Like many of us here at NemesisBird.com, our friend Matt Sabatine has grown up birding the fields and forests of Pennsylvania. Recently Matt was able to work in northwestern PA with grasslands birds, and offers some insights into his research with this guest post. Enjoy!
As part of my internship practicum at Penn State, I was employed this summer to lead a crew of field technicians conducting research for a post-doctoral research associate with the Center for Native Grasslands Management at the University of Tennessee. My boss, Dr. Chris Lituma, is a conservation biologist/ecologist focusing primarily on grassland birds. Our research this summer focused on grassland bird species, such as Bobolinks, Eastern Meadowlarks and Savannah Sparrows. Though our focus was on these species, the overall study encompasses several regions across the United States, and a much wider range of grassland obligates that are either found rarely around our study sites or not at all. These species include but are not limited to: Dickcissels, (native) Northern Bobwhites, Henslow’s Sparrows and Grasshopper Sparrows. Our work included three separate protocols: point counts in each of our 25 study sites (all located in Crawford County, PA), collecting vegetation sample data, and setting bee/pollinator traps – each once per month per field.
Of our 25 fields, about half were exotic cool-season grasses typical in rural Pennsylvania, and about half were planted switchgrass. Switchgrass has become a hot topic of late, because it is a native warm-season grass cultivated for biomass production. As such, the focal point of the study is to examine the ecological diversity in each type of field (representative PA grasses vs. switchgrass), and how they compare and contrast. Nest searching and monitoring was also an integral part of the research, especially as we compare the nesting success/occurrence of these birds between the two types of fields. Presumably, after data are analyzed, steps will be taken accordingly as it relates to land conservation and preservation or land use. The main pasture grasses we encountered in cool-season grass pastures included, but were not limited to: rye grass, orchard grass, barnyard grass, timothy grass and numerous different kinds of forbs. Our field season was from May 13, 2014 to July 31, 2014.
While I have long been familiar with typical PA pastures dominated by exotic grasses because they are typically the locales I associate with going to see Bobolinks, meadowlarks and other such species; switchgrass, a native grass was completely foreign to me. In spite of the fact that switchgrass is common in the area, and our switchgrass study sites were often quite large and spanned several acres of land, switchgrass appeared to lack biological diversity when planted as a monoculture crop. Switchgrass is typically thought of as having high conservation and wildlife value when grown with other native grasses and forbs. However, given that the fields we were in consisted of high-output production fields maintained to maximize seed output, the effect switchgrass had on the biological diversity was likely substantially different than it is in more natural settings.
That being said, birds and most wildlife tended to stay out of the fields that were strictly managed for high switchgrass seed output, lending some credence to the notion that, when managed in such ways, switchgrass may not be all that valuable for wildlife. Of course, there are exceptions. As noted below in the Miscellaneous Sightings section, it was in fact a switchgrass field that offered two of the best birds of the entire field season. Additionally, switchgrass can be incredibly thick, providing good cover for animals such as groundhogs, deer and birds such as Ring-necked Pheasant, American Woodcock and possibly others in migration. Further, switchgrass at heights generally lower than 3 feet had the occasional Savannah, Swamp and Song Sparrow, with Song Sparrows being the most common and consistent. Nevertheless, speaking on a per-acre basis, even the switchgrass fields that did have Savannah Sparrows would pale in comparison to the number of birds that would inhabit the more typical cool-season grass pastures of similar size. However, we did only study the switchgrass fields for a few month period over the summer, and I don’t have the knowledge or experience to speculate biological diversity in switchgrass as it relates to different seasons, latitudes, climate conditions, or any number of other factors that may influence such complex ecological systems. Given how thick and wet switchgrass can be, I would venture to guess that it may be better served as a stop-over for migrants than it is for breeding birds, the latter of which clearly avoid these fields almost en masse. If I had to guess, I’d say that it is a suitable pit stop for birds that rely heavily upon thick cover. The migratory species that come to mind when considering switchgrass fields would be Sora, Swamp Sparrow, Wilson’s Snipe, American Woodcock, and possibly even more uncommon secretive species such as Sedge Wren, Marsh Wren, Le Conte’s Sparrow, Nelson’s Sparrow, Black Rail and Yellow Rail. If I had to guess, I’d say of that latter and rarer group, at least a few individuals of those species seek refuge in the switchgrass fields in western PA a few times per year, either in spring or fall (probably both). Further, switchgrass fields may well be suitable in winter for raptors that generally rely upon tall or thick grasses to hunt rodents, such as Short-eared Owls, Rough-legged Hawks and Northern Harriers. Given that I don’t have experience with switchgrass outside the spring/summer season, it may well be just as devoid of wildlife in those other seasons as it has been this summer.
In stark contrast were the exotic cool-season grass pastures which was where all of the action was. We were able to find 44 nests on the season, all but one being in the native grass pastures. The nest breakdown of what we were able to find and monitor until nesting success or failure is as follows: 34 Red-winged Blackbird, 6 Savannah Sparrow, 2 Bobolink, 1 Eastern Meadowlark and 1 Wild Turkey. Only the turkey nest was in switchgrass, lending further credence to the fact that the only birds (or animals, for that matter) that really make use of this habitat are the ones heavily reliant upon thick grass cover. Further, while we were only able to find 6 Savannah Sparrow nests, 2 Bobolink nests and 1 meadowlark nest, there were surely many, many more of those species that either successfully nested in the exotic cool-season grass pastures or at least attempted to. In contrast, the switchgrass fields had 0 meadowlarks, and Savannah Sparrows were only detected very sporadically and inconsistently. We only detected Bobolinks on a small handful of occasions, either in the very beginning of the season or the very end, indicating that those observations were likely migrants passing through.
While it became quickly and increasingly obvious that most of the birds preferred the exotic cool-season pastures, it also was quickly apparent that these birds encounter an increasing number of obstacles to overcome in order to achieve nesting success and survival. We observed nearly all (!) of our pasture fields get cut either at or before the half-way point in the season (7 out of 10). Of course in these fields, it halted breeding activity and brought ruin upon the eggs, hatchlings or fledglings in those fields. The fact that these fields get cut during the breeding season is bad enough and perhaps the biggest reason grassland species are in such peril, but to exacerbate the situation, they are often done at inconsistent and subjective times, thus not at all allowing the birds the evolutionary mechanisms to properly adapt. Most of our fields got cut more than once over the 2 and-a-half month period, often after the adult birds were able to vacate after the first cut and then return to these areas, almost ensuring nesting failure. For species like Bobolinks, which typically nest once and don’t re-nest even after a nesting failure, there is little hope for their long-term breeding success in these situations.
In addition to the cutting and haying of these pasture fields, a number of factors are in play that are actively contributing to the decline of these grassland species. They include pesticide use, non-native animals and anthropogenic interferences, such as land development. There are many additional atypical factors contributing to the decline of native grassland bird species that most people wouldn’t even consider. For example, at one of our pasture study sites, I watched a male Bobolink essentially decapitate himself as he flew into the sharp wire of an electric fence at the border of the field as he chased away a Red-winged Blackbird. Non-native critters that are particularly cause for concern include: feral cats, very unfortunately abundant in these rural areas; and cows and horses that use these pastures for grazing. Of the 9 combined nests comprised of Savannah Sparrows (6), Bobolinks (2) and Eastern Meadowlarks (1), only 3 of them (two Savannah Sparrows, one Bobolink) were able to successfully fledge young. Two of the Savannah Sparrow nests were in fields that got cut, and two more were trampled by cows just as the chicks were about to fledge; the meadowlark chicks were also trampled by cows, and the other Bobolink nest’s chicks were killed. Needless to say, the long-term success of many of our grassland species face a long, long row to hoe.
Miscellaneous Bird Sightings
My crew and I ran into a few noteworthy birds in this wonderful, if under-birded, part of the state over the course of the field season. On our first day of training, May 14, we encountered two of our best birds for the season: a singing male SEDGE WREN (which I obtained voice recordings from) and two singing male HENSLOW’S SPARROWS, all three birds being, interestingly enough, in one of our wet-ish switchgrass fields, perhaps lending some credence to switchgrass being useful as a stopover for migrants. Neither the Sedge Wren nor the Henslow’s were present on a subsequent visit in late May before the field got mowed, indicating they were all likely migrants. A male SUMMER TANAGER was noted in a riparian area next to one of our study sites on June 17, one of at least 6 Summer Tanagers to have occurred between Crawford/Erie Counties in the spring/early summer of 2014. A CLAY-COLORED SPARROW was also heard singing in one of our switchgrass fields on May 23, but also not heard on subsequent visits, again indicative of a passing-through migrant. A MERLIN was observed at one of our study sites on June 5, and though not noted by us on subsequent visits, was actually reported by a local birder in mid-July from the same area, almost surely referencing the same individual we saw, possibly/probably indicating nesting activity nearby. NORTHERN HARRIERS, uncommon and local breeders in the state, were noted only once each, at two of our study sites, on May 19 and June 24, respectively. WILSON’S SNIPES were noted on four occasions spanning June 5 and July 2 at a specific wet area in one of our fields, indicating, at the very least, a nesting attempt. In addition to these uncommon birds and/or uncommon breeders in the state, it was a real joy to be able to experience nesting species that I’m not particularly used to running into this time of year in Pennsylvania: Purple Finches, Yellow-bellied Sapsuckers, Mourning Warblers, Northern Waterthrushes, Red-shouldered Hawks, Alder Flycatchers, etc.
Surely it’s obvious and common knowledge to the people who study these things for a living, but to me the biggest surprise was seeing how unproductive and desolate the switchgrass fields were, especially compared to the ecologically richer exotic cool-season grass pasture fields. Why there is such a huge difference between the two, why switchgrass seems to be, for all intents and purposes, completely worthless, I have no idea. And while I have known for many years that our grassland birds are in decline and face an ominous future in the face of increased development, changes in land use and additional negative anthropogenic factors, it was almost shocking to see first-hand just how bad these birds are doing. I hope for the best, but realistically fear for, and expect, the worst, as it relates to the long-term success of species like Bobolinks, Eastern Meadowlarks, Grasshopper Sparrows, and many of our other native grassland bird species. It’s scary to think that their situation is not only this bad now, but is likely to get much, much worse. In spite of this, I am proud and happy to have been able to contribute to the scientific and scholarly understanding of the mechanisms at play in this ongoing battle, and hope that our research this summer will contribute to invaluable research conclusions, which will hopefully lead to a better approach to the management of these delicate and fragile ecosystems.