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Current Distribution, Relative Abundance, and Landscape-Level Habitat Associations of the Cerulean Warbler (Setophaga cerulea) along the Lower Roanoke River in North Carolina
John P. Carpenter and Jean Richter

Southeastern Naturalist, Volume 12, Issue 4 (2013): 723–737

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723 J.P. Carpenter and J. Richter 22001133 SOUTSoHuEthAeSaTsEteRrnN NNaAtTurUaRliAstLIST 1V2o(4l.) :1722,3 N–7o3. 74 Current Distribution, Relative Abundance, and Landscape- Level Habitat Associations of the Cerulean Warbler (Setophaga cerulea) along the Lower Roanoke River in North Carolina John P. Carpenter1,* and Jean Richter2 Abstract - Setophaga cerulea (Cerulean Warbler) has been inadequately monitored along the Roanoke River in North Carolina since a breeding population was discovered there in 1972. Our objectives were to estimate the Cerulean Warbler’s current population size and distribution along the river, and evaluate landscape habitat characteristics in the Roanoke River Basin among areas used and unused by the same species. In May 2001 and 2011, we surveyed for singing male Cerulean Warblers, primarily by boat, along approximately 160 km of the Roanoke River from Weldon to Williamston in northeast North Carolina. We found Cerulean Warblers in three distinct groups along the Roanoke River during both survey years; however, we detected at least 32.4% fewer males in 2011 (n = 23) than in 2001 (n = 34). The landscape within 500 m of areas used by Cerulean Warblers had significanlty less crop cover, blackwater floodplain (i.e., swamp) forest, and variation in mean canopy height than unused landscapes we surveyed. These same differences existed at distances up to 1 km, but several additional dissimilarities became evident at this scale, including presence of more evergreen plantations and a greater fragmentation of the dominant forested land cover at used versus unused landscapes. We recommend continued monitoring of the Cerulean Warbler along the Roanoke River, increased habitat protection, and encourage an in-depth investigation into management strategies to sustain this population. Introduction In North Carolina, Setophaga cerulea Wilson (Cerulean Warbler) reaches its highest density during the breeding season within the Blue Ridge ecoregion; however, the species has also been encountered throughout the state in both the Piedmont and Coastal Plain (Fig. 1). Although many records from the latter two ecoregions are of a single bird encountered most likely during migration, territorial Cerulean Warbler males were first identified within North Carolina’s coastal plain along the Roanoke River in June 1972 (Lynch 1973). Subsequent boat surveys during the mid-1970s and early 1980s along various portions of the river in Halifax, Northampton, Bertie, and Martin counties produced estimates of at least 40 pairs (Lynch 1981, Parnell 1977). Lynch (1981) reported that approximately 80% of the Cerulean Warbler population occurred along a 60-km river segment from Halifax to Palmyra in Halifax County. In 1992 and 1993, Sallabanks et al. (2000) studied swamp and levee forest bird communities along a 150-km portion of the lower Roanoke River from Halifax to Plymouth, and found Cerulean 1North Carolina Wildlife Resources Commission, 1751 Varsity Drive, Raleigh, NC 27606. 2US Fish and Wildlife Service, Roanoke River NWR, PO Box 430, Windsor, NC 27983. *Corresponding author - john.carpenter@ncwildlife.org. J.P. Carpenter and J. Richter 2013 Southeastern Naturalist Vol. 12, No. 4 724 Warblers only on upstream levee transects. More recent but less thorough surveys of the river from Weldon to Halifax in June 1987, and from Weldon to NC Hwy 258 in late May 1999 resulted in 11 and 7 singing Cerulean Warbler males, respectively (Davis 1999, LeGrand 1988). The Roanoke population is highly isolated and separated by at least 345 km from the nearest breeding group in the mountains of western North Carolina. Historically, Cerulean Warblers bred along the Chickahominy River in Virginia, but are now believed to have been extirpated from that area due to heavy residential development near the river’s headwaters. Although recent expeditions have yet to confirm the warbler’s presence, the middle portion of the Chickahominy is still considered pristine and may support the species (B.D. Watts, College of William and Mary, Williamsburg, VA, pers. comm.). The Cerulean Warbler has experienced a population decline exceeding 4.0% per year, or nearly 70% of its breeding population, in the eastern United States from 1966–2002 (Rich et al. 2004). More recent range-wide estimates suggest that the already imperiled Cerulean Warbler’s status has worsened, with declines of 4.6% per year from 2003–2008 and 8.9% from 2007–2008 (Ziolkowski et al. 2010). As is the Figure 1. Approximate locations for total number (A) and month encountered (B) of adult Cerulean Warblers in North Carolina from 1981–2010 (Cornell Lab of Ornithology 2011, Fiala 2011). 725 J.P. Carpenter and J. Richter 2013 Southeastern Naturalist Vol. 12, No. 4 case for most wildlife, the Cerulean Warbler’s decline is attributed to the loss and degradation of the habitats used throughout its life cycle, which during the breeding season often consists of large forested tracts with tall deciduous trees (Hamel 2000a, b). Parasitism by the Molothrus ater Boddaert (Brown-headed Cowbird), and shortened rotation periods of managed forests have also been cited as potential contributing factors (Hamel 2000a, b). The Cerulean Warbler now receives limited protection under both federal and state laws. The US Fish and Wildlife Service (USFWS) included it on the Birds of Management Concern list (USFWS 2006), and it is ranked as a special concern species by the NC Wildlife Resouces Commission (NCWRC 2005). Results from the breeding bird survey’s (BBS) roadside protocol offer little insight into the health of the Cerulean Warbler population along the Roanoke River floodplain, which occurs along remote stretches of the river and far from BBS survey routes. As a result, it has been difficult to monitor the status of this population consistently over time. Our study objectives were to 1) estimate the Cerulean Warbler’s current population size and distribution along the lower Roanoke River by surveying for singing males, and 2) compare landscape-level habitat characteristics of areas used and unused by the target species to help explain the warbler’s abundance and distribution patterns. Study Area We concentrated our efforts along roughly 160 km of the Roanoke River from Weldon to the outlet of Conine Creek east of Williamston in northeast North Carolina (Fig. 2). This area corresponds to the portion of the river surveyed during the most recent and comprehensive census to date (Lynch 1981). The lower Roanoke River basin is considered one of the most pristine examples of intact bottomland forest in the eastern United States (Fig. 3; Townsend 2001) and also supports some of the highest bird densities and avian species richness reported for similar habitats (Sallabanks et al. 2000). Nonetheless, large portions of the basin have been heavily influenced by human land uses and altered hydrology, the latter of which greatly effects the distribution of plant species among the floodplains (Townsend 2001). The main habitats in our study area are classified as brownwater levee forests (high, medium, and low subtypes), bottomland hardwoods (high, low, and swamp transition subtypes), and cypress-gum swamp habitats (Schafale 2012). The average upper canopy reaches a height of 30 m and is relatively continuous throughout these communities (Sallabanks et al. 2000). The brownwater levee forest high-subtype canopy is distinguished by Fraxinus pennsylvanica Marsh. (Green Ash), Celtis laevigata Willd. (Sugarberry), Platanus occidentalis L. (American Sycamore), Betula nigra L. (River Birch), Acer negundo L. (Boxelder), and Ulmus americana L. (American Elm). Lindera benzoin (L.) Blume (Spicebush), Asimina triloba (L.) Dunal (Pawpaw), Aesculus sylvatica W. Bartram (Buckeye), as well as locally abundant Arundinaria gigantea (Walter) Muhl. (Cane), may be found throughout the shrub layer (Lynch 1981). The brownwater bottomland hardwood J.P. Carpenter and J. Richter 2013 Southeastern Naturalist Vol. 12, No. 4 726 high subtype occurs in areas where flooding is more prevalent, with Quercus spp. (oaks), Carya spp. (hickories), and Liquidambar styraciflua L. (Sweetgum) replaced by more water-tolerant species in the swamp transition subtype, including Quercus laurifolia Michx. (Laurel Oak) and Taxodium distichum (L.) Rich. (Bald Cypress) (Schafale 2012). Cypress-gum swamps (brownwater subtype) are flooded for long periods and characterized by Nyssa aquatica L. (Water Tupelo), Nyssa biflora Walter (Swamp Tupelo), and Bald Cypress, with very little to no mid- or understory (Schafale 2012). Agricultural lands can be found in varying densities Figure 2. Study area surveyed for Cerulean Warblers along the Roanoke River, NC, from May 12–14 2001, and from May 14–15 and May 28–29 2011. 727 J.P. Carpenter and J. Richter 2013 Southeastern Naturalist Vol. 12, No. 4 Figure 3. A segment of the Roanoke River (left) and habitat used by a Cerulean Warbler male (right) near Weldon, NC, May 2011. and sizes throughout the floodplains but are often restricted to higher elevated terraces (Sallabanks et al. 2000). Beginning in the early 1980s, The Nature Conservancy (TNC), USFWS, and NCWRC began a major land-acquisition project encompassing over 36,400 ha along the Roanoke River to protect the river’s floodplain forests and promote future conservation efforts. Methods Bird surveys We surveyed for singing Cerulean Warbler males from May 12–14 in 2001, and May 14–15 and May 28–29 in 2011. Surveys were conducted primarily by boat, and motors were occasionally used to quickly bypass areas that did not appear to be suitable Cerulean Warbler habitat (e.g., cleared fields, forest stands with low canopy heights). Several areas inaccessible by boat and adjacent to the river were also investigated on foot. Although we attempted to mimic foot survey routes to ameliorate comparison between years, not all areas surveyed in 2001 were revisited in 2011, and some new locations were visited only in 2011. Observations began at sunrise and ended at approximately 11:00 am; however, a few surveys continued until 12:00–1:00 pm if birds were still actively singing. Playback of a conspecific Cerulean Warbler song was periodically used to elicit the response of males. In 2011, we revisited areas of concentrated Cerulean Warbler activity during the second survey weekend and considered encounters independent if the nearest singing neighbor was >200 m away (Robbins et al. 2010). Recreational-grade global positioning system (GPS) units were used to record approximate locations of Cerulean Warbler males. When possible, we recorded locations directly beneath singing males; otherwise, GPS coordinates were taken from boats nearby the birds. Data analyses Spatial distribution. Because of the Cerulean Warbler’s tendency to form colonylike groups in some parts of its range (Hamel 2000a, b), we performed a 2nd-order J.P. Carpenter and J. Richter 2013 Southeastern Naturalist Vol. 12, No. 4 728 point-pattern analysis using Ripley’s K function to determine if the population was aggregated, uniform, or exhibited complete spatial randomness (CSR) over a range of distances (Ripley 1976). We used PASSaGE version 2 to estimate K(d), which is equal to the average number of points (i.e., locations of Cerulean Warbler males) within a given distance (d) divided by the total number of points per unit area, or λ = n / A (Rosenberg and Anderson 2011). We analyzed patterns up to 25% of the maximum distance between points at 100-m intervals and used a weighted edge correction to control for boundary edge effects (Diggle 1983, Haase 1995). A linear transformation of K(d), known as L(d) and equal to √(K(d)/π) - d, was performed to stabilize the variance whereby values >0 indicate clumping, values <0 indicate a uniform distribution, and values equal to 0 indicate CSR (Hessburg et al. 2010). We performed 499 randomized simulations to construct a 95% confidence envelope of the observed patterns to create a new point pattern using the same number of points but with random locations (Rosenberg and Anderson 2011). Landscape associations. Landscape-level habitat characteristics, including predominance of deciduous forest cover (Rodewald 2004, Thompson et al. 2012, Wood et al. 2006, but see McElhone et al. 2011), forest tract size (Hamel et al. 2005, Robbins et al. 1989), and distance to mountaintop mining operations (Weakland and Wood 2005), have been shown to influence the Cerulean Warbler’s selection of breeding habitat. Therefore, to obtain a better understanding of their macro-habitat requirements in the Roanoke River basin and to help ascertain whether or not their populations are limited by the composition and configuration of the surrounding landscape, we compared landscape features within areas used and unused by Cerulean Warblers. We defined used habitat as GPS locations of Cerulean Warbler males and unused habitat as randomly generated points placed along the river within the study area where the species was not detected (Fig. 2). We examined habitat at two scales by creating 500-m and 1-km buffers around each location. We chose 500 m because it is a size at which many neotropical species have been shown to associate significantly with at least one landscape variable (Lichstein et al. 2002), and 1 km due to its use in other landscape studies of Cerulean Warblers (Rodewald 2004, Weakland and Wood 2005). We calculated the percentage of land-cover types and landscape-fragmentation metrics (McGarigal and Marks 1995) using the Southeast Gap Analysis Project’s 2001 30-m2 land-cover data set (SEGAP; USGS 2008) and the ArcGIS extension Patch Grid FRAGSTATS interface (ESRI 2008, Rempel et al. 2010). We also incorporated 18-m2 footprint light detection and ranging (LiDAR) data from the 2001 NC floodplain mapping program (Newcomb and Mitasova 2009) to assess canopy height and its variability across the landscape. We masked all hydrological areas and removed values >60 m in height from the LiDAR data to ensure that no mamade structures were included in the analysis. We included only sites where Cerulean Warblers were detected in the 2001 survey because of the temporal similarity with the spatial data. All of our variables displayed skewed or bimodal distributions, and our attempts to normalize them using logarithmic and square root transformations were 729 J.P. Carpenter and J. Richter 2013 Southeastern Naturalist Vol. 12, No. 4 unsuccessful. Therefore, we used Mann-Whitney U-tests to compare median values of landscape variables from used and unused plots. All statistical analyses were performed in SPSS® version 15 (SPSS, Inc. 2006), unless described elsewhere. Results We detected a total of 38 Cerulean Warbler males in 2001 and 24 (19 on May 14–15, and 5 on May 28–29) in 2011. When comparing only males encountered along routes that were surveyed both years, we counted 34 and 23 Cerulean Warblers in 2001 and 2011, respectively. More Brown-headed Cowbirds were detected overall in 2001 (n = 137) than in 2011 (n = 63), and during encounters with Ceruelan Warblers in 2001 (n = 20) than in 2011 (n = 3). Cerulean Warblers were found in three distinct, spatially clustered groups along the Roanoke River (Figs. 4, 5). The first group’s occurrence began near the town of Weldon and extended to the south end of Mush Island where we detected 17 birds in 2001, one of which was an outlier roughly 11.5 km downstream, and 11 birds in 2011. The second group was in the vicinity of Buzzard’s Point with 10 birds detected in 2001 and 9 in 2011. The third group ranged from near Black Gut, on Broadneck Swamp, to Poplar Point with 9 and 5 birds heard there in 2001 and 2011, respectively. Most singing Cerulean males were found in areas associated with levee forests dominated by Green Ash, Sweetgum, American Sycamore, Acer rubrum L. (Red Maple), and Acer saccharinum L. (Silver Maple). Figure 4. Adjusted Ripley’s K (L[d]) for Cerulean Warbler distribution along the Roanoke River. Values >0 indicate clumping, values <0 indicate a uniform distribution, and values equal to 0 indicate complete spatial randomness (CSR). J.P. Carpenter and J. Richter 2013 Southeastern Naturalist Vol. 12, No. 4 730 We detected differences between areas used and unused by Cerulean Warblers at two different scales (Table 1). The landscape within 500 m of areas used by Cerulean Warblers had significanlty less blackwater floodplain (i.e., canopy dominated by Bald Cypress and Swamp Tupelo) forest (Z = -2.53, P < 0.01), less crop cover (Z = -2.66, P < 0.01), and less variation in mean canopy height (Z = -3.41, P < 0.00) Figure 5. Distribution of Cerulean Warbler males detected during surveys of the Roanoke River in May 2001 and 2011. Land cover data from 2001 (top) and 2006 (bottom) National Land Cover Database. 731 J.P. Carpenter and J. Richter 2013 Southeastern Naturalist Vol. 12, No. 4 Table 1. Comparisons of landscape metrics within 500 m and 1 km of locations used and unused by Cerulean Warbler males along the Roanoke River, 2001. Values are median (interquartile range) for Mann-Whitney U-tests. Basis of analysis was Southeast Gap Analysis Project’s 2001 land-cover data set (USGS 2008). An “a” next to P-value indicates where differences significant exist at an alpha level ≤ 0.05. 500 m 1 km Landscape variable Used Unused Z P Used Unused Z P Fragmentation Mean nearest neighbor (m) 73.1 (47.8) 70.1 (33.4) -0.11 0.91 75.0 (42.9) 77.5 (29.2) -0.03 0.98 Number of patches 53.0 (91.8) 69.5 (72.0) -0.80 0.42 175.5 (274.0) 210.0 (163.5) -0.27 0.79 Edge density (m/ha) 157.6 (195.1) 166.1 (146.8) -0.23 0.82 156.3 (164.4) 145.8 (116.6) -0.53 0.60 Shannon diversity index 1.5 (1.4) 1.6 (0.9) -0.34 0.74 1.6 (1.1) 1.6 (0.8) -0.27 0.79 Total core area (ha) 40.5 (34.5) 41.6 (23.7) -0.23 0.82 171.8 (120.2) 190.4 (80.6) -0.80 0.43 Largest patch index (%) 34.9 (40.1) 40.0 (21.0) -0.10 0.92 22.4 (41.8) 40.5 (22.4) -2.12 0.03a Landscape shape index 4.6 (4.3) 4.8 (3.2) -0.19 0.85 8.0 (7.3) 7.6 (5.2) -0.53 0.60 Patch richness 12.5 (7.8) 12.5 (6.0) -0.69 0.49 15.0 (3.0) 15.0 (4.5) -1.22 0.22 Land cover Dry mesic oak (%) 15.8 (37.5) 6.8 (13.1) -1.38 0.20 13.9 (29.1) 6.9 (12.9) -1.28 0.20 Mesic hardwood/mixed (%) 0.1 (1.7) 0.0 (2.2) -0.06 0.95 0.5 (2.3) 0.1 (2.6) -0.11 0.95 Peatland pocosin (%) 0.3 (1.8) 0.1 (1.1) -1.65 0.10 0.6 (1.6) 0.2 (1.1) -1.70 0.09 Blackwater floodplain (%) 0.0 (0.0) 0.0 (0.0) -2.53 0.01a 0.0 (0.0) 0.0 (0.0) -2.04 0.04a Brownwater floodplain (%) 30.7 (77.9) 45.2 (46.5) -0.40 0.70 31.9 (66.4) 48.4 (50.8) -0.26 0.80 Pasture (%) 0.3 (1.0) 0.6 (1.8) -1.61 0.11 0.9 (2.6) 1.3 (2.8) -1.29 0.20 Crop (%) 1.6 (7.2) 8.2 (22.8) -2.66 0.01a 9.6 (17.6) 14.8 (20.0) -2.37 0.02a Evergreen plantation (%) 1.5 (8.0) 0.5 (1.7) -1.32 0.19 5.2 (11.2) 0.7 (2.2) -2.28 0.02a Clearcut (%) 0.0 (0.1) 0.0 (0.1) -0.72 0.47 0.1 (0.3) 0.0 (0.1) -1.80 0.07 Shrub/scrub (%) 0.1 (1.3) 0.3 (1.0) -0.30 0.77 0.5 (2.3) 0.4 (1.0) -0.37 0.71 High development (%) 0.0 (0.0) 0.0 (0.0) 0.00 1.00 0.0 (0.0) 0.0 (0.0) -0.04 0.97 Canopy Height (m) 19.1 (16.3) 18.0 (8.2) -0.43 0.67 18.0 (13.8) 16.0 (6.4) -0.48 0.63 Maximum height (m) 36.5 (3.7) 36.8 (5.0) -0.93 0.36 39.2 (5.0) 38.5 (5.8) -1.07 0.28 Deviation in height (m) 7.9 (3.3) 10.1 (3.0) -3.41 0.00a 8.6 (3.2) 10.4 (2.9) -2.94 0.00a J.P. Carpenter and J. Richter 2013 Southeastern Naturalist Vol. 12, No. 4 732 than unused landscapes. These same differences existed at distances up to 1 km; however, used areas at this latter scale also had significanlty more evergreen plantations (-2.28, P < 0.02) and greater fragmentation within the brownwater floodplain forests (Largest Patch Index: Z = -2.12, P < 0.03). Dissimilarities between the two landscapes also approached signficance at the 1-km scale in that used habitat had more extensive peatland pocosin (Z = -1.70, P < 0.09) and clearcuts (Z = -1.80, P < 0.07) than unused habitat. Discussion We detected 32.4% fewer Cerulean Warbler males in 2011 than in 2001 along the lower Roanoke River of North Carolina. Recently, population declines have been reported in several regions on the periphery of the Cerulean Warbler’s core breeding range, including Ontario (Environment Canada 2011), northern Alabama (J.P. Carpenter, pers. obs.), Maryland (P. Stango, Maryland Department of Natual Resources, Annapolis, MD, pers. comm.), Delaware (Breeding Bird Atlas Explorer 2011), Connecticut (G. Krukar, Connecticut Department of Energy and Environmental Protection, Hartford, CT, pers. comm.), and Oklahoma (Cavalieri et al. 2011). It has been asserted that changes in climate have altered the peak availability of songbird prey, and that this mismatch in bird arrival and food quantity has caused declines in bird populations (Both et al. 2006). Cerulean Warblers are considered an early migrant, arriving at and departing from their breeding grounds before most other wood-warbler species (Dunn and Garrett 1997). This adaptation constrains them to typically raising only a single brood per season (Hamel 2000a), and, theoretically, makes them more susceptible to reduced insect availability during this contracted period when energy demand is high. We detected slight trends in warming and reduced precipitation during the months April–August from 2001–2011 (Fig. 6; State Climate Office of North Carolina 2012); however, changes in mean temperature (R2 = 0.31), number of days >35 °C (95 °F) (R2 = 0.11) and mean rainfall (R2 = 0.09) were not significant. Although the decline suggested by our survey results is troubling, the volume of noise produced by a periodical Magicicada spp. (cicada) outbreak in 2011 may have drowned out distant male Cerulean Warbler songs, and even Brown-head Cowbird songs, thereby affecting our estimates. Furthermore, because it was difficult to standardize observer skill, float speeds, and the use of playbacks, our ability to more accurately compare results between years may have been compromised. Clearly, Cerulean Warblers exhibited a clumped distribution along the Roanoke River at several scales. This may not have always been the case because a large portion of the segment of the Roanoke River most heavily used by Cerulean Warblers in the mid- to late 1970s is now completely devoid of singing males. In 2001, we conducted a crude habitat evaluation along the river and documented numerous clearcuts with minimal riparian buffers (J. Richter, unpubl. data). This loss of hardwood levee forest, primarily along the Occoneechee Neck, would have occurred outside of the time period during which we conducted our landscape analysis, but 733 J.P. Carpenter and J. Richter 2013 Southeastern Naturalist Vol. 12, No. 4 may now be represented by the greater percentage of row-crop cover present in unused areas throughout the floodplain and toward the upland. We detected relatively few differences in the composition and configuration of landscape metrics between areas used and unused by Cerulean Warblers. As described earlier, the forested habitats directly adjacent to the Roanoke River are more diverse than the single cover-type (i.e., brownwater floodplain forest) depicted in the SEGAP schema that dominated our study area. The ecotone between a levee forest and tupelo/cypress swamp, although less abrupt than that of a clearcut or crop field, appears to also act as a barrier to Cerulean Warbler dispersal within our study landscape and downstream beyond Williamston, NC. Cerulean Warblers have demonstrated some resiliency to changing land-use practices and disturbances that interrupt the contiguous forest cover they typically favor (Carpenter et al. 2011, Jones et al. 2001, Rodewald 2004, Weakland and Wood 2005); nonetheless, uncertainty remains regarding the threshold at which the birds can tolerate such alterations. Within the lower Roanoke River basin, the combined presence of agriculture, evergreen plantations, swamp forest and clearcuts, as well as a more highly variable canopy height, suggests that the landscape farther away from currently occupied habitat may not be suitable for establishment of additional territories, and further study Figure 6. Mean maximum temperature, number of days >35 °C (95 °F), and mean rainfall observed from April–August 2001–2011, at the NC Department of Agriculture’s Peanut Belt Research Station in Lewiston, NC (36.13°N, 77.18°W). J.P. Carpenter and J. Richter 2013 Southeastern Naturalist Vol. 12, No. 4 734 might yield insights into what the Cerulean Warblers’ thresholds of tolerance to disturbance might be. While beyond the scope of this paper, the importance of smaller, plot-level vegetation characteristics, such as canopy gaps and vertical structure, have been suggested as more consequential to Cerulean Warbler habitat selection than the quantity and arrangement of broad-scale features (McElhone et al. 2011). According to Buehler et al. (2008), Cerulean Warblers in general, and especially those in agriculturally-dominated landscapes, are unable to reliably maintain stable populations because of high rates of nestling predation, brood reduction, risks associated with long-distance migration, and loss of wintering habitat. Therefore, we assume that the Roanoke River population is a sink, where mortality outpaces reproduction or immigration, due to its small size, restricted habitat availability, and geographic isolation. The potential of the Cerulean Warbler population on the Roanoke River to reach 100 pairs (Hunter et al. 2001) cannot be achieved without adequate monitoring, management, and most importantly, increased habitat protection. We highly recommend consistent monitoring in the Roanoke River basin to determine whether our results indicate a truly persistent decline. We also recommend evaluation of microhabitat features of sites used by the species, estimation of reproductive success, and an investigation into management protocols used elsewhere, and their compatibility for Cerulean Warbler management in the Roanoke River basin. Furthermore, additional surveys for Cerulean Warblers are needed on other major waterways in eastern North Carolina where suitable habitat may be present, such as the Meherrin, Tar, and Neuse rivers, as well as Fishing and Swift creeks. Acknowledgments Funding for our study was provided by North Carolina State Wildlife Grants (SWG) program of the USFWS. We especially thank Coastal Lumber Company and Brad Antil for granting access to their property. We are indebted to many individuals who volunteered their time to assist with these surveys: David Allen, Jack Baker, Brady Beck, Matt Connolly, Derb Carter, Ed Corey, John Finnegan, Charlotte Goesche, Boyd Goss, Jeffrey Hall, Elaine Hammond, John Hammond, John Hardister, Jeff Horton, Cynthia Janes, Adam Johnson, Harry LeGrand, J. Merrill Lynch, Brian McLean, Nora Murdock, Eddie Owens, Chuck Peoples, Johnny Parks, Will Rowland, Doak Wilkins, and John Wright. Dr. Yong Wang graciously provided statistical assistance. The comments of two anonymous reviewers and Ron Taylor were vital to the publication of this manuscript and are greatly appreciated. Literature Cited Both, C., S. Bouwhuis, C.M. Lessells, and M.E. Visser. 2006. Climate change and population declines in a long-distance migratory bird. Nature 441:81–83 Breeding Bird Atlas Explorer. 2011. 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