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 26 Vol. XXI PROBLEM: DO BIRDS MATE FOR LIFE ? By J. EUGENE LAW WITH ONE PHOTO BY r. E. WYMAN IlE excellent article entitled "Evidence that many birds remain mated for life", by F. C. Willard (CoNooR, xx, 1918, p. 167), is pregnant with prob- lems for the bird ecologist. Another angle of view may further emphasize the value of intensive study, such as Mr. Willard's article indicates, and the ne- cessity of carefully recording in the minutest detail every incident in a bird's life history. Fig. 10. NEST OF CALIFORNIA BLACK-HEADED GROSBEAK COlI - STRUCTED MAINLY OF WILD OATS. THE EGGS SHOWN ARE BORROWED, AS THE TWO EGGS ORIGINALLY FOUND HD BEEN DESTROYED WHEN THE NEST WAS NEXT VISITED. THE STRIPS AT TOP AND RIGHT ARE EACII ELEVEN INCHES LONG. Photo by L. E. Wyman. The precariousness of life among birds leads one, even though paired birds: normally remained so, to doubt so uniform an escape from fatality as would follow, did tile numerous incidents noted cover pairs mated throughout tile period of Mr. Willard's observations. If lost mates were replaced, no doubt tile surviving mate drew the new one to the old home of tile survivor'. Male hum- mingbirds are notoriously indifferent to any family relations, furtiler than the actual act of fertilization. The Anna Hummingbird is pugnaciously solitary 'The writer has had two pairs of Anthony Towhees about his acre-plot home for five years. These birds seemed beyond question to be paired throughout the year and consequently for life. At least twice during that time one of these four individuals was killed in a mouse trap, soon to be replaced by a new mate.