J. Avian Biol. 40: 34
41, 2009
doi: 10.1111/j.1600-048X.2008.04377.x
# 2009 The Authors. J. Compilation # 2009 J. Avian Biol.
Received 17 September 2007, accepted 19 May 2008

Plumage brightness predicts non-breeding season territory quality
in a long-distance migratory songbird, the American redstart
Setophaga ruticilla
Matthew W. Reudink, Colin E. Studds, Peter P. Marra, T. Kurt Kyser and Laurene M. Ratcliffe
M. W. Reudink (correspondence) and L. M. Ratcliffe, Dept. of Biology, Queen’s Univ., Kingston, ON K7L 3N6 Canada and Smithsonian
Migr. Bird Center, 3001 Connecticut Ave. NW, Washington, DC 20008 USA. Email: mattreudink@gmail.com. 
 C. E. Studds and P. P.
Marra, Smithsonian Migr. Bird Center, 3001 Connecticut Ave. NW, Washington, DC 20008 USA. 
 T. K. Kyser,Dept. of Geological Sciences
and Engineering, Queen’s Univ., Kingston, ON K7L 3N6 Canada.

Many species of birds exhibit brilliant ornamental plumage, yet most research on the function and evolution of plumage
has been confined to the breeding season. In the American redstart Setophaga ruticilla, a long-distance NeotropicalNearctic migratory bird, the acquisition of a winter territory in high-quality habitat advances spring departure and
subsequent arrival on breeding areas, and increases reproductive success and annual survival. Here, we show that males
holding winter territories in high-quality, black mangrove habitats in Jamaica have brighter yellow-orange tail feathers
than males occupying territories in poor-quality second-growth scrub habitats. Moreover, males arriving on the breeding
grounds from higher-quality winter habitats (inferred by stable-carbon isotopes) also had brighter tail feathers. Because
behavioral dominance plays an important role in the acquisition of winter territories, plumage brightness may also be
related to fighting ability and the acquisition and maintenance of territories in high-quality habitat. These results
highlight the need for further research on the relationships between plumage coloration, behavior, and the ecology of
over-wintering migratory birds.

Study of the function of plumage coloration during the
breeding season has informed much of what we know about
the elaboration of ornamental traits through sexual selection
and female choice (Hill 2006). In many species, plumage is
highly variable and phenotypically plastic and can be
influenced by both the environment (Linville and Breitwisch 1997, McGraw and Hill 2001), and individual
condition at the time of molt (Figuerola et al 2003, Saks
et al. 2003). This variation in plumage coloration can be
used by conspecifics to gather information about an
individual’s quality as a potential mate or competitor
(Zahavi 1977, Andersson 1994). Many breeding season
studies have now confirmed that females can use this
information to inform social (e.g., Hill 1990, Johnsen et al.
1998, MacDougall and Montgomerie 2003, Senar et al.
2005, for review, see Hill 2006), and extra-pair mating
decisions (Sundberg and Dixon 1996, Yerzinac and Weatherhead 1997, Thusius et al. 2001) 
 the result of which can
lead to increased variance in male mating success and the
elaboration of ornamental traits (Albrecht et al. 2007,
Dolan et al. 2007, Webster et al. 2007).
However, plumage can also function as a signal of
individual quality during the non-breeding season. Variation in plumage coloration can indicate social dominance
(Maynard Smith and Harper 1988, Mennill et al. 2003),

34

and experimental studies have shown that manipulation of
signals can alter dominance status (Peek 1972, Rohwer
1985, Holberton et al. 1989, Pryke et al. 2002, Pryke and
Andersson 2003), suggesting that social selection can be an
important force in the evolution of plumage traits (for
review, see Senar 2006). Yet, despite the widespread
evidence for plumage-based status signaling systems in
temperate (and some tropical) species, little is known about
whether plumage functions as a signal in migratory birds
during the non-breeding season (but see Stutchbury 1994).
This is not surprising given the relative paucity of
information on the over-wintering ecology and behavior
of migratory birds (Greenberg and Marra 2005). By
examining only one phase of the annual cycle, we ignore
potential factors that may influence the evolution of
ornamental plumage. This work is of particular relevance,
as new studies are beginning to reveal how non-breeding
season events may influence an individual’s life-history
traits, ecology, and behavior (e.g. Studds et al. 2008).
For plumage to act as a status signal, it must advertise
information about an individual’s dominance status or
competitive ability (Rohwer 1975). These plumage-based
signals may include, but are not limited to, badge size (e.g.,
epaulet size: Eckert and Weatherhead 1987, bib size: Møller
1987, McGraw et al. 2003) or coloration based on melanin

(Mennill et al. 2003), carotenoids (Wolfenbarger 1999,
McGraw and Hill 2000, Pryke et al. 2002), or feather
microstructure (Alonso-Alvarez et al. 2004). Melanin is
synthesized internally from amino acids and is not acquired
directly from the diet (Hill 2002), although the honesty of
the signal may be maintained by nutrient limitation
(McGraw 2007) and social reinforcement mechanisms
(Senar 2006), or mediated by testosterone levels during
molt (Hill 2002). Carotenoids cannot be synthesized
naturally, and therefore must be ingested through diet,
modified (depending on the pigment), and deposited (Hill
2002, 2006). Thus, only males in good condition with
access to high-quality food should be able to signal with
carotenoid pigments, making this a potential honest
indicator of male quality (Hill 1999, Pryke et al. 2001).
For a plumage-based status signaling system to exist,
there must be variation in plumage that can be used to
assess individual quality and a system in which assessing the
fighting ability or dominance status of consepecifics confers
an advantage (Rohwer 1975). American redstarts Setophaga
ruticilla, a small long-distance migratory songbird, are
ideally suited to the study of plumage-based signaling
during the nonbreeding period. American redstarts are
highly variable in both carotenoid- and melanin-based
plumage (Sherry and Holmes 1997; see Methods, Study
species), and dominance relationships play a critical role in
obtaining and maintaining high-quality winter territories
(Marra 2000). Furthermore, redstarts use a distinctive tail
fanning display during aggressive interactions (Sherry and
Holmes 1997), suggesting that aspects of tail coloration
could be important signals. Dominance behavior and
competitive interactions lead to age- and sex-biased habitat
segregation, with adult males occupying the majority of
territories in high-quality habitats in our study sites in
Jamaica (Marra et al. 1993, Marra 2000). Individuals overwintering in high-quality, mangrove territories experience
higher food availability than those in second-growth scrub
and this influences arrival date and reproductive success on
breeding areas (Marra et al. 1998, Norris et al. 2004a,
Studds and Marra 2007), as well as annual return rates
(Marra and Holmes 2001). Interestingly, female redstarts
able to acquire and maintain territories in high-quality
habitats are larger and more aggressive than females in poorquality habitat (Marra 2000). However, male redstarts do
not differ in body size between habitat types (Marra 2000).
One hypothesis for this sex-specific difference is that for
males, territory acquisition is mediated through plumagebased status signaling.
Here, we test if plumage coloration is associated with
territory occupancy across a habitat quality gradient in
Jamaica. Specifically, we test for differences in brightness,
chroma, and hue in tail feathers of male American redstarts
holding territories in black mangrove forest (high-quality),
and second-growth scrub (low-quality). Additionally, we
test if the relationship between plumage color and winter
habitat quality carries over onto the breeding grounds in
Ontario, Canada.

Methods
Study species
Our study species was the American redstart, a small (7
8 g)
and widespread Nearctic- Neotropical migratory songbird.
American redstarts breed throughout much of North
America and winter throughout the Caribbean, Mexico,
and parts of Central and northern South America (Sherry
and Holmes 1997). Recent work suggests that American
redstarts over-wintering in the Caribbean breed in the
northeastern United States and southeastern Canada,
including Ontario (Norris et al. 2006). American redstarts
are sexually dimorphic; males exhibit delayed plumage
maturation, with highly variable plumage coloration both
within and between age classes. Individuals undergo a single
pre-basic molt at the end of the breeding season and retain
those feathers through the following breeding season
(Sherry and Holmes 1997). In their first winter (and
subsequent breeding season), males are greenish-gray with
yellow carotenoid-based patches on their wings, tail, and
flanks. These males lack bibs entirely, but some individuals
adventitiously molt in small patches of black feathers on the
breast, back and head during winter. After their first
breeding season, males molt into their definitive plumage:
black upperparts and head with a white belly, salmonorange carotenoid-based patches on the wings, tail and
flanks and a black bib (Sherry and Holmes 1997). Studies
from the breeding grounds suggest that bib size is related to
breeding-season performance (Perrault et al. 1997), though
the function of the carotenoid-based patches has not yet
been investigated.
Study sites
Over-wintering American redstarts were captured in highquality (black mangrove) and low-quality (second-growth
scrub) habitats from Dec.-March 2002
2006 at Font Hill
Nature Preserve, Westmoreland Parish, Jamaica, West
Indies (188 02?N, 778 57?W; see Marra 2000). Sample
numbers varied yearly based on accessibility to different
habitats and the duration of our stay. Work on the breeding
grounds was conducted May
July 2006 at the Queen’s
Univ. Biological Station, Chaffey’s Lock, Ontario, Canada
(448 34?N, 768 19?W).
Tissue sampling
All birds were captured in mist nets either through passive
blanket netting or using song playbacks accompanied by a
decoy, and banded with a single US Fish and Wildlife
Service or Canadian Wildlife Service band and 2
3 color
bands for individual identification. On the breeding
grounds in May 2006, birds were captured within 5 d of
arrival and 2
3 mm of the central claw from each foot was
collected; claw samples in Jamaica were obtained in March
2006. For all birds, we recorded wing chord (mm) and

35

plucked a single tail feather (R3) for color and stablehydrogen isotope analysis.
Color analysis and bib size scoring
Reflectance spectra from tail feathers was obtained by
measuring percent reflectance across the bird visual spectrum (320
700 nm) using an Ocean Optics USB2000
spectrometer attached to a PX-2 xenon pulsed light source.
The probe was held at a 908 angle to the feather surface and
housed in a rubber sheath to keep the probe at a constant
distance from the feather surface and ensure we captured
light only from the PX-2 light source. All feathers were
mounted on minimally reflective (B5% reflectance) black

paper (Colorline #142 Ebony). To standardize our measurements, we took readings from a dark (sealed black velvet
lined box) and white (spectralon) standard between each
measurement. Three to five measurements were taken
haphazardly within the yellow/orange region of each tail
feather, avoiding the rachis (see Fig. 1 for reflectance
spectra). Tail feathers were chosen for our analysis because
they are frequently fanned in aggressive displays (Sherry and
Holmes 1997). Plumage coloration was quantified by
calculating standard measures of brightness, hue, and
chroma (Montgomerie 2006; Table 1). Brightness was
calculated as the mean reflectance across the bird visual
spectrum (320
700 nm). Hue was calculated via segment
classification (adapted from Endler 1990; Montgomerie
2006; Table 1). Because American redstart feathers exhibit
two distinct spectral peaks (UV and yellow/red), we
measured both UV and red chroma, which is the light
reflected in the UV or red portion of the spectrum (320

415 nm and 575
700 nm respectively) divided by the total
reflectance. Bib size was ranked in the hand on a scale of
1
5 (1small, 5large; Lemon et al. 1992).
Stable-carbon isotope analysis
Because of differences in plant water stress and photosynthetic system, d13C signatures in plant tissues vary among
different habitat types in the tropics (Lajtha and Marshall
1994). C3 plants and plants experiencing little water stress
generally have more negative d13C signatures compared to
C4 plants and water-stressed plants (Lajtha and Marshall
1994). These signatures are transferred up the food chain,
and eventually incorporated into birds’ tissues. Thus, by
sampling bird tissues, such as claws, on arrival in Canada,
we can infer information about the habitat that bird
occupied during the non-breeding period (Marra et al.
1998). In Jamaica, black mangrove forests are inundated
with water for much of the year and plants experience less
water-stress than the highly seasonal second-growth scrub,
resulting in more negative d13C signatures in plants and
animals in that environment (Marra et al. 1998). Thus, by
capturing birds upon arrival on the breeding grounds, it is
possible to infer the quality of winter habitat. In separate
populations of breeding American redstarts, Marra et al.
(1998) and Norris et al. (2004a) showed that birds arriving
earlier on the breeding grounds had more negative d13C
signatures. Furthermore, Norris et al. (2004a) found birds
with more negative d13C signatures ultimately had higher
reproductive success. Compared to blood, d13C in claw
tissues has a relatively slow turnover rate (weeks to months)
Table 1. Formulas used to calculate color variables. Percent
reflectance was measured at each 1nm interval across the spectrum.
Bli
ntotal light reflected from the ith wavelength to the nth
wavelength (di
dn) after summing across each 1nm interval. nthe
number of 1 nm intervals between di
dn.

Figure 1. Average reflectance spectra from the yellow-orange
region of the tail feather (R3) in: (A) adult males, and (B) firstyear males holding territories in high-quality black mangrove
forest (black line: adult, n24; first-year, n12) and low-quality
second-growth scrub (gray line: adult, n 14; first-year, n12).

36

Color variable

Formula

Brightness
UV chroma
Red chroma
Hue

Bl320
700 al700
l320/n
CUV Bl320
415/Bl320
700
Cred Bl575
700/Bl320
700
Harctan([(Bl512
575 Bl320
400)/Bl320
700]/
[(Bl575
700 Bl400
512)/Bl320
700])

and, for studies of migratory birds, this signature should be
retained post-arrival on the breeding grounds, though some
integration of local isotopic signatures may occur (Bearhop
et al. 2003, 2004). For this study we included only birds
that arrived within 25 d of the first bird to arrive on the
breeding grounds. Claws samples were weighed, then
converted to CO2 in an oxidation/reduction furnace,
separated by gas chromatography, then measured for d13C
with an isotope-ratio mass spectrometer (Lajtha and
Marshall 1994, Norris et al. 2004a).
Stable-hydrogen isotope analysis
Previous work on American redstarts suggested that
plumage coloration varies geographically, with birds molting feathers at more northerly latitudes having more red
chroma than those birds molting at more southerly latitudes
(Norris et al. 2007), and that some birds that invest heavily
in late-season parental effort may molt south of the
breeding grounds, resulting in duller plumage (Norris
et al. 2004b). Because our wintering population breeds
across a relatively large geographic range (Studds et al.
2008), we used stable-hydrogen isotope (dD) analysis to
determine if there was a relationship between molt location
and brightness or red chroma and if molt location helped
explain winter habitat occupancy. Details of our stablehydrogen isotope analysis are reported in Langin et al.
(2007). Briefly, all feathers were washed in a 2:1 chloroform:methanol solution, 0.1
0.15 mg of feather was
weighed and combusted in a Finnigan TC/EA reduction
furnace at 1,4508 C and introduced into a Finnigan MAT
Delta Plus XL isotope ratio mass spectrometer. All dD
values are reported in parts per mil notation (˜) relative to
Vienna Standard Mean Ocean Water. Only feathers from
adult males were used in this analysis.
Statistical analyses
Each component of redstart feather color (brightness, UV
chroma, red chroma, and hue) was analyzed separately.
Data on feather color of birds captured in Jamaica were
examined by using analysis of variance (ANOVA) with

habitat and bird age as main effects. Unflattened wing
chord was included in the model as a linear covariate to
adjust for variation in feather color due to body size
differences. Due to small sample sizes, we pooled data from
multiple years (2002: n 5 adult, 0 first-year; 2003: n 3
adult, 0 first-year; 2004: n 11 adult, 1 first-year; 2005:
n 17 adult, 16 first-year; 2006: n 2 adult, 7 first-year).
Because of uneven sampling of adult and first-year males in
different years, we cannot clearly differentiate between age
effects and year effects; however, we have no a priori reason
to expect differences between years in which a higher
proportion of adults or first-year males were captured.
Differences in bib size between adult males over-wintering
in mangrove and scrub habitats were analyzed with an
independent samples t-test. The relationship between
feather color and stable-carbon isotope ratios in the claws
of redstarts arriving in Ontario was evaluated by using linear
regression. To validate that stable-carbon isotope ratios in
claws reflect moisture gradients in nonbreeding habitat, we
also evaluated differences between claws of Jamaican birds
occupying mangrove and scrub habitats. The residuals of
this analysis were markedly non-normal and were therefore
analyzed with a Wilcoxon rank-sum test. The effect of
molting latitude on feather color was analyzed by using
linear regression. All tests were performed in JMP 6.0.2
(SAS 2006).

Results
Relationship between habitat, bird age and
plumage color
Tail feathers of redstarts occupying territories in black
mangrove habitat were brighter than those of birds holding
territories in second-growth scrub, but did not differ in UV
chroma, red chroma, or hue (Table 2). Feathers of adult
males had significantly higher UV chroma, red chroma, and
redder hue compared to first-year males. Birds with longer
wings had significantly brighter feathers, but did not have
higher UV chroma, red chroma, or redder hue (Table 2).
Bib size of adult males did not differ between habitats
(independent samples t-test: t22 1.21, P 0.24).

Table 2. Color variables (mean9SE) calculated from reflectance spectra of adult and first-year males in over-wintering in high-quality black
mangrove forest and low-quality second-growth scrub. Bottom of table shows the results of a two-way ANOVA with age, habitat and wing
length as main effects and a habitatage interaction term (first-year males: n 12 mangrove, 12 scrub; adult males: n24 mangrove, 14
scrub). Bolded values are significant at a0.05.
Age

Habitat

Brightness

UV chroma

Red chroma

Hue

Adult

Combined
Scrub
Mangrove
Combined
Scrub
Mangrove

23.4690.52
22.5690.93
24.0090.63
21.7290.63
20.1790.89
23.2690.68
F0.82
P0.37
F9.90
P0.003
F1.80
P0.08
F2.62
P0.01

0.2290.002
0.2290.004
0.2290.003
0.2190.003
0.2190.005
0.2090.004
F4.92
P 0.03
F0.06
P 0.80
F0.40
P 0.69
F1.50
P 0.14

0.4190.005
0.4190.008
0.4190.006
0.3990.004
0.3990.006
0.3990.006
F 5.34
P 0.02
F 0.08
P 0.78
F 0.06
P 0.81
F 0.22
P 0.64

0.0290.01
0.0690.02
0.0290.01
0.0690.03
0.0490.04
0.0890.03
F6.90
P0.01
F0.74
P0.39
F0.01
P0.91
F2.64
P0.11

First-year
Effect of age
Effect of habitat
Effect of habitatage
Effect of wing length

37

Relationship between habitat (stable-carbon
isotopes) and plumage color

Relationship between molting latitude (dD) and
plumage color/habitat

Stable-carbon isotope signatures (d13C) in claws of adult
males sampled in mangrove habitats in Jamaica were
significantly more negative than those sampled in scrub
habitats (Wilcoxon rank-sum test, z2.66, P 0.008,
n 26; Fig. 2A). Adult males arriving on the breeding
grounds with signatures consistent with high-quality, wet
non-breeding season habitats (more negative d13C signatures) had brighter plumage (r2 0.31, P 0.03, n 15;
Fig. 2B), but not UV chroma (r2 0.15, P 0.14, n 15),
red chroma (r2 B0.001, P 0.96, n 15), hue (r2 0.009,
P 0.74, n 15), or bib size (r2 0.06, P 0.35, n 16).

Stable-hydrogen isotope analysis revealed that our Jamaica
population of over-wintering redstarts molted over a broad
geographic range (dD range: 59 to 100). We detected
no relationship between dD and brightness (r2 0.08,
P 0.15, n 26), red chroma (r2 B0.001, P 0.92, n 
26), UV chroma (r2 B0.001, P 0.93, n 26), or hue
(r2 0.06, P 0.39, n 26). Furthermore, we found no
difference in dD between habitat types (two-tailed t-test,
t26 1.37, P 0.18).

Discussion

Figure 2. (A) d13C signatures in claws of birds collected in
mangrove and scrub habitats. Sample size is indicated on top of
the boxes; horizontal lines represent 90th, 75th, 50th, 25th, and
10th percentiles. (B) Relationship between brightness and d3C in
claws (n 15) collected upon arrival on the breeding grounds in
Canada. Birds from wetter winter habitats (more negative d13C
signatures) have higher brightness; regression line shown.

38

In this study we used two different approaches to
demonstrate that the brightness of a carotenoid-based
plumage patch, molted at the end of the breeding season,
is associated with occupancy of high-quality winter habitats.
In our first approach we showed that birds in Jamaica
holding territories in high-quality black mangrove forest
have brighter tail feathers than birds in low-quality secondgrowth scrub. We controlled for both age and wing length
in our analyses and demonstrated that plumage brightness
predicts habitat occupancy in both age-classes, and does so
beyond any effect of body size. Second, we tested if this
pattern carried over to the breeding period and was
detectable over broad spatial scales (i.e., for birds likely
over-wintering in a range of habitat types) and found that
birds arriving on the breeding grounds in Ontario, Canada
from higher-quality winter habitats (inferred by stablecarbon isotope analysis) were brighter than birds arriving
from poor quality habitats. Our ability to detect a relationship between habitat quality (d13C) and plumage brightness
is surprising because redstarts breeding at our Ontario study
site are likely arriving from a variety of winter localities (see
Methods: Study species) and suggests that the relationship
between plumage brightness and winter habitat occupancy
occurs at broad spatial scales and across various habitat
types. Because dominance and aggression play a critical role
in territory acquisition in American redstarts (Marra 2000),
we suggest that the most plausible explanation of our results
is that plumage brightness serves as a status signal,
indicating superior fighting ability.
Under this scenario, habitat-specific plumage variation
may arise from differences in dominance and competitive
ability, where brighter birds out-compete less bright birds
for high-quality territories. Previous work on American
redstarts in Jamaica has shown that all age- and sex-classes
initially settle disproportionately in high-quality, mangrove
habitats, but that most females and first-year males are
subsequently displaced, generally by adult males (Marra
2000). These displacements are driven both by prior
residents (i.e., color-banded birds that held territories in
the previous year) and by newly arriving birds, suggesting
that both prior residency and intrinsic dominance are
important in determining the outcomes of dominance
interactions. Also, playback experiments demonstrate that
birds in mangrove territories show higher aggressive
territorial responses compared to those in scrub, suggesting
that differences in aggression likely determine the outcome

of dominance-based territory occupancy (Marra 2000).
However, additional experiments are necessary to determine
if plumage brightness reflects competitive ability and
aggression. For example, it would be informative to
measure the intensity of aggressive encounters (e.g., by
presenting models and vocalization playbacks to territory
holders, Marra 2000) in relation to male plumage or
examine the effects of plumage manipulations on males’
ability to obtain and retain a territory in high-quality
habitat. Furthermore, if feather brightness is indeed acting
as a status signal, it will be necessary to understand the
mechanisms that maintain signal honesty.
Our finding that feather brightness, not red chroma, is
positively related to territory quality is counter-intuitive.
Generally, yellow-orange plumage coloration acts as an
honest signal of quality by revealing carotenoid deposition,
whereby increasing carotenoid deposition increases red
chroma and decreases feather brightness (Andersson and
Prager 2006). However, highly reflective (bright) yelloworange coloration is the product of both carotenoid
deposition and structural coloration (Shawkey and Hill
2005), and brightness has been shown to be an indicator of
condition and quality (Saks et al. 2003, Stein and Uy
2006). Regardless of the mechanisms that lead to increased
brightness, our results indicate that plumage brightness is a
good predictor of habitat quality and suggests that further
investigation is warranted.
Factors other than dominance-based status signaling
might also be responsible for our observed patterns of
habitat-specific plumage variation. One possible explanation is that birds in the more open, scrub habitat may be
exposed to harsher environmental conditions, such as UV
irradiation and feather abrasion, leading to decreased
feather reflectance. Plumage of male linnets Carduelis
cannabina exposed to higher sunlight UV irradiation
increased in hue, saturation, and brightness (Blanco et al.
2005). If UV irradiation similarly affects plumage color in
American redstarts, birds in the more open and harsh scrub
habitats should be brighter than those in mangrove, yet we
observe the opposite pattern, with birds in the shady,
mangrove habitat having brighter plumage.
Another hypothesis is that because the light environment
differs between scrub and mangrove forests, brighter
individuals may be better suited to the dark environment
of the mangrove forests (Endler 1992, Marchetti 1993). For
example, the amount of white on the tail feathers of
Myioborus redstarts increases the effectiveness of flushpursuit foraging (Mumme 2002) and darker conditions
favor larger white tail patches (Jablonski et al. 2006).
American redstarts also use a moderate amount of tailfanning to elicit a flush response from prey (Sherry and
Holmes 1997). However, all age- and sex-classes of redstarts
settle disproportionately in mangrove habitats upon arrival
to Jamaica, but as density increases, dominant individuals
then displace subordinates to scrub habitat (Marra 2000).
Furthermore, removal experiments in Jamaica demonstrate
that redstarts in poor-quality scrub habitat readily move in
and occupy mangrove habitat (Marra et al. 1993, Studds
and Marra 2005). Thus, it is unlikely that birds settle
differentially in mangrove and scrub habitats based on the
suitability of their feather brightness for eliciting a flush
response from prey items.

A final hypothesis is that patterns of habitat occupancy
in Jamaica may be related to geographic variation in
plumage coloration across the breeding range, whereby
birds from different breeding/molting locations settle
differentially in high- and low-quality habitats. A recent
study by Norris et al. (2007) suggested that red chroma in
American redstart feathers varies geographically across the
breeding range, with birds from more northerly locations
(inferred by stable-hydrogen isotope analysis) having higher
red chroma values, indicative of higher carotenoid content.
Although, our stable-hydrogen isotope dD) analyses indicate that our over-wintering population molts over a
broad latitudinal range (dD range: 59 to 100 ˜), we
failed to detect a relationship between dD and plumage
color. However, because the Norris et al. (2007) study was
based on samples collected across the wintering range, it is
possible that geographic variation in feather color is
detectable at broad spatial scales (i.e., across the entire
range of the species), but not within a single over-wintering
population. In addition to the lack of relationship between
brightness or red chroma and molting latitude, we found no
difference in dD between habitat types, suggesting that
plumage brightness, not molt location, is a good predictor
of non-breeding habitat occupancy.
Studies that have examined the role of plumage traits
under varying scenarios (e.g., male-male competition versus
female mate choice) and throughout the annual cycle have
provided insight into the dual utility of ornamental traits
(McGraw and Hill 2000, Alonso-Alvarez et al. 2004,
Griggio et al. 2007), and the evolution of multiple
ornaments (Andersson et al. 2002). Athough our study
suggests that tail feather brightness may be a potential signal
on the wintering grounds, the function of this and other
plumage traits must be examined within the context of the
entire annual cycle and under different conditions (e.g.,
female mate choice). In breeding populations of American
redstarts, previous work suggests that birds with smaller bibs
have higher pairing success (Lemon et al. 1992) and our
preliminary analyses suggest a potential role for tail feather
brightness in sexual signaling (M W Reudink, unpubl.
data). Longitudinal studies on the same individuals across
years, combined with experimental studies, will provide
important insights into the dynamics of these signaling
systems. Such approaches are important for understanding
if high-quality individuals are able to produce bright
feathers each year regardless of environmental conditions,
or if plumage coloration is highly dependent on environment and is thus a phenotypically plastic trait that reveals
more about condition/environment at molt rather than
intrinsic quality. Finally, studies conducted during different
phases of the annual cycle can provide insight into how
selection acts on both single and multiple ornaments
throughout the year. We suggest that study of plumage
during the non-breeding season in long-distance migratory
birds is an overlooked avenue that may provide insight into
the function and evolution of ornamental traits.
Acknowledgements 
 We thank R. Montgomerie for the use of his
color analysis equipment, software, and expertise. K. Klassen and
A. Vuletich provided invaluable support during isotope analysis.
R. Montgomerie, R. Germain, R. Reudink, T. Murphy, and J.
Nocera provided insightful comments on earlier drafts of this

39

manuscript. We gratefully acknowledge the hard work and
dedication of numerous field assistants, without whom this work
would not be possible. Funding was provided by Queen’s Univ.,
NSERC, Canadian Foundation for Innovation, Ontario Innovation Trust, Sigma Xi, the American Ornithologists’ Union, the
Canadian Society of Ornithologists, the American Museum of
Natural History, and the National Science Foundation. All
methods conducted in this study complied with the laws of the
nations of Jamaica and Canada.

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