The Number of Ross' Geese in Central North America
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THE NUMBER OF ROSS ’ GEESE IN CENTRAL NORTH AMERICA J. P. PREVETT AND C. D. MAcINNES Department of Zoology University of Western Ontario London 72, Ontario, Canada During intensive field studies of wintering prediction with evidence from recoveries in Blue Geese ( Anser [ = Chen] caerulescens) Texas of Ross ’ Geese banded near Kindersley, in Texas and Louisiana, we found Ross ’ Geese Saskatchewan. (Anser [ = Chen] rossii) to be more abundant Our observations and results from banding and widespread than expected. Concurrent studies have shown that Dzubins’ prediction observations on the Hudson Bay coast showed was correct, and that MacInnes and Coach a parallel increase in numbers of Ross ’ Geese (1963) were wrong. In this paper we show nesting in colonies of Blue Geese. This doc- that a real increase in the numbers of Ross ’ uments a recent expansion in the range of the Geese is in progress in central North America, Ross ’ Goose, since the species has heretofore and that there is definitely interchange be- been restricted to nesting on part of the coast tween the Hudson Bay breeding localities and of Queen Maud Gulf in the central Canadian the California wintering grounds of the nesters Arctic and wintering almost exclusively in the of Queen Maud Gulf. Central Valley of California (see fig. 1, derived We follow Coach (1961) in referring both from Ryder 1969; Dzubin 1965; Kozlik et al. Blue and Lesser Snow Geese to a single spe- 1959). cies, Anser [= Chen] caerulescens, which we About 1960, records of Ross ’ Geese began to shall call the Blue Goose. All references in- increase dramatically in the central United clude both blue and snow color phases unless States (Trauger, unpubl.). At the same time, the otherwise specified. species was discovered nesting in the Hudson Bay drainage area (Barry and Eisenhart METHODS 1958; MacInnes and Coach 1963). Since Ross ’ Sight records were accumulated during a field study Geese were reported at Churchill, Manitoba, of family groun behavior of Blue Geese. Because in 1771 (Hearne 1795), and since there were the latter study required precise determination of scattered records in the Mississippi Valley the ratio of neckbanded to unmarked Blue Geese, every goose recorded was examined carefully, making since about 1900 (Smart 1960)) MacInnes and available an unbiased estimate of the proportion of Coach concluded that the increase in sight Ross ’ Geese in each flock. records was due primarily to increased ornitho- Examination was by 16-69 x telescope, at ranges logical activity rather than a change in the of less than 250 m. At that distance Ross ’ Geese were abundance of the species. They further sug- easily identified, particularly by their shorter, heavier neck, short bill, and more rounded head. Juvenile gested that there might be a small population Ross ’ Geese were readily distinguished from young, of Ross ’ Geese, breeding on the Hudson Bay white-phase Blue Geese by their much whiter plu- coast and wintering in Texas and Louisiana, mage. After mid-December, it became increasingly which was separate from the major concentra- difficult to separate adult and immature Ross ’ Geese tion of the species. in the field; therefore, all winter records were listed as adults. Hybrids of Ross ’ and BIue Geese were Dzubin (1965) described in detail changes seen occasionally (Trauger et al. 1971); these could in the distribution of Ross ’ Geese from the usually be distinguished only at distances of less than major population as their center of fall activity about 150 m. Beyond that distance most hybrids moved eastward from Alberta into Saskatch- were probably called Ross ’ Geese. ewan. His observations led him to “predict In large flocks of wintering geese, it is normally impossible to check every individual; in such cases a that sightings, reports and recoveries of Ross ’ sampling procedure was used (see MacInnes 1966: Geese through most states of the CentraI and 541). Repeated counts taken from a single flock were Mississippi Flyways will become more numer- averaged; this is the source of fractional numbers of ous over the next several years.” He proposed Ross ’ Geese in the tables. that these would stem from continued east- Figure 1 shows the migration and winter range of Blue Geese nesting at McConnell River, N.W.T. (69” ward wandering from the Queen Maud Gulf- 5ON,’ 94”25W),’ based on 4458 recoveries of banded California populations and reinforced the birds, the location of recoveries of Ross ’ Geese [43Il The Condor 74:431-438, 1972 432 J. I.’ PREVETT AND C. D. MACINNES RECOVERY FREQUENCIES : BLUE GEESE l-19 a 20-99 m 100+ m ROSS GEESE 1 0 ROSS GEESE BREEDING, MIGR AND WINTER RANGE: FIGURE 1. Migration and winter range of Blue Geese from McConnell River, N.W.T.; pattern of recoveries of Ross ’ Geese banded at McConnell River; and breeding, migration, and winter distribution of the main pop- ulation of Ross ’ Geese. NUMBER OF ROSS ’ GEESE IN CENTRAL NORTH AMERICA 433 TABLE 1. Frequencies of Ross ’ Geese per 1000 Blue Geese at migration stopover points. Positions of localities are shown in figure 1. Blue Geese Ross ’ Geese Frequency of Ross ’ Geese Adult YoUIg’ Adult Young Adult Y 011ng All ages Sand’ Lake ( 9) Fall 1968 18,402 5,324 19 15 1.03 2.82 1.43 Fall 1969 48,949 20,555 61 22 1.25 1.07 1.19 Spring 1970 6,587 2,055 18 3L - - 0.08 DeSoto (10) Fall 1968 8,972 1,551 5 0.56 2.58 0.86 Fall 1969 12,930 6,350 11 2 0.85 0.79 0.83 Plattsmouth (11) Fall 1968 5,771 934 ; 25 0.871.24 5.350.77 1.091.49 Fall 1969 5,650 2,603 Squaw Creek (12) Fall 1968 17,612 4,087 6 5 0.34 1.22 0.51 Fall 19691 25,175 17,163 15 7 0.60 0.41 0.52 Spring 1969 7,307 1,310 24 a - - 2.79 Spring 1970 21,193 15,477 31 n - - 0.85 il Adults and young not distinguished in spring. banded at McConnell River, and the breeding, mi- ferent goose flocks were examined in some lo- gration, and winter range of the main population of calities in 1968. For example, in the Aransas- Ross ’ Geese. Localities visited during this study and Calhoun area, nearly one-third of the recorded other places referred to in the paper are shown in figure 2. count of Blue Geese in February 1968 was from a single flock which contained no ROSS ’ RESULTS Geese. Only 1700 geese were examined near Port Lavaca, where the highest frequencies of Ross ’ Goose frequencies at fall migration stop- Ross ’ Geese were recorded in the two follow- over points (expressed throughout this paper ing seasons. No Ross ’ Geese were seen in the as the number of Ross ’ Geese per 1000 Blue course of the 1968 counts, but two were iden- Geese) appear in table 1. These ratios are dif- tified after the counts were completed. Since ficult to interpret, since at the localities visited, 1968 was the first winter of the survey, it is Blue Geese are known to stem in varying pro- possible that lack of experience resuIted in portions from different nesting colonies (Coach some Ross ’ Geese being missed. However, be- 1961; Prevett, unpubl. ) . cause frequencies of Ross ’ Geese were con- Wintering ground frequencies of Ross ’ Geese sistently low, even in the large Rice Prairies are show in table 2. ClearIy, fewer Ross ’ Geese sample, we believe that the difference was real were seen in the winter of 1967-68 than in although it may have been smaller than in- either 1968-69 (P < 0.001) or 1969-70 (P < dicated. O.OOl), although the latter two winters pro- Frequencies were estimated from ground duced similar results (P > 0.10). OnIy 4 counts. However, it was impossible to esti- weeks were spent on the wintering grounds in mate the total number of geese in each flock, the first winter, compared to lo-12 weeks in nor could we achieve complete coverage of all subsequent years, so samples were small. A flocks. Therefore, estimates of the total pop- particularly serious aspect was that few dif- ulation of Blue Geese on the wintering grounds TABLE 2. Frequencies (f) of Ross ’ Geese per 1000 Blue Geese at wintering areas on the Gulf Coast. Positions of localities are shown in figure 1. 1967-68 1968-69 1969-70 % % % RlW whiten Ross ’ BlW white” Ross ’ Blue whitea Ross ’ Locality Gl33e phase Geese f Geese phase Geese f Gt?EWZ phase Geex f Slabine-Lacassine (21 3,420 21 1 0.29 9,185 16 8 0.87 12,913 24 0.47 Gum Cove (20) 1,954 33 2 1.02 4,279 38 3 0.70 5,810 43 0.86 East Texas (19) 9,239 60 6 0.65 16,234 72 23 1.42 36,308 66 34 0.94 Rice Prairies ( 18) 15,924 73 22 1.38 38,462 73 116 3.02 75,200 73 205 2.73 Aransas-Calhoun ( 16 2,727 84 0 0.00 3,220 87 28 8.70 8,204 85 70.5 8.59 Lower Coast (15) 2,607 86 4 1.53 115 81 0 0.00 828 86 2 2.42 TOTAL 35,371 35 71,495 178 139,263 322.5 31Calculated from ground counts made simultaneously with frequency counts of Ross ’ Geese. 434 J. P. PREVETT AND C. D. MACINNES FIGURE 2. Locations where geese were observed during this study and other places referred to in the paper. Localities: 1 Koukdjuak River; 2 East Bay; 3 Boas River; 4 McConnell River; 5 Cape Churchill; 6 Cape Henrietta Maria; 7 Kindersley; 8 Last Mountain Lake; 9 Sand Lake N.W.R.; 10 DeSoto N.W.R.; NUMBER OF ROSS ’ GEESE IN CENTRAL NORTH AMERICA 435 TABLE 3.