A most social bird. Nat. Hist. 81(10):44-51. Marshall, Joe T. 1942. Food and habitat of the spotted owl. Condor 44:66-67. Marti, Carl D. 1974. Feeding ecology of four sympatric owls. Condor 76(1):45-61. Martin, Alexander C., Herbert S. Zim, and Arnold L. Nelson. 1951. American wildlife and plants. McGraw-Hill Book Co. Inc., New York. 500 p. Massey, Calvin L., and Noel D. Wygant. 1973. Woodpeckers: most important predator of the spruce beetle. Colo. Field Ornithol. 16:4-8. McAtee, W. L. 1911. Woodpeckers in relation to trees and wood products. U.S. Dep. Agric. Biol. Surv. Bull. 39. McClelland, B. Riley, and Sidney S. Frissell. 1975. Identifying forest snags useful for hole-nesting birds. J. For. 73(7):414-418. McGilvrey, Frank B. (Compiler). 1968. A guide to wood duck production habitat requirements. U.S. Bur. Sport Fish, and Wildl., Resource Pub. 60. 32 p. McLaren, Margaret A. 1975. Breeding biology of the boreal chickadee. Wilson Bull. 87(3):344-354. Meanley, Brooke, and Ann Gilkeson Meanley. 1958. Nesting habitat of the black-bellied tree duck in Texas. Wilson Bull. 70(1):94-95. Mendall, H. L. 1944. Food of hawks and owls in Maine. J. Wildl. Manage. 8:198-208. Miller, Alden H., and Carl E. Bock. 1972. Natural history of the Nuttall woodpecker at Hastings Reservation. Condor 74(3):284-294. Miller, Edwin V. 1941. Behavior of the Bewick wren. Condor 43(2):81-99. Morse, Thomas E., Joel L. Jakabosky, and Vernon P. McCrow. 1969. Some aspects of the breeding biology of the hooded merganser. J. Wildl. Manage. 33(3):596-604. Nelson, Morlan W. 1969. The status of the peregrine falcon in the northwest. P. 61-72. _In_ J. J. Hickey, ed. Peregrine falcon populations. Univ. of Wisconsin Press, Milwaukee. Nice, Margaret M., and Ruth H. Thomas. 1948. A nesting of the Carolina wren. Wilson Bull. 60(3):139-158. Nicholls, Thomas H., and Dwain W. Warner. 1972. Barred owl habitat use as determined by radiotelemetry. J. Wildl. Manage. 36(2):213-224. Oberholser, Harry C. 1974. The bird life of Texas. Vol. 1. Univ. of Texas Press, Austin. 530 p. Odum, Eugene P. 1941. Annual cycle of the black-capped chickadee—1. Auk 58(3):314-333. Odum, Eugene P. 1942. Annual cycle of the black-capped chickadee—3. Auk 59(4):499-531. Oliver, William W. 1970. The feeding patterns of sapsuckers on ponderosa pine in northeastern California. Condor 72(2):241. Olson, Harold. 1953. Beetle rout in the Rockies. Audubon 55(1):30-32. Packard, Fred Mallery. 1945. Birds of Rocky Mountain National Park. Auk 62(3):371-394. Palmer, Ralph S. (ed.) 1976. Handbook of North American birds. Vol. 3. Yale Univ. Press, New Haven, Conn. 560 p. Pearson, T. Gilbert (ed.) 1936. Birds of America.