A Natural History of Millbrook Marsh,
A Wetland In An Urbanizing Setting

Birds

Among the birds inventoried at Millbrook Marsh up to this point (Table 6-14) are several identified as wetland obligates, often found in an aquatic habitat at some stage of life. The Belted kingfisher breeds in riparian or open water zones and dives for fish. The Common yellowthroat is a facultative wetland bird found in moist grassy or shrubby areas. A flycatcher, the Eastern phoebe, will nest under overhanging cliffs or banks, under bridges, and in farm buildings. The Killdeer is one of the banded plovers who forage for insects and small aquatic animals on shores or grasslands. Mallards depend on wetlands for feeding and breed in emergent wetlands, open water, and riparian zones. Song sparrows are especially abundant in moist areas with shrubs, hedgerows, and wood margins. The Warbling Vireo breeds in riparian zones and the Great Blue Heron will breed in emergent wetlands, open water, and riparian zones. The other wetland obligate, facultative wetland, and facultative birds found so far at Millbrook Marsh are the Green heron, Wood duck, Common snipe, Tree swallow, Tufted titmouse, Gray catbird, Yellow warbler, Red-winged blackbird, Indigo bunting, Lincoln’s sparrow, Swamp sparrow, and Song sparrow.

The majority of the birds at Millbrook Marsh, as in most wetlands, are wetland generalists. They take advantage of the increased food and cover of the wetland habitat, but are not restricted to it. In Pennsylvania, 60% of birds depend partially on some type of aquatic ecosystem. Many of the wetland specialists are uncommon or very secretive in behavior, and therefore, may be easily missed during inventories (Brauning 1989.) Though not preferred by some species due to size, cover type, or surrounding land use, Millbrook Marsh could still support several of the wetland specialists not identified up to now. The Marsh wren (Cistothorus pallustris), a Pennsylvania Threatened passerine (songbird), nests in emergent cattails or sedges and rarely chooses marshes smaller than one acre in size (Brauning 1989). Though it has not been identified in Millbrook Marsh, the correct habitat does exist here. It was noted by M. Woods in 1952 that the Marsh wren had been recorded regularly within a 24 km radius of State College, though in very small numbers. It was seen in 1977 within 40 km (25 mi) of State College (Wood 1980), but was not noted for Centre County during the 7-year period (from 1983 to 1989) for the Atlas of Breeding Birds in Pennsylvania.

The Prothonotary warbler (Protonotaria citrea) is a Pennsylvania Rare species, and breeds only in riparian zones or forested wetlands. It was noted in 1992 as a possible breeder in Centre County though competition with other cavity nesters may be limiting populations. Millbrook Marsh is most likely not forested enough (T. O’Connell, pers. comm.), though they are sometimes attracted to nest boxes placed over standing water or along the edge of a stream (Brauning 1992). Other wetland specialists that should be looked for in Millbrook Marsh include the Alder flycatcher (Empidonax alnorum), Northern rough-winged swallow (Stelgidopteryx serripennis), and the Winter wren (Troglodytes troglodytes). In 1952 the Northern waterthrush (Seiurus noveboracensis) and Louisiana waterthrush (Seiurus motacilla) were both common spring and fall transients in the State College vicinity (Wood 1952). They were also observed within 40 km of State College in 1977 (Wood 1980). The Millbrook Marsh area may be too open to accommodate the waterthrushes.

Of the non-passerines, there are some endangered, threatened, or rare birds restricted to emergent wetlands that might be found in Millbrook Marsh. They are the American bittern (Botaurus lentiginosus), Least bittern (Ixobrychus exilis), and Green-winged teal (Anas crecca), though bitterns and other rare species are associated with large wetlands (Brauning 1989). Other birds with a distinct possibility of being found in Millbrook Marsh include the Virginia rail (Rallus limicola) and Sora (Porzana carolina). There is a small possibility of finding the Sedge wren (Cistothorus platensis), Common moorhen (Gallinula chloropus), and Black rail (Laterallus jamaicensis). The American bittern prefers extensive freshwater emergent marshes, but will occasionally summer in smaller marsh areas, in bogs, ponds, or wet meadows. It was noted in Centre County, and breeding was a probability (Brauning 1992). One American bittern was recorded as wintering at Centre Furnace Pond, now known as the Duck Pond, in 1949-50 (Wood 1952). The Least bittern was also noted in Centre County, though it would be less likely to find it at Millbrook since it prefers large deep-water cattail marshes with scattered shrubs and small trees (Brauning 1992). They are sometimes found in smaller marshes and in 1952 it was a rare spring and fall transient in the 24 km (15 mi) surrounding State College (Wood 1952).

The Green-winged teal is relatively secretive during breeding and difficult to survey accurately. It breeds in emergent wetlands, with Pennsylvania being the edge of its breeding range. There was one possible breeding location at the southern edge of Centre County (Brauning 1992). In 1952 it was reported as a common spring and fall transient within 24 km (15 mi) of State College, occasionally wintering in the area (Wood 1952). The Virginia rail needs cattail and sedge for nesting, and does not need an especially large area. It was found probably breeding in Centre County (Brauning 1992). In 1952 it was considered an uncommon spring and fall transient and rare summer resident, as were Soras (Wood 1952). Soras, found breeding in the State College region, nest in marshes, bogs and wet meadows, but their preference is cattails and sedges with mud and standing water (Brauning 1992). The Green heron is a breeder in the State College vicinity (Brauning 1992) and was considered to be a common spring and fall transient as well as summer resident in 1952 (Wood 1952). Playback on taped calls were tried in Millbrook during 1997 and 1998 to survey the secretive bitterns and rails, but with no success (T. O’Connell, pers. comm.).

Many raptors are also closely associated with wetlands for food and breeding habitat. Identified recently in Millbrook Marsh was the Red-tailed Hawk, an upland species that often hunts voles in meadows and wetlands, and the American Kestrel, with nests in hollow trees and hunting grounds of meadows and wetlands along floodplains. The Red-tailed Hawk is a frequent flyer over Farm 12 (Tamminga, pers. comm.), but whether it nests at Millbrook is unknown. The uncommon Cooper’s hawk has also been identified recently in the marsh. It is usually found in open woodlands and wood margins.

There are several other Pennsylvanian birds of prey that utilize emergent wetlands and might probably be found benefiting from Millbrook Marsh. The Northern harrier (Circus cyaneus), also known as the Marsh Hawk, requires grassy vegetation to conceal its nest, and hunts rodents such as the meadow vole, amphibians, reptiles, and small to medium sized birds. In 1952 it was considered a common spring and fall transient with a small number being summer and winter residents (Wood 1952). There were possible nesting sites scattered throughout Centre County in 1992 (Brauning 1992). The Short-eared Owl (Asio flammeus) was previously called the Marsh Owl and hunts during the day. It was an uncommon and irregular winter visitor in 1952 (Wood 1952). The Great-horned Owl (Bubo virginianus), hunts in floodplains, as does the Long-eared Owl, (Asio otus) which is nesting in the State College area (Brauning 1992) but only occurred in small numbers in 1952. The Common Screech Owl (Otus asio), like the Great-horned Owl, was uncommon in 1952. It too is now found nesting in the State College area (Brauning 1992). The nest site is often in tree cavities in and around wetlands and the diet is made up of rodents and other vertebrates and invertebrates associated with wetlands. The Barn Owl (Tyto alba) is often dependent on voles and shrews, and often nests in old barns and silos adjacent to fields or grazed meadows. In 1952 they were commonly nesting in silos around State College (Wood 1952). One of the smallest owls, the Saw-whet Owl (Aegolius acadicus), is only about the size of a robin, and nests in cavities found along streams or small wooded wetlands (Rymon 1989). They were seen as very rare winter visitors in 1952, but might have been underestimated (Wood 1952). They are probably breeding in the vicinity of State College (Brauning 1992).

Millbrook Marsh offers a wide variety of cover types and foods despite its somewhat small size. Habitat requirements are met for many of the birds discussed here, though due to marsh area and level of activity in the surrounding area, not all will be found. Besides wetland area, the occurrence of some wetland species is dependent upon other variables such as proximity to large water bodies or other wetlands, forest proximity or size, and water depth in the wetland (Watts 1993, Cashen 1998) for example. Cashen (1998) found that in general, wetland area-dependent species tended to be long distance migrants that nested on or near the ground. He considered a wetland greater than 4 ha to be fairly large. The smallest of 42 wetland study sites was 0.65 ha and the largest was 20.43 ha. The probability of detecting 32 wetland bird species considered to be area dependent was determined for restored wetlands in Pennsylvania (Cashen 1998). Of the birds that might be found in Millbrook Marsh, those for which the probability is at least 70% are the Marsh wren, Rough-winged swallow, Northern waterthrush, Green-winged teal, Virginia rail, Sora, and Common moorhen. The following Table 6-14 lists the 52 bird species that have been sighted recently at Millbrook Marsh.

Table 6-14
Millbrook Marsh Bird Inventory 1995-1998

Common Name Scientific Name

Brooks
et al. 1996

CWC
2/25 1995

1996

1994 to 1998*

Mallard # Anas platyrhynchos

*

 

*

*

Wood duck # Aix sponsa      

*

Coopers hawk Accipiter cooperii      

*

Sharp-shinned hawk Accipiter striatus      

*

American kestrel Falco sparverius      

*

Red-tailed hawk Buteo jamaicensis      

*

Great blue heron # Ardea herodias  

*

 

*

Green heron # Butorides striatus      

*

Killdeer Charadrius vociferus

*

 

*

*

Common snipe # Gallinago gallinago      

*

Mourning dove Zenaida macroura

*

   

*

Rock dove Columba livia

*

   

*

Belted kingfisher # Ceryle alcyon

*

   

*

Downy woodpecker Picoides pubescens      

*

Northern flicker Colaptes auratus

*

   

*

Eastern kingbird Tyrannus tyrannus      

*

Eastern phoebe Sayornis phoebe

*

   

*

Willow flycatcher Empidonax traillii

*

   

*

Barn swallow Hirundo rustica

*

 

*

*

Tree swallow + Tachycineta bicolor      

*

Blue jay Cyanocitta cristata

*

   

*

American crow Corvus brachyrhynchos

*

 

*

*

Black-capped chickadee Parus atricapillus      

*

Tufted titmouse + Parus bicolor      

*

House wren Troglodytes aedon

*

   

*

Northern mockingbird Mimus polyglottos      

*

Gray catbird + Dumetella carolinensis

*

*

 

*

American robin Turdus migratorius

*

   

*

Eastern bluebird Sialia sialis      

*

Cedar waxwing Bombycilla cedrorum

*

 

*

*

European starling Sturnus vulgaris

*

   

*

Red-eyed vireo Vireo olivaceus  

*

 

*

Warbling vireo Vireo gilvus

*

   

*

Yellow warbler + Dendroica petechia

*

   

*

Common yellowthroat Å Geothlypis trichas

*

   

*

American redstart Setophaga ruticilla      

*

House sparrow Passer domesticus      

*

Red-winged blackbird Å Agelaius phoeniceus

*

 

*

*

Common grackle Quiscalus major

*

   

*

Brownheaded cowbird Molothrus ater

*

 

*

*

Northern cardinal Cardinalis cardinalis

*

   

*

Indigo bunting + Passerina cyanea

*

   

*

House finch Carpodacus mixicanus

*

   

*

American goldfinch Carduelis tristis

*

 

*

*

Dark-eyed junco Junco hyemalis      

*

American tree sparrow Spizella arborea

*

 

*

*

Chipping sparrow Spizella passerina

*

   

*

Field sparrow Spizella pusilla

*

*

 

*

White-throated sparrow Zonotrichia albicollis      

*

Lincoln’s sparrow + Melospiza lincolnii      

*

Swamp sparrow # Melospiza georgiana      

*

Song sparrow + Melospiza melodia

*

 

*

*

Species Richness = 52

# = Obligate Wetland Species
Å = Facultative Wetland Species
+ = Facultative Species
* 1994-1998 bird species observed during formal point counts (M. Gaudette and T. O’Connell pers. comm) and informal birding walks (T. O’Connell and R. Brooks, pers. comm.)

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