Survival, Movements, and Habitat Use of Fledgling Veeries (Catharus fuscescens) in Northeastern Pennsylvania.
Recruitment by migratory passerines requires their young survive not only to fledging, but also that they survive the postfledging period, considered to be the 2 to 3 mo period following fledging during which the young birds learn to care for themselves as they accumulate fat reserves for migration (Anders et al., 1997; Vega Rivera et al., 1998). Although much less studied than the nesting period, interest in the postfledging period has grown as researchers have documented its importance in passerine demography and conservation. For example some studies have documented high rates of mortality, exceeding 50% during this period (Anders et al., 1997; Rush and Stutchbury, 2008; Ausprey and Rodewald, 2011; Streby and Anderson, 2013), or have documented rates of survival that differ greatly among species, habitat types, or regions (see Cox et al, 2014, for review). Further, studies of several passerine species have revealed habitat shifts in which fledglings use, and survive better in, habitats that differ greatly from those used by adults during the nesting period (Anders et al., 1998; Vega Rivera et al., 1998; White et al., 2005; King et al, 2006; Dittmar et al., 2014). For most species, however, basic measures of survival and behavior during the postfledgling period remain unstudied.
For most passerines, the postfledging period can be broadly divided into two subperiods based on the level of dependence of the fledglings on their parents. The initial subperiod, representing the first 2 to 4 wk after fledging, has usually been called the dependent period and appears to be the most challenging in terms of survival. Newly-fledged young of altricial birds are normally not fully developed at the time of fledging and are dependent on parental food deliveries as they learn to fly, forage for themselves, and to detect and evade predators. Previous studies report high mortality rates of fledgling passerines during the dependent period, with mortality rates especially high during the first several days after fledging (e.g., King et al., 2006; Rush and Stutchbury, 2008; Moore et al, 2010, Hache et al., 2014). The remainder of the postfledging period has typically been called the independent period. During this subperiod, fledglings no longer require parental care and often exhibit a high survival rate similar to that of adults, at least until migration (Cox et al., 2014, Naef-Daenzer and Griiebler, 2016). For most species it is during this subperiod that fledglings leave their natal home ranges, dispersing to other sites to build up fat reserves for migration, and perhaps to investigate future breeding territories (Anders et al., 1998; Vitz and Rodewald, 2010).
The Veery (Catharus fuscescens) is an area-sensitive, Neotropical migrant passerine that breeds within a variety of moist deciduous forest types, particularly those with a well-developed understory (Heckscher et al, 2017). This species typically forages and nests on or near the ground with most elevated nests built in shrubs, small trees, or on clumps of dead debris (Heckscher, 2004; Heckscher et al., 2017). Over the past 40 y (1966-2015), the Veery has declined at an annual rate of 1.13% over much of its range (Sauer et al., 2017). This decline likely relates to habitat loss and degradation on both its wintering and breeding grounds (Heckscher et al., 2017). Although habitat use and success during the nesting period of the Veery has been well-studied with several recent studies in the eastern United States (e.g., Heckscher, 2004; Kearns et al, 2006; Schmidt et al, 2006; Dellinger et al., 2007), most aspects of this species' postfledging period remain unstudied. Knowledge of factors impacting fledgling survival or habitat use during this period are needed both to inform management strategies for this declining species and to contribute broadly to conservation efforts of mature forest passerines, in general. During summer 2013 and 2014, I used radiotelemetry to study juvenile Veeries primarily during their dependent period in a region dominated largely by mature deciduous forest in northeastern Pennsylvania. In Pennsylvania the Veery prefers damp, intermediate-elevation forests with a dense understory and often a component of eastern hemlock (Tsuga canadensis), and has exhibited relatively stable population trends over the past several decades (Bolgiano, 2012; Sauer et al, 2017). The objective of my study was to document survival, movement patterns, and habitat use of juvenile Veeries during the early postfledging period in a landscape dominated by mature forest.
The study was conducted within the 1436 ha Nescopeck State Park (NSP) Luzeme County, northeastern Pennsylvania (41[degrees]4'32"N, 75[degrees]54'32"W). NSP is a long narrow tract centered along a 9.7 km stretch of Nescopeck Creek. The park is mostly forested with dry deciduous forest at higher elevations (350-450 m) away from the creek and moist, mixed deciduous-coniferous forest along the creek at lower elevations (300-350 m). The surrounding landscape is also largely forested, including additional state conservation lands managed primarily for wildlife and recreation covering over 5000 ha. Research was conducted mainly within 500 m of the creek channel, along an approximately 2 km stretch of the creek in the western half of the park. Habitat in this area consisted largely of mature mixed-forest with an overstory dominated by red maple (Acer rubrum), white oaks (Quercus alba and Q. bicolor), American beech (Fagas grandifolia), and scattered stands of eastern hemlock. The woody understory and subcanopy layers were well-developed and diverse. The area also contained ~25 ha of old field habitat maintained by the state park. Timber harvest has occurred regularly in various parts of NSP and on adjacent state lands. However, in the study area there was little early successional forest beyond narrow maintained strips along the road and some trails.
RADIOTRACKING OF FLEDGLINGS
Between mid-May and early July 2013 and 2014, Veery nests were located using adult behaviors to delineate territories and systematically searching the understory vegetation. Upon locating a nest, I used a short extendable mirror to check nest contents and recorded a detailed description of the nest site with global positioning system (GPS) coordinates to allow for relocation. Nest were revisited every 2-3 d to monitor nest status and to estimate hatching date.
Veery nestlings typically fledge between 9 and 12 d after hatching (C.B. Goguen, unpubl.). Therefore, at 8 or 9 d, I weighed and measured wing chord length of each nestling, and then banded each with a U.S. Geological Survey aluminum band and one to three colored plastic bands. A radiotransmitter (0.75 g; model A2435, Advanced Telemetry Systems, Isanti, MN) was also attached to one randomly selected nestling from each nest. Radiotransmitters weighed ~3.0% of nestling body mass at the time of attachment (25.1 [+ or -] 0.36 g; n= 29), with an expected battery life of 36 d. Initially, the radiotransmitter was glued directly to the skin on the back of a nestling using a quick-drying cyanoacrylate (i.e., "super-glue") adhesive gel. Because of retention problems with the adhesive, I subsequently switched to a figure eight, leg-loop harness (Rappole and Tipton, 1991) made of elastic sewing cord. Transmitters attached with adhesive were only retained an average of 9.5 d (n= 12), whereas only one of 17 birds fitted with a harness shed its transmitter. After radiotransmitter attachment, all nestlings were returned to the nest together. Each nest was revisited daily to confirm when radiotagged nestlings fledged. I searched for fledged, radiotagged birds on foot every 1-3 d using a hand-held, 3-element Yagi antennae. Once a bird was relocated, its location was determined using a GPS unit and I recorded its perching height and substrate, presence or absence of parents, and broad habitat type (see "Habitat sampling" below). If a bird was not detected, I systematically increased my search area, in particular seeking higher elevation sites for scanning. Further, I continued scanning for these missing transmitter frequencies throughout the study site for the remainder of the summer tracking period while searching for other tagged birds.
To describe fledgling habitat use, a suite of habitat characteristics was measured at the relocation sites (hereafter, "fledgling use sites") and paired random points. Fledgling use sites were centered on the exact position at which the fledgling was first observed, assuming that tracking had not influenced the fledgling's position. This was likely a valid assumption while fledglings were young and had limited mobility (i.e., up to 2 wk postfledge), but may have been less valid with older, highly-mobile fledglings. Random sites were located by pacing 50 m from the fledgling use site in a direction determined by rotating a compass dial for several seconds, without looking, and using the final bearing indicated by the index line. I chose 50 m between use and random sites given this distance was far enough typically to capture different habitat features at that scale, yet close enough that even a young fledgling could easily move between locations (Vitz and Rodewald, 2011). Due to the rapid death of some fledglings and fieldwork time constraints, I was only able to perform habitat sampling on a subset of birds, conducting the sampling, at most, every other time a bird was relocated.
The same plot-based habitat sampling was performed for both location types. Within a 5 m radius of the sampling point, percent ground cover, percent mid-story cover, understory woody plant species richness, and sapling density were measured, and within an 11.3 m radius tree density was mesaured, by species and size. From these data, analyses was focused on the following nine variables that broadly described aspects of understory and overstory cover and were previously identified as important in fledgling survival and habitat use (e.g., Anders et al., 1998; King et al., 2006; Vitz and Rodewald, 2011): (1) live, woody ground cover, visually estimated as the percentage of ground below 0.5 m covered by live, woody plants; (2) open, unvegetated ground cover, a measure of understory openness, visually estimated as the percentage of ground below 0.5 m not covered by live plants; (3 and 4) mid-story cover from 0-1 m and from 1-2 m, with both measured using a vegetation profile board (Nudds, 1977) set at the sampling point, with cover assessed from 5 m away in the four cardinal directions; (5) understory woody plant species richness, measured by a direct count; (6) sapling density, measured by counting all woody stems between 2-8 cm diameter at breast height (DBH); (7) density of small trees (8-23 cm DBH), measured as all species combined; (8) density of large trees (>23 cm DBH), measured as all species combined; and (9) density of eastern hemlock trees (>8 cm DBH).
The following categories were used to describe broad habitat use and potentially document shifts in habitat use as fledglings aged: Moist forest--closed canopy forest dominated by species adapted to moist conditions (e.g., red maple, American beech, eastern hemlock); Dry forest--closed canopy, deciduous forest dominated by species associated with dryer environments [e.g., northern red oak (Quercus rubra), chestnut oak (Q. montana)]', Forested swamp--forest with mostly closed canopy but overlaying broad areas of shrubby or herbaceous wetlands; Shrub-dominated swamp--open wetlands lacking a closed canopy and dominated by dense winterberry (Ilex verticillata), spicebush (Lindera benzoin), or buttonbush (Cephalanthus occidentalis); and Old field--open habitats dominated by grasses and forbs but invaded, to varying degrees, by woody shrubs. Because forest edges along fields often supported denser understory cover than adjacent forests due to sunlight availability, I recorded when fledglings were detected within 3 m of the edge between forest and old field habitats, identifying these areas as "forest-field edge" habitats.
Initially, basic analyses were conducted to determine if radiotransmitter attachment method (glued-on versus harness) affected patterns of fledgling survival or behavior (e.g., mean movement distances). No significant differences were apparent; therefore, subsequent analyses combined all individuals.
Fledgling survival was analyzed from both years combined using the Kaplan-Meier product limit estimator (Kaplan and Meier, 1958). The Kaplan-Meier procedure estimates survival as the proportion of individuals surviving across time intervals (e.g., days), with the probability of surviving to a given point in time estimated as the cumulative probability of surviving each of the preceding time intervals (Lee, 1992). In this analysis, individuals that shed their transmitters were censored at the time the fledgling was last detected alive. Censored observations are those that did not experience the event of interest, in this case death, during the study period, and therefore survival information in regard to this event is only partially known (Hougaard 1999). This analysis was limited to the first 21 d of the postfledging period given that was the time frame in which I was able to relocate all radiotagged birds; I was unable to detect some radiotagged birds beyond 21 d and had no way to know if these disappearances were due to sudden long-distance movements, transmitter failure, or to death and removal by a predator. This 21 d period corresponds to the postfledging-dependent period in the closely related Swainson's Thrush (Catharus ustulatus; White and Faaborg, 2008) and Wood Thrush (Hylocichla mustelina; Anders et al., 1998).
To describe movement patterns of fledglings, the linear distance of each relocation of a fledgling back to its nest was calculated. Movements for each fledgling were summarized by calculating a mean distance from the nest in 3 d time intervals (e.g., 0-3 d, 4-6 d, 7-9 d, etc.). These individual means were used in calculating mean movement patterns, by age, for the collection of radiotagged birds as a whole.
Due to the limited number of radiotagged fledglings for which I was able to perform habitat sampling (n = 19), only univariate tests were used for comparisons rather than multivariate modeling approaches. First, I tested whether habitat characteristics of use sites differed by fledgling age. In these analyses, habitat measures for each fledgling were summarized by averaging values for each variable across all of its use sites in each of three age intervals (1-7 d, 8-14 d, and 15-21 d postfledge), treating the individual fledgling as the replicate. I then compared medians among these three groups for each habitat variable using Kruskal-Wallis one-way ANOVA. Because none of the variables differed by age category, the data were combined among all age intervals for subsequent analyses. To compare habitat characteristics between fledgling use sites and random sites, habitat measures for each fledgling were summarized by averaging values for each variable across all of its use and random sites, again treating the individual fledgling as the replicate. A paired-sample Wilcoxon signed rank test (Sokal and Rohlf, 2011) was used to compare habitat characteristics at use sites to those at paired random sites. All analyses were performed using the statistical package SPSS Statistics 22 (IBM Corporation, Somers, New York). Because many habitat comparisons involved nonparametric tests, the median and range are reported, in addition to the mean ([+ or -]se), in many cases. Statistical significance for all tests was indicated by P [less than or equal to] 0.05.
In total 29 fledglings were radiotagged (20 in 2013, 9 in 2014), of which six died during tracking. Given the modest sample sizes, I did not attempt to test for differences in survival among the two years. However, the percentage of radiotagged birds that died was nearly identical in both (20% in 2013, 22% in 2014).
Survival rate for the 21 d postfledging period was 0.78 [+ or -] 0.08. Of the six mortality events, five occurred within the first 5 d postfledging, with the final event occurring at 9 d. All deaths appeared to be due to predation, although in most cases it was impossible to know if a fledgling had died first of some other cause (e.g., starvation), and was then scavenged. Two deaths were attributed to eastern chipmunks (Tamias striatus), both involving young that had recently fledged (2 and 3.5 d postfledging). In one of these cases, the transmitter was tracked to an underground chipmunk burrow. In the other the dead, largely-intact radiotagged bird was found buried under leaf litter, typical of chipmunk caching behavior (Reitsma et al, 1990). Both deaths in 2014 were attributed to Broad-winged Hawks (Buteo platypterus) and involved slightly older young (4.5 and 9 d postfledging); both transmitters were recovered in raptor pellets in the vicinity of a hawk nest. For the remaining two deaths, the transmitter was recovered in association with Veery feathers and body parts, but the identity of the predator was unknown.
FLEDGLING BEHAVIOR AND MOVEMENTS
Radiotagged fledglings were often detected in proximity to at least one parent. However, the probability of locating a fledgling with a parent declined as it aged; parents were detected at 94.8% of 116 relocations during days one through nine but were detected at only 48.3% of 29 detections between days 15 and 21 ([[chi square].sub.1,145] = 40.59, P < 0.001).
Throughout the 21 d postfledging period, radiotagged fledglings were consistently located at low perches or on the ground and were rarely observed above 3 m (Table 1). Overall, fledglings were most commonly observed perching in live deciduous trees or shrubs (61.1% of 180 observations), on the ground (20.6%), or on fallen dead branches or logs (12.8%). Of the 110 observations of fledglings perched in deciduous trees or shrubs, 28.2% occurred in American beech, by far the most commonly-used plant substrate.
On day one postfledging, radiotagged birds were located, on average, 29.4 [+ or -] 7.2 m from the nest. As fledgling age increased, the mean distance at which they were detected from their nest also increased (Table 1). By 19-21 d postfledging, radiotagged birds were located, on average, >300 m from their nests (Table 1). However, there was considerable variation among individuals at this age range, with one fledgling located >750 m from its nest, whereas another remained <70 m from its nest and likely still within its natal territory.
Over both years habitat associated with fledgling relocations were sampled for 19 radiotagged birds (14 in 2013, 5 in 2014). Compared to random sites, fledgling use sites had, on average, 1.9 times more woody ground cover, 1.8 times greater mid-story cover from 0-1 m, 2.7 times greater mid-story cover from 1-2 m, and 2.1 times greater sapling density, but had 0.7 times lower density of eastern hemlock trees (Table 2). Of the 180 fledgling relocations, the majority were found in moist forest (70.0%). However, the proportion of relocations in moist forest declined as the fledglings aged, and the diversity of habitats used increased (Table 3).
Veery postfledging survival patterns were consistent with past studies of other passerine species with most mortality concentrated within the first few days postfledging, and predators as the primary mortality source (Kershner et al., 2004; King et al, 2006; Rush and Stutchberry, 2008; Eng et al., 2009; Ausprey and Rodewald, 2011). These patterns likely result from the high vulnerability of newly-fledged young, given their initial limited mobility and inexperience at recognizing and responding to potential predators. In contrast the 21 d fledgling survival rate was quite high. Cox et al. (2014) compiled survival rates during the first 20-21 d postfledging from 24 published studies of passerine birds, finding a range of 0.23 to 0.87 and a mean survival rate of 0.58. The survival rate for this same period observed in my study (0.78) lies near the top of this range and is even high relative to rates observed in most other studies of similar-sized or larger thrush species (summarized in Cox et al., 2014). Perhaps this high survival rate reflects the widespread availability of dense understory cover within my study site; several studies of forest breeding passerines have found a positive correlation between understory vegetation density and postfledging survival (King et al., 2006; Ausprey and Rodewald, 2011; Vitz and Rodewald, 2011).
On average Veery fledglings moved gradually away from their nest as they aged, but there was considerable variation in movement patterns among individuals, particularly during the third week postfledge. This variation could reflect differences in the spatial distribution of important cover or foraging microhabitats among nesting territories (Wightman, 2009; Streby and Andersen, 2013) or in the condition of young at fledging (Vitz and Rodewald, 2010). This variation could also reflect variation in timing of postfledging dispersal. Postfledging dispersal refers to the movement of juveniles away from their natal territories, presumably occurring as they gain independence (Anders et al, 1998; White and Faaborg, 2008; Ausprey and Rodewald, 2013). The timing of this dispersal is often identified by the observation of a sudden large movement away from the natal range (Anders et al., 1998; White and Faaborg, 2008). Of 10 birds monitored through 21 d postfledging, five exhibited large (>350 m) movements away from their natal territories during the third week of tracking. Of the remaining birds, three others exhibited large, sudden movements after 21 d (one each at 22-24 d, 25-27 d, and 31-33 d) (C.B. Goguen, unpubl.). The remaining two fledglings, were each still detected <200 m from their nests at 28-30 d postfledge and then were never detected again (C.B. Goguen, unpubl.), perhaps due to their sudden dispersal.
Fledglings of mature forest passerines often exhibit a preference for dense understory vegetation during the postfledging period (e.g., Anders et al., 1998; King et al., 2006; Rush and Stutchbury, 2008; Ausprey and Rodewald, 2011; Vitz and Rodewald, 2011). I found similar patterns of microhabitat use for Veery fledglings. This apparent preference by fledglings for dense understory presumably relates to concealment from predators, but greater thermal cover or fruit abundance are other possible advantages (Anders et al., 1998; White et al., 2005). In my study American beech was particularly favored as a perching substrate. This is probably because older beech trees often develop dense thickets of root-sprouted saplings around their trunks (Harlow et al., 1979). When a beech thicket was present near a nest, it was common for young fledglings to move rapidly to this feature, sometimes remaining for several days.
In populations of some mature-forest breeding passerines, fledglings have been found to exhibit shifts in habitat using broad habitat types that differ greatly from their natal habitats --particularly early successional forest (Anders et al., 1998; White et al., 2005; Vitz and Rodewald, 2006; Streby and Andersen, 2013; Dittmar et al., 2014). These shifts appear to be related to the increased availability of low, dense woody cover in these habitats but could also relate to increased fruit availability or other factors (Vitz and Rodewald, 2006). Although Veery fledglings used a greater diversity of habitat types as they aged, overall, these fledglings used the same broad habitat types as adults did for nesting, primarily moist forest habitats. This lack of a shift in broad habitat use could be due to a variety of causes. First, it may simply be that habitat shifts were not observed because certain high-quality postfledging habitats were unavailable. Beyond old field habitat, which was used only rarely by fledglings, large patches of early-successional forest were unavailable in the immediate vicinity of my study. Second, it is also possible that the mature-forest nesting habitats in my study area contained adequate areas of dense understory cover such that movement to other nonnesting habitat types was unnecessary (e.g., Streby and Andersen, 2013; Hache et al., 2014). Finally, shifts in broad habitat use could be age-related and may be more apparent in independent fledglings. For example, Wood Thrush fledglings primarily exhibited shifts in habitat use only after reaching independence and dispersing from their natal home ranges (Anders et al, 1998). This dispersal occurred, on average, at 22 d postfledging. Given that my study encompassed only 21 d post fledging, and captured little information about postdispersal habitat use, it is possible that other nonbreeding habitat types, such as early-successional forests, could be sought after by older, independent fledglings after they dispersed more widely into the landscape.
The postfledging period is an important part of a passerines's life cycle, yet basic knowledge of survival and habitat use is lacking for most species (Cox et al, 2014). Within my study area, dependent Veery fledglings exhibited a high survival rate, and used the dense, low microhabitats that they required within the same mature forest habitats that were used for nesting. This study provides the first descriptions of survival and habitat use by fledglings of this declining species. However, there are also limitations that are worth acknowledging. First, these results were based on a modest sample of fledglings collected over just two breeding seasons. A longer-term study would better document the level of annual variation in fledgling survival and would reveal whether the high survival rates observed are typical for this study site. Second, the study was limited to a single, apparently high-quality site. Additional research is needed in different landscapes and under different landscape influences (e.g., timber harvest, urbanization) to better investigate how these factors impact fledgling survival and behavior in this species. Finally, these results were also limited to the postfledging dependent period. Study of the postfledging independent period is also needed as these older and wider-ranging fledglings may use and benefit from a broader suite of habitat types than dependent fledglings, knowledge of which could be important from a conservation perspective.
Acknowledgments.--I thank K. Dolecki and R. Pouffary for assistance with fieldwork. Access and logistical support for this research was provided by the Pennsylvania Department of Conservation and Natural Resources and the staff of Nescopeck State Park. Funding and support for this research was provided by Faculty Research Development Grants from the Pennsylvania State University, Hazleton. Banding and radio-tagging were performed under the author's federal and state bird banding permits, and all methods were carried out with the approval of the Pennsylvania State University Institutional Animal Care and Use Committee, protocol #39918.
Anders, A. D., D. C. Dearborn, J. Faaborg, and F. R. Thompson III. 1997. Juvenile survival in a population of neotropical migrant birds. Conserv. Biol., 11:698-707.
--, J. Faaborg, and F. R. Thompson III. 1998. Postfledging dispersal, habitat use, and home-range size of juvenile Wood Thrushes. Auk, 115:349-358.
Ausprey, I.J. and A. D. Rodewald. 2011. Postfledging survivorship and habitat selection across a rural-to-urban landscape gradient. Auk, 128:293-302.
--and--. 2013. Post-fledging dispersal timing and natal range size of two songbird species in an urbanizing landscape. Condor, 115:102-114.
Bolgiano, N. C. 2012. Veery. P. 322-323. In: A.M Wilson, D.W. Brauning, and R.S. Mulvihill (eds.). Second atlas of breeding birds in Pennsylvania. Penn State University Press, University Park, Pennsylvania.
Cox, W. A., F. R. Thompson III, A. S. Cox, and J. Faaborg. 2014. Post-fledging survival in passerine birds and the value of post-fledging studies to conservation. J. Wildl. Manage., 78:183-193.
Dellinger, R. L., P. Bohall Wood, and P. 1). Keyser. 2007. Occurrence and nest survival of four thrush species on a managed central Appalachian forest. For. Ecol. Manage., 243:248-258.
Dittmar, E. M.. D. A. Cimprich. J. H. Sperry, and P.J. Weatherhead. 2014. Habitat selection by juvenile Black-capped Vireos following independence from parental care. J. Wildl. Manage., 78:1005-1011.
Eng, M. L., B.J. M. Stutchbury, D. M. Burke, and K. A. Elliott. 2009. Influence of forest management on pre- and post-fledging productivity of a Neotropical migratory songbird in a highly fragmented landscape. Can. J. For. Res., 41:2009-2019.
Hache, S., E. M. Bayne, and M. Villard. 2014. Postharvest regeneration, sciurid abundance, and postfledging survival and movements in an Ovenbird population. Condor, 116:102-112.
Harlow, W. M., E. S. Harrar, and F. M. White. 1979. Textbook of dendrology. Sixth edition. McGraw Hill, New York, New York.
Heckscher, C. M. 2004. Veery nest sites in a Mid-Atlantic Piedmont forest: vegetative physiognomy and use of alien shrubs. Atner. Midi. Nat., 151:326-337.
--, L. R. Bevier, A. F. Poole, W. Moskoff, P. Pyle, and M. A. Patten. 2017. Veery (Catharus fuscescens), version 3.0. The Birds of North America Online: http://doi.org/10.2173/bna.veery.03. Accessed 24 May 2018.
Hougaard, P. 1999. Fundamentals of survival data. Biometrics, 55:13-22.
Kaplan, E. I. and P. Meier. 1958. Nonparametric estimation from incomplete observations. J. Atner. Stat. Assoc., 53:457-481.
Kearns, L. J., E. D. Silverman, and K. R. Hall. 2006. Black-throated Blue Warbler and Veery abundance in relation to understory composition in northern Michigan forests. Wilson J. Omithol., 118:461-470.
Kershner, E. L., J. W. Walk, and R. E. Warner. 2004. Postfledging movements and survival of juvenile Eastern Meadowlarks (Sturnella magna) in Illinois. Auk, 121:1146-1154.
King, D. I., R. M. Degraaf, M. I,. Smith, and J. P. Buonaccorsi. 2006. Habitat selection and habitat-specific survival of fledgling Ovenbirds (Seiurus aurocapilla). J. Zool., 269:414-421.
Lee, E. T. 1992. Statistical methods for survival data analysis. John Wiley and Sons, Inc., New York.
Moore, L. C., B.J. M. Stutchbury, D. M. Burke, and K. A. Elliott. 2010. Effects of forest management on postfledging survival of Rose-breasted Grosbeaks (Pheucticus ludovicianus). Auk, 127:185-194.
Naef-Daenzer, B. and M. U. Gruebler. 2016. Post-fledging survival of altricial birds: ecological determinants and adaptation. J. Field Omithol., 87:227-250.
Nudds, T. D. 1977. Quantifying the vegetation structure of wildlife cover. Wild. Soc. Bull, 5:113-117.
Rappole. J. H. and A. R. Tipton. 1991. New harness design for attachment of radio transmitters to small passerines. J. Field Omithol., 62:335-337.
Reitsma, L. R., R. T. Holmes, and T. W. Sherry. 1990. Effects of removal of red squirrels, Tamiasciurus hudonicus, and eastern chipmunks, 'lamias striatus, on nest predation in a northern hardwood forest: an artificial nest experiment. Oikos, 57:375-380.
Rush, S. A. .and B.J. M. Stutchbury. 2008. Survival of fledgling Hooded Warblers (Wilsonia citrina) in small and large forest fragments. Auk, 125:183-191.
Sauer, J. R., D. K. Niven, J. E. Hines, D.J. Ziolkowski, Jr, K. L. Pardieck, J. E. Fallon, and W. A. Link. 2017. The North American Breeding Bird Survey, results and analysis 1966-2015. Version 2.07.2017, USGS Patuxent Wildlife Research Center, Laurel, MD. http://www.mbr-pwrc.usgs.gov/bbs/ bbs.html. Accessed 31 August 2017.
Schmidt, K. A., R. S. Ostfeld, and K. N. Smyth. 2006. Spatial heterogeneity in predator activity, nest survivorship, and nest-site selection in two forest thrushes. Oecologia, 148:22-29.
Sokal, R. R. and F. J. Rohlf. 2011. Biometry. Fourth edition. W. H. Freeman, New York, New York.
Streby, H. M. and D. E. Anderson. 2013. Movements, cover-type selection, and survival of Ovenbirds in managed deciduous and mixed coniferous-deciduous forests. For. Ecol. Manage., 287:9-16.
Vega Rivera, J. H., J. H. Rappole, W. J. McShea, and C. A. Haas. 1998. Wood Thrush postfledging movements and habitat use in northern Virginia. Condor, 100:69-78.
Vitz, A. C. and A. D. Rodewald. 2006. Can regenerating clearcuts benefit mature-forest songbirds? An examination of post-breeding ecology. Biol. Consent., 127:477-486.
--and--. 2010. Movements of fledgling Ovenbirds (Seiurus aurocapilla) and Worm-eating Warbler (Helmitheros vermivorum) within and beyond the natal home range. Auk, 127:364-371.
--and--. 2011. Influence of condition and habitat use on survival of post-fledging songbirds. Condor, 113:400-411.
White, J. D. and J. Faaborg. 2008. Post-fledging movement and spatial habitat-use patterns of juvenile Swainson's Thrushes. Wilson J. Ornithol., 120:62-73.
--. T. Gardali, F. R. Thompson III, and J. Faaborg. 2005. Resource selection by juvenile Swainson's Thrushes during the postfledging period. Condor, 107:388-401.
Wightman, C. S. 2009. Survival and movements of fledgling Western Bluebirds. Southwestern Nat., 54:248-252.
Submitted 5 June 2018
Accepted 1 October 2018
CHRISTOPHER B. GOGUEN (1)
Science Program, Pennsylvania Stale University, 76 University Dr., Hazleton, 18202
(1) Corresponding author: (570) 450-3088; e-mail: firstname.lastname@example.org
Table 1.--Movement patterns and perching heights, by age, of radio-tagged Veery (Catharusfuscescms) fledglings monitored during their first three wk postfledging in northeastern Pennsylvania, 2013 and 2014 Days after fledging 0-3 4-6 [n.sup.1] 29 24 Distance from nest (m): Mean 42.6 [+ or -] 5.5 63.8 [+ or -] 6.7 +SE Range 5.0-127.2 11.2-126.4 Perch height (m): Mean 0.8 [+ or -] 0.1 1.4 [+ or -] 0.3 [+ or -] SE Range 0-2.0 0-5.0 Days after fledging 7-9 10-12 [n.sup.1] 20 12 Distance from nest (m): Mean 73.9 [+ or -] 10.9 100.1 [+ or -] 25.6 +SE Range 12.5-192.1 5.0-325.9 Perch height (m): Mean 2.2 [+ or -] 0.5 1.3 [+ or -] 0.4 [+ or -] SE Range 0-8.0 0-3.8 Days after fledging 13-15 16-18 [n.sup.1] 12 12 Distance from nest (m): Mean 135.7 [+ or -] 27.6 211.9 [+ or -] 47.8 +SE Range 28.5-364.6 25.5-620.0 Perch height (m): Mean 1.4 [+ or -] 0.3 1.5 [+ or -] 0.3 [+ or -] SE Range 0-3.0 0-3.1 19-21 [n.sup.1] 10 Distance from nest (m): Mean 333.0 [+ or -] 61.6 +SE Range 68.2-766.1 Perch height (m): Mean 2.4 [+ or -] 0.7 [+ or -] SE Range 0.6-7.0 (1) Number of radiotagged fledglings from which "Distance from nest" and Perch height" statistics were calculated in each age period Table 2.--Microhabitat features associated with sites used by radiotagged Veery (Calliarus fuscescens) fledglings compared to associated, random sites. Values for all sites are based on n = 19 and are from data collected in northeastern Pennsylvania, 2013 and 2014 Fledgling use sites Mean (se) Median, range Mean (se) Ground cover (%): Live woody 23.6 (2.2) 22.0, 10.3-47.5 12.6 (1.9) Open, unvegetaled 44.9 (2.9) 42.0, 24.0-64.3 50.5 (4.0) Mid-story cover (%): 0-1.0 m 46.0 (3.5) 46.8, 25.9-81.9 25.0 (2.6) 1.0-2.0 m 32.7 (2.9) 34.1, 12.8-57.5 12.2 (1.9) Understory woody plant 9.4 (0.6) 9.8, 3.0-14.5 8.2 (0.6) species richness: Sapling density 16.7 (2.3) 15.3, 2.0-41.3 7.8 (1.5) (Stms/0.008 ha) (2) Tree density (Stms/0.04 ha): All small (8-23 cm DBH) 10.3 (1.1) 11.0, 0.0-20.0 11.2 (1.1) All large (>23 cm DBH) 6.6 (0.6) 6.5, 3.0-12.0 7.8 (0.6) E. hemlock (>8 cm DBH) 0.8 (0.3) 0.0, 0-4.5 2.6 (0.9) Random sites Median, range P (1) Ground cover (%): Live woody 12.3, 2.0-40.0 0.002 Open, unvegetaled 50.0, 27.4-90.5 0.34 Mid-story cover (%): 0-1.0 m 23.4, 5.6-49.1 0.001 1.0-2.0 m 11.9, 0.9-34.7 <0.001 Understory woody plant 8.0, 3.5-14.0 0.29 species richness: Sapling density 6.0, 0.5-27.2 <0.001 (Stms/0.008 ha) (2) Tree density (Stms/0.04 ha): All small (8-23 cm DBH) 10.0, 4.5-24.0 0.45 All large (>23 cm DBH) 7.3, 3.0-12.5 0.10 E. hemlock (>8 cm DBH) 0.5, 0-12.0 0.007 (1) p-value from paired-sample Wilcoxon signed rank tests comparing fledgling use and random sites (2) Saplings were woody stems 2-8 cm DBH Table 3.--Broad habitat types used during the first three wk postfledging by 29 radio-tagged Veeries (Catharus fuscescens) in northeastern Pennsylvania, 2013 and 2014 % use, based on broad habitat types (1) Days fledged [n.sup.2] MF (C) FS FFE DF SDS OF 0 to 7 104 76.9 10.6 8.7 2.9 1.0 0.0 8 to 14 46 65.2 15.2 8.7 2.2 8.7 0.0 15 to 21 30 53.3 6.7 13.3 13.3 6.7 6.7 All (0 to 21) 180 70.0 11.1 9.4 4.4 3.9 1.1 (1) Broad habitat types include: moist forest (MF); forested swamp (FS); forest-field edge (FFE); dry forest (DF); shrub-dominated swamp (SDS), and; old field (OF). See "Methods" for a description of each habitat type (2) Number of fledgling relocations on which the percentages are based, in each age period (3) The proportion of relocations in moist forest habitat relative to all other habitat types combined declined across the three age periods ([[chi square].sub.2,180] = 0.84, P = 0.03)
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|Author:||Goguen, Christopher B.|
|Publication:||The American Midland Naturalist|
|Date:||Jan 1, 2019|
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