242 BULLETIN UNITED STATES GEOLOGICAL SUEVEY. 



l)lumage* in that region of continued droughts, which embraces, besides 

 the peninsula of Lower California, the whole of the desert region of 

 the Southwestern United States and Western Mexico. 



Younger specimens (probably in the second year), of which No. 12670 is 

 a fair example, have the forehead dusky-slate, there being only a few 

 white feathers in the crown ; the cheeks strongly tinged with buff. The 

 specimen alluded to is equally dark with that from Cape Flattery, W. 

 T., and that from Mexico. 



Seasonal variations. — Although the plumage of this species is essen- 

 tially the same throughout the year, there are certain differences depend- 

 ing on the season which are worthy of note. In the spring, or at the 

 commencement of the breeding season, the bill, except on the culmen, 

 is almost entirely yellow (generally a wax-yellow, brighter on the lower 

 mandible) ; and the bare orbital space cobalt-blue, while from the occiput 

 grow two long, slender, pendant, black plumes. After the young are 

 hatched, these plumes are dropped, the bare skin around the eye has 

 changed to a yellowish-green hue, and the upper mandible become 

 almost wholly dusky blackish-olive, with only the tomia and lower 

 mandible yellowish. Of some twenty specimens killed June 11, 1877, 

 at the Little Cypress Swamp, of Knox Co., Indiana, none had the white 

 occipital plumes, while the bill and orbits were colored as last stated 

 above. These birds were all shot at their breeding grounds, where 

 were about one hundred and fifty occupied nests, mostly containing 

 full-grown young.t Dissection of numerous specimens proved that no 

 appreciable difference exists between the sexes, except in the smaller 

 average size of the females. A male killed at Washington, 13. C, April 

 9, 1875, and consequently in perfect p^mage, had the bill and soft parts 

 colored as follows : — Bill dull wax-yellow, brighter on the lower mandi- 

 ble ; bare orbital space cobalt-blue ; iris bright chrome-yellow ; legs 

 black, the tibise inclining to brownish ; soles of tees dull grayish naples- 

 yellow. A female obtained in spring at Mount Carmel, 111., was simi- 

 larly colored. 



Nine of the specimens alluded to above averaged about sevQn pounds 

 in weight, the maximum being a little less than eight, and the mini- 

 mum over six. Although busily engaged in feeding their very vora- 

 cious young, they were in good condition. " 



* In birds of black, red, or other brilliant colors, these tints are intensified, rather 

 than diluted, in such climates ! 



t These nests were all on very large and tall "Sycamore" trees {Platanus occidentaKs), 

 mostly at a height of about 90 to 100 feet from the ground, many of them higher ; none 

 were accessible. The Herons had apparently chosen these trees in preference to the 

 equally tall cypresses, oa.ks, gums, etc., on account of the protective color of the 

 branches, whose pale drab or silver-gray aspect corresponded so perfectly in color with 

 the prevailing hue of the birds that it was quite impossible to distinguish them from 

 crooked upright branches when they sat perfectly quiet, as was usually the case. In 

 fact, all those shot were killed either on the wing or just after alighting. 



