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Bird community changes and habitat succession: How does the restoration of the Cache River Wetlands affect the avian communities? Fran Wachter PLB 570 Interdisciplinary Science Seminar Spring 2012 INTRODUCTION In the Midwestern United States, fragmentation of once large and continuous tracts of bottomland hardwood forests has significantly decreased wetland habitat available to avian communities. (Andren, 1994) Restoration efforts to remediate this habitat loss often rely on the processes of succession for reforestation to gradually connect and enlarge existing tracts of bottomland forests. Since restoration began in the bottomland forests of Cache River Wetlands and the Cypress Creek National Wildlife Refuge in Southern Illinois in the 1990’s, biologists have been studying the relationship between forest fragmentation, avian communities and nest predation of the neo-tropical migratory songbirds that breed in the wetland (e.g. the Prothonotary warbler) (Hoover, 2009). Additionally, Brown-headed cowbirds parasitize the nests of the Prothonotary warblers. (Hoover & Reetz, 2006) This high level of brood parasitism can be directly linked to forest fragmentation. My study will focus on surveying the songbird communities in four distinct levels of succession and to determine how the songbird community changes with habitat succession. Habitat Fragmentation Habitat fragmentation is the reduction or loss of habitat as it is subdivided into smaller sections. This can occur due to natural causes such as hurricanes, fires, etc. but most often it is the work of human actions. There are three major components to habitat fragmentation: loss of the original habitat, reduction in habitat patch size, and an increase in isolation of habitat patches. Biological diversity is reduced by all three of these components. (Wilcox 1980, Wilcox and Murphy 1985). In landscapes that are highly fragmented, the distribution or arrangement of the habitat patches is critical. The species 2 diversity decreases exponentially as the distance between habitat patches increases when only 10%-30% of the original landscape remains. The total area of habitat is of greater importance to biological diversity than the position of the individual “islands” of habitat when more than 30% of the original landscape remains. (Andren, 1994) Whether a single large area of habitat or several small areas will protect more biological species (SLOSS) addresses conservation of populations after habitat fragmentation. (Wilcox & Murphy, 1985) Also important are the community interactions between species at the time of the fragmentation. For example, one must consider how the elimination of one species directly affects the survival of another. Reforestation The stages of succession and habitats as they change over time (Clements, 1916) have been documented on landscapes across the planet. The directional change in vegetation over ecological time can be predicted and monitored. Primary succession includes landscapes with no biological legacy such as a newly formed island differs greatly from a secondary succession landscape which has a biological legacy in the form of seeds, roots, and some live plants such as Mt. St. Helens after its eruption. However, the restoration of an entire watershed is a project at such a grand scale that it is quite rare. Reforestation of bottomland forests in wetland areas can have positive impact to reduce nest predation and brood parasitism. The concern is that more often than not, the management plans for restoration projects are based more on speculation and less on true data from the restoration site (Hoover & Robinson, 1999). Long-term restoration studies allow 3 scientists to track biological populations over the lifetime of many species and document their responses to the levels of succession (Hoover & Robinson, 1999). Nest Predation The number one cause of reproductive failure in birds is nest predation. (Nice, 1957, Ricklefs, 1969, Martin, 1993.) In fragmented landscapes, the number of nest predations increases and often allows the predators to come into contact with a larger number of nests. In fact, in highly fragmented habitats, there may be very few nest sites safe from predation. (Robinson, et al., 1995, Heske at al., 2001) The principal that disturbed habitats are invaded more easily than pristine landscapes refer specifically to the richness of the home species. (Simberloff, 1986) In a fragmented bottomland forest, the three predators that are most effective hunters are raccoons (Procyon lotor) snakes, and southern flying squirrels (Glaucomys volans) In a study of 1156 nest predation events, raccoons were responsible for 73%, snakes were responsible for15%, and southern flying squirrels were identified with 7% (Hoover, 2005). However, rates of nest predation decreased when the nests were over water deeper than 60 cm. Primarily, it was the raccoons, the most prevalent predator, that were reluctant to swim through the deep water to reach the nests. (Hoover, 2005) For birds breeding in bottomland forests, the draining of wetlands can be detrimental to their reproductive success. Brood parasitism has a negative effect on the reproductive success of host birds. The cuckoo (Cuculidae) in Europe and the Brown-headed cowbird (Molothrus ater) in North America are two such avian parasites. The Brown-headed cowbird once followed huge 4 bison herds across the Great Plains feasting on the available insects accompanying the migration. Not having time to make a nest and incubate their own eggs, the cowbird would fly into the edge of the nearest forest and deposit their eggs into the nest of a host species. Today cowbirds continue to feed in pastures and row crops. Many shrubland birds will eject cowbird eggs from their nest or abandon the nest altogether. The Baltimore Oriole, American Robin, and Warbling Vireo are examples of these shrubland species (Robinson & Herkert, 1997). In forests, however, the evolution of defense skills has been much slower and 30-90% of migratory songbirds are parasitized. Three arguments have been addressed by scientists to why the host bird accepts parasitic eggs. They do not choose nest sites inaccessible to cowbirds, nor do they defend their nests or desert nests that have been parasitized (Hoover, 2002). Evolutionary lag or the short time of coexistence is one school of thought. (Hoover & Robinson, 2007). The inability to recognize or reject parasitism is explained by evolutionary equilibrium. A more recent discovery may include “mafia-like” behavior by the cowbird to the nests of the host. In a study of 472 nest boxes, researchers discovered that when they removed the cowbird eggs from the host nest, 56% of the time, the cowbird would return and destroy the host eggs. Only 6% of the hosts that accepted the parasitic eggs were depredated (Hoover & Robinson, 2007). This “mafia-like” behavior has also been recorded in one species of cuckoo. This predatory behavior may slow the evolution of rejection behaviors of the cowbird hosts that live in the bottomland forests (Hoover, 2003). There are at least 100 species of cowbird hosts. Prothonotary Warblers in the Cache River Wetlands 5 The Prothonotary warbler (Protonotaria citrea) is a neo-tropical migratory songbird that prefers to breed over water within forested wetlands. The Cache River Watershed provides this unique habitat. The Prothonotary warbler is also an indicator of the hydrological condition of the bottomland forest. Research implies that conservation activities such as plugging lateral gullies, and natural processes such as beaver built structures that hold water in forested areas contribute to the success of the reproductivity of the warblers (Hoover, 2010). It has also been studied that the site fidelity of the Prothonotary warbler is directly related to the rate of brood success (Hoover, 2003). Over 80% of the double-brooded individuals, returned to the site in following years. There is a relationship between the reproductive success and the decision to return to a specific nesting site (Hoover & Hauber, 2007). Clutch size decreases with the number of parasitic eggs in the nest. The success of both the warbler and the cowbird eggs decreased for both, but were always higher for the cowbird nestlings (Hoover, 2002). Nest predation is not affected whatsoever by the number of host or parasitic eggs in the nest. Study Description The Cache River Wetlands include the Cypress Creek National Wildlife Refuge and the Cache River State Natural Area in southern Illinois. This provides an outstanding opportunity to study the relationship between the restoration of the bottomland forest and the avian community. The natural processes that affect value and function of the bird habitat can be evaluated. This study will include a bird survey in restored fields at varying ages. The research will survey fields from corn fields (age 0 years) to early successional grasslands (age 1-3 years) to shrubby/old field habitat (age 5-10 years) to 6 young forest (age 11-15 years). Some plots would be next to bottomland forest; some would not. In particular, the study will be: Documenting how the bird community changes with habitat succession Documenting the songbird host community (those species present that could be parasitized by cowbirds) in restored areas Documenting whether any female cowbirds are detected by the surveys and if so at what age of succession Shedding light on how long it takes for bottomland forest restoration plots to start functioning as forest habitat for breeding birds Shedding light on how the restoration may reduce the severity of cowbird parasitism for songbirds in nearby mature forests. Additionally, the researcher will be learning to identify by sight and by song approximately 20 of the main species that would be encountered. Objectives The objective is to determine how the communities of songbirds change with habitat succession and to understand how the restoration of the fragmented forest may reduce the severity of cowbird parasitism for songbirds nesting in nearby mature forest. It is predicted that the survey of bird communities will show a relationship between the age of forest succession and the species of bird present. An additional prediction is that the severity of brood parasitism in the mature forest will be reduced by the restoration of the bottomland. Therefore, if the severity of brood parasitism has been reduced by the 7 restoration of the bottomland forest, then there will be fewer female Brown-headed cowbirds detected by the survey. Methods Fields to be surveyed will be identified using ARC Maps and field tours Figure 1. Sites Add’s Branch Corridor and Hickory Bottoms Figure 2. Sites Main Tract, Porter Bottoms and Porter Bottoms East 8 Figure 3. Sites Buttonland Swamp & Limekiln Slough Figure 4. Sites Boss Island, Wildcat Bluff, Heron Pond 1 & 2 9 Bird identification will utilize visual sightings as well as song recognition. The data collected in each of the successional areas will be monitored on a daily basis for the duration of the study. The data recorded will first compare the similarly aged sample plots to each other and also compare younger restoration areas to older restoration habitat. 10 REFERENCES Andren,H. (1994). Effects of habitat fragmentation on birds and mammals in landscapes with different proportions of suitable habitat: a review, OIKOS, 71, 355-366. Clements, F.E. (1916). Plant Succesion: An Analysis of the Development of Vegetation. Washington: Carnegie Institute of Washington, Press of Gibson Brothers. Heske, E.J., Robinson, S.K., Brawn, J.D., (2001). Nest predation and neotropical migrant songbirds: piecing together the fragments. Wildlife Society Bulletin 29, 52-61. Hoover, J. P., & Robinson, S.K. (1999) Monitoring the long-term nesting success, site fidelity, and population dynamics of a neotropical migratory bird: Implications for floodplain restoration, 1-22. Hoover, J.P. (2003). Multiple Effects if brood parasitism reduce the reproductive success of prothonotary warblers, Protonotaria citea. Animal Behaviour 65:923-934. Hoover, J.P. (2003). Experiments and observations of pprothonotary warblers indicate a lack of adaptive responses to brood parasitism. Animal Behaviour 65: 935-944. Hoover, J.P. (2003). Decision rules for site fidelity in a migratory bird, the prothonotary warbler. Ecology 84: 416-430. Hoover, J.P. (2006). Water depth influence nest predation for a wetland-dependent bird in fragmented bottomland forests. Biological Conservation 127: 37-45. 11 Hoover, J.P., K. Yasukawa, and M.E. Hauber. (2006). Spatially and temporally structured avian brood parasitism affects the fitness benefits of hosts’ rejection strategies. Animal Behaviour 72: 881-890. Hoover, J.P., and M.J. Reetz. (2006). Brood parasitism increases provisioning rate, and reduces offspring recruitment and adult return rates, in a cowbird host. Oecologia 149: 165-173. Hoover, J.P., & Robinson, S.K., (2007). Retaliatory mafia behavior by a parasitic cowbird favors host acceptance of parasitic eggs. PNAS 104: 4479-4483. Hoover, J.P., & M.E. Hauber. (2007). Individual patterns of habitat and nest-site use by hosts promote transgenerational transmission of avian brood parasitism status. Journal of Animal Ecology 76: 1208-1214. Hoover, J.P., (2009). Effects of hydrologic restoration on birds breading in forested wetlands. Wetlands 29: 563-573. Hoover, J.P., (2010). Prothonotary warblers as indicators of hydrological conditions in bottomland forests. Partners in Flight Conference: Tundra to Tropics: 128-137. Illinois Natural History Survey (INHS). (1997). Cowbird parasitism in different habitats. Available online at <http://www.inhs.uiuc.edu/inhsreports/nov-dec97/cowbird.html. Illinois Natural History Survey (INHS). (2002). Responses to nest predation and brood parasitism in a migratory songbird. Available online at <http://www.inhs.uiuc.edu/inhsreports/winter-02/birds.html. Martin, T.E., (1993). Nest predation and nest sites. Bioscience 43: 523-532. 12 Nice, M.M., (1957). Nesting success of altricial birds. Auk 74: 305-321. Ricklefs, R.E., (1969). An analysis of nesting mortality in birds. Smithsonian Contributions in Zoology 9: 1-48. Robinson, S.K., Thompson, III, F.R., Donovan, T.M., Whitehead, D.R., Faaborg, J., (1995). Regional forest fragmentation and the nesting success of migratory birds. Science 267: 1897-1990. Simberloff, D. & Von Holle, B., (1999). Positive interactions of nonindigenous species: invasion meltdown? Biological Invasions 1: 21-32. Simberloff, D. (1986). Introduced insects: A biogeographic and systematic perspective. Ecology of Biological Invasions of North America and Hawaii, pp3-26. Wilcox, B.A., & Murphy, D.D., (1985). The effects of fragmentation on extinction. American Society of Naturalists 125: 879-887. 13