112 U.S. NATIONAL MUSEUM BULLETIN 233 



races of the warbler, palmarum and hypochrysea, and two of the 

 parasite, ater and artemisiae. Knight (1906) recorded a nest found by 

 Morrell near Pittsfield, Maine, with 2 eggs of the warbler and 2 of the 

 cowbird. Strong (1919) found a nest with a similar combination of 

 eggs at Penobscot, Maine. Morrell collected a nest with 1 cowbird 

 egg and 2 warbler eggs at Pittsfield, Maine, on May 27, 1891, a set 

 now in the U.S. National Museum. Clayton (1914) found another 

 nest with 1 cowbird egg and 2 warbler eggs; unfortunately, the 

 locality for this record was not reported. 



The above instances relate to the so-called yellow palm warbler 

 (hypochrysea) and the eastern form of the cowbird. Two parasitized 

 nests of the western race of host (palmarum) and parasite (artemisiae) 

 were found in Alberta by T. E. Randall, who kindly informed me of 

 the records. In the collections of the Carnegie Museum there is a 

 set of 2 eggs of the palm warbler and 1 of the cowbird, collected at 

 Fawcett, Alberta, on June 3, 1941. 



Ovenbird 



Seiurus aurocapillus (Linnaeus) 



The ovenbird is a very frequent host of the brown-headed cowbird, 

 and, in this respect, it is something of a puzzle. As a rule, the cow- 

 bu'd seldom bothers forest birds but prefers open nests buUt in open 

 country. The ovenbird is strictly a bird of the forest floor, building 

 a covered nest, and yet it is victimized very commonly. Over 280 

 records have been noted, distributed among provinces of Canada — 

 Alberta, Saskatchewan, Ontario, and Quebec — and the following 

 of the United States: Massachusetts, Connecticut, New York, New 

 Jersey, Pennsylvania, Ohio, Indiana, Illinois, Michigan, Minnesota, 

 and Iowa. All the records relate to the nominate race of the oven- 

 bird; those from Alberta and Saskatchewan involve the western race 

 of the cowbird, artemisiae; all the others, the eastern race, ater. 



The extent to which the ovenbu'd is victimized in some parts of its 

 range is shown in the data produced by Hann (1937, p. 213) in Michi- 

 gan. Out of all the nests which received eggs, 52 percent were 

 parasitized by the cowbird. Of the total number of ovenbird eggs 

 laid, 63.4 percent hatched and 43.5 percent fledged. The greatest 

 loss was due to predators; but the next greatest loss, to cowbirds, 

 estimated as being responsible for the loss of 18 percent of ovenbird 

 eggs and young. The chief loss was due to the removal of eggs by 

 the cowbird. Out of 40 cowbird eggs, however, only 22 hatched, 

 10 fledged, and probably not more than 5 survived to leave the woods 

 in which they were born. In light of these data, the ovenbird does 

 not appear to be a particularly favorable host for the parasite when 

 compared with the song sparrow, for instance, or the red-eyed vireo. 



