Jan., 1914 
NOTES ON THE DERBY EI.YCATCHER 
13 
and early evening, they are most active and noisy. Tlieir call note.s can then be 
heard in every cjiiarter of the city and the birds themselves are most in evidence, 
snatching flies over heaps of refuse in the gutters, hawkdng about the plazas, or 
“kingbirding” an unlucky Black Vulture. Activity, though, is by no means con- 
fined to these periods. Birds may be found at almost any hour of the day. On 
two occasions one (probably the same individual) was seen about an arc-light 
long after dark. It may have been attracted by the light, but in my own mind 
there is no doubt that the insects which buzzed around the globe in swarms were 
the real reason for the bird’s presence, as it appeared in no way confused and 
kept well outside the most brilliant circle of illumination. Owing to this fact, 
and also because the light was quite high up, 1 could not actually see the bird 
catch anything, though its frequent short and erratic flights would indicate that 
this was the object. Its perch seemed to be directly above the shade. The first 
time was on March 29 and the second, April i. When I returned from the 
coast the last of July the bird was nowhere to be seen, though I went twice to 
look for it. W. B. Judson has noticed the Black Phoebe doing the same thing 
(see Condor, hi, 1901, page 186), and it would not be surprising to find with 
a little more observation that this trait has become common among others of the 
larger Tyrannidre. More than once, too. the evening "concierto" was broken 
into by an outburst of “Chio” yells, provoked probably by some hunting Barn 
Owl {Ahico, sp. ?), several of which used the near-by cathedral tower as a day- 
light retreat. 
As is the case with many other common and well-known varieties, the 
native name of “Chio” is derived from the Derby’s call note, which may best be 
written che-oh, or chee-o, generally given rather slowly, but under stress of 
excitement or anger losing entirely its deliberate qualitv and becoming shrill and 
hurried. At such times, too, and particularly at the nest where the jiarents 
become almost frantic, these notes are interspersed and plentifully larded with 
extremely Kingbird-like expletives. 
One other species may at first sight be mistaken for derbianus, namely, the 
Mexican Boat-billed Flycatcher {McgaryncJius pitangiia inc.vicanus) , being 
almost identical in size and markings, and with a very similar call note. How- 
ever, the absence of the light rufous wing and tail markings so conspicuous in 
the Derby, with shorter tail and heavier bill (which last is distinguishable at 
ciuite a distance), serve to differentiate the two. This resemblance is of course 
merely superficial, and except for the points mentioned and a "Tyrannine” dis- 
position they have nothing in common. As would be expected, no local distinc- 
tion is made between them, both being known as “Chio’’, and even the Giraud 
Flycatcher is universally referred to as “Chia", or the female. 
Too few specimens were prepared to allow of any definite conclusions 
regarding food habits except that insects form the entire bill of fare. Stomachs 
examined contained small beetles, wasps and small grasshoppers, of relative 
abundance in the order named, as well as a great assortment of flying insects 
which I was not expert enough to identify. Flowever, the diet must vary a good 
deal with the locality as well as with the season. 
