HOST RELATIONS OF PARASITIC COWBIRDS 93 



as Green County, Pennsylvania, the incidence of cowbird parasitism 

 is very high, as shown by Jacobs (1924, pp. 52-54) and S. S. Dickey 

 (1934, pp. 179-184), who together found no fewer than 17 parasitized 

 nests. In the experience of the latter observer, 8 out of 23 nests 

 found near Waynesburg had been molested. In no other area has 

 this warbler been reported to this extent as a cowbird host. Near 

 West Chester, Pennsylvania, Ladd (1887b, pp. 149-151) found 24 

 nests, 3 of which contained eggs of the cowbird. The total available 

 records range from Connecticut, Nev/ York, New Jersey, Maryland, 

 and Pennsylvania to Indiana, West Virginia, Kentucky, and Iowa. 



This warbler has been found to hatch and rear young cowbirds. 

 Ladd (1887a, p. 110) noted a nest containing one young cowbird, 

 nearly fully fledged, plus an addled cowbu'd egg and 5 eggs of the host. 

 Dickey (loc. cit.) near Blacksville, West Virginia, observed a nest 

 with three young warblers and two young cowbirds. 



All the records for this host involve the eastern, nominate race of 

 the parasite. The latter may be said to be important only locally in 

 the demography of this warbler; even here it is not apparent that this 

 host plays a great role in the economy of the cowbird. 



Golden-winged Warbler 



Vermivora chrysoptera (Linnaeus) 



The golden-winged warbler is an occasional victim of the bro^vn- 

 headed cowbu'd. I have been able to learn of 17 definite records 

 in addition to mere statements in the literature that this warbler 

 is a cowbird host. The records come from Massachusetts, New York, 

 New Jersey, Pennsylvania, Alichigan, and Wisconsin. In Greene 

 County, Pennsylvania, Jacobs (1904, pp. 19-21) found 20 nests, 

 of which 6 were parasitized. This, together with the fact that at 

 least four more parasitized nests recently have been reported from 

 Michigan (Wallace, 1945, p. 174; Detroit Audubon Soc, 1953, p. 72; 

 1954, p. 86; 1956, p. 86), qualifies our concept and points to the 

 conclusion that, where it occurs in any numbers, this warbler is a 

 regular victim. As many as 4 cowbird eggs have been found in 

 a single nest. Not only have eggs of the cowbu'd been found in 

 nests of this species, but also young of the parasite have been reared 

 by golden-winged warblers in at least three cases — in two of v/hich 

 the young of the host survived together with the young parasite. 

 In one of these cases, a nest found in Springfield Township, there 

 were 3 eggs of the warbler and 2 of the cowbird when the nest was 

 discovered on May 30, 1952; by June 8 there were two young of 

 each. The other instance was an observation m Clyde Township, 

 July 3, 1954; a pair of golden-wmged warblers was in attendance 

 upon two recently fledged young of their own and one of the cowbird. 



