Revista de Biología Tropical, ISSN: 2215-2075, Vol. 72: e55265, enero-diciembre 2024 (Publicado Feb. 29, 2024)

Precipitation explains Wood Thrush (Hylocichla mustelina)

occupancy patterns in Northern Costa Rica

Natalie V. Sánchez1, 2*; https://orcid.org/0000-0002-2105-1777

Katherine Bonilla Badilla3; https://orcid.org/0000-0002-1717-6526

Cesar Augusto Estevo4; https://orcid.org/0000-0002-6898-3678

1. Department of Integrative Biology, University of Windsor, Ontario, Canada.

2. Guanacaste Dry Forest Conservation Fund, Costa Rica; natingui@gmail.com, nvsanchez@uwindsor.ca

(Correspondence*)

3. Escuela de Biología, Universidad de Costa Rica, San Pedro, Montes de Oca, San José, Costa Rica; kia.2604@gmail.com

4. Department of Biological Sciences, University of Alberta, Alberta, Canada; estevo@ualberta.ca

Received 27-V-2023. Corrected 16-XI-2023. Accepted 16-II-2024.

ABSTRACT

Introduction: The Wood Thrush is a migratory bird that has experienced dramatic declines in its populations in

recent decades. This species overwinters in forest fragments with intermediate levels of habitat modification in

Central America. However, more studies detailing the use of remnant forests through time are needed to eluci-

date the threats this species faces in the wintering grounds.

Objective: To understand the effects of environmental and forest structure variables on the occupancy of Wood

Thrush in Northern Costa Rica.

Methods: The study area was the Área de Conservación Guanacaste (ACG), located in Northern Costa Rica,

in December 2016, and during the 2018-2019 migration season. We estimated Wood Thrush occupancy and

detection probability in four locations of ACG (dry forest, cloud forest, and two locations in the wet forest) using

single-season occupancy models. We also estimated Wood Thrush occupancy and probability of persistence in

different months in three vegetation types (open area, secondary forest, and old-growth forest) in the wet forest

of ACG using a multi-season occupancy model approach.

Results: Wood Thrush occupancy was best described by precipitation in the four locations of the ACG; the

probability of occupancy increased with precipitation. The average occupancy of Wood Thrushes varied with

vegetation type: open area with shrubs and forest edge (0.69 ± 0.09), secondary forest (0.46 ± 0.1), and old-growth

forest (0.61 ± 0.1). Wood Thrush probability of persistence responded partially to changes in precipitation, with

an unexpected increase in persistence when the rainfall continued decreasing in the season.

Conclusion: Wood Thrush occupancy was best predicted by changes in precipitation considering a larger spatial

scale. Its probability of persistence partially varied with precipitation. An increase in persistence closer to Spring

migration might be explained by the start of the breeding season of resident birds, potentially reducing territorial

conflicts and conserving energy before migration. The long-term protection of wet forests in Northern Costa

Rica is of paramount importance for the conservation of Wood Thrushes in their wintering grounds.

Key words: Multi-season occupancy models; wintering grounds; neotropical migratory birds; occupancy; play-

back; point counts; Costa Rica.

https://doi.org/10.15517/rev.biol.trop..v72i1.55265

CONSERVATION

2Revista de Biología Tropical, ISSN: 2215-2075 Vol. 72: e55265, enero-diciembre 2024 (Publicado Feb. 29, 2024)

INTRODUCTION

Nearctic-Neotropical migratory birds

are species that breed in North America and

migrate to Southern locations to spend the

winter in tropical latitudes in Central and

South America. They depend on the wintering

grounds and migration stopover sites in tropi-

cal regions to fuel, spend long periods in differ-

ent habitats, and then return to their breeding

grounds (Amaya-Espinel & Hostetler, 2019;

Gómez et al., 2017). The quality of the win-

tering grounds has a significant influence on

the body condition, survival, and reproductive

success of migrants (Marra et al., 1998; Marra

& Holmes, 2001; Ruiz-Sánchez et al., 2017).

Currently, land use change and deforestation of

these regions threaten or imperil the stability of

some migratory bird populations through time

(Billington et al., 1996; Rappole & McDonald,

1994; Taylor & Stutchbury, 2016).

Recent studies using large datasets have

reported the decline of populations of many

Neotropical migratory birds in North America

with insights from across their distribution

(Ballard et al., 2003; Robbins et al., 1989;

Rosenberg et al., 2019). These data come main-

ly from bird counts on their breeding grounds.

However, some population parameters such as

occupancy and conditions in terms of habi-

tat and resources available in the Neotropics

(non-breeding sites) are not fully understood.

Understanding the population status of these

mobile taxa requires the study of the occupancy

in their geographic range across the annual

cycle. At specific times of the annual cycle,

Central America concentrates high numbers

of Nearctic-Neotropical migratory birds (La

RESUMEN

Patrones de ocurrencia del Zorzal del Bosque (Hylocichla mustelina) explicados

por la precipitación en el Norte de Costa Rica

Introducción: El Zorzal del Bosque es un ave migratoria que ha experimentado caídas dramáticas en sus pobla-

ciones en las últimas décadas. Esta especie pasa el invierno en fragmentos de bosque con niveles intermedios

de modificación de hábitat en Centroamérica. Sin embargo, se necesitan más estudios que detallen el uso de los

bosques remanentes a lo largo del tiempo para dilucidar las amenazas que enfrenta esta especie en las zonas de

invernada.

Objetivo: Comprender los efectos de variables ambientales y de estructura del bosque en la ocurrencia del Zorzal

del Bosque en el Norte de Costa Rica.

Métodos: El área de estudio fue el Área de Conservación Guanacaste (ACG), ubicada en el Norte de Costa Rica,

en diciembre de 2016, y en la temporada migratoria 2018-2019. Estimamos la ocurrencia y la probabilidad de

detección del Zorzal del Bosque en cuatro ubicaciones de ACG (bosque seco, bosque nuboso y dos ubicaciones

en el bosque húmedo) utilizando modelos de ocurrencia de una sola temporada. También estimamos la ocurren-

cia del Zorzal del Bosque y la probabilidad de persistencia en diferentes meses en tres tipos de vegetación (área

abierta, bosque secundario y bosque primario) en el bosque húmedo de ACG utilizando un enfoque de modelo

de ocurrencia multi-estacional.

Resultados: La ocurrencia del Zorzal del Bosque estuvo mejor descrita por la precipitación en las cuatro locali-

dades del ACG; la probabilidad de ocurrencia aumentó con las precipitaciones. La ocurrencia media de zorzales

varió con el tipo de vegetación: área abierta con arbustos y borde de bosque (0.69 ± 0.09), bosque secundario

(0.46 ± 0.1) y bosque primario (0.61 ± 0.1). La probabilidad de persistencia del zorzal respondió parcialmente a

cambios en la precipitación, con un aumento inesperado en la persistencia cuando las precipitaciones continuaron

disminuyendo en la temporada.

Conclusión: La ocurrecia del Zorzal del Bosque varió con la precipitación considerando una escala espacial

mayor. Su probabilidad de persistencia varió parcialmente con la precipitación. Un aumento en la persistencia

más cerca de la migración de primavera podría explicarse por el inicio de la temporada de reproducción de las

aves residentes, lo que podría reducir los conflictos territoriales y conservar energía antes de la migración. La

protección a largo plazo de los bosques húmedos en el norte de Costa Rica es de suma importancia para la con-

servación de los Zorzales del Bosque en sus zonas de invernada.

Palabras clave: modelos de ocurrencia multi-estacional; territorios de invierno; aves migratorias neotropicales;

ocurrencia; reproducción de canto; puntos de conteo; Costa Rica.

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 72: e55265, enero-diciembre 2024 (Publicado Feb. 29, 2024)

Sorte et al., 2017). Therefore, surveys of highly

threaten migratory species in different forest

types in tropical regions during the non-breed-

ing season are key to preserve habitats and to

implement conservation actions.

The Wood Thrush (Hylocichla mustelina)

is one of the Neotropical migratory birds expe-

riencing dramatic population declines in recent

decades (Rosenberg et al., 2019; Sauer et al.,

2013). In their wintering grounds in Central

America, the main processes that contribute

to its decline are habitat loss and deforestation

(Rosenberg et al., 2019). Nonetheless, there are

protected and private forests remnants, and

some agricultural practices (e.g., shaded cof-

fee plantations) that provide important role as

habitat for Neotropical migratory birds (Boza,

1993; Powell et al., 1992), especially in areas

with high concentrations of individuals of vul-

nerable species in Mexico, Honduras, Costa

Rica (La Sorte et al., 2017), and South America

(Bayly et al., 2016). Geolocator data for migrat-

ing Wood Thrushes indicate rapid long-dis-

tance movements and substantial time spent in

certain areas in Central America (Stutchbury et

al., 2009). A study in Belize found that the num-

ber of individuals was higher in less disturbed

forests in comparison with more open areas,

and the different habitats varied in precipitation

through time resulting in changes in resource

availability and Wood Thrushes body condition

(McKinnon et al., 2015). More studies detail-

ing the use of remnant forests (Roberts, 2011)

through time are needed to elucidate the threats

in the wintering grounds relative to those in the

breeding grounds (Stanley et al., 2015; Stutch-

bury et al., 2009).

The main goal of this study was to estimate

the occupancy of Wood Thrush in Northern

Costa Rica considering forest types and envi-

ronmental variables with point count data.

We asked the following questions: (a) What is

the variation in the occupancy and detection

probability of Wood Thrush in different forest

types? We recorded the detection history (pres-

ence/absence) of Wood Thrush in three differ-

ent forest types: dry forest in the Pacific slope,

wet forests in the Caribbean slope (two sites),

and in the cloud forest located in the Guana-

caste Mountain Range dividing the two slopes

(Janzen et al., 2016). These forests are land pro-

tected in the Área de Conservación Guanacaste

(ACG). At these locations, we explored how the

forest types and the average precipitation influ-

enced Wood Thrush occupancy. We incorpo-

rated precipitation as a predictor of occupancy,

since rain patterns are known to influence

food-resource availability for migratory birds

(Santillan et al., 2018). (b) What is the varia-

tion in occupancy of Wood Thrush in different

vegetation types of the Caribbean wet forest

and the probability of persistence through the

months in the migration season? Previous stud-

ies have reported that the Wood Thrush pre-

ferred habitat in the wintering grounds is the

rain forest (Stanley et al., 2015; Winker et al.,

1990); therefore, we decided to explore further

its habitat preference in the Caribbean forest of

ACG. We considered the influence of vegeta-

tion structure and precipitation in the wet forest

as predictors of occupancy during a migration

period (2018-2019). To answer this question,

we used multi-season occupancy models. We

predicted that the probability of a site being

occupied by Wood Thrush in time t and time

t+1 (survivorship of a site) would increase with

precipitation. As stated above, the habitat in the

wintering grounds may be limited for migra-

tory birds, and the conditions can change from

year to year; for Wood Thrush, not all the areas

are suitable when on the wintering grounds.

If true, we expected those good or acceptable

habitats would be occupied by Wood Thrush

early in the season and that individuals would

remain in these areas throughout the over-win-

tering period. If birds are not detected as time

passes in the over-wintering season, we assume

that they have died or moved. Although, it is

more likely that relative changes in occupancy

over a small spatial scale may suggest that birds

have moved from one area to another. Here,

we contributed to the understanding of Wood

Thrush occupancy in a key conservation region

of Costa Rica.

4Revista de Biología Tropical, ISSN: 2215-2075 Vol. 72: e55265, enero-diciembre 2024 (Publicado Feb. 29, 2024)

MATERIALS AND METHODS

Study species: Wood Thrush (Hylocichla

mustelina) over-winter in late-successional for-

ests and forest fragments with intermediate

levels of habitat modification in Central Amer-

ica; from late Fall (August) until early Spring

(March). In Costa Rica, they defend feeding

territories from conspecifics (Roberts, 2007).

They present high fidelity to their territories,

specifically in large fragments and continuous

forests (Roberts, 2007). As part of this territo-

rial behavior, they respond to recorded play-

backs, using both calls and songs (pers. obs.;

Yahner & Ross, 1995). Wood Thrush mostly

forages on the ground looking for litter arthro-

pods mixed with fruit from understory shrubs

and small trees (Roberts, 2007).

Study site: The study was carried out in

the Área de Conservación Guanacaste (ACG)

with an extension of 160 000 + ha, located in

Northern Costa Rica (Fig. 1A), during Decem-

ber 2016, and in the 2018-2019 migration

season. This region has three major vegetation

types: dry forest (Pacific slope Sector Santa

Rosa), cloud forest (Volcán Cacao in Guana-

caste Mountain Range; hereafter Cacao), and

wet forest (Pitilla Biological Station in the

Caribbean slope) (Janzen et al., 2016) (Fig. 1B).

The variation in forest types across the region

provides an opportunity to explore where these

birds spend in Northern Costa Rica most of the

time, which forest types have a higher occu-

pancy, and whether the precipitation has an

influence across the study areas.

Precipitation patters across the study areas

are variable. Sector Santa Rosa has two defined

seasons: the dry season from December to

April (high temperatures regularly exceeding

37 °C, low relative humidity and near absence

of precipitation) and the rainy season from May

Fig. 1. A. Study sites in the Área de Conservación Guanacaste (ACG): Santa Rosa, Volcán Cacao, Pitilla Biological Station,

and Leiva Biological Station, located in Northern Costa Rica. B. Pictures of the four study locations showing the different

forest types (dry forest, cloud forest, and wet forest). C. Pictures of three different vegetation structure sites in Pitilla

Biological Station (wet forest). A picture of the study species, Wood Thrush (Hylocichla mustelina), is included in the figure

(Photo: Adrian Delgado).

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 72: e55265, enero-diciembre 2024 (Publicado Feb. 29, 2024)

to November; with a mean annual precipitation

of 1 700 mm and a mean annual temperature

of 25 °C (Kalacska et al., 2004; Woodworth et

al., 2018). The mean annual precipitation in

the wet forests in ACG varied from 1 060-4 782

mm (data from Pitilla Meteorological Station

2016-2019), usually receiving ~ 4 000 mm of

rain falls between May and February. The cloud

forest area in Volcan Cacao has a mean average

temperature of 18.5-21.7 °C (10 °C in Decem-

ber and January) and 3 000 mm of rain falls

between May and January (Lindblad, 2001).

Point counts: To record the presence and

absence of Wood Thrush, we performed point

counts in December 2016: nine point counts

in Santa Rosa (10.8379° N, 85.7051° W), eight

in Cacao (10.9337° N, 85.4482° W), ten in Pit-

illa (10.9892° N, 85.4258° W), and 13 in Leiva

(10.943220° N, 85.317962° W); 40-point counts

total. Each point count was separated by 200 m

along trails at each site. We performed the point

counts over three consecutive days at each site.

One observer performed active point

counts for three consecutive days (NVS) from

0530-0930 h. The observer played the call of

a Wood Thrush recorded in Costa Rica (by

Peter Boesman 2011) for 12 s at the beginning

of each point (Fig. 2) and waited for 10 min,

recording whether the response was a response

call or a visual detection of the bird, both audi-

tory and visual detection, or no detection.

Migratory birds such as Wood Thrushes and

Golden-winged Warblers responded to play-

backs (Kubel & Yahner, 2007; Yahner & Ross,

1995). The use of playbacks was expected to

increase the probability of detection of Wood

Thrushes and this technique was a consistent

way to define a point counts protocol for the

study species.

To understand the variation of Wood

Thrush occupancy during the non-breeding

season, we performed active point counts in the

Caribbean sector of ACG, at Pitilla Biological

Station, in November 2018, December 2018,

January 2019, and February 2019. The point

counts were performed by three local paratax-

onomists that were familiar with the Wood

Thrush calls and their responses to playbacks

(calls or approaches to the sound source). Each

person was assigned to an area with a dif-

ferent vegetation structure: open area (forest

edge along a trail with dense understory at the

edge), secondary forest, and old-growth forest

(Fig. 1C). The parataxonomists recorded the

presence and absence of Wood Thrush in nine

points for the secondary and the old-growth

forest, and in 12 points in the open area; follow-

ing the same protocol described above.

Statistical analysis: Wood Thrush occu-

pancy and detection probability for the four

sectors of ACG were estimated using single-

season occupancy models (MacKenzie et al.,

Fig. 2. A. Spectrographic view of the 12 s stimulus created to perform an active point count of a Wood Thrush call. B. Zoom

in view of the Wood Thrush call.

6Revista de Biología Tropical, ISSN: 2215-2075 Vol. 72: e55265, enero-diciembre 2024 (Publicado Feb. 29, 2024)

2003; MacKenzie et al., 2017). Occupancy (psi)

is defined as the probability that a randomly

selected site or a sampling unit in an area

of interest is occupied by a species; a site is

occupied even with the detection of a single

individual (MacKenzie et al., 2006). Julian Date

and the site (ACG sector) were also included

as covariates to account for the effect of sample

day and different forest types, respectively.

We used daily precipitation for the three con-

secutive days of counts and temperature as site

covariates. To select the best model describing

the Wood Thrush occupancy, we used Akaike’s

Information Criterion adjusted for small sam-

ple size (AICc) (Burnham et al., 1995); we

ranked the models by the difference (AICc)

from the best-fitted model (AICmin).

We estimated Wood Thrush occupancy

in different months in each vegetation type in

the wet forest at Pitilla Biological Station using

a multi-season occupancy model approach

(MacKenzie et al., 2003; Webber et al., 2013).

This type of model uses data from multiple

sample periods, and the assumption of popula-

tion closure is not expected between periods.

We used daily precipitation collected a week

prior to the survey days as a site covariate to

explain Wood Thrush persistence. Site was

used as a proxy for the movement of individuals

in three vegetation types (open area, second-

ary forest, and old-growth forest). We defined

movement when a site was occupied in time t

and not occupied in time t+1. For the analysis,

we divided the four months into three periods

of time: period one (Nov-Dec 2018), period

two (Dec 2018-Jan 2019), and period three

(Jan-Feb 2019). The multi-season occupancy

model calculated the parameter extinction (ε)

used here as the probability of persistence (the

probability of a site being occupied in a time

t and the occupied in a time t+1) from one

period to the next period. Multi-season mod-

els based on maximum likelihoods estimated

occupancy (psi), colonization (γ), extinction

(ε), and detection probability (p) for each site.

We performed the occupancy models for single

and multi-season data using PRESENCE soft-

ware (Hines, 2006).

RESULTS

Wood Thrush occupancy was best

described by precipitation in the four sectors at

the ACG, Costa Rica. As precipitation increased,

the probability of Wood Thrush occupancy

increased (Fig. 3, Table 1). The forest type (site)

or Julian Date did not influence Wood Thrush

Fig. 3. Wood Thrush occupancy estimate explained by precipitation (mm) at the Área de Conservación Guanacaste (ACG),

Northern Costa Rica. Point count data were collected in four ACG sectors (Santa Rosa, Cacao, Pitilla, and Leiva). Dashed

lines indicate 95% CI intervals.

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 72: e55265, enero-diciembre 2024 (Publicado Feb. 29, 2024)

occupancy or detection probability (Table 1).

The wet forest had the highest Wood Thrush

occupancy (Leiva and Pitilla sectors).

In the wet forest, we reported the occu-

pancy at each vegetation type and how the

probability of persistence varied according to

changes in precipitation across the seasons. The

occupancy of Wood Thrushes was higher in

the open area (0.69 ± 0.09 SE), followed by the

old-growth forest (0.61 ± 0.1 SE), and then the

secondary forest (0.46 ± 0.1 SE). Wood Thrush

probability of persistence in each site varied

with precipitation, from November to Decem-

ber there was an increase in precipitation,

then precipitation decreased from December to

January (Fig. 4). In those sampling periods, the

probability of persistence changed from high

persistence as the rainfall increased (Nov-Dec)

and changed to lower persistence (Dec-Jan) as

the rainfall decreased (Fig. 5). From January to

February the precipitation continued decreas-

ing (Fig. 4); however, the probability of persis-

tence of Wood Thrush in a site increased from

January to February (Fig. 5).

DISCUSSION

Single-season occupancy results: These

findings are congruent with studies for Wood

Thrush (McKinnon et al., 2015) and other

migrants elsewhere in the wintering grounds

(Cespedes & Bayly, 2019; McKellar et al., 2013),

showing a positive association between Wood

Thrush occupancy and precipitation. Precipita-

tion patterns are related with arthropod abun-

dance in tropical forests, and consequently

Fig. 4. Average precipitation (mm) collected for three days (gray dots) in a week previous to the point counts in Pitilla, Área

de Conservación Guanacaste, Northern Costa Rica.

Table 1

Single season Wood Thrush occupancy (psi) models

including detection probability (p). The covariates are

precipitation (prep), temperature (temp), site (Área de

Conservación Guanacaste sectors) and Julian Date (JDate).

Models were ranked from the lowest to the highest AICc

value.

Models nPars AICc delta AICc AICwt

psi(prep)p(.) 3 75.000 0.000 0.642

psi(temp)p(.) 3 77.910 2.820 0.157

psi(site)p(.) 5 78.620 3.530 0.110

psi(.)p(.) Null 2 80.230 5.140 1.049

psi(.)p(JDate) 3 80.780 5.690 0.037

psi(.)p(sites) 5 84.910 9.820 0.005

nPars = number of parameters.

8Revista de Biología Tropical, ISSN: 2215-2075 Vol. 72: e55265, enero-diciembre 2024 (Publicado Feb. 29, 2024)

with habitat quality for migrant birds (Brown &

Sherry, 2006; Sherry & Holmes, 1996). There-

fore, higher occupancy is expected to change as

the precipitation changes across the landscape.

This region, the Western region of the ACG

(wet forest), is particularly important since

precipitation patterns change from the dry to

the wet forest throughout the migration period.

Multi-season occupancy results: We

observed 60 % of the point counts occupied

during November-December by wood thrush-

es, and a decrease on the probability of per-

sistence for the period December-January, in

all the sampled sites. We predicted higher

persistence of wood thrushes with higher levels

of precipitation; therefore, it was expected to

observe less persistence as the levels of precipi-

tation decreased. However, for the last period

(Jan-Feb) we expected to continue observing

low Wood Thrush persistence, but we found

an increase in persistence that was not related

to precipitation. From January to February, as

precipitation continued to decrease, we expect-

ed even more movements in the last season;

however, it was the opposite according to the

precipitation pattern.

The rationale of expecting more wood

thrushes detections with increased precipitation

(higher probability of persistence in a site

from time t to time t+1) is associated with

the relationship of precipitation with resource

availability in terms of abundance of leaf-litter

invertebrates in tropical wet forests (Lieber-

man & Dock, 1982). Therefore, Wood Thrush

individuals would invest less time looking for

food. As precipitation decreases because of the

entrance of the dry season (Hilje et al., 2015)

and therefore a decrease in food availability, it

is expected that the birds invest more time for-

aging than in the previous period (Nov-Dec),

decreasing the probability of persistence on the

site. During the last season (Jan-Feb), Wood

Thrushes decreased the movements, or in other

words, the persistence probability was about

40 % on the sites, higher in comparison with

the previous survey period (Fig. 5). A possible

explanation for this pattern is the start of the

breeding season of many resident birds (Stutch-

bury & Morton, 2001). In this scenario, Wood

Thrushes might remain in the same areas, even

though precipitation decreases, and therefore

the abundance of leaf-litter arthropods decreas-

es, to avoid conflict with territorial species

such as wrens, ant-birds, and resident thrushes

that share similar foraging substrates (Sánchez

et al., 2014; Stratford & Stouffer, 2013). The

increase of detections on the same sites during

Fig. 5. Probability of persistence (survival of the sampling site) indicating Wood Thrush persistence in multiple months

(periods) at Pitilla Biological Station, Área de Conservación Guanacaste. November December 2018-January February 2019.

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 72: e55265, enero-diciembre 2024 (Publicado Feb. 29, 2024)

the survey period are also congruent with the

establishment of Wood Thrush winter territo-

ries reported by Roberts (2007) and Roberts

(2011). Therefore, they might be less mobile

and avoiding conflicts with resident birds or

saving energy before the spring migration.

In conclusion, we modeled Wood Thrush

occupancy in Northern Costa Rica and the role

of precipitation in four different sites within

the Área de Conservación Guanacaste. Con-

sidering the three forest types (dry forest, cloud

forest, and wet forest), we detected more birds

in the wet forest of Northern Guanacaste, Costa

Rica. In the wet forest, the probability of a site

being occupied varied with precipitation which

is correlated with food availability. Currently,

the wet forests in Central America should be

considered priority for Wood Thrush conser-

vation. It is necessary; however, to evaluate the

quality of protected and non-protected areas

in terms of resources that these forests provide

and evaluate the actual condition of the indi-

vidual in the wintering grounds, as well as their

interactions with resident species.

Ethical statement: the authors declare that

they all agree with this publication and made

significant contributions; that there is no con-

flict of interest of any kind; and that we fol-

lowed all pertinent ethical and legal procedures

and requirements. All financial sources are fully

and clearly stated in the acknowledgments sec-

tion. A signed document has been filed in the

journal archives.

ACKNOWLEDGMENTS

We thank the personnel from Sector Santa

Rosa, Cacao, Leiva Biological Station, and Pit-

illa Biological Station at Área de Conservación

Guanacaste for logistical support, especially

Roger Blanco, Alejandro Masís, María Marta

Chavarría y Felipe Chavarría. Eric Palola and

Monique Gilbert provided logistic and financial

support through Guanacaste Dry Forest Con-

servation Fund. This research project is under

the Research Permits: ACG-PI-007-2016, ACG-

PI-008-2017, and ACG-PI-018-2018. Frank

Joyce provided thoughtful comments at early

stages of the manuscript. We also thank Frank

Joyce for his help in the planning of the study,

design, and visits to the studied areas looking

for Wood Thrushes. Two anonymous review-

ers provided helpful comments to improve

the manuscript. We sincerely thank four local

parataxonomits Calixto Moraga, Petrona Ríos,

Freddy Quesada, and Manuel Ríos, who collect-

ed all Wood Thrush occupancy data at Pitilla

Biological Station, their participation was fun-

damental for this project. We also thank Pablo

Elizondo for help with data collection design.

Finally, we thank Daniel and Winnie Janzen for

scientific advice. US Fish and Wildlife Service

and Guanacaste Dry Forest Conservation Fund

provided financial support.

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