188 U. S. NATIONAL MUSEUM BULLETIN 211 



The behavior of the tricolored redwing is quite distinctive, as men- 

 tioned above, and its voice is quite different. 



Enemies. — The densely populated breeding colonies of tricolored 

 redwings, with thousands of nests filled with eggs or small young, 

 offer tempting chances for predators, furred or feathered, to enjoy a 

 "field day"; many colonies have suffered heavy predation, and some 

 have been almost, or quite annihilated. Lack and Emlen (1939) 

 report two cases of mass desertion of nests, with destruction of eggs; 

 of one of these, they say: "One colony near Marysville was reported 

 to contain about 60,000 birds up to May 12. At the time of our first 

 visit on May 16 only a few hundred were left. An examination of 

 about one hundred nests revealed that more than the three-fourths 

 contained freshly broken eggs or minute shell chips; only a few were 

 undisturbed and these latter contained freshly laid eggs. On June 2 

 no adult birds were seen in the vicinity; of 114 nests examined, 62 

 contained shell chips, 46 others were empty and 6 contained newly 

 hatched, but dead, young. Some of these nests showed small holes 

 in the lining, as if made by birds' beaks." 



Mailliard (1900) found a number of deserted nests in a colony in 

 Madera County: "Those in the more exposed situations seemed to 

 have been robbed, probably by the Buteo swainsoni, which were num- 

 erous in the neighborhood and one pair of which had a nest in a tall 

 poplar tree but a few yards away, and possibly by some of the many 

 Nycticorax n. naevius which simply swarmed in the most attractive 

 spots. * * * 



"The crop of one Buteo swainsoni contained two young just hatched 

 and also the remains of two others with portions of the shell still 

 sticking to them and which must have been just on the point of hatch- 

 ing. These were apparently the young of A. tricolor." 



Neff (1937) writes: "Heermann wrote in 1853 of the large numbers 

 of Tri-colored Red-wings shot for the market. This practice still 

 continues, and during the past 5 years it is probable that fully 300,000 

 blackbirds of the combined red-winged group have been marketed 

 from the Sacramento Valley, with no apparent change in the status of 

 any of the kinds involved. During the winter of 1935-36, 88,000 

 blackbirds were shipped from Biggs alone. * * * 



"Destruction of the birds by man, of nesting sites through drainage 

 or reclamation, of nests by predators or by the elements, and other 

 factors, have played their part. All combined, however, they have 

 made only fractional inroads on this species during the period covered 

 by this report." 



This last statement is quite reassuring in view of the fears, expressed 

 only 5 years previously, that the wholesale poisoning of rodents with 

 thallium and the still more destructive campaigns against this black- 



