Digital Nature Walk - Quinnipiac River Estuary (Winter)
Last weekend, I went for a little walk at the Eugene B. Fargeorge Preserve in New Haven, Connecticut. At only 32 acres, this property of the New Haven Land Trust isn’t very big, but what it lacks in size, it more than makes up for in interesting habitat and excellent opportunities for viewing wildlife. Starting from a small, inconspicuous parking area on Quinnipiac Avenue and running about a quarter of a mile along the edge of the property, a gravel service road acts as the backbone of the preserve’s humble trail system, which consists of two small loops — the Meadow Walk and the River Walk. The former will take you through a mixture of open, grassy marshland and thickets of various shrubs, vines, and small trees, while the latter leads to an old, wooden bird blind with an excellent view of Quinnipiac River and its tidal marshes. Both trails are great for a nature walk in any season, but I especially like to visit in the winter, when there is often a lot more going on than you might expect. Below, I have recorded the highlights of my walk, with commentary about the plants, animals, and ecological processes I observed, plus some pictures of varying quality (the wind by the water was, like, 30 miles an hour and I take a lot of these pictures on my phone through binoculars, so please, go easy on me!) Crappy pictures aside, I hope you enjoy— let’s begin our walk!
Meadow Walk:
This past year broke a nearly two-year drought here in Connecticut with a summer of quick, powerful storms and long, drizzly days. Now, as we move into the winter of 2024, conditions remain wet, and violent swings in temperature have made sure that the resulting precipitation has taken every form imaginable, from snow to rain to sleet and back again, all in the span of a few weeks (welcome to New England…or climate change…it’s hard to tell). All this rain and snow melt has resulted in a lot of flooding, from which the Quinnipiac estuary was not spared. While the flood waters themselves had receded to easily dodgeable puddles by the time I set off down the Meadow Walk, the signs of what had been were still caked to the trail in the form of mats of dead marsh grass, washed up by the tides. A fair-sized rock, deposited snuggly in the midst a thicket of reeds, marked the depth the water had reached further down towards edge of the marsh.
Combined with several downed trees and shrubs, all this made for a bit of a violent scene, but in truth, these kinds of storms and flooding events are an important part of saltwater marsh ecology. At the end of the growing season, the smooth cordgrass (Spartina alterniflora) which dominates the marsh’s plant community goes dormant and its aboveground shoots begin to dieback. When large storms come along, the shoots are broken off and swept up in the tides, where they either wash ashore like the material seen in the picture below or are pulled out to sea. All this dead plant material — called detritus — acts as an important foundation for food chains in the marsh itself and in the ocean beyond. The detritus which washes ashore or remains in the marsh is fed upon by bacteria, fungi, and various invertebrates and, overtime, the nutrients contained within the shoots are recycled back into the soil. The detritus washed out to sea, meanwhile, serves as a vital food source for young fish and invertebrates, which are in turn fed upon by other fish and by humans (Wainright et al. 2000; Montemayor et al. 2011).
While storms can leave marshes with some short-term damage, they are quite resistant in the long term. The thick mats of grass that cover a healthy marsh act as a shield against erosion, preventing excessive loss of sediment and protecting the marsh from being slowly washed away (Leonardi et al 2018). Salt marsh vegetation also plays a crucial role in lessening the risk of flooding in surrounding uplands by dissipating wave energy and storm surges which might overwise continue uninterrupted to shore. One study from 2014, which tested the buffering abilities of a transplanted sample of saltmarsh grass and sediment in a wave tank, found that the marsh grass was able to reduce wave height by as much as 18% over a distance of forty meters (Möller et al). In a world where powerful storms are becoming more and more common as a result of climate change, saltmarshes can play an important role in protecting coastal communities from flood damage.
In areas where the dead marsh grass did not provide a dry (ish) mat to stand on, the Meadow Walk remined pretty muddy and in these spots, I found lots of well-preserved animal footprints, including the raccoon (Procyon lotor) tracks pictured above. Along with deer and squirrel, raccoon prints are probably among the most common animal tracks that you will find in the northeast (especially around wetlands like this one), but they still never cease to thrill me with their uniqueness. Raccoon prints often appear in a very particular pattern, with a front print and a hind print appearing directly next to each other. This pattern is unique to raccoons, so even in cases where the tracks are in poor condition, you can still identify them if they consistently show it. If not, you’ll have to examine the tracks themselves, which will look remarkably like little, five-fingered human hands. Like humans, raccoons use their hands to pick up and manipulate objects in their environment, thought they typically do so by holding objects between their palms rather than grasping them with their fingers, which have fairly limited mobility (Iwaniuk and Wishaw 1999). Raccoons also have an acute sense of touch, which becomes even more sensitive when the receptors in their skin are submerged in water (Rasmusson and Turnbull 1986). This is why you will sometimes see raccoons “washing” their food before eating — they are not trying to get dirt or other contaminates off of it, but are feeling the object, trying to get more information about what it is before sticking it in their mouths (Zeveloff 2002).
While I was examining the raccoon prints, I kept listening for the large flocks of birds I usually find on the Meadow Walk, which take advantage of the cover and food provided by the thickets of shrubs and vines. At that moment, however, I wasn’t hearing much of anything except for the quiet peeping of a small flock of white-throated sparrows (Zonotrichia albicollis) feeding in the underbrush. These cryptic little sparrows only show up in this part of Connecticut during the winter, when they fly south from their Canadian breeding grounds to the relative warmth of New England. Like most sparrows, their plumage is fairly drab, but their song — a clear, whistled recitative that provides some much-needed oral color in an otherwise silent winter forest — is absolutely beautiful. The individual pictured above has a white head with black stripes running across it, but this is not the species’ universal coloration — about half of individuals have white heads and the other half have tan heads. Many bird species display similar color variations among individuals, but what makes the white-throated sparrow special is that the two different color morphs appear to be connected on the genetic level to different behaviors. This means that the two morphs not only look differently but act differently too. White-headed individuals are typically more aggressive, spending much of their time singing and chasing other birds away from their territories, while the tan-headed individuals are typically more docile and nurturing (Kopachena and Fall 1993A; Kopachena and Fall 1993B). At the beginning of their mating season, the more aggressive white-headed female sparrows quickly find and pair off with the more nurturing tan-headed males (which are more likely to stick around and help take care of the young), leaving the tan-headed females to mate with the white-headed males (Houtman and Falls 1994). As a result, most mating pairs consist of one white-headed individual and one tan-headed individual.
After spending more time than I’d care admit trying and failing to photograph the sparrows, I finally gave up and decided to focus instead on the thicket of shrubs and vines that they were feeding in. Unfortunately, most of the plants I found here were non-native, invasive species, including autumn olive (Elaeagnus umbellata), Japanese honeysuckle (Lonicera Japonica), and oriental bittersweet (Celastrus orbiculatus). On the side of the trail closer to the edge of the marsh, however, there was at least one native species pushing back — the groundsel tree or saltbush (Baccharis halimifolia). Groundsel trees belong to the same family as sunflowers and asters (Asteraceae) and are the only member in eastern North America that reaches tree size. They are what botanists call halophytes, meaning that they are among the few plants which can tolerate the high-salt conditions of river estuaries, brackish marshes, and seashores. Different halophytes have different adaptations for surviving in high salt conditions, ranging from excreting the salt that they take in back out from their leaves to isolating the salt in small cavities within their cells called vacuoles. I found a blog post by a researcher at the University of Delaware claiming that groundsel trees use the latter methods to resist damage from excess salt accumulation, but have not been able to independently back up this claim with a peer-reviewed source, so you’ll have to take it with a grain of salt (hah!). Because of their wind-blown seeds and weedy growth habit, groundsel trees are able to easily colonize new habitats and spread quickly, especially in salt-heavy areas where they have a competitive advantage over other species. As a result, they have become invasive in European and Australian salt marshes and, in parts of their native range, have even started to spread inland along major roadways, where the use of deicing salts has created high-salinity soils in which they thrive.
Past the groundsel tree, growing tall in the water around the edges of the marsh, is another halophyte, the status of which is a bit more confusing than either the native groundsel tree or the invasive shrubs and vines further back from the shore. The common reed (Phragmites australis), often referred to as “phrag” by aquatic ecologists and wetland managers, is native to North America, but has a highly cosmopolitan distribution, with a native subspecies also found in Europe and Asia. This Eurasian subspecies (Phragmites australis australis) was introduced to North America in the early 1800s and has since become invasive. Common reeds can grow very tall — up to 20 feet! — and the Eurasian subspecies spreads quickly and aggressively through clonal reproduction, shading out native marsh grasses which tend to be much shorter in height. The resulting dense, single-species stands of phrag can provide shelter for some more generalist wetland birds, such as red-winged blackbirds (Agelaius phoeniceus) and marsh wrens (Cistothorus palustris), but may degrade habitat for specialists like the saltmarsh sparrow (Ammospiza caudacuta), which seem to prefer nesting in the native, short grasses (Guntenspergen and Nordby 2006; Lambert et al. 2010). Phrag also grows in freshwater and can be seen around the edges of ponds and lakes, as well as in the drainage ditches along the sides of highways.
River Walk:
After I had completed one full loop on the Meadow Walk, I took a side trail that cut through the thicket to the River Walk, which runs west towards the water. Despite its name, much of the River Walk consists of similar habitat to that found on Meadow Walk, all be it with a few taller oak trees (Quercus spp.) towering above the mostly invasive understory. It was here, towards the beginning the trail, that I finally found the large numbers of songbirds that I was used to from previous winter visits. This particular flock consisted mostly of American robins (Turdus migratorius), but also included a few yellow-rumped warblers (Setophaga coronata) and black-capped chickadees (Poecile atricapillus). I stopped to watch for a little while, trying to figure out why they were all gathered in this particular spot, and soon found my answer when I observed the robin pictured below plucking berries from one of the eastern red ceders (Juniperus virginiana) growing all along the side of the path.
Technically, the eastern red ceder isn’t really a ceder, but a member of the juniper family. What’s more, its berries are not really berries, but heavily modified seed cones. A berry is a fruit and, as we've previously discussed with the gingko tree, all fruits have ovaries, while the cones of conifer trees, such as the eastern red cedar, do not. The cone’s berry-like appearance and texture are the result of the cone scales shrinking and fusing to create a waxy outer coating around the seeds within. Whatever you want to call them, ceder berries are ecologically very important because they mature during the height of the winter and so provide a crucial food source for songbirds during a difficult time of the year. This is especially true for the aptly named ceder waxwing (Bombycilla cedrorum), one of the only birds in North America that feeds exclusively on fruit (technically cones in this case), as well as for the less picky American robin. In one study out of Texas, a single waxwing was found to consume an average of 683 Ashe juniper berries (a close relative of eastern red ceder) each day, while robins were found to consume an average of 555 (Chavez-Ramirez and Slack 1994)! Both species gather in large flocks to feed and are able to strip single trees of their berries in a very short amount of time. This makes them excellent seed dispersers, since by the time the berries have *ahem* passed, the birds have usually moved on from the tree that they originally came from, allowing that tree to spread its young into new areas. Seeds from berries that have passed through a bird's digestive system are also between 1.5 and 3.5 times more likely to germinate, so this arrangement quite advantageous for both the birds and the ceders (Holthuijzen and Sharik 1985).
Leaving the robins to their feast, I continued down the path until, finally, the thicket gave way to the open, wind-swept expanse of the salt marsh and the churning Quinnipiac River just beyond. Even on days like this, when temperatures plunge below freezing, the water here in the estuary remains ice free due to its high salt content. When mixed into solution, salt ions surround water molecules and buffer their interactions with each other, keeping them from joining together into ice crystals until temperatures reach well below freezing. For ducks, geese, and other waterfowl that depend on open water for food or safety from predators, this makes estuaries and seashores crucial winter habitat. The Eugene B. Fargeorge Preserve is an excellent place to see wintering ducks and it is one of the main reasons I like to come around during this time of the year. Arriving at a small bird blind sitting on the shore of the river, I slipped inside and started to scan the water with my binoculars.
In general, there are two kinds of waterfowl that you will see in a winter estuary, divided by the method that they use to find food. The first group, known as the dabbling ducks, is probably the most familiar, as it includes mallards (Anas platyrhynchos) and American black ducks (Anas rubripes), two of the most common North American species. Dabbling ducks feed by leaning forward with their feet in the air and their heads underwater, moving their necks back and forth to forage for aquatic plants and invertebrates on the bottom. Because they remain floating on the surface while they are feeding, dabbling ducks require shallow water and so will typically be found in the marshy part of an estuary, rather than out on the river, where the water is deeper. On this particular morning, I saw a number of mallards and black ducks feeding in the shallow channels running through the saltmarsh on either side of the bird blind, as well as a small group of gadwalls (Mareca strepera). These beautifully understated ducks breed in the marshes and potholes of the central prairie states during the summer and can be easily identified in flight by the distinctive white patches on their wings. They usually feed by dabbling, but also have a reputation for stealing food from other, smaller waterfowl, especially American coots (Fulica americana).
The second group of waterfowl that you are likely to see in a winter estuary are the diving ducks, which as the name implies, feed by diving down below the surface of the water. In order to do this, diving ducks make themselves less buoyant by compressing their feathers to squeeze out the air trapped between them; while underwater, most hold their wings tightly against the sides of their bodies, while using their feet to paddle. Some diving ducks, such as the mergansers, feet primarily on fish and even have serrated bills to help them hold onto their slippery prey. Others, like the adorable buffleheads (Bucephala albeola) that I saw feeding out in the middle of the river, trawl the bottom for aquatic plants and invertebrates. These buffleheads, like the white-throated sparrows I saw in the thicket, probably spent the summer up in the boreal forests, where they nest in old tree cavities created by northern flickers (Colaptes auratus). Not long after all the eggs in a bufflehead nest have hatched, the mother coaxes her chicks to jump out of the tree cavity and follow her down to the water. This jump can be as much as 50 fifty in height, but the ducklings are not harmed when they hit the ground below — they are so light that they build up very little momentum as they fall and so the opposing force of the ground upon impact is not enough to hurt them.
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Well, that’s about it — I hope you enjoyed the walk! If you live in the New Haven area, I would highly recommend checking out the Eugene B. Fargeorge Preserve. If not, I’d encourage you to explore a wetland (saltwater or freshwater) wherever you may be and see what you can find. Just remember to be careful and respectful of the plants and animals that live there — these habitats can be delicate, so it's especially important to stay on approved trails or boardwalks! From there, you should still be able to see a lot — it's an amazing world out there and there’s always something interesting happening, even on the coldest day of the year!
Sources:
Chavez-Ramirez, F., & Slack, R. D. (1994). Effects of avian foraging and post-foraging behavior on seed dispersal patterns of Ashe juniper. Oikos, 40–46.
Guntenspergen, G. R., & Nordby, J. C. (2006). The impact of invasive plants on tidal-marsh vertebrate species: common reed (Phragmites australis) and smooth cordgrass (Spartina alterniflora) as case studies. Studies in Avian Biology, 32, 229.
Holthuijzen, A. M., & Sharik, T. L. (1985). The avian seed dispersal system of eastern red cedar (Juniperus virginiana). Canadian Journal of Botany, 63(9), 1508–1515.
Horncastle, V. J., Hellgren, E. C., Mayer, P. M., Engle, D. M., & Leslie, D. M. (2004). Differential consumption of eastern red cedar (Juniperus virginiana) by avian and mammalian guilds: implications for tree invasion. The American Midland Naturalist, 152(2), 255–267.
Houtman, A. M., & Falls, J. B. (1994). Negative assortative mating in the white-throated sparrow, Zonotrichia albicollis: the role of mate choice and intra-sexual competition. Animal Behaviour, 48(2), 377–383.
Iwaniuk, A. N., & Whishaw, I. Q. (1999). How skilled are the skilled limb movements of the raccoon (Procyon lotor)? Behavioral Brain Research, 99(1), 35–44.
Kopachena J. G., & Falls J. B. (1993A). Re-evaluation of morph-specific variations in parental behavior of the white-throated sparrow. The Wilson Bulletin 105: 48–59.
Kopachena, J. G., & Falls, J. B. (1993B). Aggressive performance as a behavioral correlate of plumage polymorphism in the white-throated sparrow (Zonotrichia albicollis). Behaviour, 124(3–4), 249–266.
Lambert, A. M., Dudley, T. L., & Saltonstall, K. (2010). Ecology and impacts of the large-statured invasive grasses Arundo donax and Phragmites australis in North America. Invasive Plant Science and Management, 3(4), 489–494.
Leonardi, N., Carnacina, I., Donatelli, C., Ganju, N. K., Plater, A. J., Schuerch, M., & Temmerman, S. (2018). Dynamic interactions between coastal storms and salt marshes: A review. Geomorphology, 301, 92–107.
Möller, I., Kudella, M., Rupprecht, F., Spencer, T., Paul, M., Van Wesenbeeck, B. K., … & Schimmels, S. (2014). Wave attenuation over coastal salt marshes under storm surge conditions. Nature Geoscience, 7(10), 727–731.
Montemayor, D. I., Addino, M., Fanjul, E., Escapa, M., Alvarez, M. F., Botto, F., & Iribarne, O. O. (2011). Effect of dominant Spartina species on salt marsh detritus production in SW Atlantic estuaries. Journal of sea research, 66(2), 104–110.
Rasmusson, D. D., & Turnbull, B. G. (1986). Sensory innervation of the raccoon forepaw: 2. Response properties and classification of slowly adapting fibers. Somatosensory Research, 4(1), 63–75.
Wainright, S. C., Weinstein, M. P., Able, K. W., & Currin, C. A. (2000). Relative importance of benthic microalgae, phytoplankton and the detritus of smooth cordgrass Spartina alterniflora and the common reed Phragmites australis to brackish-marsh food webs. Marine Ecology Progress Series, 200, 77–91.
Zeveloff, S. I. (2002). Raccoons: a natural history. UBC Press.
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