DUSKY SEASIDE SPARROW 851 



That the diisk}^ really merits the specific status the A.O.U. Check- 

 List has always accorded it is questionable. Though its intense black 

 streaking makes it by far the most distinctive of the seaside sparrows, 

 its basic color pattern, habits, and behavior leave no question of its 

 close relationship to the other recognized forms of the seaside complex. 

 Ludlow Griscom (1944) argued: ''A. nigrescens (Ridgway) is a small 

 local population in an extreme development of the dark phase. It 

 possesses two absolute characters in the heavy black streaking on a 

 white ground below and tlie loss of the yellow postocular [sic] stripe. 

 It has, consequentl}^, real claims to specific distinctness. A modern 

 school of thought would unhesitatingly reduce it to subspecific rank, 

 on the indisputable grounds that the dih''erences between any Seaside 

 and any Sharp-tailed Sparrow are the real specific criteria with which 

 Nature has supplied us." 



Unfortunately neither of Griscom's two "absolute characters" for 

 the dusky's specificity is valid and he (1944) admitted "that the whiter 

 under parts of mirabilis deprive nigrescens of one of the latter's 

 absolute characters." As black streaks occur in several other popu- 

 lations, notabl}'" in A. m. juncicola, their presence in nigrescens is not 

 a difference of pattern, but of degree. As for the alleged "loss of the 

 yellow postocular stripe," the yellow does not extend behind the eye 

 in any seaside population, and that of the preocular, or supraloral, 

 stripe is every bit as well marked in the dusky as it is in all other adult 

 seasides. 



Whether or not the dusky's reproductive isolation has progressed 

 to the point of specificity will probably never be put to the test, as 

 Sutton hoped, by its possible breeding in sympatry with other sea- 

 sides that might invade its range. Today it is more isolated geo- 

 graphically than it has been since it was discovered. The nearest 

 breeding grounds of pelonota are now 75 miles northward beyond 

 Matanzas Inlet; the nearest peninsulae are 125 westward across 

 Florida on the gulf coast; from Titusville southward to the range of 

 mirabilis beyond Cape Sable lie 250 miles of coastline that ofi'er few 

 suitable marshlands and contain no known breeding seaside sparrows. 



Since 1956 the entire breeding range of the dusky on the east side 

 of the Indian River has been impounded for mosquito control pur- 

 poses by earthen dikes thrown up around the perimeter of the salt 

 marshes, which are now kept covered with from 4 to 12 inches of 

 fresh water. This treatment, though unquestionably superior and 

 preferable to the use of insecticides, is causing marked changes in the 

 salt marsh vegetation. The stands of bunch grass {Spartina hackeri) 

 and black rush (Juncus roemarianus) in which the duskies nest are 

 thinning out and are giving way to cattails (Typha). Over the last 

 few years the dusky population appears to have decreased markedly, 



