1 of 1

Small Grassland Restorations May Not Be Enough to

Restore Local Bird Diversity

Department of Biology, Sacred Heart University, Fairfield, CT

Jonathan Austin & Alexandra Belotti Mentor: J.H. Mattei

Introduction

Coastal Grasslands are one the rarest occurring ecosystems in New England.
In habitats that maintain a high abundance of native plant species, there is a potential for positive ecological responses in the local and surrounding habitats (Kroll et al. 2014)
Roughly 14 acres of the grassland at Stratford Point, CT is populated mainly by Andropogon gerardii, Sorghastrum nutans, and Panicum virgatum in dense clumps providing a suitable habitat for a variety of fauna including birds
Phragmites australis and Artemisia vulgaris are invasive plant species highly present in the coastal grasslands at Stratford Point (O’Keefe et al. 2021)
Because community structure has great influence on the positive or negative effects of a habitat (Dauber et al. 2003), it was hypothesized that rare ground bird species would increase in abundance and richness in response to restoration at Stratford Point especially during spring and fall migratory periods.

�

As many as 296 species have been observed at Stratford Point (eBird.org). However, the number of species observed annually has fluctuated over the years 2010-2021, ranging from as low as 132 species in 2014 to as many as 214 species in 2015 (Fig. 3). In fact, this was the most drastic 1-year change with a 62% increase in species. In contrast, there was a 32% decrease from 2018-2019 (Fig. 3). Similar fluctuations can be observed for Bobolinks (D. oryzivorus) and Savannah Sparrows (P. sandwichensis) (Figs. 5 & 6). Spring and fall migrations change as well (Fig. 4). There is a large spring migration in 2015, but this migration is missing in 2010 and 2021. Fall migration occurred in all years reported on Fig. 4, with slight timing variations. For instance, fall migration peaked in Aug. of 2010, Oct. of 2015, and Sept. of 2021. Lastly, the number of the observations submitted on eBird has dramatically decreased (Fig. 2). In 2015, 409 observations were submitted to eBird pertaining to important grassland species including the Bobolink (D. oryzivorus), Eastern Meadowlark (S. magna), Savannah Sparrow (P. sandwichensis), Grasshopper Sparrow (A. savannarum) and more (Fig. 2). 2021 had 104 observations, only a quarter of the observations in 2015. Overall, the data showed 2015 was the most diverse year, and July through Oct. is the busiest and most diverse time of year.

Figure 8. Mugwort at Stratford Point (Artemisia vulgaris)

Methods

Grassland Restoration

20 acres of the site was seeded in the early 2000s with a mix of common grass species including little bluestem (Schizachyrium scoparium), big bluestem (Andropogon gerardii), indian grass (Sorghastrum nutans), and switchgrass (Panicum virgatum).
The site was burned in 2012 to stimulate new growth of common coastal grasses while simultaneously controlling invasive species.
Areas with high density of invasive mugwort (Artemisia vulgaris) (Figure 8) were mowed in August 2019.
Mugwort was also managed by Garlon 3A, a dicot specific herbicide, in 2019 and in 2020
Other invasive species including the common reed (Phragmites australis) and blackswallow-wort (Cynanchum louiseae) have been managed through regular mowing of the site as well as solarization

Bird Data Collection

Bird diversity was evaluated using observations obtained from eBird (ebird.org) from 2010 through 2021 to determine trends in the number of species and species abundance in response to remediation of the site We also examined 2 specific species that are known to inhabit grasslands in Connecticut (Figures 6 and 7).

�

Results

References

Dauber, J., Hirsch, M., Simmering, D., Waldhardt, R., Otte, A., and Wolters, V. (2003). Landscape structure as an indicator of biodiversity: matrix effects on species richness. Agric. Ecosyst. Environ. 98, 321–329.

Folsom-O’Keefe C., Mattei J., Leenders T., Hauser C. 2021. Stratford Point Coastal Habitat Management Plan.

Haddad, N. M., Brudvig, L. A., Clobert, J., Davies, K. F., Gonzalez, A., Holt, R. D., et al. (2015). Appliedecology: habitat fragmentation and its lasting impact on Earth’s ecosystems. Sci. Adv

Kroll, A. J., Ren, Y., Jones, J. E., Giovanini, J., Perry, R. W., Thill, R. E., et al. (2014). Avian community composition associated with interactions between local and landscape habitat attributes. For. Ecol. Manage. 326, 46–57.

Silva TW, Fontana CS. 2021. Remnants of Native Vegetation Surrounding Do Not Affect the Diversity and Density of Birds in Brazilian Grassland-Restoration Sites. Fron. Ecol. and Evol. 8: 1-7.

Forest Service, Pacific Northwest Region. 1996. Triclopyr: Herbicide Information Profile. United States Department of Agriculture.

�

Figure 4. Bird species counts by month in 2010, 2015, and 2021..

Figure 2. Number of eBird observations in 2015 and 2021

Figure 6. Savannah Sparrow (Passerculus sancwichensis) counts by year

Figure 7. Bobolink (Dolichonyx oryzivorus) counts by year

Click to add te

Discussion

The low number of observations in 2021 as compared to 2015 and prior could be due to the COVID-19 pandemic. This was especially noticeable in the spring migratory season of 2021.
The high species richness of Spring 2015 could be due to the high restoration activity in 2014.
The low species richness of 2021 could be due to low observation numbers, but the recent mowing to control invasive plant species in 2019 must also be taken into consideration.
Herbicide Garlon 3A was used in 2019 and 2020 and is known to be toxic to birds and reduces reproduction rates (Forest Service, 1996).
The burning in 2012 must be taken into consideration when analyzing the dip in the number of species present from 2012-2014.
The jump in species richness from 2014- 2018 occurred post restoration until mowing and herbicide application. Bobolinks and Savannah Sparrows exhibited similar dips in abundance in 2013/2014 and 2019.

Photo Credit: Bryan Calk. 6 Jan 2019, Macaulay Library, eBIrd.org

Photo Credit: Ryan Sanderson. 3 July 2020, Macaulay Library, eBird.org

Figure 3. Bird species counts by year

Figure 5. Coastal grasslands populated with Switchgrass (Panicum virgatum) and Indiangrass (Sorghastrum nutans)

Figure 1. Location of Stratford Point Grassland Site