FINAL REPORT FOR YEAR THREE OF THE EFFECTS OF HABITAT FRAGMENTATION (SELECTIVE LOGGING) ON ADJACENT SITES AT THE TRAIL OF TEARS STATE FOREST (EFFECTS OF SELECTIVE LOGGING ON NEOTROPICAL MIGRANT BIRDS) Contract No .: Prepared by : Dr. Scott K . Robinson Illinois Natural History Survey . 607 E. Peabody Drive Champaign, IL 61820 Attention: Dr. Peter Stengel National Fish and Wildlife Foundation 1120 Connecticut Ave .; N.W. #900 Washington, D .C. 20036 and Mr. Vernon Kleen IL Department of Conservation Division of Natural Heritage Lincoln Tower Plaza 524 South Second Street Springfield, IL 62701-1787 0 7 2 INTRODUCTION This report summarizes the results of the third year of a study of the effects of selective logging on nesting forest songbirds, especially neotropical migrants. Remarkably little is known about how selective logging alters bird community composition, brood parasitism levels and rates of nest depredation (see enclosed review of the literature) . The goal of this study is to compare bird community composition and nesting success in recently (55 years), old (12-year), and adjacent uncut ravines in the Trail of Tears State Forest, including the Ozark Hills Nature Preserve . This report emphasizes the results of the 1992 field season, but will also compare the results with the previous two years. The final report will be prepared for the project by the end of 1993 . STUDY AREA The Trail of Tears State Forest is located in the Illinois Ozarks region of Union County in extreme southern Illinois . The topography of this 2,050-ha forest is uniform with narrow ridges and ravines covered with oak-hickory forest and tulip-tree in the wider ravines . The forest is divided into compartments of 40-100 ha, of which two were selectively logged in 1980, and two were cut in 1988 . The two recent cuts removed approximately 30% of the canopy and basal area using group selection techniques with the largest openings measuring 0 .5 ha. The two older cuts were also group cuts but one had only 15% of the basal area removed whereas the other had 45-50% removed . The older cuts look much like uncut forest with occasional patches of dense 5-8 m saplings whereas the recent cuts had conspicuous shrubby openings that allowed light to penetrate to the forest floor. The final report will present the results of our vegetation analysis . 3 METHODS Censuses. Birds were censused daily from 20 May - 30 June 1992 by 0 Doug Robinson and Scott Robinson along transects of point counts located along ridge tops and ravines using the fixed-radius point count method (6 min/point, all birds heard or seen noted as well as their distance and compass direction) . All ridges and ravines in cut areas were censused as well as 9 ridges and 6 uncut ravines. Five new ravines and 3 new ridges were censused in 1992 . All ridges and ravines censused in 1990 and 1991 were also censusedagain in 1992 . For the purposes of statistical analysis, each ravine and ridge are considered independent replicates . Each ravine was censused four times, twice by each observer and each ridge was censused once, once by each observer . Because the composition of bird communities differs greatly between ridges and ravines, each kind of transect will be compared independently . In this report, f present only data on Neotropical migrants that build open-cup nests and a few residents and short-distance migrants that accept cowbird eggs (e .g ., Northern Cardinal and Rufous-sided Towhee), or that depredate or parasitize bird nests (Blue Jay, Brown-headed Cowbird) . All census data present results from 70-m fixed radius point counts, which give a density estimate based on singing males (or females) detected per circle of a 70-m radius . This estimate provides an index of abundance, but probably underestimates the population densities because not all birds vocalize during 6-min point counts . To facilitate comparisons with other studies we noted 3-min and 5-min subtotals during our censuses . Points were located 150-m apart along transects and all points were averaged together to obtain a single value for each ridge and ravine . Each route was censused at 7- 10 day intervals on average . For cowbirds, we separated registrations according to kind of vocalizations . We assumed that all long "rattle" calls were given by females and 4 calculated separate abundance estimates of males and females . We calculated an index of cowbird pressure by dividing the female cowbird abundance by the total of all hosts recorded within the same area ("cowbird :host ratio"). Nest searching and monitoring. An effort was made to equalize searching in each cut type . Each time a nest was located a flag was placed at least 5 m away and its location was mapped in relation to the census trail . We concentrated our efforts on the Acadian Flycatcher, Wood Thrush, Kentucky Warbler, and Northern Cardinal because they were the only four species abundant enough in each cut type to obtain sufficient sample sizes for intraspecific analyses. Data for other species are also included . Nests were monitored every two days until they were abandoned, depredated, destroyed, or fledged young . If exact dates of laying or hatching were known, nests were not monitored for 8 and 5 days, respectively, to minimize possible effects of observer visitation on predation rates . During the study, Steve Bailey, Caleb Morse, Lonny Morse, Rob Lu-Olendorf, Any Suarez, and Steve Amundsen found the majority of nests . Jason Weber, Jean Lu-Olendorf, Stavros Daniels, John Knapstein, and Rebecca Whitehead did the majority of nest monitoring . Artificial Nest Experiments. Miguel Marini, a Ph .D. student, placed . artificial eggs baited with quail eggs (ground, shrub, and sapling nests) in each cut type for three 1 5-day periods in two replicates of each cut type to compare predation rates . The results of this experiment . will be reported separately (Marini and Robinson, in prep.). MistNetting. Leslie Jette, a M.S. student ran 14 nets 7 times at 7-10 day intervals in two ravines of each cut type to compare populations and productivity. The results of this study will be reported separately when the project is completed 5 at the end of her second field season (1993) and will be included in the final report. RESULTS Census data. Abundances of most species varied according to cut type in 1992 (Tables 1 and 2). Several canopy nesters were less abundant in selective cuts as predicted because of the reduction in canopy volume . Red-eyed and Yellow-throated vireos both were significantly (Mann-Whitney U Test, P < 0 .05) less abundant in recently cut ravines and ridges. Other canopy nesters (Scarlet and Summer tanagers, Eastern Wood-Pewee, Cerulean and Yellow-throated Warblers, and Northern Parula) were equally abundant in cut and uncut ridges and ravines. The sapling-nesting Acadian Flycatcher was significantly (P < 0 .05) less abundant in cut ravines, but not on ridges . Shrub-nesting species were generally more abundant in cut plots, especially in recently cut areas . Indigo Buntings, Hooded Warblers, Rufous- sided Towhees and White-eyed vireos were largely restricted to recent cuts (Tables 1 and 2). Wood Thrushes were significantly more abundant on cut ridges but were less abundant (P > 0 .05) in cut ravines . Northern Cardinals were also significantly more abundant in selectively cut ridges, but not in ravines (Tables 1 and 2). Ground-nesting birds showed a mixed response to selective cutting . Ovenbirds, which prefer bare ground, were significantly less abundant in uncut ravines, but not uncut ridges whereas Kentucky Warblers were much (P < 0 .01) more abundant in cut ridges and ravines . Louisiana Waterthrushes and Worm- eating Warblers were equally abundant in each cut type, although Worm-eating Warblers were less abundant in old-cut ravines (Table 1) . 6 Blue Jays, were generally most abundant in cut ridges and ravines (Tables 1 and 2), but the difference was only significant for ridges (Table 2) . 7 Cowbird abundance did not vary significantly with cut type, nor did cowbird:host ratios (Tables 1 and 2) . There was extensive variation among ridges and ravines, but not with cut type . Nest parasitism . Few significant differences were detected among cut types in parasitism levels (Table 3) . Acadian Flycatchers, for which we have the largest sample, did not differ significantly among ravines in parasitism levels . Wood Thrushes were parasitized less often (P = 0 .04, Fisher Exact test) in old cuts than in uncut ravines . Kentucky Warblers, on the other hand, were parasitized significantly (P = 0 .03, Fisher Exact test) less often in uncut than in recent cuts even though they were much more abundant in recent cuts (Tables 1 and 2) . Northern Cardinals showed the opposite pattern, but the difference was not significant (P = 0.07) . In general, parasitism levels were highest in the recent cuts, largely because species that were mostly restricted to cut ravines (White- 0 eyed Vireo, Hooded Warbler, Rufous-sided Towhee, and Indigo bunting) were heavily parasitized (Table 3) . Nest Predatiort . Nest predation levels were high for most species in most sites (Table 4) . Wood Thrushes were depredated significantly less often in recent cuts than in the other cuts, but none of the other comparisons were significant. Kentucky Warblers had much lower predation rates in old cuts, but the difference was not significant (P = .11) . DISCUSSION The results of the 1992 field season showed similar trends to previous years (Tables 5, 6, 7, 8) . Canopy species were generally equally or slightly less abundant in selective cuts than in uncut ravines (Tables 5 and 6) . Shrub-nesting 0 7 species were generally much more abundant in recent cuts in all three years (Tables 5 and 6) . Ground nesters showed the usual mixed reaction with Ovenbirds preferring uncut and Kentucky Warblers strongly preferring recent cuts.