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Historic Status

On August 15, 1883, Charles W. and W.J. Townsend shot and killed two mockingbirds in Arlington before the species gained the descriptive term “northern.” This early sighting signaled the beginning of a definite expansion of the range of the species, although, as Charles commented in a note to The Auk, mockingbirds were well known to have bred in Springfield on several occasions by that time (Townsend 1884). Forbush noted their northerly breeding range expansion by the 1920s as most likely a permanent change since they had by then reached Nova Scotia and Newfoundland as strays. But, he postulated, “as it normally winters near its summer home, the severe winters of New England are likely to hold it in check, and prevent it from becoming common here” (Forbush 1929). Forbush could not foresee the invasion of Multiflora Rose in the 1930s, and the effect that abundant food supply would have on the mockingbird’s population for the next few decades (Veit & Petersen 1993).

Atlas 1 Distribution

The Northern Mockingbird had already completed much of its expansion into Massachusetts by the time of Atlas 1. The Marble Valleys had over 80% block occupancy, but the Berkshire Highlands and Lower Berkshire Hills both had less than 20%. This illustrates a fact thatholds true throughout the state: Northern Mockingbirds tend to flourish in settled areas at lower elevations. While the Berkshire Transition Zone and Vermont Piedmont had relatively few mockers, the low-elevation Connecticut River Valley reported them from 95% of the blocks in the region. The Lower Worcester Plateau also had almost twice the block occupancy rate of the higher Worcester Plateau. All of the regions to the east of the Worcester Plateau had 75% block occupancy or more, with the Boston Basin even exceeding 90%.

Atlas 2 Distribution and Change

Surprisingly, the picture that Atlas 2 paints of the species’ status is decidedly mixed and complex. Several western regions posted small losses, and using the effort-controlled data the Marble Valleys lost mockingbirds in 16 blocks, or 41% of the region, and the smaller Taconics region posted a loss of 5 blocks – 33% of the region. Interestingly, the area of New York state adjacent to these western ecoregions had stable Northern Mockingbird Atlas results (McGowan & Corwin 2008). The Connecticut River Valley showed an impressive and nearly contiguous swath of block occupancy, as did the Coastal Plains. In the southeastern part of the state however, mockingbirds disappeared from dozens of blocks while being newly detected in just over 20, indicating potential shifts in the location of suitable habitat for mockingbirds in those regions.

Atlas 1 Map

Atlas 2 Map

Atlas Change Map