556 U.S. NATIONAL MUSEUM BULLETIN 237 part i 



One of the more peculiar, if not species-specific attributes of the 

 green-tailed towhee is the "rodent-run," as it has been termed by 

 A. H. Miller (1951a). In Colorado, a greentail running across an 

 open space was taken for a chipmunk and shot by mistake (R. B. 

 Roclcwell and A, Wetmore, 1914). Not dissimilar running has been 

 observed in birds associated with nests; thus F. M. Bailey (1902) 

 says: "One that Mr. Bailey found on its nest on Donner Peak, 

 California, ran silently for five or six rods through the brush, and then 

 stopped, to tempt him away from its brood." In Utah, A. H. Miller 

 (1934) reported a nest from which a bird flushed "in the characteristic 

 'green-tail' manner, that is, by dropping to the ground and running 

 with tail elevated, thus resembling a chipmunk running through the 

 brush." In focusing attention on the "rodent-run," A. H. Miller 

 (1951a), after pointing out that the species commonly places its nests 

 a foot or two above the ground in sagebrush and other low bushes 

 (between which are open aUeyways), provides the following discussion: 



The resemblance of the flushing towhee to a chipmunk [of which several related 

 species were common in the sagebrush country] has the following specific aspects: 

 the size of the bird is similar to that of a chipmunk; the tail of similar length and 

 breadth, is held elevated in both; the motion is fast and even, that is, distinct 

 saltations are absent, whereas they are present in the usual hopping gait of the 

 towhee; the run is in a straight line except as altered by major obstructions; the 

 take-off from the bush by dropping nearly straight down without use of wings is 

 mammal-like. Although the back of the towhee is not striped as in chipmunks, 

 it is to be noted that the longitudinal stripes of rapidly running chipmunks are 

 not conspicuous anyway. The dull green and brown of the running towhee 

 actually presents a dusky streak that is similar to that presented by the prevail- 

 ingly brown-backed chipmunk. 



The effectiveness of the towhee-chipmunk resemblance is attested by the dozen 

 or more instances in which I have been deceived by it, not realizing until after 

 the towhee had run into cover fifteen j^ards or more away that it was a bird and 

 was now giving an alarm note. A retracing of my steps then disclosed a nest. 

 Of course I do not know how many more times I have been completely deceived. 

 Surely coyotes, which are common predators in the region, must frequently be 

 led to pursue the apparent chipmunk racing through a clearing rather than to 

 relate the movement to the easily attacked towhee nest from which the bird has 

 dropped. Whether or not pursued, the bird would at least momentarily be con- 

 fused with a chipmunk, and the significance of the bird-and-nest situation escape 

 the predator, 



Williamson * * * has postulated the origin of the rodent-run in shore birds, 

 or at least that in the Purple Sandpiper, from a substitute or displacement ac- 

 tivity w^hich, first by chance, has had special value in protection, and under 

 selective forces has become perfected and regularly utilized at appropriate times. 

 In the Green-tailed Towhee, origin from substitute activity is not evident to me. 

 The rodent-run here would seem to be a direct modification of a general tendency 

 to run or hop rapidly on the ground when closely pursued. But it should be 

 stressed that for distraction purposes the modifications and refinements of the 

 escape movement entailed in the nest-departure run to varying degree all bear 

 resemblance to the mammalian copy. 



