Composition of the Songbird Community at the DePauw Nature Park and Arboretum

1. Ovenbird (Oven) Wood Thrush (WOTH) Worm Eating Warbler (WEWA) Composition of the Songbird Community at the DePauw Nature Park and Arboretum Libby Allard, V. Artman, K. Reed, K. Koehler, Department of Biology, DePauw University, Greencastle, IN 46135 Red-eyed Vireo (REVI) Acadian Flycatcher (ACFL) Indigo Bunting (INBU) Black-and-white warbler Generally, songbird populations were higher in 2005 than 2004. Populations of all species increased except for the Indigo Bunting. The Cerulean Warbler, a rare and dangerously declining species in North America, showed higher populations in 2005 but only occurred in both years at Quarry South. Despite Ohio’s larger sites, the 2005 Cerulean Warbler population at Quarry South was over double that of Ohio. Northern Cardinals were the predominant bird species in both the Arboretum and Quarry Hillside, while Acadian Flycatchers were the predominant bird species in Quarry South. Wood Thrush levels were much lower at the DePauw sites than those in Ohio. Red-eyed Vireo levels were highest in the Arboretum, but are comparable to those of Ohio. In Ohio, however, Acadian Flycatchers were in the minority with Ovenbirds having the dominant population percentage. Although the Ovenbird range encompasses westcentral Indiana, Ovenbirds were absent from the DePauw sites. Other breeding species that were present in Ohio but absent in DePauw’s sites were the Black-and-white Warbler, the Hooded Warbler, and the Worm-eating Warbler. • Discussion: • Acadian Flycatcher levels at our sites were surprisingly large, considering the habitat preference of the species. ACFLs are typically associated with mature forest, along with the Worm-eating Warbler, Hooded Warbler, Black and White Warbler, Red-eyed Vireo, Wood Thrush, and Ovenbird.* The three warbler species and Ovenbird were absent from the Nature Park, while ACFLs were abundant. Why the difference? It is possible that since the Ohio sites were so large, ACFLs were more spread out, having fewer territories per unit of area. This does not explain why levels were so high in the Nature Park, though. Even more surprising is that while the Arboretum is the oldest of the three sites with the typically most ideal conditions for the ACFL (less understory and more mature trees), QS seemed to attract the most ACFLs. As an insectivore, ACFLs may possibly be attracted to the greater number of mosquitoes in QS. • ACFL chose nest sites where there was less understory, which is consistent with the evidence that ACFLs prefer a more mature forest. However, our data show that ACFL nesting success was actually higher at DePauw’s sites than in the more mature forests in Ohio. Higher nest placement for ACFL was positively correlated with nesting success in previous studies.* Thus, a more mature forest would have taller trees and more successful nests.* Contrary to this evidence, our initial data suggests that lower nests were more successful. However, our data are inconclusive given small sample sizes. We also found that smaller diameters of ACFL nesting trees may positively affect nesting success. Some nest predators may only be able to climb larger trees to consume nest contents, leaving nests in smaller trees protected. • The Cerulean Warbler is another species which provokes interest. Population levels for 2004 and 2005 were both larger than that of Ohio, but only in Quarry South. Quarry Hillside and the Arboretum have no Cerulean Warblers. Why was this species only found in Quarry South? After analyzing the vegetation data in the CERW territories, they seem to prefer similar conditions as the ACFL. No CERW nests could be found, so nesting success couldn’t be calculated. The large population levels in Quarry South may be attributable to either (a) events during migration or on wintering grounds affecting mortality in the CERW population* or (b) microscopic parasites negatively affecting population levels in Ohio. • Northern Cardinaland Indigo Bunting levels were much higher than in Ohio. NOCA is an edge-dwelling, fragmentation-loving species.* In our sites they only chose territories along borders (powerlines, streams, or meadows). As the Indiana forest ages, there will be less clearings and more dense forest—thus, NOCA levels may decline as there will be less suitable habitat. INBU is an early successional species that is usually found in meadows.* Surprisingly, they were common in Quarry South and preferred to nest in the low shrubs growing throughout this site. Their populations may decline in future years as understory decreases and tree height increases. • Implications and Future Research: • Further research on the topic of songbirds is important because it relates to the health of the ecosystem and may provide information that affects forest management decisions. On a more specific level, further research may address specific species of songbirds, some of which are of significant conservation concern. • Further research could address important ecological concerns, such as: • What environmental factors could further increase population levels of the Cerulean Warbler? • How could we manage the Nature Park to attract additional species of native songbirds, such as the Ovenbird and Hooded Warbler? • How does the composition of invertebrates affect the type of songbirds abiding in the three study sites? • Does a correlation exist between levels of leaf litter and abundance and distribution of songbirds? • How do we minimize spread of invasive plant species without affecting songbird habitat? Introduction: DePauw’s Arboretum and Nature Park contain many different habitats. Vegetation and forest continuity vary, affecting the fauna that inhabit different regions. We collected data on songbird and plant communities at three forested sites: the Arboretum (ARB, 5 ha), Quarry South (QS, 10 ha), and Quarry Hillside (QH, 10 ha). Until recently there have been little data collected describing the composition of the songbird community at the three DePauw sites. Comparable data were collected in Ohio at four 25-30 ha sites from 1995 to 1999. The Ohio forest was used as a comparison because some species of songbirds that range from Indiana to Ohio are only present in the Ohio sites. The sites in Ohio also represent relatively undisturbed mature forest, dominated by a mix of oak and hickory, typical overstory trees in the region. The sites in Ohio are also situated in a relatively unfragmented landscape. Here, we describe the composition of the songbird community within these sites, examining the relationship between songbirds and the habitat characteristics, and comparing our data with data collected in similar conditions in Ohio. Hypothesis: Differences in songbird communities between Indiana and Ohio sites are related to the age of the forest and possibly to the extent of forest fragmentation. Methods: We conducted bird surveys during May and June. We recorded locations of singing and calling birds. Twelve bird surveys were conducted, four at each site, between the hours of 5am and 10am. We made a map for each bird species and plotted points where each observation occurred. We used clusters of observations to estimate the relative number and position of breeding pairs and their territories. Also, we collected nesting success data during the breeding season. BBIRD protocol (Martin et al. 1995) was used when searching for and monitoring nests. Nests were revisited every 3-5 days until the nest was no longer active. Daily nest survival rates were calculated using the Mayfield method. We collected vegetation data at randomly located plots and nest sites following BBIRD protocol. We counted shrubs and seedlings by species and size class within a 5 m radius of each random point and nest and estimated percent cover of understory vegetation. Within an 11.3 m radius we counted trees and snags (dead trees) by species and size class. We cored one tree at each plot to estimate the relative age of the forest. We measured height of nests. Results: The daily nest survival rate of the Acadian Flycatcher increased by roughly 2.5% between 2004 and 2005, and the 2005 rate exceeds that of Ohio. The daily nest survival rate of Indigo Bunting decreased by 3% from 2004 to 2005. The age of the forest stands in the Arboretum was estimated at 100 years, while both Quarry Hillside and Quarry South were estimated between 30-60 years. Forests at the Ohio sites were estimated to be slightly more mature (100-120 years). Understory vegetation in the Arboretum was generally less dense than that of Quarry Hillside or Quarry South. Acadian Flycatchers typically selected nest sites with less understory vegetation within the forest. Acknowledgments: A thank you to my group, my professor, and my parents, who made this project possible. Cerulean Warbler (CERW) Scarlet Tanager (SCTA) Hooded Warbler (HOWA)