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 Jan., 1914 NOTES ON THE DERBY iLYCATCHER 13 and early evening, they are most active and noisy. Their call notes can then be heard in every quarter of the city and the birds themselves are most in evidence, snatching flies over heaps of refuse in the gutters, hawking 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 o.f illumination. Owing to this fact, and also because the light was quite high up, I 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 t. 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 CoroR, nI, 9oI, page 86), and it would not be surprising to find with a little more observation that this trait has become common among others of the larger Tyrannidve. More than once, too, the evening "concierto" was broken into by an outburst of "Chio" yells, provoked probably b.y some hunting Barn Owl (.4luco, 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 quality and becoming shrill and hurried. At such times, too, and particularly at the nest where the parents l>ecome 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 (Megarynchus pitangua mexicanus), being ahnost 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 (vhich last is distinguishable at quite 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. Stonachs 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. However, the diet must vary a good deal with the locality as well as with the season.