John James Audubon named the Henslow's Sparrow in honor of his good friend John Stevens Henslow, a professor of botany at Cambridge and teacher of Charles Darwin.
There is evidence of a significant decline across the species' range and there has been a loss of grassland habitats in New York State in recent years. Breeding Bird Survey data show a possible decline of 18.7% per year between 1980 and 2006 in New York (Sauer et al. 2007). When comparing data from the first and second breeding bird atlases, an 80% decrease is noted with Henslow's sparrows reported in 348 blocks (Andrle and Carroll 1988) and 70 blocks (McGowan and Corwin 2008), respectively. McGowan and Corwin (2008) describe this decline as "the largest proportional decline in any formerly common species in the Atlas."
As with most grassland birds in the last few decades, Henslow's Sparrow populations have been significantly declining. Analyzed Breeding Bird Survey data from New York showed that the population may have declined by as much as 18.7% per year between 1980 and 2006 (Sauer et al. 2007). During the first Breeding Bird Atlas (1980-1985), Henslow's Sparrows were found in 348 blocks. Two-hundred thirteen of those blocks were reported with probable or confirmed breeding (Andrle and Carroll 1988). The second Breeding Bird Atlas reported 70 blocks with Henslow's Sparrows. Probable or confirmed breeding was reported in 57 of those blocks (McGowan and Corwin 2008). Areas in New York where Henslow's Sparrows are persisting rely on human disturbances to maintain the grassland habitat. For example, farming practices and military practices at the Fort Drum Military Reservation have maintained the grassland habitat in Jefferson County. However, there are areas where Henslow's Sparrows are no longer found, indicating possible habitat changes range wide (McGowan and Corwin 2008). Even with the recent declines, it is possible that Henslow's Sparrows are more abundant and widespread in New York now than they were in the early 1900s (Levine 1998).
Henslow's Sparrows were first documented in New York in 1844 on Long Island. It is not known if Henslow's Sparrows were found in New York prior to European settlement but, there were probably areas with suitable habitat such as wet meadows (Levine 1998). After European settlement, the landscape of New York began to change with forests being logged and cleared for farming. In the early 1900s, they were considered a local breeder that was uncommon or rare in the state. Between the 1920s and 1940s Henslow's Sparrow populations appeared to be increasing as they were reported from many new locations. Then, as early as the 1950s, reports became less frequent and they were no longer found on the south shore of Long Island (Andrle and Carroll 1988). Analysis of Breeding Bird Survey data from 1966-2006 for New York show that Henslow's Sparrow populations appear to be decreasing at a rate of approximately 12.1% per year (Sauer et al. 2007).
The most significant threat to Henslow's Sparrows is the loss of suitable grassland habitat. Economic factors have affected the viability of farms in New York. Many farmers have intensified their farming practices, converted hayfields to row crops, or abandoned farming altogether (Andrle and Carroll 1988, Post 2004, McGowan and Corwin 2008). Remaining hayfields are often mowed earlier and more frequently to increase production. As a result, the mortality rate of young in those fields is high and sometimes adults are killed during mowing. As farms are abandoned they are lost to development or the land reverts to shrublands and forests. Grasslands are becoming more scattered and isolated, reducing connectivity (Post 2004). Wetland loss is also a threat because this species often nests in nearby damp or wet meadows. As wetlands are drained for development any associated wet meadows are also lost (Andrle and Carroll 1988).
Management practices and restoration may be necessary to preserve remaining grassland habitat for this species in New York. Several strategies could be used to preserve and protect grassland habitat for this species. Identify public lands with Henslow's Sparrow populations where management may be more easily implemented. Develop education and outreach programs in areas where Henslow's Sparrows persist that are aimed at grassland management and preservation. Implementing a program in New York similar to the Conservation Reserve Program, would likely be beneficial to Henslow's Sparrow populations and many other grassland birds.
This species prefers large fields that have grasses that are at least 30 cm high (NatureServe 2019). Management strategies include mowing, burning, and grazing grasslands that ideally would be greater than 30 contiguous hectares (NatureServe 2019). If that is not an option, then a complex of smaller grasslands that are near each other should allow for birds to move between sites (Herkert 1998). Mowing and burning should be done in the spring, before birds arrive, or in the fall after migration has started. A rotational schedule is recommended because the habitat will not be suitable again for one or two growing seasons after treatment (Herkert 1998). Woody vegetation should be removed when it reaches the height of the herbaceous vegetation (Herkert 1998). Some research in New York has suggested that Henslow’s Sparrows do not have the same habitat requirements in the east as other regions. Smith and Smith (1990) found that birds preferred areas with high productivity, high annual growth, and tolerate grazing with the removal of up to 60% of the annual productivity of herbaceous biomass.
The effects of certain farming practices on breeding populations should be evaluated. For instance, it would be beneficial to determine how different mowing frequencies and how different intensities of grazing affect Henslow's Sparrow populations. Some studies have suggested that populations in the east may have different habitat requirements than other locations (NatureServe 2019). It would also be beneficial to know how mowing versus prescribed burning affects populations.
The Henslow's Sparrow is a grassland species, preferring tall, dense, grassy fields without woody vegetation. Wet grasslands are also used. Peterson (1983) found them in large, ungrazed fields with a variety of moisture regimes and without woody invasion. They were also found on hilltops. Bull (1974) described their habitat preference in New York as "grassy fields and meadows with scattered bushes and herbaceous plants, both in wet and dry situations." They can tolerate lightly to moderately grazed pastures (NatureServe 2005).
In New York State, Henslow's Sparrow populations occur in central and western New York and in a few locations in the Hudson River Valley. Currently, the largest populations are found in Jefferson County. During the first Breeding Bird Atlas (1980-1985), Henslow's sparrows were reported as probable or confirmed breeders in 213 blocks. The Breeding Bird Atlas 2000 reported probable and confirmed breeding in 57 blocks (McGowan and Corwin 2008), indicating a sharp decline in breeding birds. According to Breeding Bird Atlas 2000 data and the New York Natural Heritage Database, Henslow's sparrows are no longer found in the following counties: Broome, Cortland, Delaware, Fulton, Herkimer, Madison, Oneida, Onondaga, Otsego, Saratoga, Schenectady, Schoharie, St. Lawrence, Tioga, and Wayne (McGowan and Corwin 2008, New York Natural Heritage Program 2005).
Breeding: Henslow's Sparrows breed locally from southeastern South Dakota (at least formerly), across the Great Lakes region of the eastern U.S. (southeastern Minnesota, north-central Wisconsin, northern Michigan) and southern Canada (southern Ontario, formerly southern Quebec) to New England and New York, south to central Kansas, northeastern Oklahoma, southwestern and central Missouri, southern Illinois, northern Kentucky, central West Virginia, eastern Virginia, northern Tennessee, and central and eastern North Carolina. Formerly the breeding range included eastern Texas. Non-breeding: Outside of the breeding season Henslow's Sparrows are found in coastal states from South Carolina south to Florida, west to Texas, casually north to Illinois, Indiana, New England, and Nova Scotia (Smith 1992 cited in NatureServe 2005, AOU 1998 cited in NatureServe 2005).
Henslow's Sparrows can be identified by the large, flat head, large gray bill, and short tail. Wings are reddish. The head, nape, and most of the central crown are olive-colored. Sexes are similar, but can be determined in hand during the breeding season by the cloacal protuberance in males and brood patch in females. Henslow's Sparrows fly low and jerkily with a twisting motion of the tail. Juveniles are clay-colored above and their head and back are streaked with black. They are a faint yellow below with traces of buff on the throat and chin. Typically, the sides of the throat are unstreaked, but streaking can be found on some individuals. Nests are found on or near the ground and can be either open or dome-shaped. When nests are built off the ground, they are attached to grasses or forbs. Nests are loosely woven with dead grass and lined with finer grasses and hair. Vocalizations are described as a short, quiet "see-lick" or a hiccupping "tsi-lick." Calls can sometimes be heard on quiet summer nights. Henslow's sparrows are shy and secretive. Typically, they are heard rather than seen. Therefore, it is important to be able to identify this species by its song, especially for census and survey work.
Henslow's Sparrow has a large, flat head; large, gray bill; and a short tail. Vocalizations are a quiet "see-likc" or hiccupping "tsi-lick."
Observations of adults or vocalizations are the best way to identify Henslow's Sparrow.
This bird perches on the tops of weed stalks to sing. When flushed, it flies low, short distances before dropping into the weeds.
Henslow's Sparrows eat insects, mostly grasshoppers and beetles. Seeds are consumed during the winter months.
Henslow's Sparrows are most often observed or heard during the peak of their breeding season between mid-June and mid-July. They are more likely to be heard rather than seen. Sometimes they are heard calling on quiet summer nights.
The time of year you would expect to find Henslow's Sparrow active and reproducing in New York.
Ammodramus henslowii (Audubon, 1829)
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This guide was authored by: Shaw, Hollie Y.
Information for this guide was last updated on: June 28, 2019
Please cite this page as:
New York Natural Heritage Program. 2021. Online Conservation Guide for Ammodramus henslowii. Available from: https://guides.nynhp.org/henslows-sparrow/. Accessed October 23, 2021.