358 BULLETIN i9 6, UNITED STATES NATIONAL MUSEUM 



sound is characteristic of this one species aDd, once heard, is readily 

 remembered and recognized. 



L. A. Stimson, writing (MS.) of the gnatcatcher in its winter quarters 

 in southern Florida, mentions another note, "a shorter, more abrupt 

 call with less of the zz quality." 



Enemies.— It is little short of incredible that so tiny a bird as the 

 gnatcatcher can and does successfully fill the role of foster parent to 

 the young of the much larger cowbird (Molothrus ater), but there are 

 many instances of this on record. Dr. Herbert Friedmann (1929) 

 recorded the gnatcatcher as "a not uncommon victim [of the cow- 

 bird] and in some places a fairly common one." It must indeed be 

 the smallest North American species thus victimized. An extreme 

 case is given by M. G. Vaiden (MS.), who, writing from the Yazoo- 

 Mississippi Delta of Mississippi, states that he has examined 12 

 nests of the gnatcatcher since 1919 and has found only two of them 

 without cowbirds' eggs. In one instance, on June 4, 1939, he found 

 a nest that "contained four gnatcatcher eggs and three cowbird 's 

 eggs," implying that other parasitized nests examined by him had 

 contained fewer than three. In another nest he found "two young 

 gnatcatchers and two young of the cowbird." Of the two nests that 

 had not contained cowbird's eggs, only one was definitely immune, 

 since the gnatcatcher was incubating her own eggs when discovered. 

 In the other, the gnatcatcher had only commenced to lay, for the nest 

 contained but a single egg, and the observer concluded that the 

 cowbird "just had not located the nest yet," for he is "of the opinion 

 it later on did have cowbird eggs." Thus we have a known 83 percent 

 and a possible 92 percent parasitization, which is, of course, too high 

 for any species to survive if it applied to more than restricted areas. 

 Ben J. Blincoe (1923) watched a pair of gnatcatchers attacking 

 persistently a female cowbird and driving it away. 



The gnatcatcher probably suffers to some extent from predators 

 and nest marauders — undoubtedly a few are taken by sharp-shinned 

 hawks and screech owls, and perhaps some others succumb to attacks 

 by loggerhead and migrant shrikes— but there is nothing to indicate 

 that this species is singled out, nor, on the other hand, would it be 

 expected to enjoy greater immunity than other species of comparable 

 size within its range. However, a surprising instance of seemingly 

 selective predation- — though this may be as localized in its application 

 as is the gnatcatcher-cowbird relation just cited from Mississippi — 

 was given by S. A. Grimes, of Jacksonville, Fla., who wrote (1928): 



Probably the greatest enemy of the Gnatcatcher is the Florida Blue Jay 

 [Cyanocitta cristata florincola]. I have seen the Jay in the act of pilfering the 

 smaller bird's nest perhaps a score of times. One such episode remains singularly 

 vivid in my memory * * * When the Jay alighted on the rim of the nest, 



