Northern Mockingbird Mimus Polyglottos
Northern Mockingbird Mimus polyglottos
The Northern Mockingbird, a relative new comer to much of Vermont, has increased markedly both in numbers and distribution in the state during recent decades. Currently the mockingbird appears to be spreading northward through the Lake Champlain and Connecticut River valleys and laterally / along the major drainage systems into the center of the state. Reasons for this recent population growth are obscure. Beddall (1963) identified a warming trend that be gan about 1900, and decreased hunting as demand from the caged bird trade dropped, April, males are vigorously announcing as significant factors in the mockingbird's their territorial intentions. As unmated increase in New England. This advance is males carry nesting material to likely nest still occurring, and it will be particularly in sites within their territories (Laskey 1962), teresting to compare this species' distri nest-building activity may not be absolute bution in 10 or 20 years with that found proof of breeding. Only three Vermont Atlas during the Atlas Project effort. The mqcking Project records were of nest building. In bird has gained a substantial hold in the more southerly climates, mockingbirds have Eastern Foothills and Champlain Lowlands, been known to raise up to four broods per where it was found in 62% and S2% of the season. Atlas Project priority blocks, respectively. Early nests are generally placed in coni The Taconic Mountains, where mocking fers (Laskey 1962), whereas later nests may birds were recorded in 38% of the priority be situated in any available dense shrubbery, blocks, is the only other region that cur such as rose hedges. The compact nest of rently supports a significant population. twigs and leaves lined with rootlets, built by Northern Mockingbirds are well known both members of the pair, may be 0.6-3 m throughout their range for their vocal abili (2-10 ft) above the ground-rarely, IS m ties. As their name implies, they can mimic (So ft). Earlier nests tend to be placed lower almost anything within their hearing. Al than later ones. Nests are relatively easy to though they channel most territorial behav locate and account for more than half of all ior into song, which is given from elevated confirmations in Vermont. From 4 to 6 blue perches or, occasionally, in flight, clashes or green eggs, heavily marked with brown, on the borders of territories may also result are laid and incubated by the female. Both in defiant males sparring for advantage incubation and nestling periods normally with sideways hops along their disputed last 12 to 13 days. Adults are highly defen boundaries. sive during this period. The two Vermont Although reputedly permanent residents egg dates reported are June 9 and July I; throughout their range (from southern Ore all Vermont nestling dates, July 7 through gon east to northern Utah, Wyoming, New August S, could be of second broods, as foundland and Nova Scotia, and south to could the recorded fledgling dates of July 13 southern Baja California and the West In through August 6 (three records). Horwich dies), wintering mockingbirds in Vermont (196S) indicated that young begin feeding retreat to the densest cover in the vicinity themselves at 17 days of age (4- S days past with the onset of cold weather. Multiflora fledging), and fledglings may beg until 44 rose thickets are particularly favored. By days of age. Early nests in Illinois (Graber et
254 Species Confirmed as Breeders in Vermont 7)" '1" ,,"
No. of priority blocks in which recorded TOTAL 42 (23%) Possible breeding: I2 (28.5% of total) Probable breeding: 13 (3 1.0% of total) Confirmed breeding: I7 (40.5% of total)
Physiographic regions in which recorded % of c:11. % of species' no. of region's total priority priority priority ••• blocks blocks blocks DOD Champlain Lowlands I6 52 38 o Green Mountains 2 4 5 North Central 0 0 0 Northeast Highlands 2 I2 JO I East Central 5 2 o 43" Taconic Mountains 6 38 14 10, 30 30 I I Eastern Foothills I5 62 36 o
7)" '1" al. I970) had very low (9%) fledgling suc and force the young to disperse to unoc cess; the dearth of early breeding season cupied areas. Banding studies in Tennessee nesting records in Vermont may result from (Laskey I962) indicated that young may dis a similar high failure rate among early nest perse up to 320 km (200 mil away. Fall dis ing attempts. persal of fledglings may colonize new areas Although mockingbirds forage extensively in Vermont. Extralimital sightings of North on the ground and feed primarily on insects, ern Mockingbirds are more common in the they are extremely fond of fruits and ber spring, however, in Vermont. Both fall dis ries. Wintering birds seem particularly at persal and short-range spring migration may tracted to multiflora rose hips, probably prove to be factors in this species' north because thickets of this introduced plant ward expansion. provide both food and cover in abundance. DOUGLAS P. KIBBE The mockingbird's expansion may be related to the success of this planting. During the fall adults establish wintering territories, either as pairs or as individuals,
Northern Mockingbird 255