102 



BULLETIN 326, U. S. DEPAETMEXT OF AGBICULTrBE. 



PRAIRIE WARBLER. Dendroica discolor (Vieillot). 

 Reixita, Bijirita Galaxa. 



The prairie warbler is apparently much more common as a migrant than as 

 a true winter visitant. Bowdish (1902-3, p. 19) records it on September 23, 

 1900, and the last birds seen in the present investigations were noted on April 

 10, on Culebra Island. In Porto Rico these birds occur at the highest altitudes 

 (above Aibonito, at 2,000 feet), and are found in brushy growths, in pastures 

 where there are thickets, and along the hedges of emajagua (Paritium tili- 

 accum). Dry, brushy growths back of the beaches also are favorite places, and 

 many live in the dry forests of Vieques. In spring there was a marked diurnal 

 movement toward the west, and on Vieques there were distinct waves of migra- 

 tion on March 19 and March 27. Another was noted on Culebra Island on 

 April 9. In each case the birds were in company with many other warblers. 



Food. — For the study of the food of the prairie warbler 15 stomachs, taken 

 in December, January, March, and April, were available. Animal food forms 

 the entire content. The largest single item in these stomachs is composed of 

 Fulgoridn?, which comprise 42. 7S per cent of the food and were found in nine 

 stomachs. Other bug remains, mainly fragments of an ambush bug (Plujmata 

 sp.), make up 1 per cent. Three birds had eaten leaf beetles (2.9 per cent) 

 and one a weevil (0.2 per cent). Other beetle remains, among which a longi- 

 corn, a skin beetle, and a click beetle were identified, make up 12.9 per cent. 

 Caterpillars found by five birds and moths by two make 12.7 per cent, while 

 fly remains in two amount to 0.35 per cent. Ants in four stomachs form 3.72 

 per cent of the total, while other Hymenoptera, captured by a single^ bird, come 

 to only 0.1 per cent. The only questionable part of the food of this bird is 

 found in the large number of spiders eaten (19.59 per cent). These are found 

 in eight, or more than half, of the stomachs examined. Miscellaneous animal 

 matter totals 3.76 per cent. 



Among beneficial species the prairie warbler ranks high, as practically four- 

 fifths of its food is composed of harmful insects. Its destruction of spiders is a 

 questionable benefit, but it consumes such large numbers of lantern flies ( Fulgor- 

 ida?) that there can be no doubt as to its usefulness. In common with other 

 birds of the same family, the wood warblers, it feeds to a considerable extent 

 on ants while in Porto Rico, insects that in the Tropics are very destructive. 



The following were identified in these stomachs : 



Ormenis sp. 

 Pliymata sp 



HBMIPTEEA. 



COLEOPTERA. 



Gryptocephalus sp. 



ARACHXIDA. 



Wala vernolis 



Theridula triangularis 

 Tioellus sp 



BLACK-POLL WARBLER. Dendroica striata (J. R. Forster). 

 Reixita, Bijirita Estriada. Bijirita Rayada. 



Gundlach (1S7S, p. 1S1) observed the black-poll warbler, a rare migrant in 

 Porto Rico, in October at Aguadilla, and records one as seen at Bayamon. 

 Stahl (1SS3. p. 139) had a male taken in Porto Rico in his collection, and (1887, 

 p. 451) says that the birds arrive the middle of August. 



ADELAIDE'S WARBLER. Dendroica adelaida* Baird. 

 Reixita, Bijirita Adelaida, Bijirita Mariposera. 



A fairly common resident species in Porto Rico, Adelaide's warbler occurs 

 in most parts of the island, but is local in distribution. The only ones seen at 



