CONTOPUS BRACHYRHYNCHUS. 155 



a month's time the sexes of these may be distinguished. After another 

 month the males begin to sing, and are frequently seen pursuing one 

 another over the fields. It is only at the end of April, three months after 

 the old birds have disappeared, that the young also take their departure. 

 This is one of the strangest facts I have encountered in the migration 

 of birds. The autumnal cold and wet weather seems to be the imme- 

 diate cause of the young birds' departure ; but in the adults, migration 

 appears to be an instinct quite independent of atmospheric changes. 



163. EMPIDONAX BIMACULATUS (Lafr. et d'Orb.). 

 (WING-BANDED TYRANT.) 



Empidochanes argentinus, Cab. J. f. O. 1868, p. 196. Empidonax 

 brunneus, Hidgw. N. A. B. ii. p. 363 (Parana). Empidonax bimacu- 

 latus, Scl. Ibis, 1887, p. 65. 



Description. Above umber-brown, more or less rufescent ; lores with a 

 whitish spot ; wings blackish, all the coverts broadly tipped with pale rufous, 

 forming two transverse bars ; outer margins of external secondaries of the same 

 colour ; tail brown, but not rufescent ; beneath dirty cinereous white, throat 

 and belly brighter, and with a yellowish tinge ; under wing-coverts and inner 

 margins of wing-feathers ochraceous ; upper mandible dark brown, lower 

 whitish ; feet pale brown : whole length 5-0 inches, wing 2' 6, tail 3-4. 



Hab. S.E. Brazil, Bolivia, and N. Argentina. 



This obscure species occurs in the northern wooded districts of 

 Argentina. 



164. CONTOPUS BRACHYRHYNCHUS, Cab. 

 (SHORT-BILLED TYRANT.) 



Contopus brachyrhynchus, Cab. J.f. O. 1883, p. 214. 



Description. Above cinereous, lores whitish; wings and tail, blackish, with 

 slight whitish edgings to the wing-coverts and outer secondaries ; beneath paler, 

 whitish in the middle of the belly ; flanks with a concealed white patch ; bill 

 above brown, beneath pale ; feet black : whole length 7*0 inches, wing 4-0, 

 tail 3-2. 



Hab. Northern Argentina. 



Herr Schulz, who discovered this species near Tucuman, tells us that 

 it is a summer visitor, and is usually seen perched on the tops of the 

 highest trees on the look-out for insects. 



