The analysis of the nesting season of birds near Oroville, California, by Mr. W. B. Davis, in this issue of the CownoR (pp. 151-4) has prompted me to place on record a comparable lot of information dealing with the same subject in another part of the United States, namely, near the townsite of Geary, Doniphan County, Kansas. Various features of the latter survey have already been reported upon as follows: Fig. 30. CHT SHONG NUMBS OF CUPI BIRD NTS FOUND IN CH WES PIOD OM MIMCH  MISMB IN DONIPHAN COUNt, KANSAS. general accounts of the birds were given in the University of Kansas Science Bulletin (18, 1928, pp. 517-626); analysis of relations between plants and birds (ibid., pp. 49%515); relative frequency of occurrence, CONDOR (30, 1928, pp. 180-184); en- vironmental relations, Wilson Bulletin (40, 1928, pp. 157-177). The two stations, Oroville, California, and Atchison (8 mi. from Geary), Kansas, which mark the locations of the areas studied and which have weather recording stations that furnished records of climate, are located at 39 29' N. 121 36' W. and 39 33' N. 95 10' W., respectively. In other words they are at nearly the same latitude but they are approximately fourteen hundred miles apart from west to east. The two areas are both under 1000 feet altitude, the California one being under 500 feet. Work .was done at the Kansas locality between 1921 and 1925, but most of the records were obtained in two seasons. The California records show 333 nests of 51 species and the Kansas records, 315 nests of 57 species. The chart (fig. 30) and tabulation of nests found in northeastern Kansas show that the nesting season extends from the middle of March to the middle of Septem- ber. These limits would probably be extended by the addqtion of more observations, but it is not' likely that the peak of nesting shown for the first two weeks of June would be shifted by more examples, no matter how extensive. A rough classification of the nests according to their height from the ground gives an indication of the type of nester best suited for the genera] region. The fol- lowing are the classes of heights distinguished and the number of nests found in each: under 2 feet, 30; 2 to 5, 85; 5 to 7, 43; 7 to 10, 35; 10 to 12, 17; 12 to 15, 18; 15 to 20, 20; 20 to 25, 16; 25 to 30, 10; 30 to 35, 3. Total, 277 nests. Thirty per cent or more than one-fourth of these nests were at heights between two and five feet from the ground. The distribution of the nests by habitats is notable because of the close parallel between the numbers of nests and the numbers of species observed in the same types of habitat. In the following list of ten of the habitat divisions recognized are shown (1) the number of nests found and (2) the number of kinds of birds recognized in the same type of habitat at some time of the year. Typha, 14, 26; salix-populus, 74, 101; creek-bottom, 20, 80; bluff, 98, 109; sprouts, 10, 11; orchard, 9, 21; road, 23, 43; pasture, 10, 16; yard, 36, 51; buildings, 13, 14. TABULATION OF NESTS FOUND IN DONIPHAN COUNTY. KANSAS Number of Species nests Green Heron .................................. 1 Turkey Vulture ............................ 1 Cooper Hawk ............................... 2 Red-tailed Hawk .......................... 1 Bob-white ...................................... 1 Mourning Dove ............................ 22 Yellow-billed Cuckoo .................... 27 Long-eared Owl ............................ 1 Whip-poor-will ............................ 1 Chimney Swift .............................. 2 Ruby-throated Hummingbird .... 10 Northern Flicker .......................... 1 Red-bellied Woodpeeker .............. 1 Red-headed Woodpecker ............ 5 Hairy Woodpecker ...................... 1 Downy Woodpecker ...................... 5 Kingbird ........................................ 3 Phoebe .......................................... 5 Acadian Flycatcher .................... 2 Wood Pewee .................................. 4 Tree Swallow ................................ 4 Rough-winged Swallow .............. 1 Estimated Earliest Latest date for fresh date date eggs June 5, 1923 .................. May 15 June 6, 1923 May 1 June 7, 1922 June 11, 1922 May 15 March 31, 1923 .................. April 1 June 10, 1922 May 15 April 22, 1924 July 18, 1923 May 15 June 9, 1922 Sept. 9, 1923 June 15 March 30, 1924 .................. March 15 June 14, 1923 June 1 July 16, 1923 July 18, 1923 June 15 June 4, 1923 August 5, 1922 June 15 June 10, 1923 .................. May 1 April 29, 1923 May 1 June 8, 1923 August 21, 1922 June 1 April 29, 1923 .................. May 1 May 12, 1923 June 8, 1922 May 15 June 17, 1922 June 23, 1922 June 1 April 15, 1923 June 5, 1923 May 1 June 14, 1922 June 26, 1923 June 15 June 21, 1922 July 13, 1923 June 15 June 7, 1923 June 13, 1922 May 15 May 18, 1924 .................. June I Number of Earliest Species nests date Barn Swallow .............................. 2 June 9, 1922 Blue Jay ........................................ 8 April 20, 1924 Crow .............................................. 7 March 31, 1923 Black-capped Chickadee_ ............. 5 April 14, 1923 Tufted Titmouse .......................... 3 May 19, 1923 Western House Wren ................ 6 June 9, 1922 Carolina Wren .............................. 7 April 21, 1924 Prairie Marsh Wren .................... 1 May 30, 1924 Catbird .......................................... 5 June 7, 1923 Brown Thrasher .......................... 8 May 29, 1924 Robin ............................................ 7 May 13, 1923 Wood Thrush ................................ 9 June 4, 1923 Bluebird ........................................ 7 April 14, 1923 Blue-gray Gnatcatcher ................ 4 June 4, 1923 White-eyed Vireo .......................... I June 29, 1923 Bell Vireo ...................................... 8 June 5, 1923 Red-eyed Vireo ............................ 6 June 7, 1923 Prothonotary Warbler ................ 5 June 12, 1923 Yellow Warbler ............................ 2 June 7, 1923 Kentucky Warbler ........................ I June 30, 1923 Maryland Yellow-throat .............. 3 June 7, 1923 Yellow-breasted Chat ................. 10 June 5, 1923 Yellow-headed Blackbird ............ I May 30, 1924 Red-winged Blackbird ................ 14 May 29, 1924 Orchard Oriole. ............................. 5 June 3, 1923 Baltimore Oriole .......................... 7 June 4, 1923 Bronzed Grackle .......................... I June 17, 1923 Scarlet Tanager. ........................... I June 15, 1922 Summer Tanager .......................... 3 June 21, 1923 Cardinal ........................................ 38 April 20, 1924 Rose-breasted Grosbeak .............. 2 June 13, 1923 Indigo Bunting. ........................... 18 June 8, 1923 Dickcissel ...................................... 6 June 9, 1922 Lark Sparrow .............................. 1 June 9, 1922 Field Sparrow .............................. 2 June 14, 1922 Estimated Latest date for fresh date eggs June 8, 1.923 June 1 June 16, 1922 May 15 June 11, 1922 April 15 June 9, 1922 May 1 June 28, 1923 May 15 July 11, 1923 June 15 August 28, 1923 May 15 June 15 July 16, 1923 June 15 July 18, 1923 June 1 July 16, 1923 May 15 August 9, 1922 June 1 July 16, 1923 May 15 June 19, 1922 June 15 June 15 June 17, 1922 June 15 August 23, 1921 June 15 June 23, 1922 June 15 June 8, 1923 June 1 June 1 June 12, 1923 June 1 July .,19, 1923 June 15 June 15 June 14, 1922 June 1 July 16, 1923 June 15 June 26, 1922 June 15 .................. June 1 June 15 July 15, 1923 June 15 July 19, 1923 May 15 June 17, 1923 June 15 August 23, 1922 June 15 August 23, 1923 June 15 June 1 July 18, 1923 June 1 SUMMARY OF RECORDS OF BIRDS AND CLIMATE IN DONIPHAN COUNTY, ,ANSAS, AND BUTTE COUNTY, CALIFORNIA. Temperature in Fahrenheit. Precipitation in inches. Kansas weather records from Atchison and Leavenworth; California records from Oroville. Kaasa Days of field work ................ 6 11 9 14 15 40 16 42 Number of species noted.... 41 42 64 95 124 106 73 114 Mot species in one day ...... 27 25 45 46 78 61 41 56 Nests found ........................... -- -- 4 19 34 187 55 15 20 12 9 6 200 121 62 59 34 196 64 34 36 25 78 1 315 53.5 34.80 Mean temperature. .............. 25.4 31.6 40.8 54.4 64.6 73.4 78.0 76.2 67.4 56.0 41.5 32.6 Precipitation .......................... 1.10 1.37 1.87 2.92 4.49 5.15 4.22 4.21 3.58 2.42 2.09 1.38 California Nests found ........................... -- 8 43 174 103 5 Mean temperature ............... 46.8 50.6 54.3 59.5 66.1 74.5 80.2 78.6 73.0 65.4 55.9 47.8 Precipitation ........................ 6.22 4.22 4.03 1.80 1.50 0.37 0.03 0.01 0.74 1.46 3.18 4.89 333 62.7 28.33 Turning to a more direct comparison of the nesting seasons of the birds in the two areas it is noticed first that the shapes of the two column diagrams are closely alike but that they come at different times of the year. In the Kansas locality the peak of the nesting season comes during the first two weeks of June and it is at least six weeks later than the California one, in the last half of April. These diagrams appear'to show beyond any reasonable doubt that the difference in time of nesting here represented is a true one and not merely the consequence of personal peculiarlties in methods of making or recording observations. One difference in the records, of possible significance, is that Mr. Davis' dates in every case represent time of finding fresh eggs, while mine are indicative merely of occupied nests. After closely examining the whole lot of records with this point in mind I have reached the conclusion that about as many nests were found in stages of construction as were found with young so that the final averages are comparable fairly with the California records. I might point out that my concern here is with the nesting season of all the species as a composite fauna and not an analysis of single species. The results of these two types of enquiry might differ, but preliminary studies of single species and of closely related ones indicate that single species in the two localities show the same sort of difference in nesting season as does the whole bird population. Any attempt to analyze the nesting seasons at these two localities and to interpret the differences in time, involves an understanding of the factors which determine the time of nesting. Several ways of approaching this problem have been tried by labora- tory and field workers. Usually each worker has dealt with only a single factor, vith the result that single elements have been emphasized as though they represented the chief or only influences in the problem. One fault connected with many of these explanations is the intolerance of many of their proponents toward other possible ex- planations. Circumstances which might be thought of as important to consider in the present comparison involve the following: genetic factors in species represented; conditions in the winter homes of the birds; altitude; rainfall; temperature; photo- periodism; food supply. As a basis for approaching this problem previous work on the physiology of re- production in birds and other vertebrates seems to indicate that the seasonal cycle of egg laying results from the genetic constitution of each species, which determines the manner of response to external, and seasonally variable, factors. These factors appear to influence the activity of the reproductive system through the complex and inter- related system of endocrine glands. Furthermore, the bulk of the information seems to point to the pituitary as the organ most directly concerned in coordinating the internal rhythm with external factors. As to temperature Tollenaar (1922, abstract in Exp. Sta. Rec., 48, 1923, p. 172), who worked on several kinds of wild birds over a four year period designed to show the influence of food supply and temperature on egg production during the different years, observed that the beginning of the laylng period varies with different species, but the time of beginning was somewhat correlated with the previous 10-day temperature, and more closely correlated with the temperature from January 1 to the time of laying. Possibly a slight over-emphasis of the effect of temperature was given by Rowan by the comment (Proc. Boston Soc. Nat. Hist., 39, 1929, p. 202) that "the spring recrudescence of the gonads of birds is universally attributed to rising temperatures." Rowan's own views can be expressed by quoting (op. cit.) his summarized state- ment that "it has been shown that the rhythm of the reproductive organs of the Junco (and several other species) can be interrupted almost at will by appropriate manipu- lation of the lightlng conditions." He added that these organs "appear to show a remarkable dependence on the lighting conditions" but that' "increasing periods of compulsory exercise in almost complete darkness substituted for light increases will effect recrudescence of the organs in similar manner .... It is therefore suggested that the light increases in reality afford the birds the opportunity of increasing exer- cise and that this is the crudal /actor in inducing the development of the gonads." The investigations by Rowan, Bissonnette, and others appear to demonstrate that phenomena connected with the changing length of day in spring in temperate lati- 6 5 __ 65 ' __50 --40 --,$0 I 2 &   6 Fig. 31. HYTHERGRAPHS FOR OROVILLE, CALIFORNIA, AND NORTH- EASTERN KANSAS (LEAVENWORTH AND ATCHISON). TEM- PERATURE IS REPRESENTED IN DIGRESS FAHRENHEIT, PRECIPI- TATION IN INCHES. NUMBERS BESIDE POINTS ON THE FIGURES DESIGNATE MONTHS OF THE YEAR. tudes are important in establishing the time of nesting. If the time of beginning of the breeding cycle were entirely or even largely determined by length of day, we might expect birds in the same latitude to have closely similar calendars of breeding activities. The circumstance that the two present examples represent the nesting seasons of localities at the same latitude offers an opportunity to test the applicability of this theory and to compare effects of photoperiodism with other factors. The difference in the seasons in this comparison must be due to some factor other than the one connected with light changes. Climates of the two regions are represented by hythergraphs in figure 31. Ex- aminatlon of these graphs in connection with the diagrams of the nesting seasons brings the suggestion that when the birds are beginning to nest in California the weather in Kansas is much too cold to favor nesting activities and at the peak of the season in Kansas the heat and drouth in California are not condudve to nesting. That these conditions are really unfavorable for nesting follows from Mr. Davis' suggestion of a positive correlation between availability of food for young birds and time of nesting. The availability of food whether of ahimal or plant material seems to be obviously and rather directly dependent upon favorable climatic conditions. Abundance of plant growth and the insects which depend upon it requires warmth and moisture in combination. Apparently in the two localities here dealt with the birds nest when forage con- ditions are best even if this comes six weeks later in one place than in the other and contrary to the expectation that the equality in advance of day-length might pre- scribe a common nesting season for both places. However, this condition need not be accepted as a denial of the effectiveness of the photoperiodic factor, but rather as an example of a way in which that effectiveness may be modified. In this case the modification seems to be mainly the result of varying climates which are determined by positions of the localities on the continent. It happens here that for an indicator of favorable time for nesting, graphs representing climate (precipitation and tem- perature) serve better than the advance in length of light periods as measured by chronological advance of season. Museum of Vertebrate Zoology, University of California, Berkeley, .4pril 21, 1933.