer 1989).
We show brightness of male carotenoid-based flank
plumage is associated with levels of male parental
care. Plumage brightness has been found to predict
mating success in other species, such as Goldencollared Manakins (Manacus vitellinus) (Stein and
Uy 2006). In addition, it has been linked to stronger
immune response to novel antigens (Saks et al.
2003a), suggesting it has an important role in
signaling male health status and, potentially, the
ability to provide for offspring.
The pairwise correlation analysis among all
male plumage variables revealed only one significant association; tail brightness increased with
decreasing tail redness. This suggests that in
American Redstarts, plumage brightness does not
necessarily correspond to greater feather carotenoid content (Saks et al. 2003b, Andersson and
Prager 2006). Instead, plumage brightness may be
influenced by the underlying structural matrix of
feathers (Shawkey and Hill 2005); several studies
have linked structural-based colors with condition/
individual quality (Doucet 2002, Doucet and
Montgomerie 2003) as well as the level of male
parental care (Siefferman and Hill 2003). However,
the interactions between structural and pigmentbased components of feather coloration remain
poorly understood and further research is needed to
elucidate patterns of plumage brightness.
Recent work by Kappes et al. (2009) with a
smaller sample of more southerly breeding

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THE WILSON JOURNAL OF ORNITHOLOGY N Vol. 122, No. 2, June 2010

TABLE 1. Multiple regression models examining male and female parental care variables in relation to standardized
arrival date, wing length, bib score, flank feather brightness and redness, and tail feather brightness and redness. Initial
models are shown for each model. Final models (i.e., models following removal of nonsignificant effects by stepwise
backward deletion) are also shown where predictor variables were significant. Sample size increased in the final models
where removal of nonsignificant predictor variables added additional individuals to the model that were missing
information for these variables.
Predictor variables

b

F

P

Male visits/hr/chick (initial model, n 5 31, r2 5 0.46)

Year
Standardized arrival
Wing
Bib score
Flank brightness
Flank redness (PC I)
Tail brightness
Tail redness (PC I)

0.13
0.01
0.06
0.06
0.12
0.03
20.03
20.04

0.09
0.26
0.51
0.15
3.91
0.92
0.12
1.37

0.77
0.62
0.48
0.70
0.06
0.35
0.74
0.25

Male visits/hr/chick (final model, n 5 32, r2 5 0.37)

Flank brightness

0.11

15.004

0.0006

22.45
1.34
1.50
26.74
4.81
3.40
1.31
22.19

0.18
0.20
0.03
0.14
0.52
0.84
0.02
0.24

0.68
0.66
0.88
0.71
0.48
0.37
0.89
0.63

6.39

4.34

0.05

2

Male visits/hr/chick (initial model, n 5 31, r 5 0.19)

Year
Standardized arrival
Wing
Bib score
Flank brightness
Flank redness (PC I)
Tail brightness
Tail redness (PC I)

Male visits/hr/chick (final model, n 5 32, r2 5 0.1)

Flank brightness

2

Female visits/hr/chick (initial model, n 5 31, r 5 0.42)

Year
Standardized arrival
Wing
Bib score
Flank brightness
Flank redness (PC I)
Tail brightness
Tail redness (PC I)

0.69
20.02
0.02
0.06
20.02
0.004
0.03
20.05

4.15
0.69
0.10
0.30
0.17
0.03
0.19
3.24

0.05
0.42
0.76
0.59
0.69
0.87
0.67
0.09

Female visits/hr/chick (final model, n 5 32, r2 5 0.33)

Year
Tail redness (PC I)

0.49
20.05

9.30
8.16

0.005
0.008

Female visits/hr/chick (initial model, n 5 31, r2 5 0.14)

Year
Standardized arrival
Wing
Bib score
Flank brightness
Flank redness (PC I)
Tail brightness
Tail redness (PC I)
No significant predictors

357.2
29.75
43.61
64.12
228.60
27.75
61.82
25.15

1.14
0.27
0.49
0.31
0.46
1.39
1.11
0.03

0.30
0.61
0.49
0.58
0.50
0.25
0.30
0.86

Female visits/hr/chick (final model, n 5 33)

American Redstarts, found males with brighter
flanks provisioned less than duller males, and
those with less red flanks sired more total young.
Flank brightness and tail brightness in our study,
in agreement with Kappes et al. (2009), were not
related suggesting the two plumage regions may
be used as signals in different contexts. Flank
redness (PC I) is related to genetic paternity

(indicating that it may act as a measure of genetic
quality) (Reudink et al. 2009b), and our results
suggest that flank brightness may also act as an
intersexual signal of parental care.
Recent evidence suggests American Redstart
tail feather coloration acts as an intrasexual signal.
Specifically, tail brightness is related to both
territory quality in wintering areas (Reudink et al.

Germain et al. N AMERICAN REDSTART PLUMAGE AND PARENTAL CARE

FIG. 1. Linear regression of male visits to the nest
(standardized/hr/chick) on flank feather brightness. Gray
regression line (r2 5 0.34, F1,30 5 15.29, P 5 0.0005)
includes high value (open circle). Black regression line (r2
5 0.16, F1,29 5 5.66, P 5 0.02) excludes this individual.

2009a) and polyterritorial polygyny in breeding
areas (Reudink et al. 2009b). We found no
relationship between tail brightness and either
male or female parental care; however, female
visits to the nest were negatively correlated with
the redness of male tail feathers. Plumage redness
is often associated with greater carotenoid deposition into the feather structure; high quality birds
would be assumed to have redder feathers (Saks et
al. 2003b). However, the redness of American
Redstart tail feathers has been found to significantly decrease across subsequent breeding seasons (Reudink et al. 2009b). One suggestion is
that female American Redstarts alter their level of
parental care based on the perceived age of their
mates with females providing more care when
paired with older males, although we do not
currently have the data to address this possibility.
Neither male bib size nor arrival date was
correlated with any measure of parental care by
males or females. Consistent with previous studies
(Perreault et al. 1997, Reudink et al. 2009b, but
see Lemon et al. 1992), bib size does not appear to
have a prominent signaling role; however, arrival
date has previously been shown to be an important
predictor of reproductive success (Norris et al.
2004, Reudink et al. 2009c). Reudink et al.
(2009c) demonstrated that early arriving males
were more likely to achieve polygyny than those
which arrived at a later date. However, when
males occupy multiple territories and provide care

323

FIG. 2. Linear regression of female visits to the nest
(standardized/hr/chick) on tail feather redness (PC I) (r2 5
0.15, F1,31 5 5.60, P 5 0.02). X-axis values are from low to
high, where individuals with more negative score (e.g.,
210) have tails with lower redness than those with
higher values.

for multiple nests, there may be a limit to the
amount of care one male can provide, as
evidenced by male American Redstarts providing
relatively less care at their second nest, than at
their primary nest (Secunda and Sherry 1991;
RRG, unpubl. data).
The strong relationship between both female
and male visits to the nest, and nest attendance
suggests that offspring of more ornamented males
are receiving the benefit of more care by both
parents. Our results also suggest the potential for
assortative mating, where females that provide
more care pair with males which do the same.
These data conform to models which suggest that
equality of investment in species with biparental
care is an evolutionarily stable strategy (offspring
receive a benefit from both parents providing high
amounts of care, reviewed in Wright and Cuthill
1989). Unfortunately, our data do not allow us to
differentiate the effects of individual feeding
effort from those of territory quality, as both male
and female feeding rates could be affected by
availability of food on their territory. It is also
possible that male coloration is not indicative of
parental care, but rather the association arises
from brighter males obtaining higher quality
territories and provisioning chicks more often
with less effort. Male American Redstarts able to
secure high quality territories during the overwintering season arrive earlier in breeding areas

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THE WILSON JOURNAL OF ORNITHOLOGY N Vol. 122, No. 2, June 2010

and show higher levels of realized reproductive
success (Reudink et al. 2009c). One possibility is
that socially dominant males arriving earlier from
high quality winter territories also obtain higher
quality territories during the breeding season, in
which case we should observe a relationship
between arrival and provisioning. We did not
observe a relationship between male arrival date
and parental care, but direct measurements of
territory quality are needed to discern how
variations in individual and territory quality
influence provisioning.
The brightness of male American Redstart
flank feathers may have an important role in
intersexual signaling but further research is
needed to clarify female mate choice in this
system. Experimental approaches that measure
female response to changes in male ornamentation
would be most useful. Research on the ornamental
qualities of female plumage to examine if females
with brighter carotenoid-based plumage provide
more for their offspring and pair with brighter
males would also be informative.
ACKNOWLEDGMENTS
We thank the many field assistants who contributed to
this study, and M. M. Osmond and T. D. Barran for
assistance in video analysis. V. L. Friesen, J. J. Nocera, J.
R. Foote, C. F. Richter, and K. E. Delmore provided helpful
comments on earlier versions of this manuscript. We thank
R. D. Montgomerie for use of color analysis equipment, and
F. J. S. Phelan and F. L. Connor for logistical support at
Queen’s University Biological Station. This research was
supported by the Natural Sciences and Engineering
Research Council of Canada, Queen’s University, National
Science Foundation, Smithsonian Institution, Ontario Government (MTCU), American Ornithologists’ Union, Society
of Canadian Ornithologists, Sigma Xi, and the American
Museum of Natural History.

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