An International Journal of Ecology, Evolution and Environment

Transcription

1 An International Journal of Ecology, Evolution and Environment Effects of Forest Treatments on Abundance and Spatial Characteristics of Cerulean Warbler Territories KYLE J. KAMINSKI AND KAMAL ISLAM 1 Department of Biology, Ball State University, Muncie, Indiana 47306

2

3 Am. Midl. Nat. (2013) 170: Effects of Forest Treatments on Abundance and Spatial Characteristics of Cerulean Warbler Territories KYLE J. KAMINSKI AND KAMAL ISLAM 1 Department of Biology, Ball State University, Muncie, Indiana ABSTRACT. We examined effects of forest treatments on Cerulean Warbler relative abundance and spatial attributes of territories between pretreatment ( ) and post treatment ( ) years in Yellowwood and Morgan-Monroe state forests in southern Indiana. Three management units received uneven aged harvests (patch cuts), three units received even aged harvests (shelterwood and clearcut), and three units received no treatment (control). Cerulean Warblers occurred in greater abundance at study sites that received even aged harvests than in uneven aged harvested stands based on point - count surveys. Cerulean Warblers were attracted to areas with large canopy gaps resulting from evenaged harvests. Territory sizes were not significantly smaller after harvest treatments. Cerulean Warbler territories on harvested and control sites were clustered, closer to roads and streams, and on steeper slopes with an eastern aspect compared to random sites. Our relative abundance estimates suggested that Cerulean Warblers responded positively to some types of forest treatments during the 2 y post harvest period. INTRODUCTION Cerulean Warblers (Setophaga cerulea) are migratory passerines with a breeding range that extends across the midwestern and eastern deciduous forests of the United States and parts of southern Ontario and Quebec, Canada. In South America, they winter on the eastern slopes of the northern Andes Mountains at middle and lower elevations ( m) from Colombia to Peru and regions of Venezuela (Robbins et al., 1992; Hamel, 2000). An annual range wide population decline has been estimated to be 4.1% (Sauer et al., 2008) over the past 40 y, which represents the greatest annual rate of decline among wood warblers (Jones et al., 2008). This species is listed as a top priority for conservation action by Partners in Flight (Hamel et al., 2004) with a federal and state listing of Endangered in Canada (COSEWIC, 2010) and Indiana ( pdf), respectively, and as Vulnerable worldwide by the International Union for the Conservation of Nature (BirdLife International, 2004). Cerulean Warblers prefer large tracts of mature deciduous forest (Hamel, 2000). They are most commonly found in forests featuring a heterogeneous forest structure with multiple canopy layers in multi age stands and appear to prefer many large dominant trees within their territories (Jones and Islam, 2006; Roth and Islam, 2008). Typically, in Indiana, these forests are dominated by oak-hickory (Quercus-Carya) species on the uplands, with American beech (Fagus grandifolia), red oak (Quercus rubra), sugar maple (Acer saccharum), and white ash (Fraxinus americana) as common mesic species that dominate forested ravines (Homoya et al., 1985). Several authors have noted that Cerulean Warblers are associated with canopy gaps, which are likely important to the species (e.g., Oliarnyk and Robertson, 1996; Bosworth, 2003; Wood et al., 2006). The creation of canopy gaps through forest management may help mimic mature forests (Bakermans and Rodewald, 2009). Canopy gap size may play a role in 1 Corresponding author: kislam@bsu.edu; telephone (765) /8820; fax (765)

4 112 THE AMERICAN MIDLAND NATURALIST 170(1) territories selected by Cerulean Warblers, but Cerulean Warbler occurrence and density in relation to use of openings and edges at both large and small scales require further study (Hamel et al., 2004; Weakland and Wood, 2005). There has been little research on Cerulean Warbler response to forest treatments. In West Virginia, Cerulean Warblers occurred at a lower abundance and frequency in 15 to 18 y old regenerating clearcut stands than in 70 to 80 y old mature second growth forests (Wood et al., 2005). Cerulean Warbler habitat needs, in Indiana, appeared to be supported by a y cutting cycle combined with uneven aged management and timber stand improvement practices (Register and Islam, 2008). Cerulean Warbler response to experimental habitat manipulation has been identified as an important research priority (Hamel et al., 2004). There is a need to identify characteristics of preferred vegetation structures and how to produce them on the landscape and to quantify the spatial attributes of Cerulean Warbler territories. We designed our study to assess the relative abundance and spatial characteristics of Cerulean Warbler territories before and after two methods of forest harvesting were implemented in southern Indiana. Our objectives were to: (1) measure Cerulean Warbler relative abundance and territory sizes in study areas before and after forest treatments were applied, (2) identify any changes in the degree of territory clustering 1 y post harvest, (3) identify spatial characteristics of Cerulean Warbler territories, including slope, aspect, elevation, and distance to streams, roads, and coniferous forest patches, and (4) assess the effects of forest treatments on the overall Cerulean Warbler population in our study areas. We hypothesized that Cerulean Warblers would occur in greater numbers in management units receiving forest treatments that removed fewer trees from the landscape because these treatments would mimic canopy gaps that occur naturally as tree falls, compared to more intensive treatments. METHODS Study area. The Hardwood Ecosystem Experiment (HEE), a large scale and long term (100 y ) experimental study of forest management impacts on plants and many types of animals, is a research collaboration among several institutions and organizations. Nine management units, five within Yellowwood State Forest (9444 ha located within a 6 Km radius from Lat/Long / ) and four within Morgan-Monroe State Forest (9716 ha located within a 10 Km radius from lat/long / ) in southern Indiana (Fig. 1) are in the HEE. Each management unit had a 200 ha core area, where forest treatments occurred, surrounded by a buffer (management units were arranged in area from 303 to 483 ha). Six management units received forest harvest treatments and three were selected as controls. Three management units received patch cuts to create uneven aged forests (sites 1, 7, and 8; Fig. 1). Each patch cut harvest unit received eight cuts, which created a gradient of openings ranging from 0.4 to 2 ha (Fig. 2). These openings were dispersed across ridges, north and south slopes, and bottomlands. Three management units were treated with both shelterwood and clearcut harvests, with the intent to create even aged forests (sites 3, 6, and 9; Fig. 1). Shelterwood and clearcut harvested areas each received four cuts per site (Fig. 2). Shelterwood harvests consisted of preparatory cuts that removed the under and mid story and left most of the canopy intact. Two 4 ha shelterwood harvests and two 4 ha clearcuts, applied to each of the three even aged units, occurred on slopes in each cardinal direction. The three remaining management units (2, 4, and 5; Fig. 1) remained untreated and served as control sites. Forest treatments began in Jul., 2008 after most Cerulean Warblers had left the study sites and were completed by Feb., 2009.

5 2013 KAMINSKI &ISLAM: CERULEAN WARBLER TERRITORY RESPONSE TO FOREST TREATMENT 113 FIG. 1. Location of nine study sites in Morgan, Monroe, and Brown counties in southern Indiana Years 2007 and 2008 represented pretreatment conditions and were our post treatment conditions. We conducted our study from 1 May through 15 Aug., Within each management unit, a 225 ha study site for sampling was superimposed, on each 200 ha treated and control core areas in Morgan-Monroe State Forest and Yellowwood State Forest, within a larger contiguous block of forested lands. Bird surveys. We performed 100 m fixed radius point count surveys, during May , at all sites each year. We established seven transect lines at every site, each with seven points (49 points/site) spaced 200 m apart. This distance was used to minimize duplicate samplings as male Cerulean Warblers broadcast their songs a distance of about 100 m (Jones et al., 2000; Hamel et al., 2009). Surveys were conducted between 0530 and 1030 h EST. We did not conduct surveys during periods of rain or wind that prevented vocalizations from being heard. We surveyed each point for 5 min. We initially listened for 2 min after arriving at a particular point. We then broadcasted a male Cerulean Warbler song using an audio cassette player with a speaker, for 1 min, to elicit a response from any males in the immediate area. Listening resumed again for the final 2 min (Falls, 1981). We estimated distance from the point and compass direction when a male Cerulean Warbler was detected. We used a random numbers table to identify the order in which the study sites were surveyed from first to last to eliminate potential bias on the sequence and date that units were sampled in May each year. Territory mapping. We mapped territories from 1 Jun. to 15 Jul. for the 4 y of the study. Fewer territories were demarcated in 2008 than in later years because harvests was implemented in Jul. before all territories had been delineated. For all territories, we marked trees, where a Cerulean Warbler was observed singing multiple times, with flagging tape and recorded coordinates of the tree location with a Global Positioning System (GPS). We

6 114 THE AMERICAN MIDLAND NATURALIST 170(1) FIG. 2. Examples of a shelterwood/clearcut and patch cuts (PC) harvest sites as part of the Hardwood Ecosystem Experiment. Each polygon represents a harvested area. Both sites are in Yellowwood State Forest, Indiana. Forest treatments began in Jul and were completed by Feb Black dots represent sampling grid with survey points 200 m apart revisited a known territory multiple times before final demarcation (4 to 12 song perch trees flagged). We imported coordinates of all tree points into ArcMap (ESRI, Redlands, CA) to create territory polygons using the minimum convex polygon method. Spatial characterization of territories. We obtained aerial photographs taken in 2006 from the Indiana Spatial Data Portal ( These were the most recent high resolution (15 cm pixel size) photographs available. We used aerial photographs to digitize roads, streams, and coniferous forest patches on our study sites. Aerial photographs were also used to measure the distance of Cerulean Warbler territory centroids to roads and streams in ArcMap. We obtained a digital elevation model (DEM) from the Indiana Spatial Data Portal website to identify elevation, slope, and aspect of Cerulean Warbler territories. We used the distances between the centroids of each territory and the nearest neighboring territory in a nearest neighbor analysis (Krebs, 1989), using the average nearest neighbor tool in ArcMap. We also imported the coordinates of each systematically placed survey point, where birds were not detected, and randomly selected some of these points to compare spatial characteristics of Cerulean Warbler territories to these random unused sites over 3 y ( ). Statistical analyses. We used one way Analysis of Variance (ANOVA) to examine differences in the number of Cerulean Warbler detections and territory sizes among sites designated for even aged treatments (shelterwood/clearcut), uneven aged treatments (patch cuts), and control sites prior to harvest ( ). We reasoned if there were no differences, then any differences found after harvests were a response to the treatments. We used two way repeated measures ANOVA with time (pretreatment years versus post treatment years ), group (even aged, uneven aged, and control), and their interactions to explain changes in relative abundance and territory size between pre and post harvest conditions. Independent samples t-tests were used for all landscape level

7 2013 KAMINSKI &ISLAM: CERULEAN WARBLER TERRITORY RESPONSE TO FOREST TREATMENT 115 TABLE 1. Annual Cerulean Warbler estimates of relative abundance in Yellowwood and Morgan- Monroe state forests in southern Indiana according to study site and harvest type, Forest treatments began in Jul and were completed by Feb PC 5 patch cuts, SW/CC 5 shelterwood/clearcut, n 5 Number of males detected, and R.A. 5 Relative abundance (males/km 2 ) Pre-harvest Post-harvest Site/Harvest n 2007 R.A n 2008 R.A n 2009 R.A n 2010 R.A PC (uneven-aged) SW/CC (even-aged) Control (no harvest) TOTAL comparisons between territory locations and random nonuse sites regardless of harvest. All statistical tests used were performed at a level of significance. A nearest neighbor analysis was performed in ArcMap. All nonnormal data were transformed to base of natural logarithm to approximate a normal distribution before analysis (IBMSPSS Statistics version 20). RESULTS Relative abundance. Prior to treatment ( ), we found no significant difference in the number of Cerulean Warbler detections (F , df 5 2, 15, P ) among the three groups (even aged, uneven aged, and control). We detected 94 male Cerulean Warblers in 2007, 124 in 2008, 135 in 2009, and 93 in 2010 (Table 1). Sites three (shelterwood/clearcut) and eight (patch cuts) contained the highest total detections over a 4 y period (Table 1). For the two way ANOVA, although no main effects for time and group were found, there was a significant time by group interaction (F , df 5 2, 15, P ), which would indicate that some differences occurred among the three groups after treatment. Post hoc analysis showed there was a significant decrease in mean numbers of birds detected from pretreatment years to post treatment years for uneven aged sites (F , df 5 1, 15, P ) but an increase for even aged sites (F , df 5 1, 15, P ; Table 2). We found no difference in mean number of birds detected on control sites (F , df 5 1, 15, P ; Fig. 3) between pre and post treatment years. Territory size. We observed no difference in the size of Cerulean Warbler territories (F , df 5 2, 10, P ) among the three groups (even aged, uneven aged, and control) for the two combined pretreatment years ( ). We marked 254 Cerulean Warbler territories from Mean territory sizes ranged from 0.09 ha to 0.86 ha (Table 3). We found no main effects or interactions among the three groups between pre and post treatment years (F , df 5 2, 10, P ) indicating there was no change in territory

8 116 THE AMERICAN MIDLAND NATURALIST 170(1) TABLE 2. Log transformed comparisons of mean relative abundances and territory sizes 6 1 SD (sample size) in Yellowwood and Morgan-Monroe state forests in southern Indiana according to harvest type from 2007 to Pre-harvest: 2007 and Post-harvest: 2009 and Forest treatments began in Jul and were completed by Feb PC 5 patch cuts and SW/CC 5 shelterwood/ clearcut harvests Harvest type Mean 6 1 SD (n) 2007/2008 Relative abundance Mean 6 1 SD (n) 2009/2010 Mean 6 1 SD (n) 2007/2008 Territory size Mean 6 1 SD (n) 2009/2010 PC (6) (6) (4) (4) SW/CC (6) (6) (5) (5) Control (6) (6) (4) (4) size over time for the treatment groups or control (Tables 2 and 4). We obtained ArcGIS shapefiles of the harvests from the U.S. Forest Service and determined that, in total, only 75.7 ha were actually harvested, meaning that 6.43% of the total forest within the six sites receiving harvest was removed. Spatial attributes of territories. Mean distance of territory centroids to the nearest neighboring territory centroid in 2007, 2008, and 2009 was 126.5, 188.4, and m, respectively. We performed a nearest neighbor analysis and found 82.8%, 51.8%, and 85.5% FIG. 3. Relative abundance estimates of Cerulean Warblers in response to forest treatments in southern Indiana, Forest treatments began in Jul and were completed by Feb Pre- and post-treatment relative abundance estimates were significantly different for uneven and evenaged sites but not for control sites

9 2013 KAMINSKI &ISLAM: CERULEAN WARBLER TERRITORY RESPONSE TO FOREST TREATMENT 117 TABLE 3. Annual Cerulean Warbler territory sizes in Yellowwood and Morgan-Monroe state forests in southern Indiana according to study site and harvest type, Forest treatments began in Jul and were completed by Feb PC 5 patch cuts (uneven-aged) and SW/CC 5 shelterwood/ clearcut (even-aged) harvest sites. Values reported as mean 6 1 SD Pre-harvest Post-harvest Harvest Site 2007 n territories Area (ha) 2008 n Territories Area (ha) 2009 n Territories Area (ha) 2010 n Territories Area (ha) PC SW/CC Control Total of territories were clustered in 2007, 2008, and 2009, respectively. Combined across those 3 y, we found that territories were located significantly closer to streams (P ) and roads (P ), and in areas with greater slope (P ) than corresponding unused random points (Table 5). The mean aspect of territories of degrees was different (P, 0.001) from random sites, suggesting that Cerulean Warblers preferred southeast facing slopes. There was no difference between elevation of territories and elevation of random points (P ). Cerulean Warbler territories were located closer to coniferous forest patches than expected based on their availability (P, 0.001; Table 5). DISCUSSION Cerulean Warblers were more abundant on sites in management units that received even aged harvests and were less abundant on sites that received uneven aged harvests (Fig. 3) while control site densities did not change over 4 y. Our prediction that Cerulean Warblers would occur in greater abundance in sites with small openings created by uneven aged harvests was not supported. Instead, the relative abundance estimate of Cerulean Warblers was greater for sites with larger openings in the forest canopy created by even aged harvests. In contrast another study in southern Indiana found no significant difference in the number of Cerulean Warbler detections among uneven aged stands 2 30 y old (single tree selection and a combination of group and single tree selection) and unharvested reference TABLE 4. Mean Cerulean Warbler territory sizes in Yellowwood and Morgan-Monroe state forests in southern Indiana according to harvest type from 2007 to Pre-harvest: 2007 and Post-harvest: 2009 and Forest treatments began in Jul and were completed by Feb PC 5 patch cuts and SW/CC 5 shelterwood/clearcut harvests. Values reported as mean 6 1 SD Harvest type Pre-harvest (n) Pre-harvest mean (ha) Post-harvest (n) Post-harvest mean (ha) PC (uneven-aged) SW/CC (even-aged) Control

10 118 THE AMERICAN MIDLAND NATURALIST 170(1) TABLE 5. Spatial attributes of Cerulean Warbler territories in Yellowwood and Morgan-Monroe state forests in southern Indiana, Attributes from territories are compared with attributes from random points where no birds were located, and results of two sample t-test are reported below Attribute Mean terr Mean rand P Distance to streams Distance to roads Elevation Slope Aspect (degrees) ,0.001 Distance to conifer patch ,0.001 n Terr 5 196, n Rand 5 196, Mean Terr 5 mean distance of attribute to territory (m), with exception of aspect, and Mean Rand 5 mean distance of an attribute to random location (m), with exception of aspect sites (stands y old; Register and Islam, 2008). In West Virginia, Wood et al. (2005) found that Cerulean Warblers were more abundant in y mature forests than in y old regenerating after clearcuts and two age harvests. Some plausible reasons that Cerulean Warblers occurred in areas with larger than expected canopy gaps may pertain to efficiency in energy costs, foraging areas with greater prey abundance, and increased ability to attract females. Cerulean Warblers are early breeders arriving on their breeding grounds in southern Indiana in middle to late Apr. when temperatures often fall below 5 C (Roth and Islam, 2008). Warmer temperatures associated with large canopy gaps may reduce thermoregulatory costs to the birds associated with individual maintenance (Smith and Dallman, 1996). An increase in light penetration in forest openings created by silviculture usually results in an increase in primary productivity (Fogden, 1972; Blake and Hoppes, 1986; Martin and Karr, 1986) and, in turn, may increase prey abundance (Blake and Hoppes, 1986; Smith and Dallman, 1996). Large forest openings may aid males in projecting songs to conspecific males and to attract females (Smith and Dallman, 1996). Territory sizes, although smaller after treatment, did not differ significantly from pre treatment sizes. We obtained ArcGIS shapefiles of the harvests from the U.S. Forest Service and determined that, in total, only 75.7 ha were actually harvested, meaning 6.43% of the total forest within the six sites receiving harvest was removed. Therefore, it is possible that the forest treatments were too small to cause any significant change in Cerulean Warbler territory sizes. Cerulean Warblers are known to exhibit clustered territoriality and this behavior has been attributed to conspecific attraction, selection of higher quality habitat, or both (Roth and Islam, 2007). Although fewer territories were found clustered in 2008 because of reduced sampling effort than in , we found no evidence that territories became either more or less clustered 1 y after the treatments. Cerulean Warbler territories did not occur randomly on the landscape. Cerulean Warblers preferred to establish territories in areas with southeast facing slopes and near streams, roads, and coniferous forest patches. At Big Oaks National Wildlife Refuge in Indiana, Cerulean Warblers also selected sloped areas (Roth and Islam, 2008), as was also the case in Tennessee (Buehler et al., 2006). In West Virginia, Cerulean Warblers showed a preference for north to east facing slopes (Weakland and Wood, 2005; Wood et al., 2006). Several authors have noted that Cerulean Warblers are associated with canopy gaps (Oliarnyk and Robertson, 1996; Hamel, 2000; Bosworth, 2003; Weakland and Wood, 2005; Perkins, 2006; Wood et al., 2006), explaining the association of roads and streams that we

11 2013 KAMINSKI &ISLAM: CERULEAN WARBLER TERRITORY RESPONSE TO FOREST TREATMENT 119 observed. Our findings differed from Buehler et al. (2006) who found that males selected territories farther away from streams. The apparent association between Cerulean Warbler territories and patches of coniferous forest may be spurious because no other studies have documented the importance of conifers. Coniferous patches at our study area were likely planted in the past and many of these patches occur in thin strips along streams. In summary, based on relative abundance estimates and territory sizes in the 2 y post harvest period, our findings suggested that Cerulean Warblers appear to tolerate certain forest manipulations. Cerulean Warblers: (1) responded positively to even aged harvests with treatments that created openings from 4 ha clearcuts and initial shelterwood removal, (2) responded negatively to treatments of small patch cuts from uneven aged harvests, and (3) did not alter territory sizes as a result of the treatments. At the landscape level, Cerulean Warblers territories were clustered and typically occurred on steep slopes with a southeastern aspect, and near to roads and streams. Acknowledgements. This paper is a contribution of the Hardwood Ecosystem Experiment, a partnership of the Indiana Department of Natural Resources, Purdue University, Ball State University, Indiana State University, Drake University, Indiana University of Pennsylvania, and The Nature Conservancy. We thank J.R. Wagner, R.H. Dibala, M.M. MacNeil, L.C. Young, E.B. Koscielniak, A.B. Ripley, L.E. Nelson, J.B. Grant, M.L. Holding, R.B. Stiller, and E.E. Arnold for assistance with field data collection and data entry. We also thank R.A. Kalb and C.J. Mycroft for coordinating the HEE project, and the assistance provided by K.M. Turcotte with the GIS analysis, T.C. Carter with GPS units, and J.A. Jones with statistical analyses. Our research was funded from grants from the Indiana Department of Natural Resources through Purdue University, U.S. Fish and Wildlife Service, Amos W. Butler Audubon Society, and the Ball State University chapter of Sigma Xi. We thank three anonymous reviewers for their comments and suggestions that markedly improved the manuscript. LITERATURE CITED BAKERMANS, M. H. AND A. D. RODEWALD Think globally, manage locally: the importance of steadystate forest features for a declining songbird. For. Ecol. Manage., 258: BIRDLIFE INTERNATIONAL Threatened birds of the world CD-Rom. BirdLife International, Cambridge, United Kingdom. BLAKE, J.G.AND W. G. HOPPES Influence of resource abundance on use of tree-fall gaps by birds in an isolated woodlot. Auk, 103: BOSWORTH, S. B Cerulean Warbler relative abundance and frequency of occurrence relative to large-scale edge. M.Sc. Thesis. West Virginia University, Morgantown, WV, U.S.A. BUEHLER, D. A., M. J. WELTON, AND T. A. BEACHY Predicting Cerulean Warbler habitat use in the Cumberland Mountains of Tennessee. J. Wildl. Manage., 70: COSEWIC COSEWIC assessment and status report on the Cerulean Warbler Dendroica cerulea in Canada. Committee on the Status of Endangered Wildlife in Canada, Ottawa. FALLS, J. B Mapping territories with playback: an accurate census method for songbirds. Stud. Avian Biol., 6: FOGDEN, M. P The seasonality and population dynamics of equatorial forest birds in Sarawak. Ibis., 114: HAMEL, P. B Cerulean Warbler (Dendroica cerulea). In: A. Poole and F. Gill (eds.). The Birds of North America, no Philadelphia: The Academy of Natural Sciences, Washington, DC: The American Ornithologists Union., D. K. DAWSON, AND P. D. KEYSER How we can learn more about the Cerulean Warbler (Dendroica cerulea). Auk., 121:7 14., M. J. WELTON, C.G.SMITH III, AND R. P. FORD Test of Partners in Flight effective detection distance for Cerulean Warbler. Proc. Intl. Partners in Flight Conf., 4: HOMOYA, M. A., D. B. ABRELL, J.R.ALDRICH, AND T. W. POST The natural regions of Indiana. Proc. Indiana Acad. Sci., 94:

12 120 THE AMERICAN MIDLAND NATURALIST 170(1) JONES, J., W. J. MCLEISH, AND R. J. ROBERTSON Density influences census technique accuracy for cerulean warblers in eastern Ontario. J. Field Ornith., 71:46 56., D. R. NORRIS, M. K. GIRVAN, J. J. BARG, T. K. KEYSER, AND R. J. ROBERTSON Migratory connectivity and rate of population decline in a vulnerable songbird. Condor, 110: JONES, K. AND K. ISLAM Selection of song perches by Cerulean Warblers. Proc. Indiana Acad. Sci., 115: KREBS, C. J Ecological Methodology. University of British Columbia, Harper and Rowe, New York, U.S.A. MARTIN, T. E. AND J. R. KARR Patch utilization by migrating birds: resource oriented? Ornis Scand., 17: OLIARNYK, C. J. AND R. J. ROBERTSON Breeding behavior and reproductive success of Cerulean Warblers in southeastern Ontario. Wilson Bull., 108: PERKINS, K. A Cerulean Warbler selection of forest canopy gaps. M.Sc. Thesis. West Virginia University, Morgantown, West Virginia, U.S.A. REGISTER, S. M. AND K. ISLAM Effects of silvicultural treatments on Cerulean Warbler (Dendroica cerulea) abundance in southern Indiana. For. Ecol. Manage., 255: ROBBINS, C. S., J. W. FITZPATRICK, AND P. B. HAMEL A warbler in trouble: Dendroica cerulea, p In: J. M. Hagan and D. W. Johnston (eds.). Ecology and conservation of Neotropical migrant landbirds. Smithsonian Institute Press, Washington D.C. ROTH, K. L. AND K. ISLAM Do Cerulean Warblers (Dendroica cerulea) exhibit clustered territoriality? Am. Midl. Nat., 157: AND Habitat selection and reproductive success of Cerulean Warblers in Indiana. Wilson J. Ornithol., 120: SAUER, J. R., J. E. HINES, AND J. FALLON The North American Breeding Bird Survey, results and analysis Version U.S.G.S., Patuxent Wildlife Research Center, Laurel, Maryland, U.S.A. SMITH, R.AND M. DALLMAN Forest gap use by breeding Black-throated Green Warblers. Wilson Bull., 108: WEAKLAND,C.A.AND P. B. WOOD Cerulean Warbler (Dendroica cerulea) microhabitat and landscapelevel habitat characteristics in southern West Virginia. Auk., 122: WOOD, P. B., J. P. DUGUAY, AND J. V. NICHOLS Cerulean Warbler use of regenerated clearcut and twoage harvests. Wildl. Soc. Bull., 33: , S. B. BOSWORTH, AND R. DETTMERS Cerulean Warbler abundance and occurrence relative to large scale edge and habitat characteristics. Condor, 108: SUBMITTED 12 JULY 2012 ACCEPTED 19 JANUARY 2013