In the final decades of the nineteenth century, concern was building about the status of migratory bird populations in North America. In this literature review, we describe how that concern led to a landmark conservation agreement in 1916, between the United States and Great Britain (on behalf of Canada) to conserve migratory birds shared by Canada and the United States. Drawing on published literature and our personal experience, we describe how subsequent enabling acts in both countries gave rise to efforts to better estimate population sizes and distributions, assess harvest rates and demographic impacts, design and fund landscape-level habitat conservation initiatives, and organize necessary political and regulatory processes. Executing these steps required large-scale thinking, unprecedented regional and international cooperation, ingenuity, and a commitment to scientific rigor and adaptive management. We applaud the conservation efforts begun 100 years ago with the Migratory Bird Treaty Convention. The agreement helped build the field of wildlife ecology and conservation in the twentieth century but only partially prepares us for the ecological and social challenges ahead. Ó 2017 The Wildlife Society.

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Age-related Production 76 DISCUSSION Relationship of Age to Breeding Biology of Waterfowl 86 Relationship of Age to Annual Productivity of Lesser Scaup 93 Management Implications of Age-related Productivity of Waterfowl 98 SUMMARY 101 LITERATURE CITED 105 ACKNOWLEDGEMENTS 112 APPENDIX 115 STUDY AREA Field work was conducted near Yellowknife (62028'N, 114°24'W), District of Mackenzie, Northwest Territories (Figure 1). The Yellowknife Study Area located 1 to 5 miles north of Great Slave Lake was established in 1961 by II. W. Murdy to determine waterfowl productivity in subarctic habitat. It is 15 square miles in size (h mile wide and 30 miles long) encompassing the area within k mile of both sides of the Yellowknife High way (NWT#3) fr

THIS paper describes white geese with morphological characteristics intermediate between the Ross' Goose (Chen rossii) and the Lesser Snow Goose (Chen hyperborea hyperborea). Although the parentage of these intermediate white geese is unknown, they apparently represent the hybridization of Ross' Geese and Lesser Snow Geese in the wild. Johnsgard (1960) analyzed the occurrence of intratribal hybridization among Anserini based primarily on hybrids reported by Gray (1958). Ross' Goose is known to hybridize in captivity with both the Blue Goose (Chen caerulescens) and Lesser Snow Goose (Sibley, 1938; Gray, 1958: 53). Intergeneric hybrids have been reported from avicultural collections between the Ross' Goose and the domesticated Greylag Goose (Anser anser), Emperor Goose (Philacre canagicus), and Cackling Goose (Branta canadensis minima) by Sibley (1938), and the Red-breasted Goose (Branta ruficollis) by Scott (1951: 38). Sibley (1938) also documents the intertribal hybridization of a captive Ross' Goose and Blue-winged Goose (Cyanochen cyanopterus). Wild hybrids of Ross' Geese and these species have not been reported. Scientific nomenclature follows the A.O.U. Checklist (A.O.U., 1957), although taxonomic revisions of the Anatidae suggested by Delacour and Mayr (1945), Delacour (1954), and Johnsgard (1968) have been accepted by an increasing number of waterfowl biologists. Terminology and concepts of hybridization conform with the definitions and descriptions of Mayr (1963) and Short (1969). The term "intermediate" is used to denote the apparent hybrids of Ross' Geese and Lesser Snow Geese. SOURCE O•' INTER2VIEDIATE WItlTE GEESE Twenty-four intermediate white geese were studied between 1962 and 1968 (Table 1). In addition, information is presented on 18 other intermediates to document further the occurrence and distribution of these geese. While banding waterfowl at Teo Lake (51 ø 35' N, 109 ø 24' W) near Kindersley, Saskatchewan, on 4 October 1961, Dzubin captured a goose with characteristics intermediate between the Ross' and Lesser Snow Geese. This adult female goose was carefully examined but escaped before measurements were taken. Dzubin trapped and measured a second intermediate goose, an immature female, at Teo Lake on 24 October 1962. Independently, Trauger captured an adult female intermediate goose on 29 December 1962 while cannon-netting geese at Squaw Creek National Wildlife Refuge (40 ø 05 • N, 95 ø 15' W) near Mound City, Missouri. This goose was presented to the 856 The Auk, 88: 856-875. October 1971