2007 NORTHEASTERN NATURALIST 14(4):629–636
Conspecifi c and Interspecifi c Nest Reuse by
Wood Thrush (Hylocichla mustelina)
Sonya Richmond1,*, Erica Nol2, Margaret Campbell3, and Dawn Burke4
Abstract - We report one instance of conspecifi c nest reuse by Hylocichla mustelina
(Wood Thrush) within the same breeding season, two instances of conspecifi c nest reuse
in subsequent breeding seasons, and two instances of Wood Thrushes reusing nests
originally constructed by Pheucticus ludovicianus (Rose-breasted Grosbeaks) during
a three-year study in Ontario. Rates of nest reuse were higher than previously reported
for Wood Thrush, with conspecifi c nest reuse accounting for 8–12% of the observed
nesting activity, and interspecifi c nest reuse accounting for 8–9%. Nest reuse occurred
following periods of colder minimum temperatures or greater precipitation than in other
years. We suggest that instances of nest reuse within and between breeding seasons
may occur in response to time or energy constraints on females resulting from unusual
weather conditions. Documenting instances of nest reuse behaviour contributes to our
understanding of some of the constraints experienced during breeding and may shed
light on factors affecting annual reproductive success.
Introduction
Nest reuse is reportedly uncommon in passerines with open-cup nests,
both within and between breeding seasons, and most such accounts describe
birds reusing previously successful nests built by conspecifi cs (Cavitt et al.
1999, but see Curson et al. 1996, Marshall et al. 2001). Nest reuse could be a
strategy to minimize the amount of energy spent on nest construction (Cavitt
et al. 1999), to reduce competition for limited nest sites (Curson et al. 1996),
or to maximize short-term chances of nest survival by choosing sites which
were previously successful (Styrsky 2005).
Consistent, but infrequent, nest reuse has previously been reported for
Hylocichla mustelina Gmelin (Wood Thrush), an open-cup nesting Neotropical
migratory passerine. During a nineteen-year study in a small deciduous
woodlot in Delaware, three out of 389 Wood Thrush nests (0.8%) were
reused in the same breeding season by their original occupants (Roth et al.
1996). Friesen et al. (1999) reported two instances of nest reuse within the
same breeding season (1.3%) as well as two occurrences of nest reuse in
subsequent years (1.9%). All nests successfully fl edged host young during
both nesting attempts.
1Faculty of Forestry, University of Toronto, 33 Willcocks Street, Toronto, ON, M5S
3B3, Canada. 2Watershed Ecosystems Graduate Program, Trent University, 1600 West
Bank Drive, Peterborough, ON, K9J 7B8, Canada. 3Department of Biology, Carleton
University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada. 4Southern Science
and Information Unit, Ontario Ministry of Natural Resources, 659 Exeter Road, London,
ON, N6E 1L3, Canada. *Corresponding author - sonya.richmond@utoronto.ca.
630 Northeastern Naturalist Vol. 14, No. 4
The purpose of this study was to document instances of conspecifi c and
interspecifi c nest reuse in Wood Thrushes nesting in a deciduous woodlot
in Ontario. To our knowledge, no instances of interspecifi c nest reuse have
been previously reported for Wood Thrushes. While this was not an experimental
study, we also discuss our observations in light of unusual weather
conditions, which suggest that nest reuse may be a response to time or energy
constraints experienced by females resulting from stressful conditions.
Methods
Between 2003 and 2005, we monitored sixty-four Wood Thrush nests and
sixteen Pheucticus ludovicianus Linnaeus (Rose-breasted Grosbeak) nests
in a 29.4-ha deciduous woodlot located near Keene, ON, Canada (44°15'N;
78°07'W). Dominant canopy species in the study site included Acer saccharum
Marsh. (sugar maple), Fraxinus americana Linnaeus (white ash),
Ostrya virginiana Mill. (ironwood), Thuja occidentalis Linnaeus (eastern
white cedar), and Tilia americana Linnaeus (basswood). The surrounding
landscape was predominantly agricultural, consisting of a mixture of row
crops, hay fi elds, old fi elds, pastures, and scattered small housing developments
(Phillips et al. 2004).
Nest searching and monitoring were undertaken between May and August
in each year to obtain estimates of nest success for Wood Thrushes and
Rose-breasted Grosbeaks. When we located a nest, we attached a directional
fl ag to a nearby tree containing the species code, a unique alphanumeric
identifi er for the nest, and a detailed description of the nest’s location. We
did not remove nest fl ags between breeding seasons, and in many cases, they
were still legible 1–2 years after they were initially placed, making positive
identifi cation of nest-reuse events possible.
We used a modifi ed version of the spot-mapping technique described in
Bibby et al. (1992) to collect information on territory placement and pairing
status for all territorial males of each focal species. We marked nest locations
and territories using global positioning system (GPS) units (Garmin GPS
12XL) and plotted them on a map of the study site. We classifi ed active nests
as fi rst or second nest attempts based on time during the breeding season and
observed nest initiation and failure dates within each territory. Unless previous,
unsuccessful nests had been found and monitored for a particular Wood
Thrush pair, nests found with eggs or young on or prior to June 19th were
considered fi rst nest attempts (Roth et al. 1996). Nests located after June
19th were considered to be second nest attempts, as all pairs in the study site
established territories early in the season (e.g., late May) during all years in
the study.
We monitored nests every four or fi ve days throughout the breeding season
using a mirror attached to a telescoping pole. We calculated clutch size,
date of nest initiation (day when the fi rst egg was laid), and nest-reuse status
for each nest. We obtained values for daily minimum temperatures and total
2007 S. Richmond, E. Nol, M. Campbell, and D. Burke 631
monthly precipitation for May, June, and July of each year from Environment
Canada for the study area.
We tested clutch size, nest-initiation date, temperature, and precipitation
data for normality, and the non-parametric Kruskal-Wallis statistic was
used to test for between-year differences in each of the four variables. For
variables that showed signifi cant between-year differences, we used the
Nemenyi test (Zar 1999) to make post-hoc comparisons.
Results
In this study, we report one instance of conspecifi c nest reuse by a Wood
Thrush within the same breeding season, two instances of conspecifi c nest
reuse in subsequent breeding seasons, and two instances of Wood Thrushes
reusing nests originally constructed by Rose-breasted Grosbeaks. One instance
of interspecifi c nest reuse occurred within the same breeding season,
and the other occurred in subsequent breeding seasons. In the second case,
the nest, which was originally built by a Rose-breasted Grosbeak in 2003
and reused by a Wood Thrush in 2004, was reused a third time in 2005 by
Turdus migratorius Linnaeus (American Robin). Nest reuse did not appear
to be linked to previous successes in those nests (Table 1), nor to changes in
Wood Thrush demographics (Table 2) or habitat characteristics during the
course of the study.
In 2003, one of 16 Wood Thrush pairs (6%) chose to reuse an existing
Wood Thrush nest instead of constructing a new one (Table 1). The instance
of nest reuse occurred in early July, suggesting that conspecific nest
reuse accounted for 1 of 8 second nest attempts (12%). In 2004, one of 17
Wood Thrush pairs chose to reuse a previously constructed Rose-breasted
Table 1. Conspecifi c and interspecifi c nest reuse within and between breeding seasons by Wood
Thrush in 2003, 2004, and 2005.
Nest no. / species Year 1st egg day Outcome
Original nests
1 / Wood Thrush 2003 June* Failed
2 / Wood Thrush 2004 May 23 Success
3 / Wood Thrush 2004 May 20 Failed
4 / Rose-breasted Grosbeak 2004 May 19 Failed
5 / Rose-breasted Grosbeak 2004 May 18 Success
1st nest reuse
1 / Wood Thrush 2003 July 2 Failed
2 / Wood Thrush 2005 June 2 Success
3 / Wood Thrush 2005 June 15 Success
4 / Wood Thrush 2005 May 26 Failed
5 / Wood Thrush 2004 July 22 Success
2nd nest reuse
4 / American Robin 2005 May 12 Failed
*The original Wood Thrush nest constructed in 2003 was observed with 2 host eggs on June 20th
and was depredated on the next visit, prohibiting calculation of an exact nest-initiation date.
632 Northeastern Naturalist Vol. 14, No. 4
Grosbeak nest (6%). This nest-reuse event occurred in late July, suggesting
it accounted for 1 of 11 second nest attempts (9%). In 2005, two of
17 Wood Thrush pairs used conspecific nests constructed the previous
year (12%). Based on nest-initiation dates and territorial information, one
instance probably accounted for 1 of 13 first nest attempts (8%), and the
other probably accounted for 1 of 8 second nest attempts (12%). In 2005,
one Wood Thrush pair chose to reuse a Rose-breasted Grosbeak nest constructed
the previous year (6%), which accounted for 1 of 13 (8%) first nest
attempts. Combining intra-and interspecific instances of nest reuse, 16%
of Wood Thrushes reused nests during their first attempt in 2005. None of
the nests that were reused appeared to have undergone substantial reconstruction
efforts prior to reuse as there did not appear to be fresh nesting
material in the walls or linings of these nests.
In 2004, mean minimum temperature during June (9.7 ºC) was
significantly colder than in previous and subsequent years (2003: 11.2 ºC,
2005: 12.6 ºC; H = 6.52, p = 0.04; Fig. 1a). Mean minimum temperatures
for July (2003: 14.4 ºC , 2004: 14.0 ºC, 2005: 13.2 ºC) did not differ significantly
between years (H =1.89, p = 0.39). The one instance of nest reuse
observed in 2004 occurred at the end of July (Table 1), following a period
of unusually cold weather during June and a heavy rainstorm in the middle
of July.
In 2005, mean minimum temperature during May (1.9 ºC) was significantly
colder than in previous years (2003: 6.3 ºC, 2004: 7.1 ºC; H = 22.39,
p < 0.001; Fig. 1a). All three instances of nest reuse observed in 2005 occurred
at the end of May or the beginning of June, following this period of
unusually cold weather (Table 1).
Mean precipitation per day did not significantly differ between years
for May, June, or July (p >> 0.05), probably due to high levels of variation
associated with the data (Fig. 1b). However, the total precipitation for July
2004 was considerably greater than in other months and years during this
study. This variance is partially due to a heavy rainstorm on July 14, 2004,
during which 239.8 mm of rain fell over the course of a single day.
Mean nest-initiation date (measured as mean 1st egg day) for first Wood
Thrush nests was slightly later in 2005 than in previous years (H = 5.85,
p = 0.053), but the difference was not statistically significant (Fig. 2a).
The earliest recorded 1st egg day for 2005 (May 23rd) occurred nine days
Table 2. Number of active Wood Thrush pairs and nests monitored during 2003, 2004, and 2005.
Year
2003 2004 2005
Number of pairs 16 17 17
Number of 1st nests 9 15 13
Number of 2nd nests 8 11 8
Total number of nests 17 26 21
2007 S. Richmond, E. Nol, M. Campbell, and D. Burke 633
after the first recorded date in 2003 and seven days after the first recorded
date in 2004. Mean clutch size for first nests tended to be smaller in 2005
than in previous years, but the difference was not significant (H = 6.44, p =
0.09; Fig. 2b).
Discussion
Nest reuse in Wood Thrushes occurred at a much higher rate in 2005
than in previous years. In each case, nest reuse occurred following unusual
weather conditions. In 2004, the instance of interspecific nest reuse occurred
at the very end of the breeding season, following a two-day period
of extremely heavy rainfall in late July. In 2005, all instances of nest reuse
occurred in late May and early June, towards the end of the first nesting cycle,
following a month of colder-than-usual temperatures. In all cases, nest
Figure 1. Mean
minimum temperature
(ºC) (±
SD) during May,
June, and July
for 2003, 2004,
and 2005 (a).
Total precipitation
(mm) during
May, June, and
July for 2003,
2004, and 2005
(b).
634 Northeastern Naturalist Vol. 14, No. 4
reuse occurred when time and energy constraints resulting from unusual
weather conditions could have influenced the amount of resources female
Wood Thrushes could expend on egg and nest production.
Smaller mean clutch sizes and later nest-initiation dates for first nests
in 2005 also suggested that energetic constraints may have been influencing
breeding success by limiting the amount of energy available for egg
production. Our observations of Wood Thrush behaviour also suggested
that breeding pairs spent more time feeding than usual, and that the duration
of male singing appeared to be much reduced (S. Richmond, pers.
observ.). Nest construction is estimated to take 3–6 days (Roth et al.
1996), which roughly corresponds to the delay in the average nest-initiation
date that was observed for first nests in 2005. We suggest that food
was limited and extra energy was required for metabolic functions due
to colder-than-usual spring temperatures. This hypothesis is consistent
with the observations of Powell and Rangen (2000), who found that
Figure 2. (a) Mean
nest initiation date
(± SD.) (measured
as 1st egg day, day
1 = January 1) for
fi rst Wood Thrush
nests during 2003,
2004, and 2005.
(b) Mean clutch
size (± SD.) for
fi rst Wood Thrush
nests in 2003,
2004, and 2005.
2007 S. Richmond, E. Nol, M. Campbell, and D. Burke 635
Wood Thrush nest size varied with changes in temperature and possible
time constraints imposed by the end of the breeding season. Therefore,
we propose that reuse of existing nests may have been one strategy to
minimize the amount of time and energy spent on reproduction.
While instances of conspecific nest reuse have been reported both
within and between breeding seasons, interspecific nest reuse has not
previously been documented for Wood Thrushes. We suggest that Wood
Thrushes may have selected Rose-breasted Grosbeak nests as sites for
re-nesting because they coexisted in the same habitat, the nests were of
approximately the same size and shape, and they may have been able
to maintain more of their structural integrity than Wood Thrush nests.
The only other species with a similar-sized nest in the same habitat was
the American Robin. While we did not observe any instances of Wood
Thrushes using American Robin nests, an American Robin in 2005 used a
nest that had been built by a Rose-breasted Grosbeak and then reused by
a Wood Thrush in 2004.
In this study, not all nests that were reused successfully fledged
young during the first use. While this is not usually the case in passerines,
Marshall et al. (2001) have reported the reuse of a failed Dumetella
carolinensis Linnaeus (Gray Catbird) nest. This nest was built by conspecifics
the previous year, and both nesting attempts failed. Reuse of
previously unsuccessful nests does not support the hypothesis that nest
reuse is a strategy to reduce short-term chances of nest predation. It is
also unlikely that reuse of existing nests was a strategy to reduce competition
for limited nest sites because suitable sites appeared to be abundant
and the amount of available habitat did not change during the course of
the study. As a result, we suggest that time and energy constraints resulting
from unusual weather conditions are the most likely cause of the
observed instances of nest reuse by Wood Thrushes in this study.
We suggest that nest reuse is a consistent, but infrequent part of Wood
Thrush nesting strategy, and that it can be influenced by weather conditions.
If more instances of nest reuse are documented in the future, and
more detailed behavioural observations are recorded, it may be possible
to better understand how stressful conditions such as unusual weather
patterns can alter nesting strategies by Wood Thrushes.
Acknowledgments
We would like to thank the Natural Science and Engineering Research Council
of Canada, the Ontario Ministry of Natural Resources, and Environment Canada’s
Science Horizons Youth Program for partial funding of this research. We would also
like to thank the landowners for their permission to conduct this research on their
property, and to thank Sandi Schmitter, Natalie Charland, Kerri Pigeon, Jerome
Ptigny, Sean Male, Janine McCleod, Jessica Plourde, and Christine Baljko for their
assistance in the fi eld.
636 Northeastern Naturalist Vol. 14, No. 4
Literature Cited
Bibby, C.J., N.D. Burgess, and D.A. Hill. 1992. Bird Census Techniques. Academic
Press, London, UK.
Cavitt, J.F., A.T. Pearse, and T.A. Miller. 1999. Brown Thrasher nest reuse: A timesaving
resource, protection from search-strategy predators, or cues for nest-site
selection. Condor 101:859–862.
Curson, D.R., C.B. Goguen, and N.E. Mathews. 1996. Nest-site reuse in the Western
Wood-Pewee. Wilson Bulletin 108:378–380.
Friesen, L.E., V.E. Wyatt, and M.D. Cadman. 1999. Nest reuse by Wood Thrushes
and Rose-breasted Grosbeaks. Wilson Bulletin 111:132–133.
Marshall, J.S., P.A.R. Glover, K.A. Becchi, and L.W. VanDruff. 2001. Nest reuse by
a Gray Catbird. Wilson Bulletin 113:837–338.
Phillips, J., E. Nol, D. Burke, and W. Dunford. 2004. Impacts of housing developments
on Wood Thrush nesting success in hardwood forest fragments. Condor
107:97–106.
Powell, L.A., and K.A. Ranger. 2000. Variation in Wood Thrush nest dimensions and
construction. North American Bird Bander 25:89–96.
Roth, R.R., M.S. Johnson, and T.J. Underwood. 1996. Wood Thrush (Hylocichla
mustelina). In A. Poole and F. Gill (Eds.). The Birds of North America, No. 246.
The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists’
Union, Washington, DC.
Styrsky, J.N. 2005. Infl uence of predation on nest-site reuse by an open-cup nesting
neotropical passerine. Condor 107:133–137.
Zar, J.H. 1999. Biostatistical Analysis, 4th Edition. Prentice Hall, Upper Saddle
River, NJ. 663 pp.