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).