17 (1): 20-27 (2010)

The combined effects of habitat loss, fragmentation, and degradation are believed to be responsible for the declining trends observed in many forest bird species in North America (Donovan & Flather, 2002; Sauer, Hines & Fallon, 2007). In New Brunswick, Canada, the area of untreated mature forest has declined at a rate of 1.5% per year over the past 30 y (Betts et al., 2007). Although habi-tat amount and configuration at the landscape scale seem to have a predominant effect on the occurrence of certain

bird species (Nol, Francis & Burke, 2005; Betts, Forbes & Diamond, 2007), old forest associates may be especially sensitive to local habitat features (Hagan & Meehan, 2002; Suorsa et al., 2005; Warren et al., 2005; Poulin et al., 2008). Many of these species have been shown to be sensitive to timber harvesting, even at moderate intensities (Gram et al., 2003; Jobes, Nol & Voigt, 2004; Guénette & Villard, 2005; Holmes & Pitt, 2007; Vanderwel, Malcolm & Mills, 2007). However, partial harvesting still holds the potential to provide or maintain habitat for taxa requiring either old or early-seral forest, including certain species of birds (Gram et  al., 2003; Jobes, Nol & Voigt, 2004; Holmes and Pitt, 2007; Vanderwel, Malcolm & Mills, 2007), epiphytic lichens (Edman, Eriksson & Villard, 2008), ground beetles (Vance & Nol, 2003), and salamanders (Harpole & Haas, 1999).

Short-term demographic response of an old forest specialist to experimental selection harvesting1

Jean-François POULIN2, Marc-André VILLARD & Samuel HACHÉ, Chaire de recherche du Canada en

conservation des paysages, Département de biologie, Université de Moncton, Moncton,

Nouveau-Brunswick E1A 3E9, Canada.

Abstract: The brown creeper (Certhia americana) was recently identified as one of the forest bird species most sensitive to partial harvesting in North America. However, the processes underlying this sensitivity are poorly known. In this study, we quantified the immediate, post-treatment demographic response of this species to experimental selection harvesting in plots of northern hardwood forest in northwestern New Brunswick, Canada. We mapped individual detections and nest locations in 5 pairs (1 control and 1 treatment) of 25-ha plots in the first 2 y after single-tree selection harvesting. Linear mixed models with site and landscape context as random effects showed a significant negative effect of treatment on nest density and seasonal reproductive success. The density of large-diameter trees (≥ 30 cm dbh) was significantly lower in treated plots than in controls (mean: 77 versus 112 stems·ha–1), whereas the density of potential nesting substrates (snags with peeling bark) did not decrease significantly following treatment. Hence, the density of suitable foraging substrates may represent a limiting factor for both nest density and reproductive success, and partial harvesting may not be compatible with the persistence of breeding populations of brown creeper. Patches of untreated forest should be maintained in managed forest landscapes at all times for this and other taxa requiring old forest conditions.Keywords: Certhia americana, ecological integrity, foraging substrates, forest birds, single-tree selection harvesting, umbrella species.

Résumé : Le grimpereau brun (Certhia  americana) a été récemment identifié comme étant l’une des espèces d’oiseaux forestiers les plus sensibles à la coupe partielle en Amérique du Nord. Cependant, les causes de cette sensibilité sont mal connues. Dans cette étude, nous avons évalué quantitativement la réponse démographique de cette espèce tout de suite après un traitement expérimental de récolte par jardinage dans des parcelles de forêt feuillue dans le nord-ouest du Nouveau-Brunswick, Canada. Nous avons cartographié les détections d’individus et les emplacements des nids dans 5 paires (1 témoin et 1 traitement) de parcelles de 25 hectares durant les 2 premières années après une coupe de jardinage par pied d'arbre. Des modèles linéaires mixtes avec le site et le contexte de paysage comme effets aléatoires ont montré un effet négatif significatif du traitement sur la densité de nids et le succès reproducteur saisonnier. La densité d’arbres de grand diamètre (≥ 30 cm dhp) était significativement plus faible dans les parcelles traitées que dans les témoins (en moyenne : 77 versus 112 tiges·ha–1) alors que la densité de substrats potentiels de nidification (chicots dont l’écorce se détache) n’avait pas diminué significativement après le traitement. Ainsi, la densité de substrats appropriés pour la quête alimentaire peut représenter un facteur limitant tant pour la densité de nids que pour le succès reproducteur. La coupe n’est donc peut-être pas compatible avec la persistance de populations nicheuses de grimpereau brun. Des parcelles intactes de forêt devraient être maintenues dans les paysages forestiers aménagés en tout temps pour cette espèce et d’autres taxons nécessitant des caractéristiques associées aux vieilles forêts.Mots-clés : Certhia americana, coupe de jardinage par pied d'arbre, espèce parapluie, intégrité écologique, oiseaux forestiers, substrats de quête alimentaire.

Nomenclature: Marie-Victorin, 1995; American Ornithologists’ Union, 2008.

Introduction

1Rec. 2009-06-23; acc. 2009-12-18. Associate Editor: Louis Imbeau.2Author for correspondence. Present address: Genivar, 31 avenue Marquette, Baie-Comeau, Québec G4Z 1K4, Canada, e-mail: jean.francois.poulin@genivar.com

DOI 10.2980/17-1-3297

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Studies investigating species response to partial harvesting have often classified stands in broad classes based on time since harvesting (e.g., Holmes et  al., 2004; Jobes, Nol & Voigt, 2004). This may prevent the detection of responses taking place in the first years post-harvest (Robinson & Robinson, 1999; Jobes, Nol & Voigt, 2004; Villard, Schmiegelow & Trczinski, 2007), which may pro-vide insight into the specific processes underlying species response to harvesting. To our knowledge, few studies have measured the effects of partial harvesting on the demog-raphy of old forest specialists (but see Gram et  al., 2003; Holmes & Pitt, 2007; Robertson & Hutto, 2007; Haché & Villard, in press).

In this study, we focus on one of the forest bird spe-cies deemed most sensitive to partial harvesting in North America (Vanderwel, Malcolm & Mills, 2007): the brown creeper (Certhia  americana). In North America and Eurasia, creepers (Certhia spp.) are considered to be indica-tors of sustainable forest management (Kuitunen & Helle, 1988; Kuitunen & Mäkinen, 1993; Bani et al., 2005; Suorsa et  al., 2005, Wintle et  al., 2005; Thompson et  al., 2009). The brown creeper is known to be strongly associated with old growth stands and corresponding structures in a variety of forest stand types across North America, owing primarily to its nesting and foraging requirements (Hejl et al., 2002; Poulin et  al., 2008). Because brown creepers require dead or dying trees whose bark is peeling off for nesting, partial harvesting may reduce the density of potential nesting sub-strates to the extent that they represent a limiting factor for habitat occupancy. In fact, partial harvest treatments such as single-tree selection tend to homogenize forest stand com-position and to reduce both stand age and the abundance of certain structural attributes (e.g., snags) (Angers et  al., 2005; Vanderwel, Caspersen & Woods, 2006). Brown creeper nests are mainly located in patches with a high density of large-diameter trees (Poulin et  al., 2008; see also Suorsa et  al., 2005 for the Eurasian treecreeper, C.  familiaris). It follows that the availability of large trees may also represent a limiting factor, but this has never been tested specifically.

This study aimed to measure the response of brown creeper populations to single-tree selection harvesting in order to investigate the mechanisms underlying this response. We predicted that densities of territories and nests, as well as reproductive success, would be lower in treated than in control plots. We also compared treatment effects on stand structure and the abundance of potential nest predators. We focused on the response of birds shortly after harvesting. During that period, stand structure changes rapidly, and it may never return to its pre-harvest condition due to the relatively short harvest rotation period (Jobes, Nol & Voigt, 2004). Thus, we wanted to assess the response of this species to stand structure in order to predict the effects of large-scale application of selection harvesting across managed forest landscapes.

Methods

The study was conducted during the summers of 2006, 2007, and 2008 in the Black Brook District (47° 23' N, 67° 40' w), a managed forest owned by J. D. Irving Ltd. in

northwestern New Brunswick, Canada (Figure 1). Dominant deciduous species were sugar maple (Acer  saccharum), American beech (Fagus  grandifolia), and yellow birch (Betula  alleghaniensis), with naturally regenerated con-ifers present as scattered trees or small patches, and exten-sive conifer plantations (see Guénette & Villard, 2005 for details). We focused on mature and old stands of northern hardwood forest because they are managed under partial harvest systems.

We selected 5 pairs of 25-ha plots. Study plots within each pair were separated by 4–6 km, and pairs of sites were separated by 7–35 km (Figure 1). One plot of each pair was harvested in the fall of 2006 through experimental single-tree selection, and treatment was randomly assigned except in one case, where relatively steep slopes and the pres-ence of rare plants prevented harvest operations. Treatment intensity (30 or 40% basal area removal) was adjusted so that post-harvest stand structure would be as similar as pos-sible among sites. We also instructed operators to maintain as many standing snags as possible to separate potential effects of nesting and foraging substrates as limiting factors. Treatment was also applied in a 50-m band surrounding the plot. In each study plot, we marked a 50-m grid with flag-ging tape to facilitate mapping of bird detections and nests.

We measured the diameter at breast height (dbh) and species of all live trees and snags before experimental har-vesting (2006) and after (2007) within 0.04-ha circular plots (radius of 11.28 m) systematically located at the centre of 25, 1-ha squares within each study plot. We estimated the density of balsam fir snags (mean number·ha–1) because it is the nest-ing substrate most frequently used by creepers in our study area (Poulin et al., 2008). We also calculated the density of large-diameter trees (dbh ≥ 30 cm, mean number·ha–1) to monitor changes in important foraging substrates.

Quebec

Maine, USA

New Brunswick

30 60 1200 180 240 km

XX

X

X

X

1 2

3

45

FIgurE 1. Location of study area, showing the 5 pairs of 25-ha study plots (X = plots treated through single-tree selection harvesting; black dots represent control plots) surrounded by 5-km-radius circles within which landscape metrics were quantified.

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To compare landscape composition between pairs of study plots, we measured the following metrics within a 5-km radius of the centroid of each pair of sites: proportion of untreated mature forest (deciduous, mixed, or conifer-ous); proportion of mature deciduous forest treated through uneven-aged selection harvesting; and proportion of conifer plantations of any age (Figure 2). Those metrics accounted for a mean of 74.2% (± 8.4 SD) of the land cover within the focal radius. Non-forested lands (4.0% ± 0.7), immature stands (11% ± 10), and partially harvested coniferous stands (9.7% ± 3.6) accounted for remaining land cover.

In 2007 and 2008, we conducted intensive searches for brown creepers and their nests (1 May–30 July) within each study plot and within a 50-m band around plot boundaries. We used the spot mapping method (Bibby et al., 2000) within flagged grids to delineate territories. We drew territories based on 8 standardized spot mapping visits conducted between 0530 and 1000 (22 May–29 June 2007; 22 May–01 July 2008). Other detections recorded during the breed-ing season were also used to assist with territory mapping. Unfortunately, we did not collect enough data to produce precise maps of creeper territories in 2006. All territories located within the plots were monitored. We monitored each nest every 3 d until its fate could be determined. When a nest was abandoned or depredated, we searched the plot and sur-rounding band to detect renesting attempts.

We also mapped all detections of potential nest predators (red squirrel, Tamiasciurus  hudsonicus; eastern chipmunk, Tamias  striatus) from 2006 to 2008. We estimated preda-tor abundance by calculating the mean number of detections recorded over the 8 spot mapping sessions. Corvids were

present in the study area (common raven, Corvus  corax; American Crow, C.  brachyrhynchos; grey jay, Perisoreus canadensis)  and in our study plots (blue jay, Cyanocitta cristata), but we have yet to record an instance of nest pred-ation by corvids (J. F. Poulin & M. A. Villard, unpubl. data). Hejl et al. (2002) do not consider corvids among potential predators of brown creeper nests.

We recorded nest density, the number of territories overlapping the study plots, the number of nesting attempts, the number of successful first nests (≥ 1 fledged young at first nesting attempt), nesting success (proportion of nests that were successful), and the number of successful ter-ritories (≥ 1 young fledged). The latter will be referred to as seasonal reproductive success, because birds renested within the same territory after a failed first attempt early in the season. Nest density was calculated as the maximum number of active nests (≥ 1 egg laid) recorded at a given time in each plot during the breeding season. We also deter-mined the number of territories whose area overlapped the plot by at least one half. We compiled the number of nesting attempts initiated within each plot, which included renesting attempts. We analyzed year and treatment effects on nest survival using the Mayfield logistic regression approach (sensu Hazler, 2004) and the LOGISTIC procedure in SAS 9.1 (SAS Institute, 1999). We also calculated nest survival (sensu Mayfield, 1975), assuming a nesting period of 37 d (6 for laying, 15 for incubation, 16 for nestling stage; Hejl et  al., 2002) for each year, treatment, and nesting attempt. Finally, we calculated the distance between the location of first nests and the nearest patch of untreated forest (adjacent stand or riparian buffer zone within the plot). We restricted this analysis to first nests because the location of renesting attempts is not independent of that of first nests. For treated sites, we compared the observed distribution of distances from nests to untreated forest to that measured for 100 random points per plot. We then calculated the proportion of the randomized distribution that fell below the observed mean distance.

To account for the nested structure of the data (i.e., spatially paired treatment and control plots), we examined the effects of harvest treatment on the mean value of each response variable per site using linear mixed models. We considered harvest treatment and year as fixed effects, whereas landscape context was considered as a random effect in the following model:

[1]

where y was the response variable (nest density, number of territories, number of nesting attempts, fledging suc-cess, seasonal reproductive success, and number of predator detection), μ was a constant, τ was the treatment (harvested versus control; fixed effect), bi was a parameter estimate, x represented the year (fixed effect), τ×x was the interaction between treatment and year (fixed effect), m was the land-scape context of a given pair of plots (1–5; random effect), n(m) was the plot  (context) (1–10; random effect), and ε was the error term. We also tested for a treatment effect on selected stand structure variables (density of large trees and balsam fir snags) and for treatment and year effects on the abundance index for potential predators using mixed models.

FIgurE 2. Proportional area of untreated mature forest, harvested deciduous forest (selection cuts), conifer plantations (0–50 y), harvested coniferous forest (partial cuts), immature forest, and non-forest within a 5-km radius around each of the 5 pairs of study plots.

y = μ + τ + bx + b τ×x + bm+ bn(m) + ε

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We performed all mixed models using the MIXED procedure in SAS 9.1 (SAS Institute, 1999). Pairwise comparisons of means were made using a Tukey honest significance test.

Results

Over the 2 y of the study, we found a total of 50 nests (34 in control plots; 16 in treated plots) in the 250 ha sur-veyed (Table I). Of those, 83% were built on balsam fir snags. Nest density and number of territories were twice as high in controls as in treatment plots in 2007 and 2008 (Table II). Indeed, there was a significant negative effect of single tree selection on nest density and on the numbers of territories and nesting attempts (Table III). There was also a significant year effect on the number of nesting attempts as a result of higher nesting failures in 2007 (Table III).

The number of successful first nests was lower in treated plots in 2007, though the trend was not significant (Table III). However, as predicted, there was a significant negative effect of treatment on seasonal reproductive success (Table III). Nest survival was similar between control and treatment

plots in 2007 but lower in treatment plots in 2008 (Table I). However, neither treatment (P = 0.83) nor year (P = 0.61) had a significant effect on nest survival. In 2007, there were fewer nesting attempts in treatment compared to control plots.

The abundance of each nest predator species we surveyed varied significantly between years, but not as a function of treatment (Table III, Figure 3). Red squir-rel abundance was significantly higher in 2007 than in 2008 (t = 2.7, P = 0.04), whereas that of eastern chipmunk was significantly higher in 2007 than in 2006 (t = –4.6, P < 0.01) or 2008 (t = 7.3, P < 0.01). Nesting success was low in 2007 (year of high predator abundance) and high in 2008 (year of low predator abundance) (Figure 3).

The density of balsam fir snags, a favourite nesting substrate (Poulin et al., 2008), was similar between control and treated sites for the pre-harvest year, and the difference remained non-significant after treatment (Table IV). Before treatment, the density of large-diameter trees in future treat-ment plots was significantly higher than in control plots. The treatment reversed the situation: the density of large-diameter trees became significantly lower in treated plots (Table IV). Brown creepers appeared to nest close to untreated forest (riparian buffer zones or adjacent forest patch; Figure 4). The mean distance from first nests to untreated forest was 68 m (± 15 SE, n = 13), compared to 105 m for random points (± 3 SE, n = 500), but the probability associated with the observed value was not significant (randomization test, P = 0.28; Figure 5).

tablE I. Nesting success of brown creepers in control (n = 5) and treated plots (n = 5) for first nesting attempts and over the entire breeding season.

Variable 2007 2008

Control Treatment Control Treatment

First attempt Number of nests 14 7 12 6 Nesting success (%) 50 29 67 67 Daily nest survival (%) (n) 41.4 (8) 37.0 (6) 70.1 (9) 59.0 (6)

Entire season Number of nests 20 10 14 6 Nesting success (%) 45 40 77 67 Daily nest survival (%) (n) 35.4 (13) 39.4 (9) 70.1 (9) 59.0 (6)

tablE II. Brown creeper demographic parameters in control and treatment plots in 2007 and 2008.

Variable Mean (SE) 2007 2008

Control Treatment Control Treatment

Number of territories 4.0 (0.5) 2.4 (0.5) 3.6 (0.5) 1.8 (0.2)Nest density 2.8 (0.6) 1.4 (0.4) 2.4 (0.4) 1.2 (0.2)Nesting attempts 4.0 (0.9) 2.0 (0.6) 2.8 (0.5) 1.2 (0.2)Successful first nests 1.4 (0.5) 0.4 (0.2) 1.6 (0.2) 0.8 (0.2)Seasonal reproductive success 1.8 (0.4) 0.8 (0.5) 2.0 (0.3) 0.8 (0.2)

tablE III. Effects of single-tree selection harvesting on brown creeper demographic parameters indicated by linear mixed models.

Variables Treatment Year Treatment × Year

df F  P  F  P  F  P

Number of territories 1, 8 7.7 0.02 4.6 0.07 0.2 0.68Nest density 1, 8 8.9 0.02 1.8 0.22 0.2 0.67Nesting attempts 1, 8 6.8 0.03 6.5 0.04 0.3 0.63Successful first nests 1, 8 5.1 0.05 1.8 0.22 0.2 0.67Seasonal reproductive success 1, 8 6.9 0.03 0.1 0.74 0.1 0.74Red squirrel abundance1 1, 2, 16 2.1 0.17 5.8 0.01 2.1 0.16Eastern chipmunk abundance1 1, 2, 16 1.5 0.24 27.8 < 0.01 1.5 0.23

1Analyses performed on 3 y (2006-2008).

FIgurE 3. Mean number of detections of red squirrels and eastern chip-munks and nesting success of brown creeper (± SE) (n = 10 plots). No data on brown creeper reproduction were available for 2006.

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Discussion

Single-tree selection harvesting had most of the pre-dicted effects on brown creeper demography. Nest density and seasonal reproductive success were lower in treated plots than in controls. Because the density of preferred nesting

substrates (balsam fir snags) was not significantly differ-ent between treated and control plots, the observed treat-ment effect on creeper demography is probably linked to the reduction in the density of large-diameter trees, which represent good foraging substrates (Mariani & Manuwal, 1990). Selection harvesting may result in a reduction in food abundance, quality, or accessibility, which would be consist-ent with the observed decrease in nest density in treated plots.

As reported by Poulin et  al. (2008), balsam fir snags were clearly the favourite nesting substrate of brown creep-ers. Harvest treatments generally require felling snags that may represent a safety hazard for workers (Vaillancourt et al., 2008). Indeed, elsewhere in the region, the density of balsam fir snags was lower by an average of 10 stems·ha–1

in treated relative to untreated stands (J.-F. Poulin & M.-A. Villard, unpubl. data). Hence, plots treated in this experi-ment may have provided higher-quality nesting habitat than most other post-harvest stands. To be selected for nesting, a snag must be at a specific decomposition stage, with bark starting to peel off. Also, flakes of bark must be large enough to accommodate a nest yet small enough to allow the birds to fill up the space to build their nest. Finally, creepers seem to prefer substrates offering a narrow entrance (J.-F. Poulin, pers. observ.). Hence, snag recruit-ment must be fairly high to offer suitable nesting oppor-tunities each year. Balsam fir is often affected by trunk and root rot, and it also has a shallow root system, making it highly vulnerable to windthrow, especially in partially harvested sites (Johnston, 1986; Vanderwel, Caspersen & Woods, 2006). Availability of suitable nesting substrates may thus decline faster in treated plots over the longer term. On the other hand, the ability of creepers to reuse the same snag (but different bark flakes) in successive years (J.-F. Poulin, pers. observ.) may buffer, over the short term, against a shortage of suitable nesting sites.

Nest survival was higher in control plots than in treated plots, but the difference was not significant. Nonetheless, in 2007, the number of successful first nests was 70% lower in treated plots compared to control plots, whereas the nest density was only 50% lower. Thus, first nests in treated plots were depredated at a higher rate. This might reflect greater nest detectability by visual predators in treated plots, owing to increased light intensity and lower foliage density in the understory (Yahner & Wright, 1985; Martin & Roper, 1988; Martin, 1993; but see Holway, 1991; Howlett & Stutchbury, 1996; Burhans & Thompson, 1998). This phe-nomenon may be especially important in the first few years after treatment.

In partially harvested stands, deer mouse (Peromyscus maniculatus) densities tend to be higher than in untreated

tablE Iv. Treatment effects on stand attributes indicated by linear mixed models.

Variable Pre-harvest Post-harvest1

Mean (SE) Mean (SE) Control Treatment df F  P Treatment df F  P

Density of balsam fir snags (stems·ha–1) 14 (4) 15 (2) 1, 8 0.1 0.82 12 (2) 1, 8 2.1 0.2Density of large-diameter trees (stems·ha–1; ≥ 30 cm dbh) 112 (7) 136 (6) 1, 8 8.2 0.02 77 (3) 1, 8 18.7 0.01

1Post-harvest values included in the analysis for control plots were the same as pre-harvest values because they were assumed to have remained constant.

FIgurE 4. Aerial photograph of a treated site (500 × 500 m) showing nest locations (including renesting attempts) (white dots with conifer symbol).

FIgurE 5. Frequency distribution of distance from 500 random points to nearest untreated forest within treated sites (mean = 105 m). The arrow indicates the mean distance observed from actual nests to nearest untreated forest.

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forest (Fuller, Harrison & Lachowski, 2004). However, this response was not reported for red squirrel and eastern chip-munk (Holloway & Malcolm, 2006). While nest predators did not respond significantly to the treatment in our study, they showed significant year effects. This resulted in a lower number of successful first nests, a lower nesting success, and a higher number of nesting attempts in both control and treated plots in 2007. Production of coniferous and decidu-ous seeds was high in 2006, the highest levels recorded over the past 30 y in New Brunswick seed orchards (G. Pelletier, pers. comm.). This likely explains the high abundance of nest predators we recorded in 2007.

Throughout their range, brown creepers tend to for-age on relatively large trees with textured bark (Hejl et al., 2002). Large-diameter trees may support proportionally higher densities of invertebrates (Jackson, 1979; Mariani & Manuwal, 1990), which in turn would reduce the energetic costs associated with foraging (Franzreb, 1985; Mariani & Manuwal, 1990). Furthermore, creepers have large territor-ies relative to their body size (ca. 5–10 ha in our study area, J. F. Poulin & M. A. Villard, unpubl. data), which suggests that they require large areas to meet their energetic require-ments. Brown creepers’ response to selection harvesting was out of proportion with the reduction in foraging sub-strates: harvesting 30 to 40% of tree basal area resulted in a decrease of nearly 50% in nest density, number of territories, and seasonal reproductive success. These results suggest that the quality of foraging habitat was negatively affected by single-tree selection harvesting.

Partial opening of the canopy through harvesting has been shown to change microclimatic conditions on tree trunks (Hedenås & Ericson, 2000). This phenomenon was proposed as an explanation for the negative effect of selec-tion harvesting on the abundance and fertility of 2 species of epiphytic lichens in the same region (Edman, Eriksson & Villard, 2008). This could in turn affect invertebrate commun-ities/abundance on tree trunks. Because creepers are known to deplete food resources in the vicinity of the nest during the breeding season (Jäntti et al., 2001), pairs nesting in treated plots would be expected to compensate by increasing the size of their territory. The lower densities observed in treated plots indeed suggest that creepers expanded their territories, resulting in the lower nest density we observed. Creepers might also compensate for the lower availability of food by nesting closer to untreated forest within treatment plots, but the trend we observed was not statistically significant.

Conservation strategies for bark-gleaning birds have mainly focused on the abundance of potential nesting sub-strates (but see Mannan, Meslow & Wight, 1980; Giese & Cuthbert, 2003; Lemaître & Villard, 2005). However, such strategies do not necessarily guarantee that food require-ments will be met after a given habitat alteration (Weikel & Hayes, 1999). Long-term monitoring (Johnson, 1999) or dynamic-landscape metapopulation models (Wintle et  al., 2005) would be required to assess the implications of our f indings for the probability of persistence of breeding populations of brown creepers in managed landscapes. Our results do raise concerns about the persistence of brown creepers and ecologically similar species in our study region because the vast majority of deciduous stands are currently managed under various forms of partial harvesting. Owing

to its high sensitivity to harvesting, the brown creeper rep-resents a good indicator of ecological integrity in late-seral stands (Wintle et al., 2005; Venier et al., 2007; Poulin et al., 2008). Given its relatively large territory size, it could act as an umbrella for other forest bird species requiring old forest conditions. To nest successfully, the brown creeper appar-ently requires patches of untreated, mature to old forest (see also Poulin et al., 2008). Further research should investigate the response of this species to landscape structure.

Acknowledgements

This project was supported by grants from the Natural Sciences and Engineering Research Council of Canada, the Sustainable Forest Management Network, and the New Brunswick Wildlife Trust Fund to M. A. Villard. We are grate-ful to H. Laforge, É. D’Astous, M. Ricard, S. Thériault, and M.-C. Bélair for their assistance in the field. We thank G. Pelletier (J. D. Irving Ltd.) for his advice on the design and implementation of the harvesting experiment and for giving us access to private lands and camp facilities. We also thank L. Imbeau, A. Desrochers, É. D’Astous, and two anonymous reviewers for comments on an earlier version of the manuscript.

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