20 ZOOLOGY. 



the arrow heads are much less distinct and numerous. Flanks bluish ash with a tinge of brown, each feather having a longi- 

 tudinal spot of white in its centre. Under tail coverts pale rusty white, with longitudinal bands of light brown occupying the 

 centre of the feathers. Bill blact. Feet lead color. Length nine and a half inches. 



Female. — Ilumage the same as the male. Cre^t smaller and delicate longitudinal lines of brown freckling the centres of the 

 feathers of the throat. Length nine and a half inches. 



The San Pedro river, a branch of the Gila east of Tucson, was the most western point at 

 which I observed this species ; here a flock of these birds ran before us at a quick pace, with 

 outstrecbed necks, heads elevated, crests erect and expanded, and soon disappeared among the 

 thick bushes which surrounded us on all sides. After this I saw them occasionally until I 

 arrived at Lympia Spring. Lieutenant Barton, United States army, informed me that he had 

 procured it near Fort Clarke, one hundred and twenty miles west of San Antonio, where, how- 

 ever, it is rare. This beautiful partridge is found abundantly on the open plains, often starting 

 up before us when passing over the most arid portions of our route. It also seems partial to 

 the prairie dog villages. These, covering large tracts of ground destitute of vegetation, (every- 

 thing but a stray cactus here and there being consumed by the prairie dogs,) probably offer 

 the attraction of some favorite insect. 



ACTIDURUS NAEYirS, H e e r m a n n .—Mottled Grass Plover, 



Plate VI. 



Aclidurus nairius, Heermasn, Proceed. Acad. Nat. Sc. Phil. vol. VIL 

 Tryngites rufescens. Cassis, in Gen. Rep. P. E. E. 1S5S, 739. 



Sp. Ch. — Form. — Bill slender, as long as the head; culmen straight; sides compressed towards the tip, which is slightly 

 curved; nostrils linear. Wings pointed, and when closed reaching to the end of the tail, the first primary bemg the longest. 

 Tail long, broad, and rounded, the central feathers longest. Tarsae and toes long; claws short and acute. 



Color. — The feathers of the upper parts black in the centre, with broad margins of yellowish brown ; primaries brown, the ends 

 being black narrowly tipped with white. Under surface white, becoming mottled with black two and a half inches from their 

 termini, which there change to a grayish hue. The under wing coverts, irregularly marked and mottled with black, are silver 

 gray, dusky towards the ends, but tipped and bordered with pure white. Under parts pale yellow ochre, the feathers bordered 

 with faint white. Those of the breast near the pinion of the wing having in their centre a linear spot of black. Lower part 

 of abdomen and vent of a much paler hue than the breast. Tail brown on its upper surface, the two middle feathers having a 

 bronze tinge, the others being tipped with yellowish white followed by a black band. Under surface grayish, the inner vanes 

 being mottled with minute brown spots. Bill black. Feet light yellow. Length seven and a half inches. 



While riding on the prairies near San Antonio, my attention was called to this bird from its 

 being smaller than Bartram's tatler, {Actitis hartramius,) which there abounds. It ran nimbly 

 on the ground among the grass in search of insects, uttering when disturbed a weak tweet, two 

 or tbree times repeated. The birds of this genus, unlike the Tringae, (wliich congregate in 

 large flocks showing a preference for the seashore,) migrate in small parties, resorting to the 

 fresh water ponds and streams of the interior, or seek their food on the broad grassy plains. 

 They run with great celerity. If alarmed they fly with rapidity, making wide circuitous sweeps 

 before alighting. When wounded they take to the water, swimming with facility and often 

 diving to escape danger. The nest, formed of grasses and containing four eggs, is placed on 

 the ground, whicb has been previously hollowed out. When disturbed during the breeding 

 season, the female, flying a short distance from her nest, throws herself on the ground, fluttering 

 along as if wounded, and thus decoys the intruder into following her away. Once at a safe 

 distance she takes to wing, returning to her home by a circuitous route. 



