Eastern Meadowlark Status and Nesting Success in Central Illinois

The Illinois landscape has experienced a shift since the 1950s from cattle-focused agricultural practices to expansive and intensified row crop agriculture. Prior to this evolution in farming, grassland birds were able to utilize cattle pastures and forage fields for nesting habitat. With this land cover having been replaced by row crops, grassland bird populations consequently entered a state of severe and rapid decline (85-90 percent, Warner 1994). Eastern meadowlarks (Sturnella magna), a prairie icon, have lost three quarters of their North American population since 1970, equating to ~74 million individuals (Rosenberg et al. 2019).

The USGS Breeding Bird Survey (BBS) monitors the abundance of species annually across North America and uses these data to estimate breeding season population trends. The BBS is run by volunteers who survey a 24.5-mile route, consisting of 50 survey points. Surveyors record the number of individuals of each species they hear and see at each stop during a 3-minute period, before moving to the next. In Illinois, BBS data suggests that eastern meadowlarks experienced annual declines of 3.4 percent from 1966 to 2019. The overall nesting success of adults during the breeding season has a direct impact on the number of individuals being added to the population. For this reason, we chose to investigate whether meadowlark nest success was a likely contributing factor to the recorded population declines.

Our research, funded by the Illinois Department of Natural Resources, Champaign County Audubon Society and Illinois Ornithological Society, took place during the 2022 breeding season in central Illinois, across four field sites: Kennekuk Cove County Park (Vermilion County), Sibley Pheasant Habitat Area (Ford County), Saybrook Pheasant Habitat Area (McLean County) and Monticello Field Station (Champaign County). Nests were primarily searched for using a rope-dragging technique, which is commonly used for grassland birds (Fig. 1). This tactic entails two people dragging each end of a rope while they walk, such that the slack forms a U-shape behind them. A third person follows behind the rope watching for birds flushing off nests.

Meadowlarks are ground-nesting birds, and they construct a woven nest bowl of grassy litter with at least a partial canopy (Fig. 2). Rope dragging makes finding these cryptic nests a substantially more efficient process.

Searching for nests took place from late March through early July of 2022, with most nests being found in late April to mid-May. In total, we found 28 eastern meadowlark nests, primarily via rope-dragging, systematic walking, incidental flushes and observations of breeding behaviors. Nineteen of these nests were found in cool-season grasses, and all but one of the 28 contained partial to full canopies of grasses and litter. We found rope dragging to be less effective in areas with tall (>1-meter), thick grasses as the rope did not fall low enough to prompt incubating birds to flush. Additionally, several previous studies have determined the presence of litter to be a prerequisite for meadowlark nesting habitat. For these reasons, we invested the majority of our search time in areas of shorter grass with litter present.

The vegetation type, approximate height, number of eggs/nestlings, presence/use of litter, and canopy presence were noted for each nest. Nest checks were performed every three days until completion (i.e., successful fledge or failure) to determine success rates. A nest was considered successful if at least one nestling fledged or left the nest. Of the 28 nests found, 16 successfully fledged, amounting to a total of 58 chicks, or an average of 3.6 fledges per nest. The remaining 12 nests failed due to predation (9) and abandonment due to inclement weather (1) and human interference (2). Nests were considered to have been depredated if the eggs disappeared or the nestlings were gone prior to their estimated fledge date. Grassland birds and other ground nesters are particularly susceptible to depredation by snakes, rodents and larger mammals. In addition to several snake sightings at our field sites, we observed an eastern foxsnake (Pantherophis vulpinus) depredating a nest during a routine check.

Using the data from our nest checks, we estimated nesting success (logistic exposure model) and investigated the factors impacting nesting success. We estimate that meadowlark nests have a 37.2 percent chance of surviving the 24 days from incubation to fledging. Furthermore, our analyses showed that nest stage (eggs vs nestlings) had the greatest impact on nest success. Nests with eggs only had a 40.8 percent chance of surviving incubation (13 days, Fig. 3), whereas nest that had made it to the chick stage had a 91.3 percent chance of surviving to fledge (11 days, Fig. 4). Ten of the 12 nest failures we observed occurred during the egg stage.

The results of our study showed meadowlark nest success to be comparable to previous research, and not especially low (Kershner & Bollinger 1996, Walk et al. 2010, Ribic et al. 2012, Byers et al. 2017). Though sample size was limited, these success rates may be sufficient to support our study populations. However, success rates could be higher at the selected field sites if they corresponded to the best available breeding grounds. Survival—another factor that could be driving long-term declines in this species—remains understudied, with only a few research projects focusing on juvenile survival and no known studies on adult survival. If survival during migration or the nonbreeding season is low, there would be fewer adults contributing to the population the following breeding season. Our nest searching efforts found meadowlarks to be more prevalent in areas lacking woody vegetation, with shorter grasses and litter. If Conservation Reserve Program (CRP) fields and what remains in Illinois of native prairies or other grasslands do not meet these requirements, then suitable habitat is scarce on the landscape.

To aid in grassland bird conservation efforts, landowners can delay baling or mowing until later in the summer. By this time, the peak nesting season for meadowlarks will have passed and females will have completed their first nesting attempts. Properties can also be managed to meet species-specific habitat requirements. For meadowlarks this could mean removing woody plants/shrubs, planting native cool season grasses, and retaining some grassy litter in the habitat. These efforts can help support meadowlark populations during the breeding season while continued efforts are being made across the country to investigate the cause(s) behind this species’ massive decline.

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Julie Bozzo is a recent graduate from the Ward Avian Research Lab at the University of Illinois Urbana-Champaign. She completed her master’s thesis on Eastern Meadowlark migration, nest success and response to changes in land use in Illinois.

Dr. Michael Ward is a professor with the University of Illinois and senior ornithologist with the Illinois Natural History Survey. Dr. Ward is involved with a large number of collaborative research projects with foci on avian ecology and behavior.

Michael Avara is the Avian Lab Manager. He received his B.S. from the University of Illinois, Urbana-Champaign (2007) and his M.S. from Southern Illinois University (2013). He supports lab data collection and analysis on the many diverse research projects of the lab. This includes managing the Illinois Motus Network of 17 telemetry towers across the state, working with organizations in the St. Louis Metro East to restore endangered waterbird colonies, conducting field surveys to quantify bird populations at sites across the state, and analyzing acoustic data to help refine understanding of Illinois chorus frog behavior and distribution. He has also helped in design of educational outreach materials that communicate the research of the lab.

Literature Cited
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Kershner, E. L., and E. K. Bollinger. 1996. Reproductive success of grassland birds at east-central Illinois airports. The American Midland Naturalist 136(2):358-36.

Ribic, C.A., M. Guzy, T. Anderson, D. Sample, and J. Nack. 2012. Bird Productivity and Nest Predation in Agricultural Grasslands. USGS Northern Prairie Wildlife Research Center. 257. https://digitalcommons.unl.edu/usgsnpwrc/257Rosenberg, K. V., A. M.

Dokter, P. J. Blancher, J. R. Sauer, A. C. Smith, P. A. Smith, J. C. Stanton, A. Panjabi, L. Helft, M. Parr, and P. P. Marra. 2019. Decline of the North American avifauna. Science 366(6461):120-124.

Walk, J. W., E. L. Kershner, T. J. Benson, and R. E. Warner. 2010. Nesting success of grassland birds in small patches in an agricultural landscape. The Auk 127(2):328-334.

Warner, R. E. 1994. Agricultural land use and grassland habitat in Illinois: Future shock for midwestern birds? Conservation Biology 8(1):147-156.