Research Report #35 — Cowbird
For many years scientists and naturalists have been studying and observing the flora and fauna of the Shawangunk Ridge. Foremost among them was Daniel Smiley, for whom Mohonk Preserve’s Daniel Smiley Research Center is named. Dan wrote numerous reports summarizing his observations on various topics. This regularly occurring series will feature some of these reports; some hold tremendous scientific value today and just await an interested researcher to follow up, others showcase a quirky sense of humor or highlight an oddity of nature.
Read the report: Cowbird. August, 1977. Daniel Smiley.
A Note from Paul C. Huth, Director of Research Emeritus: We are fortunate that Naturalist Daniel Smiley was an exceptional documentary observer of nearly all aspects of the ecosystem. The influence of the natural world surrounding Dan at Mohonk started from a young age, and grew at the time he attended the Mohonk School, from 1920–1926. As a project focusing on bird identification and bird migration, teacher E. R. Squibb, got the boys to assist him in recording spring migratory bird arrival dates at Mohonk starting in 1925.
In this Research Report, Dan documents his “fifty years” of observations of the native Brown- headed Cowbird, Molothrus ater, at Mohonk Lake. The Cowbird is a member of the Family Icteridae, the Family containing other bird species such as the Bobolink, meadowlarks, grackles, grosbeaks, finches, the American Goldfinch, and the House Sparrow. The Cowbird is not a nest builder. This species is considered by many to be a problem or ‘bad’ bird species, because of its long but successful evolution to become a “brood parasite,” unfortunately affecting some local populations of host species, many already under stress from habitat changes, and very negatively impacting some rare bird species and New York State species of special concern.
In the 18th century, the Brown-headed Cowbird was known as the “Buffalo Bird,” as it was usually seen associated with the large moving herds of American Bison distributed in parts of their historic range on the grasslands of the Great Plains, through the mid-west and east to New York and Pennsylvania, and southward to Texas and the Gulf Coast. By the late 18th and 19th century, during and after settlement, it became known locally as the “Cow Bunting,” “Cowpen-bird,” or “Cow-bird,” since they were commonly associated with domestic livestock, consuming grass, coarse weed, corn, and grain seeds, “searching in their droppings for undigested grains and intestinal worms,” as well as insects stirred up by the movement of the animals.
At Mohonk, Dan used the archived late 1920’s Mohonk School bird arrival records of some 60 species of birds listed by E. R. Squibb, and those of his brother Keith during the spring and summer of 1927, 1928, and 1929 to show that no Cowbirds were observed around the extensive hotel operations or in the surrounding forest. This, even with some 68 Mohonk House horses stabled in the nearby Livery and Stage sections of the historic Mohonk Barn (Nell Boucher, Mohonk Archives). Dan noted that the first appearance of the Cowbird in the above records was from 27 April 1930, “when two males and two females were seen at the edge of the (Mohonk) Garden.” And later, on 2 August, an immature Cowbird was observed. The first breeding record at Mohonk was documented in 1931, when a fledging was observed with a Song Sparrow host parent on 23 June.
Looking at his documentary Cowbird observations over the next decades, we can glean much from Dan’s broad knowledge and comparative experience. During the decades of the 1930s and 1940s, Cowbirds were being noted pretty regularly and spring arrival dates were noted.
During that period, it had “….become a regular breeding bird… ” at Mohonk. Of interest, Dan noted that “In 1953, for the first time, I recorded Cowbirds in deep woods at Duck Pond and Cedar Drive.” In 1954, he recorded “more than usual,” and again in 1959, “much more common than usual, even in the woods.” In 1960, Dan reported Cowbirds as “regular visitors” at a ground bird feeder during spring to mid-summer. From 1961 to 1965, Dan summarized the Cowbird as “…consistently ‘more than usual.’”
Cowbird spring arrival dates ranged from early April during the period of 1930 to 1955, then trended earlier to an average date of 20 March in the 1960s and 1970s, and a few years with arrivals the first week of March. Dan felt that the trend toward earlier arrival dates over time could be “related to the number of Cowbirds wintering in nearby lowlands,” and that breeding birds, both adults and young, were returning to a “home territory.” The latter, indicated to Dan, by the number of birds that he had banded at Mohonk which were documented as having returned. This, he notes, was “of considerable interest.” Dan described his insight:
“Here is a species that is presumed to have developed the parasitic pattern of reproduction because it followed the Bison herds, but through our banding records it is demonstrating a ‘sense of place.’”
Of special note, Dan obtained his bird banding licence, №4039, from the Inland Bird Banding Association in 1929. Over the next 60 years, he and his brother Keith, banded some 17,000 birds as part of their detailed bird population and migration studies centered at Mohonk.
Of Cowbird parasitism, Dan and the staff documented “21 instances on 7 host species” — Wood Thrush, Black and White Warbler, Chipping Sparrow, Towhee, Song Sparrow, Junco, and Red- eyed Vireo. Dan felt that from his observations, the Towhee, Song Sparrow, Junco and Red- eyed Vireo were “less common” over time. But, he noted, other ecosystem factors could also be at play.
As for the Cowbirds “changing status” over the years, Dan offered some “conclusions and speculations.” The first might be related to “available food” in the vicinity of Mohonk. Dan recalled that whole corn was being put out at the family residence at Mohonk in 1927 to feed released pairs of Gray Squirrels. By 1931, that bird feeding was moved to a window shelf. Later in the 1940s it was returned again to the ground. Dan reported that four Cowbirds that he banded “in 1958–1959, were caught in chipmunk live-traps at the ground feeding station.”
Other “large-scale ground-feeding stations” at Mohonk were discontinued in the early 1970s, with “small platform feeders” remaining. As a result, Dan felt that “ten (Cowbirds) are seen today (August, 1977) in the vicinity of Mohonk buildings where in the 1960’s thirty would have been gathered.” The number in the woods though, “remained fairly constant during the breeding season.” A second issue impacting the Cowbird population at Mohonk in the early years could have been Peregrine Falcon predation. Peregrine spring arrival at the Sky Top eyrie occurred in late February, and they were in the vicinity of the Sky Top eyrie well into the summer from 1926–1930, the last year of successful nesting there. Dan noted that in 1931, 1932, and 1933, the Peregrines “arrived as usual but had left by April about when the Cowbirds arrived.” From 1935 to 1947, Peregrines appeared at Sky Top later in the spring but did not stay. There were none seen there after 1947. Dan felt that the Peregrines “may have had a significant effect on the number of Cowbirds on the mountain either through predation directly, or through intimidation, causing the Cowbirds to avoid the area.”
Thinking of the interconnectedness of local ecosystem components and future research opportunities, Dan felt that if the Peregrine Falcon returned to Mohonk to nest again on Sky Top, and if bird feeding, especially on the ground was kept at a minimum, the relationship to the Cowbird population “should get a good field trial.”
Read the report: Cowbird. August, 1977. Daniel Smiley.
